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PURE BIOLOGY FOR SCIENCES BIOLOGY TEXTBOOK Dunce Name: ______________________ Dummy Index No.: ___________ CHAPTER 1: Cells: The Building Blocks of Life 1.1 CELL STRUCTURE AND ORGANIZATIONS cell – is a unit of life. protoplasm – a complex jelly-like substance in which endless chemical reactions are carried out. Consisted inside cells, 70 – 90% is water.
NUCLEUS Characteristics: - consists of a small spherical mass denser than protoplasm, the nucleoplasm. - Embedded inside cytoplasm. - Control normal cell activities Consists of: - A long thread structures called chromatin which will condense and become highly coiled structures called chromosomes. It contain heredetary materials and control cell activities. - Spherical structures called nucleoli to build up proteins. - A nuclear envelope to seperate nuclear content from surrounding cytoplasm. Importance: - for cell reproduction, - continuous life of the cell, and - repair worn-out parts. Without nucleus, i.e. red blood cell, the cell has short lifespan and cannot reproduce. CYTOPLASM is part of protoplasm surrounding the nucleus. Role: forms the larger part of the cell and the occurance of life processes.
Protoplasm exists in 2 forms: - sol (liquid) state - gel (semi-solid state) state Scientists can’t make protoplasm, while the components are known... - The exact nature is not fully known - The environmental conditions is not suitable Protoplasm has 3 parts: - Nucleus - Cytoplasm - Cell membrane
Organelles in it: - small spherical/rod-shaped organelles called mitochondria to release energy from food during respiration. - Adonesine Triphosphate (ATP) to temporarily store energy in small molecules. When needed, it can be broken down for energy.
SPECIAL ORGANELLE IN PLANT Chloroplast – sites where plant make food by combining carbon dioxide, water and sunlight to make sugar. Vacuoles – contain cell sap which has dissolved substance like sugars, mineral salts and amino acids, enclosed by special membrane tonoplast. Copyrights AF/PS/2009/2010
2 SPECIAL ORGANELLE IN ANIMAL CELL Centrioles – pair of tiny structures close to nucleus for cell division. Vacuoles – many but small, contain water and food substances
transport water and mineral salts from roots to stem and leaves. absence of cross walls allow water move easily through lumen.
CELL SURFACE MEMBRANE is a partially permeable membrane surrounding cytoplasm, controlling substances which enter/leave cell. In plants, it surround vacuoles.
lignin strengthens wall and prevent collapse of vessel.
CELLULOSE CELL WALL Only exist in plant, made of cellulose. 1.2 SPECIALIZED CELLS, TISSUES, ORGANS AND SYSTEMS Modification of Cell Structure for Specific Functions The change and development of a new cell produced into new tissues is called differentiation. EXAMPLES OF SPECIALIZED CELLS Cell Structure Adaptation to Function Root hair cell
long and narrow root hair increases surface area : volume ratio for absorption of water mineral and salts.
Red blood cell contain red pigment - haemoglobin to enable cell transport oxygen from lungs to all parts of body. circular, biconcave shape increases surface area : volume ratio for higher diffusion rate of oxygen.
The xylem vessel is a narrow, cylindrical tube enclosing a continuous space called lumen. Vessel is dead as there’s no protoplasm. Deposited on the wall is hard substance known as lignin.
xylem and lignin, bundled together provide mechanical support for plant.
Tissues, Organs and Systems. Tissue is a group of cells which have common origin and similar structures, enabling them perform a particular function. Example:epithelium – cell sheets covering internal&external body surfaces Animals: Muscle tissue, Glandular tissue, Nervous tissue, Bone tissue, etc Plants: Xylem, Pholoem, Cambium, Cork, etc N/B – tissues that connect different parts of organs together are called complex tissues. Organ is a structure made up of different tissues working together for specific function. Example: Stomach – glandular tissue, muscular tissue, connective tissue, nervous tissue. Leaves, Roots, Stems, Flowers, etc. Organ system is a system made up of several organ working together to perform a special function. Example: Digestive system, Respiratory system, Nervous system, etc END OF CHAPTER 1
CHAPTER 2:DIFFUSION, OSMOSIS, SURFACE AREA:VOLUME RATIO 2.1 DIFFUSION Difusion is the net movement of molecules/ions from a region of higher concentration to a region of lower concentration. (or simply: movement of particles down the concentration gradient.)
Diagrammatic explanation of osmosis:
The movement of particles when there is no net change of movement is known as dynamic equilibrium. Rule of concentration gradient: The steeper the concentration gradient for a substance, the faster the rate of diffusion for that substance. Diffusion and Cells Substances enter cells mainly from diffusion. Example:cell membrane is partially permeable,so allowing CO2&O2 to pass amoeba takes in water by diffusion Understandable experiment: The particles are passing through permeable membrane from both sides and would be equally blue when the concentrations are equal.
5% sucrose solution would move to 10% sucrose solution by osmosis through a partially permeable membrane. Water molecules, being smaller, move to limb A and sucrose molecules are too large to pass through. The solution in limb A continues to rise and vice versa for limb B. The solution level stop changing if both have equal concentration of water molecules. Water Potential Water potential is a measure of tendency of water to move from one place to another. Water move from higher water potential to lower water potential ∴ with the relationship of water potential, we can say: the movement of water molecules from a solution of higher water potential to solution of lower water potential through partially permeable membrane. Osmosis in Living Organisms Cell has cell surface membrane works like partially permeable membrane. When put in dilute solution, i.e. 5% sucrose solution, water molecules will enter cell, having lower water potential and sucrose molecules can’t enter due to its larger size. Hypotonic, Isotonic and Hypertonic Solution
2.2 OSMOSIS A membrane that allow some substances to pass through but not others is called partially permeable membrane. The passage of water from a dilute solution to a more concentrated solution across a partially permeable membrane is called osmosis.
The U-tube has dilute sucrose solution on arm B and more concentrated sucrose solution in arm A. Arm B has more water molecules. So, we say: - Solution in arm A is hypertonic to arm B. - Solution in arm B is hypotonic to arm A. Whilst when we have same solution concentration, i.e. both 5%, we say: - Solutions in arm A and B are isotonic. From above, we find out that the term: Hypotonic – the solution has higher water potential than the other one. Hypertonic – the solution has lower water potential than the other one. Isotonic – both the solutions have same water potential. Cell in a Solution of High Water Potential Cell sap has lower water potential if placed in a solution of high water potential. Thus, water enter through osmosis. When water molecules enter in plant/animal cell, so: IN PLANT CELL: Vacuole size increases, push all contents towards cellulose cell wall, which exerts opposing pressure preventing more water to enter. The cell is turgid. Turgor: turgidity of cell with water. Turgor pressure: pressure exerted by water on cell wall. IN ANIMAL CELL: Without cell wall to oppose the pressure, the cell will swell and may burst. Cell in a Solution of Low Water Potential Cell sap has higher water potential if placed in a solution of low water potential. Water still enter through osmosis, but water move out from cell.
Plasmolysis – shrinkage of cytoplasm from cell wall when immersed in solution of low water potential. IN ANIMAL CELL: Cell crenates and dehydrated, thus may die eventually. Crenation – the process when membrane forms spikes as water is lost and cell shrinks. Importance of Turgor in Plants - Maintain shape of soft tissues, i.e. young stems/leaves remain firm due to turgor pressure. - To move certain plant parts, i.e. change in turgor of guard cell cause opening/closing of stomata. EXTRA INFO: Why shouldn’t we put too much fertilizers? Fertilizers make soil more concentrated, causing plant flaccid. To overcome, dilute the soil to prevent wilting and dying. 2.3 ACTIVE TRANSPORT Is the process in which energy is used to move the particles of a substance from lower concentration region to higher concentration. - Is occuring when tissue respire releasing energy. - Occur only in living cells as only living cells respire. Examples of active transport: Absorption of dissolved mineral salts by root hairs glucose & amino acids absorption by cells in human small intestine 2.4 SURFACE AREA:VOLUME RATIO IN RELATION TO CELLS → The higher surface area:volume ratio, the faster the rate of diffusion.
IN PLANT CELL: Vacuole size decreases, shrinking cytoplasm from cellulose cell wall. The cell is plasmolysed but can return to original state by putting in high water potential solution.
CHAPTER 3: ENZYMES 3.1 WHAT ARE ENZYMES? Enzymes are biological catalyst made of protein which speed up/alter chemical reactions without themselves being changed at the end reaction.
Each enzyme would only react with a praticular substrate, i.e. protease for proteins, lipase for fats. The specificity of enzyme is related to its surface configuration. It’s represented by lock and key specific shown below.
DIGESTION: An Enzyme-Catalysed Process Enzyme convert complex food molecules into simpler ones to be digested. Digestion is the process by which large, insoluble food molecules into smaller, soluble food molecules. 3.2 CLASSIFICATION OF ENZYMES Enzymes can break down in molecules hydrolysis, which is the process of breaking down complex molecule into simpler molecule in which water molecules are needed. Enzyme that break down molecules by hydrolysis are hydrolases. Examples are: Carbohydrase – digests carbohydrate Amylase hydrolyse starch Cellulase hydrolyse cellulose (only plants) Protease, i.e. stomach pepsin – digests protein Lipase, i.e. pancreatic juice steapsin – digests fats DO YOU KNOW??? - Detergents may contain enzymes to digest organic stains. - Unripe pineapples and papayas can tenderize meat with their enzymes. But Also Note!!! - Fruits tenderize meat by covering it on meat before cooking as cooking fire may denature enzyme when heated in high temperatures. (see 4.3) 3.3 CHARACTERISTICS OF ENZYMES - Enzymes speed up chemical reactions - Enzymes are required in small(minute) amounts Enzyme remain unchanged during chemical reaction, so it can be used over and over again on a substrate - Enzymes are substrate specific
Temperature affects enzyme activity Enzymes have optimum working temperature but not always close to that at which they usually function. K
From graph, we know: - Enzymes are least active at low temperatures o - Enzyme reactions speed up as temperature rises. (2x per 10 C) o - Enzyme reaches optimum temperature between 40-45 C at K - Enzyme starts to denature at temperatures beyond K until D Denaturation is the three-dimensional structural change produced by proteins by heat/pH values which make them coagulate.
In (ii), the rate of reaction increases as concentration increased, but constant after point Y. The concentration is now a limiting factor.
Why do Enzymes Denature? When heated at high temperatures, enzymes undergoes changes in shape, protein become less soluble and coagulates. Hence, when the three-dimensional structure is altered, enzymes lose their active sites, making them useless now. -
pH affects enzymes enzyme denatures in extreme changes in acidity/alkalinity.
Limiting factor is a factor that directly affect the rate at which a process occur if its quantity change. -
Enzymes need coenzymes for activity Coenzyme is another compound to be bound to enzyme before they catalyse. Mostly they’re non-protein but organic compound. Examples of coenzymes: vitamin B complex
Enzymes catalyse reversible reactions A+B C+D Since most reactions in living cells are reversible, enzymes catalyse reversible reactions too.
In the above graph is rate of reaction of pepsin with pH. • The optimum pH is pH 7 • As solution gets acidic/alkaline, the reaction slows down • At pH 4 or 9, enzyme completely denatures -
Substrate and enzyme concentration affect enzyme reactions
HOWEVER, The process is usually proceed in forward direction, i.e. A + B to C + D, because the products (C + D) are not allowed to build up but are used up/removed from cell as soon they are formed. END OF CHAPTER 2 & 3 chmsabee94/5090/06/09
In (i), rate of reaction increases until point X is reached. • This is because enzyme molecule is saturated, so amount of products formed per time is same. If an enzyme act on 10 substrates and produce 10 products per second, when there’s 50 enzyme, it’ll react on 500 substrate and make 500 products.
CHAPTER 4: NUTRITION 4.1 THE NEED FOR FOOD Organisms need food to: - Provide energy for vital activities of the body - To synthesize new protoplasm for growth and repair of worn out parts of body and for reproduction - To maintain good health * Green plants make use of sun energy for photosynthesis to make food. So, this stored energy in food is potential chemical energy.
THREE MAIN GROUPS OF CARBOHYDRATES
REMEMBER: Energy is not created/destroyed, but converted from one form to another. With this there’s still a loss of energy even when resting. Example: muscle cells convert potential chemical energy to kinetic energy to move the skeleton.
Glucose is the simplest carbohyrate sugars. The formula is CnH2mOm, as if n = 6 and m = n, the formula is C6H12O6.
4.2 NUTRIENTS IN FOOD Nutrients are chemical substances in food to nourish the body. Types of Nutrients: ORGANIC (Obtained from living organisms): - Carbohydrates - Fats - Proteins - Vitamins - Dietary Fibre INORGANIC: - Water - Mineral Salts Carbohydrates Carbohydrates are organic compounds made of carbon, hydrogen and oxygen. The ratio of hydrogen to oxygen is same as water, i.e. 2:1 - Comes from mainly plants. - Are good source of energy for the body.
Functions of Carbohydrates - Source of energy - To form supporting structures, i.e. cellulose cell wall - To be converted to other organic compounds, i.e. amino acids, fats - For formation of Deoxyribonucleic Acid (DNA) - To synthesize lubricants, i.e. mucus, made of carbohydrates and proteins to trap dust particles in respiratory system - Make nectar in flower. The sugary nectar attract pollinating agent Types of sugar Sugar are sweet crystalline compounds which readily dissolves in solvent. Simple sugars/monosaccharides - Glucose - Fructose - Galactose Glucose are found in small quantities in all organisms. Fructose is common in animals. Galactose is a component of milk sugar, lactose. They both rare in organisms like mammals.
Complex sugars/disaccharides Complex sugars are called as the molecule is made of 2 molecules of simple sugars. Also called disaccharides. - Sucrose - Lactose - Maltose Sucrose - Is available in sugarcane stems and certain storage roots, i.e. beetroots and carrots. - Consists of glucose and fructose combined together. - Not found in mammals C6H12O6(glucose) + C6H12O6(fructose)→C12H22O11(sucrose) + H2O(water) Lactose - Available in milk of all mammals - Formed by glucose and galactose combined together. C6H12O6(glucose) + C6H12O6(galactose)→C12H22O11(sucrose) + H2O(water) Maltose - Available in malted cereals and sprouting grains. - Formed during partial digestion of starch - Consists of two molecules of glucose. C6H12O6(glucose) + C6H12O6(glucose)→C12H22O11(sucrose) + H2O(water) These reactions use the process condensation reaction. Condensation Reaction is a chemical reaction where 2 simple molecules joined together to form bigger molecule with removal of 1 water molecule. These sugars can return to original compositions by hydrolytic reaction. Hydrolytic Reaction is when 1 water molecule is added to split up complex molecule into its component units.
ENZYMES TO HYDROLYSE COMPLEX SUGARS: Sucrase – Sucrose + Water → Glucose + Fructose Lactase – Lactose + Water → Glucose + Galactose Maltase – Maltose + Water → Glucose + Glucose Polysaccharides Is made up of many monosaccharides molecules joined together by polymerization, a process of condensing many similar molecules to form a large molecule. Polysaccharides from condensation of many glucose molecules: - Starch - Cellulose - Glycogen Starch is made up of large number of glucose molecules condensed together as bonds. It can broken down by hydrolysing with acid. Starch is digested with amylase enzyme to form maltose which is digested again with maltase enzyme to form glucose. FACTS ABOUT STARCH: - Important source of carbohydrate - Available in vegetable foods, i.e. cereals, potatoes,etc. Test for starch: Iodine Test: Put few drops of iodine onto sample and it will produce blue-black colour. Glycogen is formed when numerous glucose molecules condense and form highly branches chained of glucose units. IT IS USED AS: - Carbohydrate storage in animals and fungi. - In mammals is stored mainly in liver and muscles WHY GLYCOGEN AS STORAGE MATERIAL? - Insoluble in water, so they don’t change osmotic pressure in cells. - Large molecules; unable to diffuse through cell membrane. - Easy to be hydrolysed to glucose when needed. - They have compact shapes; take less space.
Fun Fact: Do You Know Atheletes Take in Bananas Before Sporting? This is because bananas contain glucose which can be converted to glycogen to be stored and used whenever needed during the sport. Cellulose is the carbohydrate that forms the greater part of plant cell walls. FEATURE: - Inactive; very few organisms can digest it. - Man cannot digest it, but it forms fibre which is important for the functioning of the large intestine. SIMILARITY AND DIFFERENCE WITH STARCH: Similar: Consists of glucose linked together to form straight chains. Difference: The way cellulose is linked is different from that of starch.
OCCURENCE - butter, cheese, fatty meat, olives, nuts, castor oil seeds, palm oil -
saturated fats are fats ocurring in animal bodies. unsaturated fats are harmless fats occuring in plants, i.e. vegetable fats. cholesterol come with saturated fats and can be deposited in arteries which could cause heart disease.
Test for fats: 3 Ethanol emulsion – add 2cm of ethanol into crushed food substance in a test-tube and shake thoroughly. A temporary emulsion is observed. Add water to turn it into a permanent emulsion.
Fats can be hydrolysed with lipase enzyme. → C3H5(OH)3 + 3(C17H35COOH) C57H110O6 + 3(H2O) (Tristearin) (Water) lipase Glycerol Stearic Acid (Fatty acids) 3 mol 3 mol
Proteins Are very complex organic substances containing carbon, hydrogen, oxygen and nitrogen. Sulphur and phosphorus are also found. CHARACTERISTICS: - always present in protoplasm - most complex and largest food molecule substances. - Made up of amino acids. Amino acids linked up to form protein and one water molecule is removed. The bond between 2 amino acids is strong and known as peptides. If there are more than 2 amino acids bonded is known as polypeptides or peptones, and protein molecule is made up with one or more of this chain.
FATS AND OILS fats are solid but oils are liquid at room temperature.
NOTE: The chain of acids in protein is coiled up and weak, so it is easily broken by heat, acids and alkalis, which leads to enzyme denaturation.
APPLIANCES OF FATS - As source and storage of energy. - Insulating material, that is preventing excessive heat loss. - As a solvent for fat-soluble vitamins and other vital substances like sex hormones and related hormones. - For protoplasm constituent, especially in protoplasmic membranes.
Since protein molecule is large, it is broken down to polypeptides and into amino acids to be digested.
Fats Fats are organic elements made up of Carbon, Hydrogen and Oxygen, with the proportion of oxygen much less to hydrogen. (C57H110O6) - It provides energy. - Used as food stores by animals.
PROTEIN DEFICIENCY: When protein is lack (less than 100g), children may suffer deficiency disease called kwashiorkor, which results to make children have swollen abdomens, scaly and cracking skins.
FUNCTIONS OF PROTEINS: - Synthesizing protolasm for growth & repair of worn-out body cells. - For synthesis of enzymes and some hormones. - For formation of antibodies to combat diseases. - Source of energy. Test for Proteins: 3 BIURET TEST: Add 2 cm of egg white and add equal volume of biuret solution. Shake thoroughly and expect a purple colour change. Vitamins Vitamins are a group of chemically unrelated organic compounds required in human diet in very small amounts for normal health and development. fat-soluble vitamins can be stored in fats in the body while water-soluble vitamins cannot be stored, but to be supplied in daily diet. Vitamins Vitamin D (fat-soluble)
Sources - fish liver-oils - egg yolk - margarine - UV rays from sunlight. Vitamin D is resistant to heat and oxidation.
Vitamin C (water-soluble)
- citrus fruits - green vegetables - fruit juices Vitamin D is easily destroyed by heat.
Functions - Absorption of calcium and phosphorus from intestines. - Formation of teeth and bone. LACK: Rickets – poor teeth and soft bones, causing bowed legs and knock knees. Osteomalacia – adults; bone softening EXCESS: Bone demineralization with multiple fractures and calcification of soft tissues. - Formation of intercellular substances. - Maintain healthy epitelial tissues. LACK: Scurvy – swollen bleeding gums and loosening of teeth. Haemorrhages – internal bleeding in muscles and skin. Poor healing and swollen joints.
Vitamins Vitamin B Complex
Sources - yeast - liver - bran - dairy products - fish liver-oils - green vegetables
Functions Coenzymes in cellular respiration. LACK: Beri-beri, pellagra, pernicious anaemia. - Formation of light sensitive pigment in the retina - maintain healthy epithelial tissues.
Water Important because essential constituent of protoplasm. It is also solvent for inorganic salts and other inorganic compounds. USES: - as medium which various chemical reactions of organism occur - transporting agent for: digested food substances from intestines to other body parts; excretory products from tissue cells to excretory organs for removal; and hormones from their places of origin to body regions which require them. - a major component of blood, digestive juices and lubricant found in joints. - for hydrolytic reactions during digestion - reactant in photosynthetic process in green plants - regulate body temperature by evaporating sweat from skin surface Minerals Minerals are inorganic elements which do not provide energy but are indispensable to readily functions. Examples are: - calcium - iron minerals are obtained from plants or animals. Mammals need large quantities of Calcium, Phosphorus, Sodium, Chlorine, Potassium, and Iron. Minerals that are needed in minute amounts are called trace elements.
EXCESS: Excreted by the body
Inorganic element Calcium
Sources milk eggs cheese small fish with bones eaten cereals soya beans dark green vegetables
Children: 1 g /day Adult: lesser, more during the period pregnancy/lactation
Liver Red meat Egg yolk Bread Flour Dark green vegetables
Adult: 0.02 g / day Pregnant women: more
Functions - building bones&teeth - for normal muscle functioning -blood clotting LACK: - Rickets For formation of the: - Haemoglobin Red coloured pigment transporting oxygen in the body - Myoglobin Protein in muscle cells that stores oxygen for muscular contraction. - certain enzymes for respiration LACK: Lowering level of the haemoglobin in blood causing anaemia, can be seen by tiredness/ breathelessness.
Dietary Fibre or Roughage Roughage are indigestable fibrous materials which provides bulk to the intestinal contents and helps peristalsis. Sources are: - Fruits and vegetables - Bran - Wholemeal bread - Cereals Peristalsis – a series of wavelike, muscular movements of walls of digestive tract to enable food mixed with digestive juices. Constipation – is the absence of proper peristaltic movements resulting in undigested matter in large intestine cannot be moved and too much water absorbed making faeces hard and dry, and removing waste difficult. To overcome: Take roughage, drink enough water and exercise regularly.
4.3 FOOD VALUES AND DIET A Balanced Diet and Food Values Balance diet contains right amount of the seven nutrients to meet daily body requirements. Energy used to carry on vital life processes of body while resting is called the basal metablolism. The basal metabolic rate depends on these factors: - Climate - Body size - Age - Sex - Health - Occupation Climate Living in cold country release more heat energy than in tropic country. Thus, basal metabolic rate is higher in cold country. Body size Bigger build need more energy for basal metabolism than smaller build. Age Growing children need more energy for growth than adult. Therefore, children have higher basal metabolic rate. Sex Men have produce heat more than women due to less fatty tissue. So, men have higher basal metabolic rate. Health Thyroid gland produce thyroxine hormone to control metabolic rate. A person with under-active thyroid gland have lower metabolic rate while a person with over-active thyroid gland have higher metabolic rate.
Occupation The more active and heavy your work is, the more energy is required, thus the higher basal metabolic rate. Energy balance If you need 12 000 kJ of energy daily: - Eating less than that results in underweight - Eating more than that results in overweight During weight reducing programme: - Only intake of carbohydrate/fats should be lowered. High protein intake: - Cause excessive nitrogen in body, to be removed as urea. - Liver and kidney overwork, and may be damaged.
Problems of World Food Supplies Starvation, Malnutrition, Over-nutrition Starvation – insufficient energy in mammals or animals. To meet metabolic rate, body uses stored glycogen and fats. Whe finished, body used proteins from skeletal or heart muscles leading heart weakening Malnutrition – dietary imbalance due to deficiency or excess nutrients intake over a period of time. Lack of protein – kwashiorkor. Lack of roughage – constipation. Why starvation and malnutrition? - Increasing population growth - Unequal food distribution - Growing cash crops rather foods in developing countries Over-nutrition – intake of more energy than what a person needs. Results in obesity and coronary heart disease, which forces heart to work harder to pump blood around the body. Why dietary imbalance? - Economic constraints, i.e. prefer cheap foods - Poor eating habits – lacking of nutritional knowledge - Unwilling to follow national guidelines END OF CHAPTER 4 chmsabee94/5090/06/09
It is advised to: - Take less fats and cholesterol - Eat more fruits and vegetables - Consume less salts - Maintain healthy weight
CHAPTER 5: NUTRITION IN MAMMALS 5.1 HOLOZOIC NUTRITION Nutrition – intake of food ans process to convert food substances into living matter, i.e. cells Nutrition comprises of: FEEDING – intake of food into body DIGESTION – the process whereby large food molecules broken down into soluble and diffusable molecules to be absorbed into cells ABSORPTION – the process whereby digested taken into cells ASSIMILATION – the process whereby absorbed food materials are converted into new protoplasm/used to provide energy Holozoic nutrition – the taking in of ready-made complex organic matter for animals and involving nutritional steps. 5.2 MAMMALIAN DIGESTIVE SYSTEM Consists of gut and glands associated to it Gut consists of: - Mouth and buccal cavity - Pharynx - Oesophagus - Stomach - Small intestine - Large intestine - Anus Intestines SMALL INTESTINES: Comprises of duodenum, jejunum and ileum. LARGE INTESTINES: Made up of caecum, colon and rectum. Gland is a cell, tissue or organs that secrete chemical substance. Example: salivary gland secrete saliva.
Mouth and Buccal Cavity Food enters via mouth which leads to buccal cavity. In front of the cavity are moving lower jaws and fixed upper jaws. Food are broken with the teeth. Salivary glands produce saliva into buccal cavity. Pharynx The part of the gut from mouth to oesophagus and trachea by way of larynx or voicebox. Larynx has slit-like opening called glottis. To prevent food mass enter wind pipe, a flap-like cartilage epiglottis moves up to cover the trachea. If food masses or water enter trachea, the person would cough violently to let the food out. The Oesophagus It’s a narrow, muscular tube continuing from pharynx through plorax and diaphragm to stomach. It has 4 layers: - Serous coat outermost layer, a thin membrane that is moist and slippery to reduce friction between organs. - Smooth mucsles muscle layers next to serous coat, outer: longitudinal muscle, inner: circular muscle. Slow and sustained contractions. - Submucous coat outer part next to smooth muscles, layer of blood vessels and connective tissues - Mucous coat innermost layer, folded extensively and contain gland cells secreting slimy mucus to lubricate food for smooth moving along the gut.
Peristalsis Is the wave-like contractions of the wall of the gut caused by the two layers of smooth muscles. When circular muscle contracts, longitudinal muscle relaxes, the wall of gut constricts (become narrower and longer) and pushes bolus forward. When circular muscle relaxes, longitudinal muscle contricts, the wall of gut dilates (wider and shorter) to allow bolus pass through widened lumen. The Stomach Is distensible muscular bag with well developed muscular walls. Location: beneath diaphragm to the left side, partly covered by liver. Structure: - mucous coat of stomach has pits connected to gastric glands secreting gastric juices. - has muscular valve (pyloric sphincter) which connects to small intestine (valve contracts, entrance closed; when relaxes, entrance open-food pass) The Small Intestine Consists of: U-shaped duodenum, jejunum and ileum. Length: 6 metres Function: Wall lining secrete digestive enzymes. Organs and Glands Associated with the Gut The Liver and Gall Bladder Liver: largest gland in body. Structure: dark-red, made up of five lobes, 3 on the right and 2 on the left. Has 3 blood vessels: hepatic portal vein, hepatic vein, hepatic artery. Position: below diaphragm, to the right. Upper part touch diaphragm, lower part touch stomach and small intestine. Function: secrete bile (alkaline greenish-yellow liquid) containing bile salts and pigments to help fat digestion. Waste product as faeces. Gall Bladder: greenish-yellow bag attached to liver which stores bile.
Transporting bile to gall bladder: Bile duct let bile flow into duodenum when bile duct contracts The Pancreas Location: lies in the loop of duodenum. Connected to it by pancreatic duct. Function: - produces pancreatic juice having digestive enzymes - secrete insulin hormone to control blood sugar level and carbohydrate utilization. The Large Intestine Structure: shorter but broader than small intestine. Connected to small intestine. At junction is caecum and appendix which don’t play part in digestion but may cause appendicitis when inflamed. It’s 1.5 metres length. Consists of: - Caecum and appendix - Ascending colon runs upwards at right side of abdominal cavity - Horizontal tranverse colon - Descending colon runs downwards at left side of abdominal cavity joining rectum. Function: absorb water and mineral from undigested food matter and remove bacteria during egestion. RECTUM: stores faeced temporarily. When contracts, faeces expelled through anus. 5.3 DIGESTION IN HUMANS In the Mouth Function: stimulating salivary gland to secrete saliva to mix with food. - The mucin in saliva soften food - Chewing increase surface food area, break it into smaller pieces - The enzyme salivary amylase in saliva digest starch to maltose - Tongue roll the food into small and slippery spherical masses called bolus which later enter oesophagus via pharynx
In the Oesophagus - Moves bolus down with help of gravity and peristaltic movement In the Stomach Food stimulates gastric glands secrete gastric juices and mixes with it by peristalsis.
The enzymes in intestine: - pancreatic amylase, pancreatic lipase and trypsinogen(all protease) Enzymes in intestine: - enterokinase, erepsin(all peptidase), maltase, sucrase, lactase and intestinal lipase
GASTRIC JUICE: dilute hydrochloric acid solution having 2 enzymes, rennin and pepsin. Dilute hydrochloric acid: - Stops salivary amylase action - Changes inactive enzymes in gastric juice to be active - Provide suitable slightly acidic medium for gastric enzyme action - Kill germs and parasites
Carbohydrate digestion in small intestine: - Food enters mouth. Salivary amylase digest partial starch into maltose. - Boli enter stomach. No carbohydrate digestion occurs. - Boli enter small intestine. Starch digested to maltose. - Cellulose carbohydrate is not digested. - End products are simple sugars
The enzymes are produced inactively in the form of: - Pepsinogen - Prorennin They are later converted by acid to be rennin and pepsin.
Fat digestion in small intestine: - Bile emulsifies fats so fats are simplified and sufrace area enlarged - Emulsified fats are digested by lipase - End products are glycerol and fatty acids
PEPSIN: Digests proteins to polypeptides/peptones. It’s inactive as it will digest cells which consist of mainly proteins.
Protein digestion in small intestine: - Protein partially digested in stomach - In intestine, inactive trypsinogen converted to active trypsin enzyme by intestinal enterokinase. - Protein further digested in small intestine to polypeptides by trypsin - Polypeptides are digested by intestinal erepsin in intestinal juice - End products are amino acids Simplified diagram for protein digestion in small intestine:
RENNIN: Curdles milk protein by converting soluble milk protein (caseinogen) into insoluble one (casein) and later digested by pepsin. * If not converted to casein, it wouldn’t be digested and get to duodenum. In the Small Intestine The chyme (liquefied food) will stimulate: - Intestinal gland to secrete intestinal juice - Pancreas to secrete pancreatic juice which passes pancreatic duct to duodenum - Gall bladder to release bile. Bile passes bile duct to duodenum Note: Bile, Pancreatic juice and Intestinal juice are alkaline to neutralize acidic chyme from stomach and provide alkaline for enzyme action.
Summary of digestion in human gut
Process of Absorption Carbohydrate, protein and other substances absorption - Simple sugars, amino acids, mineral salts and vitamins pass through walls of villi into blood capillaries. - Blood transports them to other body parts. Fat absorption - Glycerol diffuse into epithelium (dissolves in water). - Fatty acids react with bile salts, forming soluble soaps, and diffuse into epithelium. - In epithelium, the soaps and glycerol combine to form fat globules and absorbed in lympathic capillary.
5.4 ABSORPTION Simple sugars, amino acids, fatty acids and glycerol are absorbed by the villi of small intestine especially of the jejunum and ileum. Adaptations of the Small Intestine for Absorbed Digested Food Products - Inner walls of small intestines are thrown into numerous transverse folds and furrows. - Small intestines has numerous finger-like projections called villi to increase surface area for efficient absorption. - Epithelial cells in villi bear microvilli - Between villi are small opening of intestinal gland to produce intestinal juice. - Intestinal wall and villi are supplied with blood vessel and lympathic vessel to carry away food substances. - Lympathic capillary transport fats away from small intestine - Blood capillary transport sugars and amino acids away
In the large intestines - Water and mineral salts absorbed here. - Undigested/unabsorbed matter are stored temporarily in rectum and egested. Egestion is removal of undigested matter from the body. 5.5 ASSIMILATION Assimilation – transport and utilization of absorbed food Sugars - The blood capillaries rich of simple sugars from small intestines unite to form larger blood vessel which forms hepatic portal vein to transport sugar to liver. - In liver, most absorbed sugars are stored as glycogen. Sometimes glucose bypass liver.
Glucose processing in liver and pancreas: - glucose oxidation during tissue respiration release energy for vital activities of the cell.
pancreas produces hormone insulin used to convert excess glucose as glycogen. Glycogen is converted back to glucose in liver when needed for energy. Amino Acids - are passed through hepatic portal vein with sugars. Are used for: - enter cells to be converted to new protoplasm - used for growth and repair of worn-out tissues - formation of enzymes and hormones Fats -
Regulation of Blood Glucose Concentration 3 Liver keeps amount of glucose in blood constant of 70-90mg/100cm blood After heavy meal: - Glucose in blood rises, excess glucose converted to glycogen by liver and stored, leaving blood having fair amount of glucose. When need glucose: - Glucose in blood drops, glycogen converted back to glucose by liver. When fasting: - Glucose in blood drops, brain send impulses to empty stomach and give hunger sensations After fasting and eating: - Blood glucose rises, brain send impulses to stomach, hunger stopped This deposition and mobilization of glycogen are controlled by the hormones insulin and adrenaline.
Lymphatic capillaries contain colourless liquid – lymph. When fats are absorbed into these capillaries, they mix with lymph to produce milky fluid – chyle. - Lymphatic capillaries join to form larger lymphatic vessels to discharge chyle into bloodstream and carries fats to all body parts. But before fats are used: - They are brought to liver - converted to oxidizable/storable forms. But when there are enough glucose, fats are not oxidized.
This Information Might be Helpful! Other Important Functions of The Liver
Use of fats: - Build protoplasm in cell membranes. - Excess stored in adipose tissues which are fat storage and insulating tissues found beneath skin, around heart and kidneys.
Iron storage Worn-out red blood cells are destroyed in spleen and the haemoglobin are brought to liver to break haemoglobin down and store iron that’s released in the process. Bile pigments are produced too.
The Liver: Functions Associated with Digestion and Assimilation Production of Bile Bile - produced by liver to emulsify fats, stored temporarily in gall bladder.
Protein Synthesis Liver produce plasma proteins such as albumins and globulins from amino acids for blood clotting with fibrinogen.
Detoxication Harmful substances such as benzoic acid, picric acid, alcohol and chloroform may be absorbed in gut. These are converted to harmless substances by liver – process is detoxication. Heat Production Heat can be produced during chemical activities in liver. The heat is distributed by blood to other body parts to regulate body temperature. END OF CHAPTER 5
CHAPTER 6: NUTRITION IN PLANTS 6.1 PHOTOSYNTHESIS Photosynthesis – the process whereby light energy is absorbed by the chlorophyll and transformed into chemical energy used in synthesis of carbohydrates from water and carbon dioxide and produces oxygen. Knowledge Required for Doing Photosynthetic Experiments - Since simplest carbohydrates are sugars, to prove photosynthesis took place, sugars must first be formed from carbon dioxide. - Sugars are formed faster than being used up, so it’s changed to starch to prevent excess for storage. (THIS ISN’T PART OF PHOTOSYNTHESIS!) - In darkness, photosynthesis stops, enzymes in leaves changed starch to sugars and transported to other plant parts. Conditions Essential for Photosynthesis - Sunlight - Carbon dioxide - Chlorophyll - Temperature (for enzyme in chloroplasts) - Water
Simplified diagram to relate light-dependent and light-independent stage:
From above: - Active energy of light converted and stored as carbohydrate molecule that is glucose. - 12 water molecules splits up to all 6 oxygen molecules and 24 hydrogen atoms. - The hydrogen reduce 6 carbon dioxide molecules to form a glucose molecule and 6 water molecules. Combining these steps, we get:
Are all the wavelengths of light used in photosynthesis? Photosynthesis occur in 2 stages: - Light-dependent stage - Light-independent stage LIGHT-DEPENDENT STAGE: Light energy is absorbed by chlorophyll to: - Convert it into chemical energy. - Split water molecules into hydrogen and oxygen – photolysis. LIGHT-INDEPENDENT STAGE: means the stage where light is not required for the activity. - Hydrogen produced reduces carbon dioxide to glucose by using chemical energy provided during light-dependent stage.
From graph, we know not all wavelength are absorbed. - Only red and blue are most effectively absorbed. - Green is hardly absorbed, therefore chlorophyll are green as it reflects most green lights. The higher the wavelength absorption, the higher the photosynthesis rate
The fate of glucose in leaves
LIGHT AND PHOTOSYNTHESIS - Light is absorbed by chlorophyll. - Light moves in waves, energy is contained in pockets called photons. - Photon is inversely proportional to light wavelength; the longer wavelength, the less energy per photon. Sunlight has spectrum of light, which red (longest wavelength) and blue (shortest wavelength) are most effective for photosynthesis Limiting factors - Carbon dioxide concentration - Light intensity - Temperature
GRAPH 1 AND 2 - as light intensity increases, photosynthesis rate increases to A and then remain constant. A is limiting factor of light. Beyond that is not - as temperature increases with same CO2 concentration, the rate doesn’t increase appreciably so temperature isn’t so limiting factor GRAPH 3 AND 4 - CO2 concentration increased, rate increased. CO2 is limiting factor - at E, limiting factor is temperature as difference is appreciable
First, CO2 and H2O produce glucose in leaf by photosynthesis. It’s used: - By cells during tissue respiration to provide energy. - To make cellulose cell walls. - Excess glucose converted to sucrose transported to storage organs to be stored as starch or other forms. - During day, sugars are formed faster and these are accumulated in leaf to be converted to starch for temporary storage in leaf. At night, photosynthesis stops, leaf enzymes reconvert it to glucose. - To react with nitrates and other mineral salts brought to the leaf to form amino acids to form proteins which is converted into new protoplasm within the cells. o Excess amino acids are stored as proteins in the leaves or carried to growing regions of plant to build new protoplasm or stored as proteins. - To reach storage organs & convert to fats – stored within these organs. Digestion and Utilization of Stored Food in Plants Stored fats, proteins and starch in storage organs can be digested to soluble and diffusable substances by the enzymes produced by storage organs when needed Digestion of Stored Food diastase
sucrose (transported away)
pepsin and erepsin
2. proteins 3. fats
polypeptides and amino acids fatty acids and glycerol
Utilization of Stored Food Digested food are carried to all plant parts, especially growing zones. - Sugars and digested fats for energy production. - Amino acids assimilated to form new protoplasm. The Importance of Photosynthesis - During photosynthesis, carbohydrates are formed which further forms fats, proteins and other organic compounds which become food to animals directly or indirectly. - Sunlight energy is converted to chemical enery which is stored within carbohydrates molecules, which is fed to animals and the energy stored is passed to them. - Coal from trees has energy from sunlight through photosynthesis. When burnt, energy produced is used to cook, machine works, etc. - Photosynthesis purifies air by removing carbon dioxide and produce oxygen for animal respiration.
Lamina - Has large surface area:volume ratio for maximum sunlight absorption. - Thin expanded lamina- carbon dioxide reach rapidly the inner laef cells. Venation Vein networks and Vein branches Carry water and mineral salts to cells in lamina and carry manufactured foods to other parts of the plant. Mid-rib Main vein that gives off branches and form a network of fine veins. Internal Structure of the Lamina
6.2 THE LEAF: NATURE’S FOOD MAKING FACTORY
The lamina on either side of mid-rib has upper epidermis. - consists of single layer closely packed cells covered with cuticle outside A green leaf is equipped with lamina, petiole and leaf base for functioning Petiole Holds lamina away from stem so lamina obtain sufficient sunlight and air.
Cuticle - Prevents excessive evapiration of water - Focuses light into mesophyll layers
MESOPHYLL LAYERS Lies below upper epidermis. - Main site of photosynthesis - Has 2 regions – palisade tissue & spongy tissue Palisade Cells Tissue Consists of 1 or 2 layers of closely packed, long cylindrical cells with axes at right angles to the epidermis. - Cells has numerous chloroplasts for maximum sunlight absorption for photosynthesis process. Chloroplast – oval-shaped structures which contain chlorophyll Spongy Mesophyll Tissue Has irregular shaped cells, containing chloroplasts too, which are loosely arranged to provide large intercellular air spaces among them.
The entry of carbon dioxide into the leaf During daylight, photosynthesis occurs, so carbon dioxide in leaf used up. Carbon dioxide concentration in leaf is lower than outside so carbon dioxide from outer enviroment diffuse into air spaces leaf and dissolves in thin film of water which covers mesophyll cells. The entry of water and mineral salts inro the leaf Veins in leaf form branches which end among mesophyll cell, containing xylem and phloem. Xylem – brings water and mineral salts to leaf from soil via roots. When out of veins, these materials diffuse cell to cell throgh leaf mesophyll. Phloem - transport sugars produced by green leaf from the raw materials to all plant cells. How Is Leaf Adapted to Photosynthesis?
LOWER EPIDERMIS Lies below mesophyll, consists of 1 layer of closely packed, covered by outer cuticle layer. Has small openings called stomata, and bounded with 2 guard cells. Differences between guard cells and epidermal cells: GUARD CELLS EPIDERMAL CELLS Bean-shaped in surface view Irregular shape Contain chloroplasts-photosynthesis Doesn’t contain chloroplasts Can make sugar Cannot make sugar Prevent water loss by closing stoma Do not regulate water amount How guard cells work: During the day Potassium concentration increases in guard cells and with sugars formed, water potential in guard cell lowers so water from outer cells enter guard cells by osmosis making it turgid. As guard cell have thicker cellulose cell wall on one side of cell, guard cell swollen and curved, pulling stoma open. During the night Sugar is used up, water leaves guard cell so it turn flaccid. Stoma closes.
6.3 MINERAL NUTRITION IN PLANTS Essential elements: Carbon Hydrogen Potassium Oxygen non-metallic Calcium metallic Nitrogen Magnesium Phosphorus Iron Sulphur
These elements occur in traces of plant and human body. - Hydrogen and Oxygen are needed for building of carbohydrates which are starting blocks in which all other glands in plants are made. They can be obtained from water that plant take in. - Carbon Dioxide is needed for photosynthesis. - Water is essential for healthy growth of plant. END OF CHAPTER 6 CHAPTER 7: TRANSPORT IN ANIMALS 7.1 THE NEED FOR A TRANSPORT SYSTEM To carry substances from one body part to another: Blood System: having the fluid blood Lymphatic System: having the fluid lymph 7.2 BLOOD STRUCTURE AND COMPOSITION OF BLOOD 55% plasma (fluid part of blood), 45% platelets Plasma Red blood cells (erythrocytes) BLOOD Blood Cells White blood cells (leucocytes) Platelets Plasma Pale yellowish in colour 90% water containing various dissolved substances: - Soluble protein: serum albumin, serum globulin, antibodies fibrinogen, prothrombin. Fibrinogen & Prothrombin: Clotting of blood; Antibodies: Fighting diseases - Dissolved mineral salt: Ions of chloride, bicarbonate (HCO3), NaSOX, NaPOX, KNOX, KPOX, Calcium. Calcium: blood clot - Food substances: Glucose, Amino Acids, Fats, Vitamins - Excretory products: urea, uric acid, creatinine - CO2, present as HCO3 ions - Hormones
Red Blood Cells (Erythrocytes)
Shape: circular, flattened, biconcave disc – centre of cell thinner than edge Characteristics: - No nucleus - Diameter less than 0.01 mm - Can squeeze through capillaries smaller than its diameter - Produced in bone marrow - Lifespan 3 – 4 months - When worn out, it’s destroyed in spleen and liver Content of RBC: HAEMOGLOBIN: a red coloured pigment protein containing iron. - Lets blood cells transport oxygen from lungs to all body cells
White Blood Cells (Leucocytes): Shape: Irregular, can change shape to squeeze among blood capillaries and between tissue cell spaces. Characteristics: - Has nucleus - Colourless and no haemoglobin - Fewer than RBC (Ratio: 700:1) - Keep body healthy by fighting disease - Lifespan: Few days Types of WBC: - Lymphocytes - Phagocytes
Lymphocytes: - Produced in lymph glands/lymph nodes - Has large rounded nucleus, few non-granular cytoplasm - Almost round shaped, rarely move
Phagocytes: - Produced in bone marrow - Ingests foreign particles, e.g bacteria (phagocytosis) - 2 kinds: monocytes – bean-shaped nucleus polymorphs – many lobed-nucleus, granular cytoplasm
Phagocytes Platelets (Thrombocytes): - Cytoplasm fragments of bone marrow, for blood clotting. FUNCTIONS OF BLOOD - Medium to carry various substances from one body part to another - Protects body against disease-carrying organisms (pathogens) Transport function of blood Blood transports the following: - Digested food substances from the intestines to all parts of body - Excretory products from tissues to respective excretory organs for removal. o Nitrogenous wastes (urea, uric acid, etc) removed by kidneys. o CO2 in cells enter blood as HCO3 ions in blood plasma. As blood passes lungs, HCO3 ions dissociate to release CO2 into lung cavities by diffusion which then expelled during expiration. - Hormones from producing glands to requiring body parts. - Fat produced in respiring body tissues (i.e. muscle, liver) to body parts to maintain stable body temperature. - Oxygen, combined with haemoglobin from lungs to all body parts.
Oxygen is carried in RBC. Haemoglobin greatly affinates with oxygen. - As blood passes through lungs, oxygen diffuses from lung cavities into cells. It’ll then combine with haemoglobin, forming a new bright red coloured compound called oxyhaemoglobin. Oxyhaemoglobin releases oxygen when encountering tissues lacking of it. - Oxygen released diffuse in solution into tissue cells to give adequate oxygen supply. Haemoglobin w/o oxygen → purplish red ∴ arteries are seen red, veins are seen bluish. Carbon Monoxide (CO) Poisoning CO combines more readily than oxygen with haemoglobin to form bright pink compound carboxyhaemoglobin. The compound does not readily release CO, so they are useless. Acclimazation to high altitudes High altitudes → more RBC - Oxygen concentration low → haemoglobin & RBC must increase to allow more oxygen transported to tissue cells per unit time. Protective function of blood Phagocytosis - Engulfing and ingesting foreign particles, i.e. bacteria by WBC - Some phagocytes may die in the process. They mix with dead bacteria forming pus. The need for phagocytosis: - One celled organisms, i.e. Amoeba, engulf food and ingest in food vacuole. The digested products are absorbed and assimilated directly in cytoplasm. - Dead cells in humans are phagocytosed to prevent inflammatory reactions by body’s immune system. - As immunity against bacteria.
Production of antibodies - Disease causing germs may produce poisonous substance toxin which also induce production of antibodies by the lymphocytes and can be found freely in the plasma. USES: - Act as antitoxin to neutralize poisonous effects of toxins. - Kill bacteria in blood. - Agglutinate (clump) bacteria together before phagocytosed. Clotting or coagulation of blood Blood exposed to air will soon clot to seal the wound. - To prevent excessive loss of blood - To prevent foreign particles entering the blood stream Haemophilia Is hereditary disease which impair normal blood-clotting system. Sufferer may die due to excessive bleeding or internal bleeding. THE CLOTTING PROCESS: - Blood vessels damaged → damaged tissues & blood platelets release enzyme → thrombokinase - Prothrombin in blood plasma activated by thrombokinase + calcium ions → thrombin - Thrombin catalyses fibrinogen (soluble) → fibrin (insoluble threads) - Fibrin threads entangle blood cells, they form clot. =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=Blood in undamaged blood vessels don’t clot as heparin from liver → anticlotting substance. - Thrombokinase released → neutralise heparin → clot takes place - Blood clot → serum (yellowish liquid with same composition of plasma but more anticlotting subtituent) left behind Organ transplant and tissue rejection Means: Replacement of damaged/diseased organs/tissue with healthy one Tissue may be rejected by recipient’s immune system as:
Organ from another person = foreign body. Lymphocytes may destroy it. Tissue may not be rejected when: The tissue transplanted is from the same person. To prevent tissue rejection: Tissue match (donor’s & recipient’s tissue must be as close as possible, i.e. brothers, sisters, parents) Usage of immuno-suppressive drugs → inhibit immune system activity Bad: Recepient prone to infections & to continue treatment forever X-Ray radiation to bone marrow & lymphoid tissue to inhibit blood cells production. Hence, slows down rejection. 7.3 THE CIRCULATORY SYSTEM Blood Circulation – The transportation of blood carrying various substances from one part part of the body to another by flowing continuously around the body through a closed system of blood vessel. - Blood is kept flowing by muscular pump of the heart o Heart relaxes → filled with blood; heart contract → squeeze blood out Large arteries leaving left side of heart – aorta - Branches to form smaller arteries and branch again to form tinier arteries called arterioles and arterioles divide to form even tinier blood vessels – capillaries Capillaries – microscopic blood vessels found between most tissue cells - Walls made of single layer of greatly flattened cells – endothelium - Endothelium enables certain substances to diffuse quickly - Branches repeatedly → more branches → large surface area → exchange of substances between blood and tissue cells - Before leaving organ/tissue, they unite - form small veins - venules When arterioles branches to capillaries, total cross-section area increases - Lowers blood pressure of capillaries → slows blood → more time for exchange of substances
ARTERIES - Have thick, muscular and elastic walls withstand pressure when pumped out of the heart (the great arteries near heart is thicker) - Thick elastic walls to maintain high blood pressure in artery - Wall elasticity permit stretching and recoiling of wall, to push blood - When artery constricts, lumen narrower, less blood flows through - When artery dilates, vice versa VEINS - Have thinner walls as the blood pressure is low. - Less elastic tissues. - Have internal valves to prevent backflow of blood. The valves are folds of the inner walls, shaped half-moon – semilunar valves - Movement of blood assisted – skeletal muscle action o Muscular excercise increases pressure exerted on veins and moves blood along quickly. Differences Table
7.4 DOUBLE CIRCULATION This means blood passes the heart twice in one complete circuit. It consists of SYSTEMIC CIRCULATION and PULMONARY CIRCULATION - In pulmonary circulation, deoxygenated blood is carried to lungs via pulmonary artery and oxygenated blood is returned to heart via pulmonary vein. - In systemic circulation, oxygenated blood is carried to all body parts from left side of heart via aorta and deoxygenated blood returned to heart via vena cava. The deoxygenated blood undergo pulmonary circulation & again systemic circulation.
Double Circulation is Important Because: - Oxygenated blood is separated from deoxygenated blood: Median septum in heart ensures complete separation and oxygenated blood flows through left side of heart while deoxygenated blood flows through right side of heart. - Blood pressure in systemic circulation is kept higher than pulmonary circulation as left ventricle, with thicker wall to withstand high pressure, pumps blood to all body parts under high pressure for faster delivery of oxygenated blood to body cells in systemic circulation while right ventricle, with thinner wall, pumps blood to lungs under low pressure to prevent lung damage.
Right Auricle Left Auricle Differences Between Systemic Circulation and Pulmonary Circulation:
Main Blood Vessels of Body
Coronary Blood Vessels: Coronary Arteries – branch from aorta to provide blood for heart muscles. Coronary Veins – they converge into main vein to transport deoxygenated blood from heart muscle tissues to right atrium Liver Blood Vessels: Hepatic Artery – brings blood to liver from heart Hepatic Vein – brings blood from liver to heart Hepatic Portal Vein – brings blood from gut to liver and breaks up into many capillaries before they converge into hepatic vein. It’s called portal vein as it carries blood from one capillary network to another. Kidney Blood Vessels: Renal Artery – brings blood to kidneys from heart Renal Vein – brings blood from kidneys to heart 7.5 OUR HEART, OUR PUMP
The heart is located in thoracic cavity between two lungs. It is protected by sternum and rib cage and surrounded by two-layered membrane called pericardium on which between these two membranes contains pericardial fluid to reduce friction when the heart is beating.
Median septum separates the left side of heart from the right side of heart. The chambers types are namely atria on the upper chambers having thin wall, and ventricles on the lower chambers, having thick walls. Atria have thin walls as it only have to force blood into ventricles with low force but ventricles need thick walls as it needs pressure force to transport blood to other body parts. The 4 chambers in heart are: Right Atrium: Upper chamber of the right side of heart. Blood from other body parts are returned via anterior and posterior vena cavae. When the atrium contracts, blood flows from right atrium into right ventricle through tricuspid valve, consisting of 3 flaps, which opens downwards. Right Ventricle: Lower chamber of right side of heart. When it contracts, blood pressure forces the flaps to close, preventing backflow of blood into right atrium after receiving blood from it. Blood then leaves the ventricle via pulmonary arch into pulmonary arteries, one to each lung, with backflow of blood prevented by semilunar valves. Left Atrium: Upper chamber of left side of heart. Oxygenated blood returned to heart via pulmonary veins which opens here. When left atrium contracts, blood enters left ventricle via bicuspid valve, consisting of 2 flaps. Left Ventricle: Lower chamber of left side of heart. When it contracts, flaps close and blood leaves ventricle via aoric arch under high pressure to all over the body and backflow is prevented by semilunar valves in aortic arch. Chordinae Tendinae attaches the bicupid and tricuspid valves to ventricle walls and prevents blood pressure from forcing the valves to open upwards into atria. HEARTBEAT Coronary contraction is termed systole while coronary relaxation is called diastole. The bicuspid and tricuspid valves are atrioventricular valves of a heart. Systole and diastole make up one heartbeat. An average person average heartbeat is 70 beats per minute (BPM).
CHAPTER 8: TRANSPORT OF MATERIALS IN FLOWERING PLANTS 8.1 FLOWERING PLANT STRUCTURE IN RELATION TO TRANSPORT TRANSPORT (VASCULAR) TISSUES Consists of xylem and phloem; for transporting materials in flowering plants Xylem 2 Functions: - Conducts water with mineral salts from roots to stems & leaves - Provides mechanical support within the plant Xylem consists of mainly vessels. Vessel – long hollow tube fetching from root to leaf. Properties: - have a continuous hollow space (lumen). - is a dead structure. - wall strengthened by a deposited substance, lignin, deposited in the form of rings (annular), spirals or pitted. Adaptation: - lumen without partition to hinder passage of water & mineral salts. - lignified walls prevent collapse of vessel. Phloem Conduct manufactured food from green parts of plant to other parts of plant Consists of: sieve tubes; companion cells SIEVE TUBES Consists of a row of elongated, thin-walled living cells – sieve tube cells Cross walls seperating the cells perforated by minute pores – sieve plates Mature sieve tube – no central vacule & nucleus, but thin cytoplasm layer Transport of food – through sieve tube cells & sieve plates cytoplasm by diffusion and active transport Companion cells – to keep the tubes alive & to assist transportation of food
INTERNAL STRUCTURE OF PLANT ORGANS Internal Structure of Dicotyledonous Stem Phloem & Xylem together – vascular bundles Vascular bundles arranged around a central region, pith. Xylem & phloem lie along same radius. Phloem outside xylem, with tissue, cambium in between. - Cambium cells divide to form new xylem and phloem tissue – thicken stem Covering layer of cells – epidermis Epidermal cells protected from evaporation from stem by cuticle. Region between vascular bundles & epidermis – cortex Cortex & pith – store food substances Internal Structure of Young Dicotyledonous Root Xylem & phloem lie on different radii, alternating with each other. Cortex – storage tissue Epidermis of root bearing hair – piliferous layer Root hair – tubular outgrowth of epidermal cell. Cuticle absent in piliferous layer Translocation of Organic Food Substances Translocation: Transport of food manufactured substances (e.g. sugars, amino acid) 1. Anaesthesize feeding aphid on plant stem and remove the body from its proboscis. A liquid oozes out from the end of proboscis when the proboscis is attached to the sieve tube of a plant. This liquid contains sugars and amino acid, which proves that translocaion of these substances occurs in sieve tubes of phloem. 2. Expose plant to CO2 radioactive carbon-14 for photosynthesis. The sugars formed contain the radioactive carbon-14 which can be detected by photographic film. It is found that the traces of this carbon occurs in phloem.
THE ENTRY OF WATER INTO THE PLANT Mineral salts are dissolved in soil water, thus, thin film of liquid surrounding each soil particle is dilute solution of mineral salts. Absorption of water and mineral salts takes place in zone of root hairs (tubular outgrowth of epidermal cells growing between soil particles coming to close contact with water surrounding them). - Sap of root hair cell has concentrated sugar and salt solutions, thus has lower water potential than soil solution and these are separated by plasma membrane of root hair cell acting as partially permeable membrane. - Water enters root hair by osmosis, which then dilutes the sap so that the sap of root hair cell is more dilute than the next cell - Water continues to pass to next inner cells until it enters xylem vessels of plant
8.2 UPTAKE OF WATER 1. Root Pressure Living cells along xylem vessels absorb ions by active transport, making xylem vessels more concentrated. Hence, water is passed from root cells up to xylem vessels up the plant by osmosis. 2. Capillary Action Water moves up inside capillary tubes in small plants (i.e. xylem vessels) by capillary action which uses adhesion forces between water molecules and xylem vessel walls to be sucked upwards. However, this doesn’t occur in tall, big plants. 3. Transpiration Pull Transpiration is the loss of water vapour (from excess water drawn from soil and tissue respiration) from the aerial parts of the plant, especially through leaf stomata.
Diffusion and Active Transport in Absorption of Dissolved Salt Partially permeable membrane does not allow sugars and starch to pass out of the root hair, but allows the passage of dissolved mineral salts via root hair by active transport against concentration gradient, as the mineral salts content in root is generally higher than that in the soil. The energy for this comes from tissue respiration in plants. Diffusion rarely takes place and only when mineral content is higher in soil. Adaptation of Root Hair to Absorption - Long and narrow for larger surface area:volume ratio to maximise rate of absorption - Cell sap is more concentrated than soil (i.e. more mineral salts, less water), allowing mineral salts enter by active transport while water by osmosis. Moreover, mineral salts in root hair is not allowed to pass out of it due to cell surface membrane - Root hair cells respire so they provide energy for active transport
Evaporation of water from inside leaf continually occurs on surfaces of leaf. Water is constantly sucked out of intercellular spaces in mesophyll layer to form thin layer of water diffusing out to surface of leaf via stomata. As water leaves the mesophyll cells, it becomes concentrated and hence draw water from neighboring cells deeper in leaves which in turn sucks water up from xylem vessel.
This creates a continuous water column running from roots up to the leaves, called transpiration stream, which creates tensional force up the plant to draw water and mineral salts which is called transpiration pull.
CHAPTER 9: RESPIRATION 9.1 WHAT IS RESPIRATION? 9.2 GASEOUS EXCHANGE IN ANIMALS 9.3 GASEOUS EXCHANGE IN PLANTS
TRANSPIRATION – IMPORTANT FOR PLANTS! Importance: - Enables transpiration pull in plants which allows continuous drawing of water and mineral salts up the plant to leaves for photosynthesis - Evaporation of water from leaf surfaces removes latent heat hence cooling down the leaves, preventing them being burnt by sun What helps transpiration? 1. Humidity of surrounding air If air is less humid, water from intercellular spaces in leaves diffuses out quickly down the steep concentration gradient. If air is humid, it hinders evaporation which in turn lowering rate of transpiration. 2. Atmospheric temperature Water evaporates faster in hot days hence increasing rate of transpiration. However when too much water is lost, stomata close, preventing further loss of water. 3. Wind In presence of wind, water vapour around the leaves from diffusion of water out of the leaves are blown away, making air less humid hence enhancing transpiration. If wind absent, the air is damp, decreasing rate of movement of water out the leaves. 4. Light In sunlight, stomata open, allowing diffusion of water out of stomata. In darkness, stomata close, preventing water to diffuse out of leaves for transpiration. WILTING When in sunlight, excessive transpiration may occur which makes a plant loses its turgor, causing leaves flaccid and the plant to droop. Advantage: Leaf folds and reduces surface area exposed to sunlight, causing guard cell flaccid and closes the stomata, reducing rate of transpiration. Disadvantage: Closed stomata reduces the entry of CO2, hindering photosynthesis. Also, water is lacked and becomes limiting factor for photosynthesis. END OF CHAPTER 8
CHAPTER 10: EXCRETION 10.1 WHAT IS EXCRETION? Catabolic activities – the process of the breakdown complex substances into simpler ones. Example: - tissue respiration - production of proteins and amino acids to form urea
Two main regions: - outer dark-red region – cortex - inner thick paler red region – medulla • Medulla consists of 12-16 conical structures called pyramids projecting into funnel-like space called renal pelvis o Renal pelvis is enlarged portion of ureter inside kidney. o Pyramids possess radial stripes due to nephrons presence, which form urine
Anabolic activities – build up of simpler substances into complex ones. - formation of new protoplasm from amino acids - conversion of glucose to glycogen in liver and muscles - photosynthesis in green plants Metabolic activities – involves chemical changes by anabolic and catabolic activitirs that go on in cells of organisms which keep it alive. Excretion – the process by which metabolic waste and toxic materials are removed from the body of an organism. 10.2 EXCRETION IN MAMMALS The Mammalian Urinary System Consists of: a pair of kidneys, a pair of ureters, a urinary bladder, a urethra KIDNEYS: are bean-shaped organs embedded in fat mass in abdominal cavity Hilus – depression on centre of concave surface of kidney where renal artery, renal vein & nerves connected to kidney. Ureter – narrow tube emerging from hilus travelling downwards to join dorsal surface of urinary bladder Urinary bladder – elastic muscular bag to store urine. When it’s full, sphincter muscle relaxes to allow urine flow to urethra and pass out the body
Excretory products Carbon dioxide Nitrogenous waste products
Excretory organs Lungs Kidneys
Urea (protein deamination) Creatinine (muscle breakdown) Lactic acid (nuclear material)
Constituents of sweat in small quantities
Kidneys Skin Lungs
Main constituent of urine Main constituent of sweat Water vapour in expired air
Excreted via intestines
Red pigments breakdown)
Longitudinal Section of a Kidney -
Remarks Gas in expired air Constituents of urine
The structure of a nephron Each nephron begins in cortex as cup-like structures called renal capsules Capsule leads to first convoluted (coiled) tubule before it straightens into medulla. In medulla, tubule U-turns in U-shaped tubule: loop of Henlé & passes back into cortex where it becomes convoluted again. Then it enters into collecting tubule which runs straight past medulla into renal pelvis. Blood enters kidney through branch of renal artery which breaks into mass of capillaries in renal capsule – glomerulus. Capsule with glomerulus – Malphigan corpuscle Blood leaving glometulus enters capillaries forming brance of renal vein.
Formation of urine Blood entering kidney – more O2, less CO2. – higher concentration of water, mineral salts, nitrogenous waste than blood leaving kidneys • nitrogenous waste+excess mineral salt=no use→remove
Table showing processes at different parts of nephron Part of nephron Process Function
What happens Small molecules in blood plasma forced into glomerulus Useful salts actively transported out of tubule into surrounding tissue Water moves out of filtrate in tubules by osmosis Selected substances are actively transported by blood capillaries into tubules
Bowman’s capsule glomerulus
Separates wastes from blood plasma
Convoluted tubules Loop of Henlé Collecting duct
Prevents loss of salts, glucose, amino acids essential to body
Convoluted tubules Loop of Henlé Collecting duct
Prevents too water loss
Diagram of nephron Urine formation involves 2 processes – ultrafiltration, selective reabsorption
Removes substances from blood
Ultrafiltration Ultrafiltration involves mechanical filtration which separates solutes of plasma: - urea from large proteins and cells The process: - Blood entering glomerulus has high hydrostatic (blood) pressure due to blood is carried from heart & afferent arteriole leaving glomerulus narrower than entrance. - High pressure forces filtrate which are small molecules (water, glucose, amino acids, urea) through the fine-pored filter from blood in glomerulus across the membrane of Bowman’s capsule which directs into nephron. - Large molecules (plasma proteins, fats, blood cells) cannot pass through the filter and therefore retained in glomerular capillaries.
Variety Constituent of Urine PROTEIN RICH DIET: More urea in urine – proteins deaminated in liver with subsequent urea formation
Selective Reabsorption If all filtrate are excreted through urea, a person would dehydrate as a lot of useful substances such as water and mineral salts are lost from the body. Therefore: - Selective reabsorption reabsorbs useful materials back into bloodstream by osmosis (water) and active transport (glucose and amino acids) through the walls of tubule into surrounding blood capillaries. - Drugs, hydrogen and potassium ions are not filtered out into capsule but later actively transported into tubules as the capillaries pass the convoluted tubules.
HEAVY INTAKE OF MEAL: More glucose present in urine from food LARGE INTAKE OF WATER: More water volume in blood – unwanted volumes excreted via urine INTAKE OF SALTY FOOD: Excess salts are excreted via urine – more salt in urine DIABETES MELLITUS: Urine contains considerable amount of glucose – body unable convert glucoso to glycogen – inability of pancreas to secrete insulin Osmoregulation in Blood – Control of Water Content Osmoregulation is the control of water and solute levels in blood to maintain a constant water potential in the body. - Kidneys (osmoregulators) decrease/increase water absorption in tubules by antidiuretic hormone (ADH) which increases the permeability of tubules and collecting duct. ADH production is regulated by pituary gland in brain.
1. A lot of water lost through the sweat 2. As blood becomes more concentrated and blood volume falls, receptors in hypothalamus of the brain are triggered 3. Pituitary gland releases more ADH 4. This increases water reabsorption at nephron. Blood becomes more dilute when urine becomes more concentrated 5. Receptors in brain note the change in blood volume and concentration 6. Pituitary gland reduces production of ADH 7. Water reabsorption is reduced. Blood becomes more concentrated. 8. Step 2 is repeated as blood is concentrated. Functions of the Kidney - Kidneys are excretory organs which removes nitrogenous wastes and excess water and salts in the form of urine - In selective reabsorption in nephron pH & composition in blood plasma maintained - Kidneys regulate salt and water balance in the body fluid • Intake of water & reduced production of sweat dilutes the blood. Kidney remove excess water as more water present of urine. • Less intake of water & increased sweat production make the blood concentrated. More water will be reabsorbed into the blood stream from tubules.
Kidney Failure When 2 kidneys fail, a person will die of poisoning of untreated metabolic wastes. This is prevented by dialysis of blood with dialysis machine on the diagram above. - Blood is withdrawn from patient’s artery and is allowed to flow through the tubing in the dialysis machine. - In tubing, used dialysis fluid is removed and fresh one containing same concentrations of salts and water as the blood is sucked up into the tubing. This is to prevent salts and water diffuse out into tubing from blood while only unwanted urea and waste products diffuse out into the dialysing solution by diffusion through partially permeable membrane walls. Big molecules (protein, blood cells) don’t pass through this membrane. Note that only diffusion occurs. - The narrow, long, coiled tubing is to increase surface area to volume ratio to speed up the rate of exchange of substances between blood and dialysis fluid. - Direction of blood flow is opposite to the flow of bathing fluid to maintain diffusion gradient for removal of waste products. - Filtered blood is returned to vein of patient. Since dialysis occurs by slow process diffusion, it need 4-6 hours, three times/week. Differences between glucose regulation in kidneys and in dialysis KIDNEYS DIALYSIS MACHINE - Small molecules are separated from - Small molecules are separated from large ones by partially permeable large ones by ultrafiltration in nephrons membrane in tubing of dialyser - Blood is sent to kidneys under high - High blood pressure is not necessary pressure to filter the filtrate as interchange occurs by diffusion - Depends mainly on active transport - Depends mainly on diffusion and osmosis END OF CHAPTER 10
CHAPTER 11: HOMEOSTASIS Need for Homeostasis If there’s drastic change within our body, it’ll affect normal reactions of organs/cells e.g. when temperature rise high, enzyme maybe inactivated or even denatured. Homeostasis – the maintenance of constant and stable internal environment of an organism. Stimulus – change from normal condition (norm) of internal environment Receptor – organs that detects changes in either external and internal environment Regulator – triggers appropriate response to restore internal environment to norm Response – counteracts change & returns internal environment to norm. Example: moving into shade to avoid sun; increase glucose level in blood. Feedback – instructions to regulator to prevent further corrective action once norm is acquired back Negative Feedback Is corrective mechanism in body to maintain normal constant internal environment.
11.1 GLUCOSE AND WATER POTENTIAL REGULATION IN MAN Regulation of Blood Glucose Concentration Importance of glucose level regulation Glucose is needed for tissue respiration to provide energy for vital activities Regulation of Glucose Level After meal, glucose level in blood rises. When we starve, glucose level decreases. • Change in blood glucose concentration – stimulus • Pancreas which is stimulated - receptor
- After heavy meal islets of Langerhans in pancreas secretes insulin which makes: • Plasma membrane now more permeable, more glucose into cells from blood • Respiration increases oxidation of glucose into carbon dioxide and water • Increases conversion of glucose to glycogen • Decreases breakdown of glycogen in liver and muscle cells • Inhibit conversion of non-carbohydrate sources (e.g. fats) to glucose in liver • Increases synthesis of lipids and proteins from glucose and amino acids - This makes the amount of glucose in blood decrease. Secretion of insulin drops and when below norm, glucagon secreted from liver which makes: • Plasma membrane less permeable – less glucose taken into cells from blood • More glycogen is broken down into glucose from liver and muscle cells • Body burns fat rather than glucose to produce energy • Less respiration to oxidate glucose - And the process repeats when glucose level turns above norm. Diabetes Mellitus It is a disease where a body is unable to control blood glucose concentration which results in increase of glucose where it exceeds kidney ability to reabsorb all glucose. • Type 1 diabetes – juvenile diabetes/insulin-dependent diabetes. Normally occurs when pancreas unable produce insulin. Affects below 30yrs old. • Type 2 diabetes – Occurs in later ages or overweight people Normally occurs when insulin receptors not stimulated by insulin Diabetes can be seen when blood glucose level is high and glucose present in urine after having a meal. Treatment – people must undergo urine test for blood glucose concentration Type 1: Inject insulin into veins daily. Also they have to eat carbohydrates to balance glucose level from being too low, added with physical exercise. Type 2: Control blood sugar level by regulating carbohydrate content in their diet.
Regulation of Water Potential – refer CHAPTER 10: EXCRETION on kidneys.
11.2 SKIN AND ITS THERMOREGULATION FUNCTION The Skin of A Human Advantages of skin: - protective covering over the general body - excretory organ of excess water and salt as sweat - regulator of body temperature as changes detected by skin Structure of a skin: Composed of: - outer, thin layer called epidermis - inner, thicker underlying layer, dermis: made of connective tissue - hypodermis containing adipose (fatty) tissue
The Epidermis – consists of mainly epithelial tissue - Prevents entry of bacteria - Prevents loss of water by evaporation from underlying tissue - Renewal of dead cells in cornified layer which constantly being rubbed off Malpighian Layer – The Need For This Layer: • Contains a pigment melanin for: - giving skin its characteristic colour - shields underlying cells againts UV radiation • Constantly dividing and replacing dead cells in cornified layer Granular Layer – The Need For This Layer: • Consists living cells from Malpighian layer which moves upwards and become flatter and dryer as they get further from blood vessels in dermis. They synthesize keratin at same time, which is flexible water-resistant protein in cornified layer & fingernails Cornified layer – The Need For This Layer: As keratin content in cells increases, a cell lose nucleus and cells die, forming a series of tightly interlocked keratin sacs. • This makes cornified layer waterproof and prevents uncontrolled water evaporation • Germs are also prevented from gaining entry into the layer unless there’s a cut • The layer act as protective layer over body surfaces, preventing mechanical injuries Cells in this layer rubbed off every 2 weeks or so, so cornified layer replaced by cells pushing up from the granular layer The Dermis – mostly connective tissue with fibrous connective tissue, blood capillaries, sensory cells, glands and hair follicles Hair – is a dead structure made of epithelial cell which have been cornified by keratin. Hair becomes white when melanin production falls. The production of hair: • Malpighian layer sinks into dermis forming hollow tube – hair follicle • At base of follicle is mass of tissue containing nerve endings and blood capillaries which makes up hair papilla covered with epidermal cells, and erector muscles. - capillaries nourish cells in papilla and remove wastes - epidermal cells constantly divides and pushed upwards where it die, forming hair - Erector muscle contracts and alter the angle between hair and skin to vary the amount of air that can be trapped by hair
Glands – sebaceous glands and sweat glands Sebaceous glands Characteristics: - derived from epidermis, has two of them open into hair follicle Function: - release oily substances – sebum made up of fatty acids & waxes, which: • Lubricates hair, making hair supple • Keeps skin soft and smooth • Prevents dehydration of skin • Keeps hair follicle free from dust and bacteria Alteration: - under hormonal influence, e.g. puberty, excessive sebum is secreted which blocks follicle and forms whitehead which multiplies bacteria present on skin in the follicle, causing inflammatory reaction to acne. Sweat glands Characteristics: - occur in dermis, which is a coiled tubular gland formed by a downgrowth from epidermis - it forms a tight knot in the dermis provided with blood capillaries
Sense Receptors Function: Found in dermis and epidermis, they enable us feel pain, pressure or temperature changes in external environment Blood vessels/capillaries Presence: In numerous in our dermis. Function: has loops and shunts to vary blood flow in capillaries to control temperature with the help of vasomotor nerves in arterioles • In vasoconstriction, smooth muscles in walls of arterioles contracts, making arterioles constrict so decreased blood flow to the capillary loop near the skin and blood instead flow through shunt vessel. Since blood carrying heat flow less to near skin surface, heat loss is reduced. • In vasodilation, smooth muscles in walls of arterioles relaxes due to high blood pressure when heat has to be lost. This causes arterioles dilate so more blood flow to the capillary loop near the skin and around sweat glands. Since blood carrying heat flow more to near skin surface, heat loss is reduced. Also more blood flow to sweat glands increases the sweat amount which is evaporated and more heat loss from skin surface
Secretion: - sweat is secreted from the blood in the capillaries, which flows through narrow tube: sweat duct; then out through sweat pore on skin surface Function: - release sweat having mainly water, inorganic salts and little organic waste. • Sweat excretes as little metabolic wastes are removed from body • Sweat helps temperature regulation when sweat evaporates on the skin surface, removing latent heat Alteration: - Sweat began to be produced in groin, anal area and armpits only at puberty. They release odorless fluid on which bacteria feed on protein and oily substances, causing odor in line with activity of bacteria Subcutaneous Fat Description: These are several layers of adipose cells where fat is stored. Function: - The fat in the cells serves as insulating layer - It stores fat, therefore known as fat storage
HEAT GAIN Animals gain heat from environment and cell reactions within body. Poikilothermic animals: cold-blooded animals which are unable to maintain body temperature physiologically and rely heat from external environment – ectothermic Homoiothermic animals: warm-blooded animals able to maintain a constant body temperature regardless the environment and rely on internal sources – endothermic
HEAT LOSS Heat is lost : - through skin by convection, radiation and conduction - by evaporation of sweat produced by heat of the body - in faeces and urine and in expired air from the lungs Advantages of Thermoregulation in the Body • Warm-blooded animals can remain active throughout the day even years, regardless external environment temperature • Enzymes work best at constant optimum temperature of about body temperature • Animals don’t need to hibernate; they can continue to feed throughout the year • Animals can exploit and colonize many areas with different climatic conditions The Hypothalamus of the brain It monitors the blood temperature passing through it. It has 2 parts: • heat loss center • heat gain center Uses of hypothalamus: • detect temperature changes information in external environment from skin receptor • monitors the blood temperature passing through it
When external temperature is low, Stimulus: • skin thermoreceptors detect decrease in blood and skin temperature; hypothalamus detect change in blood temperature – brain send impulses to effectors. Corrective mechanism: • vasomotor contract arterioles in skin (vasoconstriction) – less blood carrying heat to skin which results less heat is lost by conduction, convection and radiation • sweat glands less active: less or no sweating – less latent heat removed • hair erector muscles contract – more warm air trapped & insulates (less effective) • skeletal muscles contract and relax repeatedly – shivering – heat production raised • metabolic rate increased – increased heat production by cells Negative feedback: body temperature raised
THE PROCESS OF THERMOREGULATION When external temperature is high, Stimulus: • skin thermoreceptors detect increase in blood and skin temperature; hypothalamus detect change in blood temperature – brain send impulses to effectors. Corrective mechanism: • vasomotor dilate arterioles in skin – more blood carrying heat to skin which heat is lost by conduction, convection and radiation • sweat glands active: increased sweating – sweat evaporate, latent heat removed • hair erector muscles in skin relax – less warm air trapped • rapid breathing – heat lost during expiration • metabolic rate decreased – decreased heat production by cells Negative feedback: body temperature lowered
END OF CHAPTER 10
CHAPTER 12: COORDINATION AND RESPONSE 12.1 THE NERVOUS SYSTEM Sensitivity – the ability to respond to stimulus. Response to stimulus in verterbrates: Involuntary actions: activities not under control of the will, e.g. peristalsis, heartbeat Voluntary actions: activities under control of the will NERVOUS SYSTEM IN MAMMALS Nervous system coordinates and controls the work of all systems in the body Nervous system in mammals comprises of: • Central Nervous System (CNS) comprising brain and spinal cord • Peripheral Nervous System (PNS) comprising cranial nerves from brain to all head parts, and spinal nerves from spinal cord and receptor organs - Receptors keep CNS informed of change in surroundings, produce message as electrical impulses: nerve impulses, which is sent to CNS by nerves. If impulse is sent to muscles, then muscle moves the body part away. Muscles are therefore effectors The Nervous Tissue It is made up of nerve cells called neurones. There are 3 types of neurons: • Sensory/Receptor neurones – transmit impulses from sense organs to CNS • Motor/Effector neurones – transmit impulses from CNS to effectors • Intermediate/Relay neurones – found in CNS
A neurone consists of a cell body containing nucleus and nerve fibres. Nerve fibres: - There are 2 types of nerve fibres: - Nerve fibre that transmits impulses away from cell body – axon - Nerve fibre that transmits impulses towards cell body – dendrons - The terminal branches at the ends of nerve fibres are called dendrites - Nerve fibres are enclosed by a layer of fatty substances – myelin sheath - Sheath serves as insulating layer - It is surrounded by thin membrane neurilemma – providing nourishment for fibre - It is not continuous like nerve fibres; it is seperated by nodes of Ranvier where neurilemma sinks down and comes in contact with the fibre. The nodes speed up transmission of impulses along fibre The Central Nervous System Nervous tissue of CNS has 2 distinct regions: grey matter and white matter - Grey matter consists of cell bodies of neurons and forms outer layers of brains and central portions of spinal cord. - White matter consists of nerve fibres and forms the central part of brain and outer layers of the spinal cord. The Synapse Electric pulses are transmitted from axon of a neuron to dendron of another neurone across a small gap called synapse (a junction between 2 neurones) Nerve impulses that reach axon end are converted to chemicals neurotransmitters into the synapse. These chemicals trigger impulse in dendrites of following neurone. If neurone ends in muscle or gland (effectors), the chemicals stimulate the effectors.
a nerve fibre
The Brain of a Mammal
Midbrain Consists of optic lobes. They deal with input from various organs: 1. Relay messages from ears 2. Controls visual reflexes such as movement of eyeballs 3. Filters sensory input before they reach concious regions of brain (e.g. a mother can sleep although there’s loud traffic noise but awake when her baby cries) Hindbrain Cerebellum lies behind optic lobes with many folds and is large. - It controls muscular co-ordination especially in maintaining body balance
The mammalian brain is divided into 3 parts: - Forebrain – includes cerebrum, thalamus, hypothalamus and pituitary gland - Midbrain - Hindbrain – consists of cerebellum and medulla oblongata
Medulla oblongata lies below cerebellum. Its posterior narrows down into spinal cord - It controls involuntary actions such as heartbeat, breathing, blood circulation and contraction and relaxation of blood vessels. A direct blow here could cause death. Spinal Cord and Spinal Nerves Spinal cord extends from medulla oblongata to end of vertebral columns. Spinal nerves emerge at intervals along length of spinal cord. (PNS&CNS diagram)
Forebrain Cerebrum of brain is made up of 2 cerebral hemispheres – the largest parts in brain. - They concerned with intelligence, memory, learning, voluntary actions & emotions Thalamus sorts data, suppresses signals and enhnces others before sending the sorted information to appropriate brain centre for further interpretation and integration. The floor of cerebral hemisphere is hypothalamus - It controls and monitors body’s activities like thermoregulation & osmoregulation. Other functions are: • Controlling automatic nervous system (control involuntary actions in the body) • Regulating food intake through hunger sensation • Inducing sleep or wakefulness • Controlling emotions • Controlling endocrine system through its control of pituitary gland Pituitary gland is attached to hypothalamus, secreting ADH and other hormones.
Structure of the spinal cord: - Has grey and white matter, where grey matter is inside while white matter outside - In the middle of spinal cord runs a narrow central canal containing cerebrospinal fluid which brings nutrients to the cord - Relay/intermediate neurones lie in grey matter of spinal cord, where they form synapses with receptor and effector neurones which enable impulses to be transmitted from receptor neurones to effector neurones Structure of the spinal nerves: - Spinal nerve divides into 2 roots before it joins the spinal cord • Dorsal roots join dorsal part of spinal cord and contain receptor neurones Cell body of the neurones aggregate in small swelling – dorsal root ganglion The axon end in grey matter of spinal cord; dendron become sensory fibres in dorsal root and spinal nerve • Ventral roots attached to ventral part of spinal cord and contain effector neurones Cell bodies of neurones lie in grey matter of spinal cord. Axon leave spinal cord to enter ventral root and spinal nerve - Nerve fibres from both roots converge into spinal nerve, where it contain both receptor and effector neurones. It is called mixed fibre - Spinal nerve subdivide into branches supplying nerve fibres to various parts of body - Sensory and motor neurones soon separate going to their destinations How these work hand-in-hand to make you feel someone touches your hand - Receptors in hand stimulated – impulses transmitted through receptor neurons to grey matter in spinal cord. - Neurones in spinal cord conduct impulses to brain and the touch is felt when impulses reach cerebrum Voluntary Actions – the response to a specific stimulus with conscious control Reflex Actions – immediate response to a specific stimulus without conscious control The events of reflex action on the picture on the right is as follows: 1. Heat on object stimulates nerve endings (receptor) in the skin. 2. Impulses are produced. Impulses travel along receptor neurone to spinal cord. 3. In spinal cord, impulses are transmittes across synapse to relay neurone then across another synapse to effector neurone. 4. Impulses leave spinal cord along effector neurone to effector 5. Biceps muscle (effector) contracts to suddenly withdraw hand from the object.
Spinal and Cranial Reflexes Spinial reflex actions are controlled by spinal cord. Cranial reflex actions are controlled by brain and usually occur in head region. Reflex Arc It is the nervous pathway by which impulses can travel from receptor to effector. Reflex arc consists of: - receptors - receptor neurone - reflex centre (spinal cord/brain) - effector neurone - effectors Below is a simple reflex arc of the example given above
Conditioned reflex It is the reflex action to a fixed stimuli acquired from past experience e.g.: Plums might be sour and not tasty for the first sight but once we tried it for a number of times, we find it mouth watering and salivary gland secretes saliva.
12.2 THE ENDOCRINE SYSTEM Hormones Hormones are chemical messengers in animals which assist the nervous system in co-ordinating various parts of the body, ensuring they develop and work harmoniously ENDOCRINE GLANDS Exocrine glands are glands having duct to carry the secretion to be poured out of the body (e.g. salivary glands, sweat glands) Endocrine glands are glands which do not have duct to carry the secretion. The hormone secreted passes directly into bloodstream to be distrubuted around the body. They secrete gland internally (e.g. adrenal glands, thyroid gland) - Pituitary gland is the master gland whih secretes hormones which controls activity of a particular gland - Some glands don’t function until the organism reaches certain age e.g. gonads - Divided into 2: short-lived hormone(adrenaline) and long-term hormone(thyroxine) Hormonal and Nervous Control Hormonal control serves as means of co-ordination within the body. - Stimulus causes transmission of messages to target organ (effector) Differences between nervous and hormonal controls Nervous control Hormonal control - Involves nervous impulses (electrical - Involves hormones (chemical substances) signals) - Impulses transmitted by neurones - Hormones transported by blood - Quick response - Slow response - Response short-lived - Response may be short-lived or long-lived - May be voluntary or involuntary - Always involuntary - Usually localized (only one target - May affect more than one target organ organ affected) The table next shows endocrine glands and their secretion
12.3 THE EYE
Structure Tear gland Tear duct Eyebrow Eyelashes Sclera Cornea Choroid Ciliary muscles Iris Pupil Retina Yellow spot Blind spot Aqueous humour Vitreous humour Optic nerve
Eyeball is located within a depression in the skull (the orbit) so only front part’s visible. It’s attached to orbit by 6 rectus muscles for rotating eyeball without moving head. Structure Conjunctiva Eyelids
Function Lies on the outer corner of the upper eyelid to secrete tears which lubricates the eye and cleanse eye from dust particles Drains excess tears into nasal cavity Shades eye & catches drops of sweat from entering to irritate eye Stiff hairs along eyelids to trap dust particles and irritants It’s the outermost layer of the eye which is a tough, white, fibrous coat, forming protective layer for eye and gives eye its shape Transparent coat of eye on the visible outer part which allows light to pass through and refracted Layer under sclera containing network of capillaries to nourish the eye and pigmented black to prevent total internal reflection of light Anterior part of choroid which work with suspensory ligaments to alter the length and thickness of lens Circular disc-shaped structure which gives eye colour and alters size of pupil to control the amount of light which can enter. This also prevents excessive exposure to light which may damage eye It’s a hole in the centre of iris which allows light to enter the eye It’s the innermost layer of eye where image is formed as it consists of photoreceptors connected to optic nerve Also called fovea. It is a shallow yellow depression where cones are most concentrated so it gives sharpest vision when light is focused here. Found just over optic nerve and has no photoreceptors so it’s insensitive to light causing no image formed when light falls here Watery fluid in the small chamber in front of iris and lens used to refract light into the eye and keeps eyeball firm Transparent jelly-like fluid in the large chamber behind the lens used to refract light into the eye and keeps the eyeball firm Transmit impulses to brain when retinal photoreceptors stimulated
Controlling pupil size
Function Thin transparent membrane covering the exposed part of eyeball Movable flap which can control the amount of light entering the eye, prevents mechanical damage to eyeball and spreads tears throughout the eye to lubricate conjunctiva, everytime we blink
Circular muscles arranged in circle around the pupil works antagonistically with radial muscles arranged radially around the pupil
Lens is adjusted by ciliary muscles and suspensory ligaments (antagonistic muscles) so that light rays are accurately focused onto the retina
In dim light Circular muscles relax while radial muscles contract, pulling the pupil to dilate, maximising the amount of light entering the eye. In bright light Circular muscles contract while radial muscles relax, decreasing size of pupil to prevent excessive light from damaging the retina. About our Retina The retina consists of light-sensitive cells – photoreceptors – where image is formed. Photoreceptors: (a) Rods Contains visual purple which is a pigment helping for vision in dim light. The pigment bleaches in bright light and hence when we look into the dark from bright room, we may not be able to distinguish objects as it takes time for visual purple to reform. The reform needs vitamin A, so without it, we may not be able to see in dim light, suffering night-blindness. (b) Cones Contains less light-sensitive red, green and blue cones having separate pigments which absorb different light wavelengths for colour vision in bright light. They work together to create different colours hence completing spectrum of light on retina. Controlling lens size for Accomodation Accomodation means the ability of the eye to adjust the lens so that images of any distances are formed accurately on the retina. Light reflected from object falls onto retina after refracted by cornea and aqueous humour and further refracted to converge and focus on retina by lens. The image formed stimulates the rods or cones to create impulses to be transmitted via optic nerve to the brain which interprets the impulses so that we can see it upright and same size because real image formed on retina is inverted, reversed and diminished.
Focusing Distant Objects Ciliary muscles relax to pull suspensory ligaments so that it contract and pull the lens to flatten and becomes less convex. This allows the almost “parallel” distant light rays to be less refracted so that it can be sharply formed on retina. Focusing Near Objects Ciliary muscles contract to slacken the pull on suspensory ligaments so that the lens attached to it thickens and becomes more convex. This diverges the light rays further so that images are formed sharply on retina. The closer the object, the more ciliary muscles contract to make lens more convex so that it can make the object as focused as possible on retina, but when the contraction is at its maximum, if the object is placed any more nearer, the image will be blurred as the lens can’t be further adjusted. The point where the image formed starts to blur is near point of the eye. END OF CHAPTER 12
CHAPTER 13: SUPPORT, MOVEMENT AND LOCOMOTION Support, Movement and Locomotion Support means the skeleton which holds up the body structure and shape. Movement means the change in position of one body part in relation of another part. Locomotion means the movement of the whole body from one place to another.
13.2 JOINTS Joint is the location where 2 or more bones make contact for movement and support. - Ball and socket joint located at shoulder, allows free movement in many planes. - Hinge joint is located at elbow which allows movement in one plane only. (Refer Fig. 13.1 on previous page)
13.1 BONES Functions of a Bone - They act as levers by working hand-in-hand with muscles which provides force for movement for locomotion. - They support the body clear of the ground. - They provide protection (e.g. skull)
13.3 ANTAGONISTIC MUSCLES Antagonistic muscles are muscles which are usually arranged in pairs to work together but producing opposite effects (e.g. biceps and triceps) Movement of Bones by Muscle at a Joint Tendons are tough fibrous tissues which attach muscles to bones. They don’t stretch. Ligaments are eleastic issues attaching bones to each other. They stretch a little. When a muscle contracts, it shortens and when it relaxes, it gets to its original length by contraction of another muscle in antagonistic pair because muscles can only pull, that is, to contract/shorten. For example, muscles in your arm – biceps and triceps. Biceps contracts while triceps relaxes when you raise your arm so that biceps pull ligaments up your lower arm. Vice versa happens when you lower your arm. END OF CHAPTER 13
Humerus runs from the shoulder to elbow as the longest forelimb bone. It connects the scapula to lower arm bones Radius is the bone on forearm extending from side of elvow to thummb and side wrist. It is longer and bigger than ulna. Ulna is placed at the middle side of forearm parallel to radius. Scapula connects to humerus forming ball and socket joint.
CHAPTER 14: USE AND ABUSE OF DRUGS 14.1 INTRODUCTORY ON DRUGS Drug is externally administered chemical substances that modifies/affects chemical reactions in the body. 14.2 MEDICINAL DRUGS - drugs taken under medical supervision to treat diseases, relieve pain and in surgery. Antibiotics - Antibiotics are chemicals, usually produced by certain bacteria and moulds, that are used to treat many infectious diseases caused by microorganisms • Antibiotics aren’t useful on viruses. When a person acquiring viral infection given antibiotic: prevent him getting bacterial infection as his resistance is very lowered. Four types of antibiotics: - Penicillin made by fungus Penicillum. They interfere metabolic functions of microorganisms from producing enzyme to synthesize their cell wall. - Cephalosporins made by mould Cephalosporium. Useful against bacteria which have developed resistance against penicillin. - Tetracyclines made by bacterium Streptomyces aureofaciens. They attack a wide variety of bacteria, therefore called broad-spectrum antibiotics. - Erythromycins attack bacteria affected by penicillin. They are useful against bacteria which have developed resistance against penicillin. Antibiotics work in 2 ways: - Prevents bacterium from making essential components of the cell wall which makes it easier for body’s immune system to destroy it. E.g. penicillin - Damages protein-producing machinery inside cytoplasm of bacterium, preventing it from dividing. E.g. tetracycline Anaesthetics and Analgesics Anaesthetics are drugs that make body unable to feel pain, e.g. novoacain and cocaine causes loss of sensation around injected area. Applied for tooth extraction. Analgesics relieve pain without causing numbness/affecting consciousness, e.g. aspirin relieves minor pain and reduces fever. If taken in large dose causes side effect
14.3 ALCOHOL Alcohols are rapidly absorbed into bloodstream from intestine & broken down in liver The Effects of Alcohol on the Nervous System - Alcohol is a depressant which slows down brain functions • It causes increased anxiety • It reduces nervous tension and worries and stimulates appetite • It makes the drinker carefree as alcohol takes away his inhibitions • It reduces the drinker’s self-control which causes a person to take personal and social liberties which they may regret when alcohol effects have worn off. - Increased consumption of alcohol creates observable effects of intoxication • It causes slurred speech • It causes blurred vision and poor muscular co-ordination – the person becomes clumsy and unable to walk properly • It deters the drinker’s judgement, e.g. he underestimates speed causing speeding - More areas of brain are pulled, drinker becomes anaesthetized and unconscious • High alcohol levels paralyzes medulla oblongata or hind brain, which controls breathing and heartbeat, contributing to death - Frequent consumption of alcohol makes a person addicted • They neglect work & families - exhibit violent behaviours towards family members • They commit crimes under influence of alcohol The Effects of Alcohol on the Digestive System • Stimulates acid secretion in stomach – increased risk of gastric ulcers • Prolonged alcohol abuse damages liver leading to liver cirrhosis (disease in which liver cells destroyed and replaced with fibrous tissues making liver less functioning). It can cause haemorrhage in liver and liver failure – causing death Withdrawal Symptoms When a person stops drinking alcohol, they experience symptoms (e.g. illness, mental disturbance, etc.) which makes it hard for them to give up their drinking habit.
14.4 ABUSE OF DRUGS Drug abuse can cause: - Tolerance – condition where a person has to keep on taking more and more of a drug to achieve the same effect - Addiction/Dependance – condition where a person experiences withdrawal symptoms (e.g. physical illness – nausea, vommiting, uncontrolled trembling; mental disturbance – cause anxiety, depression) if he does not take the drug
14.5 SMOKING Why do young people smoke? - They smoke as they believe smoking is a symbol of adulthood, under the effect of advertisements from cigarette companies trying to give impression that maturity, social status, happiness and success are linked with smoking.
Types of Drugs Stimulant Drugs: These drugs stimulate CNS, e.g. cocaine, amphetamine. - Amphetamines are used to counteract depression and hunger, and prevent fatigue
- They smoke out of curiosity as they want to experience what smoking is all about, but addictive drugs in smoke makes smokers difficult to give up smoking.
- They smoke to cover their weaknesses such as failing in studies or sports.
- They imitate their parents who smoke. Depressant Drugs: Drugs which slows down brain functions and induce sleepiness. - Alcohols and sleeping pills can make you sleepy Hallucinogenic Drugs: These drugs cause a person to experience hallucinations, illusion and distorted images. - E.g. Marijuana, Lysergic Acid Diethylamide (LSD) Opiates: These are narcotic drugs which relieve pain and induce sleep and stupor. - E.g. Opium, Morphine, Heroin Heroin – The Opiate Heroin is a powerful depressant which sedates and relieves pain Danger - User commit crime under drug influence as they need money to get heroin supply. - User becomes rapidly addicted & needs larger dosage to produce same sensation - User has to use the drug more often to avoid withdrawal symptoms (i.e. anxiety, stomach upsets, sweating, goosebumps, watering of eyes, vommiting, diarrhoea, convulsion, hallucinations and death), leading them to misery as they desperately need to obtain more money for the drugs, so they turn to crime - Injecting shared unsterilized and contaminated needles into vein results in transmission of hepatitis B and human immunodeficiency virus (HIV) causing AIDS (Acquired Immune Deficiency Syndrome)
- They want to be accepted as members of group of friends who smoke as their friends’ persistent teasing and urging make them not sporting enough if they don’t smoke. This is called ‘peer group’ pressure. A Goodbye From Being Socially Acceptable... Why Could This Happen? Smoking’s no more considered fashionable due to harm to smokers & people around - Scientists provide scientific evidence on harmful effects of smoking, therefore making people aware of dangers of smoking to health. - Smoking has been recognised to have been causing significant number of death and disability around the world by lung and heart cancer. - Smoking harms people around smokers by passive smoking, that is, non-smokers breathe in smoke exhaled by smokers, exposing them to smoking-related diseases. What is in That Smoke? - Nicotine This is addictive drug present in tobacco. Profession: • First stimulates the brain, making smoker feel alert and relaxes muscles, while later dulls the brain and senses • Causes release of adrenaline – increasing heartbeat rate and blood pressure
• Makes blood clot easily – increasing risk of blood clots blocking blood vessels, leading to heart attack if clots block coronary arteries, or stroke if clots block capillaries of the brain - Carbon Monoxide Profession: • Reduces the capacity of haemoglobin transporting oxygen
Without immediate treatment, the cancer may spread to other neighboring cells and organs, increasing risk of mouth, throat, pancreas, kidney & urinary bladder cancer. - Chronic bronchitis epithelium lining bronchi inner surfaces to lungs become inflamed & narrowed, and excessive mucus is produced, reducing air flow in air passages making breathing difficult and forces a person to cough and sneeze persistently to clear air passages, making lungs more likely infected by bacteria. It also increase production of pleghm.
• Speeds fat deposition on inner arteries walls, narrowing lumen (atherosclerosis) • Damage lining of blood vessels – increase tendency of blood clot & block vessels - Tar This is brown sticky substance that accumulates in lungs during smoking Profession • Cell division in lungs continuously replase air sacs membrane. Tar containing many carcinogenic(cancer-causing) chemicals induces cells to divide at abnormal rate. Uncontrolled multiplication of cells causes outgrowths of tissue (cancer) which block off air sacs, reducing efficiency for gaseous exchange • Paralyse cilia lining, preventing cilia removing dust particles from lungs & trachea - Irritants (e.g. hydrogen cyanide, acrolein) Profession: • Paralyse cilia in air passages and weaken walls of alveoli • Irritate cells lining air passages causing them to produce mucus which in turn causes smokers’ cough which bursts the weakened walls of alveoli causing a decrease in wall area as many minute alveoli coalesce to form reduced number of enlarged alveoli, reducing surface for gaseous ecxhange in lungs. (emphysema) Smoking-Related Diseases - Lung cancer Carcinogenic substances in cigarette smoke may cause abnormal growth of bronchial tube wall. The growth blocks bronchial wall, making breathing difficult.
- Emphysema it is associated with chronic bronchitis and smoking. The partition walls between alveoli break down due to intense coughing, enlarging air spaces and decreases surface area of lungs, thus reducing absorption of oxygen. Lungs over-inflated with air and lose elasticity and makes breathing difficult. The person spends lots of energy to breathe & sneeze, and he suffers severe breathelessness/slight exertion. Smoking and Pregnancy Effect of Carbon Monoxide on fetus: Carbon monoxide combines with haemoglobin to form carboxyhaemoglobin which cannot transport oxygen, reducing amount of oxygen reaching fetus through placenta. Effect of Nicotine on fetus: Nicotine causes arteries bringing blood to placenta narrower – food substances reaching fetus is reduced. The mother suffers lack of oxygen or chronic bronchitis. Dangers of smoking to fetus: - Fetus brain development affected – child may have learning difficulties in later life - Fetus grows more slowly causing underweight & may die within first few days of life. - There is higher risk of baby born prematurely - There is greater risk of miscarriage - The baby has greater risk of being born dead.
CHAPTER 15: MICROORGANISMS AND BIOTECHNOLOGY 15.1 MICROORGANISMS Viruses Structure: - Made up of a nucleic acid (DNA or RNA) enclosed in protein coat
Mode of life: Types: saprophytic – feed on decaying organic matter parasitic – causing diseases on plants and animals autotrophic – manufactures food using energy from sun or inorganic matter
Mode of life: - Attacks on a living cell called host cell. - Do not carry out living processes outside host cell, i.e. feed, respire, excrete, grow, reproduce, but inside host cell replicates by taking over biochemical systems of host cell and later bursts, releasing viruses to infect new cell.
Respiratory System: Aerobic – requires oxygen for respiration Anaerobic – doesn’t require oxygen Both aerobic and anaerobic – survives in conditions with and without oxygen.
Against virus: - Natural immune system in body – antibodies, kill these. Antibiotics for bacteria only. Bacteria These are living cells visible under light microscope, bigger than viruses. Structure: - Has cell surface membrane, cytoplasm and cell wall. - Has DNA which is bactrial chromosomes that contains genes of bacterium which gives properties and characteristics as it doesn’t have nucleus as it has no nuclear envelope. There are smaller rings of DNA – plasmids, which can be used as carrier. - Most cannot move but some which moves has long, hair-like threads called flagella which beats to enable bacteria move in fluid medium.
Reproduction System: Binary fission – bacterial cell copies its DNA and splits in half to form two new cells. Fungi They are saprophytes which feeds on decaying organic matter Structure:
Types: - Cocci (spherical shaped bacteria) - Bacilli (rod shaped bacteria) - Vibrio (comma shaped bacteria) - Spirilla (spiral shaped bacteria)
CHAPTER 16: REPRODUCTION IN (a) ANIMALS AND (b) PLANTS 16.1 INTRODUCTORY ON REPRODUCTION Significance of Reproduction Reproduction is the production of new individuals from the parents. It is important to prevent extinction of an organism.
Diploid Cell and Haploid Cell Diploid cells are cells containing complete number of chromosomes, i.e. 2n. They exist in pairs and can be found in all body cells. Haploid cells are cells containing half the complete number of chromosomes, i.e. n. They are unpaired and found in gametes.
Gametes Gametes are sex cells produced by gonads of humans/plants.
In humans, diploid number is 46 while haploid number in gametes is 23. Meiosis and Mitosis Meiosis is the cell division by which gametes having haploid number are made from parent cell. The diploid number of chromosomes is restored when gametes fuse to form a zygote. Mitosis is the cell division by which parent cells divide and multiply to form new cells which are identical to parent cells and diploid. 16.2 REPRODUCTION IN ANIMALS Human body cell have 46 chromosomes in form of 23 pairs. One member of each pair comes from one parent and another from other parent.
Asexual Reproduction and Sexual Reproduction Asexual Reproduction: produce genetically identical offsprings involving one parent Benefit Drawback A species with desired characteristics can There’s higher risk of having diseases – be produced in massive scale they don’t have genetic variation Sexual Reproduction: production of dissimilar offsprings by fusion of haploid nuclei to form its diploid zygote Differences between Sexual and Asexual Reproduction Sexual Asexual Involves 2 parents Involves single parent Offsprings are genetically different to their Offsprings are genetically identical to parents their parents Occurs by meiosis Occurs by mitosis Involves fusion of nuclei of gametes No fertilization occurs Shows genetic variations and has Absent or fewer genetic variation, so it evolutionary significance has not much evolutionary significance
In sperm or ovum, 2 nuclei of gametes of ovum and sperm from mother and father fuse to form a zygote and each of them contain haploid number of chromosomes, i.e. 23. Hence when they fuse, the haploid number of chromosomes adds up and zygote formed will have diploid number of 46 chromosomes. Then the zygote divides by mitosis and puts the diploid number of chromosomes in all cells in the child except ovum/sperm cell. 16.2a THE STRUCTURE OF HUMAN REPRODUCTORY ORGANS The Male Reproductive System
Testes (sing: testis) are male gonads producing sperms from the coiled tubules and testosterone (male sex hormone). Millions of sperms are produced per ejaculation. Sperm/spermatozoon: - Has a head of about 2.5 nanometre with large nucleus containing haploid set of chromosomes, little cytoplasm and an acrosome, which is a sac containing enzymes to break down the part of egg membranes so sperm can penetrate during fertilization. - The middle piece contains mitochondria which provide energy for activity of sperm. - Has a tail (flagellum) to enable sperm swim toward the egg.
The Female Reproductive System Ovaries (sing: ovary) are female gonads producing ovum which develop inside overies and female sex hormones (oegesterone and progesterone). Only one ovum is produced per ovulation. Ovum: It is spherical with diameter of about 120 nanometre as largest cell in human body containing large nucleus having haploid set of chromosomes, abundant cytoplasm and a plasma membrane which is surrounded by an outer membrane.
Scrotum is pouch-like extension of the skin between the thighs where testis is kept. They are outside the body as sperm development needs temperature lower than body
Oviduct is a narrow muscular tube which transports ovum from ovary to uterus. Fertilization occurs in here.
Epididymis stores the sperms temporarily in inactive form before entering sperm duct .
Uterus is where embryo is attached and develops. The inner lining (endometrium) is soft and smooth which is broken down during menstruation.
Sperm duct is a tube that transports sperm from testis to urethre Cervix is the lower circular lining of uterus which leads to vagina. Seminal vesicle, prostate gland and Cowper’s gland secrete a slippery fluid which mixes with sperms called semen to provide nutrients and enzymes to nourish the sperms and activate them so that they swim actively.
Vagina receives and deposits semen during intercourse and acts as birth canal. Vulva is the opening of the vagina.
Urethra is a tube passing through the centre of penis to the exterior. Semen and urine don’t pass through at same time as the base of urinary bladder is a circular band of muscle called sphincter muscles which prevents coming out of urine during ejaculation. Penis is erectile organ where erectile tissues and numerous blood spaces are present When blood spaces filled with blood, penis becomes erect and hard.
16.2b PUBERTY Puberty is time of active growth in humans during a person stages from child to adult. Reproductive system begins to work properly and secondary sex characteristics brought about by sex hormones. In girls start at age 11 while in boys at age 14.
16.2c FERTILIZATION 16.2d FAMILY PLANNING 16.2e SEXUALLY TRANSMITTED DISEASES Signs are observable and measurable Symptoms are something that can be felt or described by patient. ================================================================= Syphilis is an STD passed on by spirochete from infected partner. 16.3 REPRODUCTION IN PLANTS
CHAPTER 17: HEREDITY 17.1 MONOHYBRID INHERITANCE Understanding The Terms Monohybrid inheritance – inheritance of one distinct features only (e.g. tall & short) Trait – characteristics variation shown (e.g. tall/short, smooth/wrinkled, white/purple) True-Breeding Plant – plants with particular trait that will only produce offspring of that same trait only. (e.g. plant producing yellow seed produces plants producing yellow seeds only) P Generation – parental/initial generation Fn Generation – n represents the order of filial generation, e.g. F1 represents first filial generation, F2 represents second filial generation and so and so for.
A Conclusion Hereditary factors (or alleles) are responsible for transmission of characteristics. These factors appear in pairs in cells of organisms, controlling characteristics of the organisms. If the factors differ in the cell (i.e. one dominant, one recessive or heterozygous), only dominant factor show its characteristics. The two factors in each pair separate during gamete formation and each will contain either one of the factors. The fusion of gametes restores the diploid zygote which unite at random thus contain 2 factors and characteristic is predictable by rational number. Let T as dominant factor (true-breeding yellow seed) and t as recessive factor (truebreeding green seed).
Mendel experiment By crossing true-breeding yellow seed plant with true-breeding green seed plant, all yellow seed of F1 generation is produced. When F1 is self-pollinated, it produces 6,022 yellow seeds and 2,001 green seeds totalling 8,023 seeds. In ratio yellow to green is 3:1. Since the F1 generation is always yellow by true-breeding seeds, yellow trait is known as dominant while green is recessive. Mendel performed same experiment with 6 other different traits: Trait
Ratio of dominant to recessive 3:1
651 on stem
207 at tip
purple/white? Purple Purple smooth seed/ Smooth Smooth wrikled seed? yellow seed/ Yellow Yellow green seed? inflated pod/ Inflated Inflated wrinkled pod? green pod/ Green Green yellow pod? flowers on On stem On stem stem/ at tip? tall/short? Tall Tall Table 17.1 Mendel’s results
17.2 UNDERSTANDING GENETICAL TERMS Gene is a unit of hereditary material in DNA of chromosome which shows the specific organism characteristic for that gene(e.g.in above, all genotypes are genes for color) Allele is alternative form of the gene. Alleles for same gene (e.g. for color) appear on same gene locus on each pair of homologous chromosome. (e.g. in above, T and t are alleles for color genes)different genes homozygous recessive alleles paternal
Copyrights AF/PS/2009/2010 alleles of homozygous same gene dominant alleles
Chromosome is a thread-like structure in nucleus which carries genetic material of the impending new organism as Deoxyribonucleic Acid (DNA) molecule.
If the individual is heterozygous Half of total offsprings show dominant trait while other half recessive trait in ratio 1:1
Dominant allele expresses itself whenever the allele is present in the genotype. A dominant allele is denoted with capital letters, e.g. T Recessive allele will express itself only if the genotype is homozygous recessive. A recessive allele is denoted with lowercase letters, e.g. t Homozygous means the two alleles of a gene pair is the same, e.g. TT, tt. A truebred organism is always homozygous dominant, TT, or homozygous recessive, tt. Heterozygous means the two alleles of a gene pair is different, e.g. Tt Phenotype is description of physical expression of a trait (e.g. height, eye color, etc.) Genotype is genetic make up of an organism (e.g. TT or Tt for yellow, tt for green) 17.3 DETERMINING THE GENOTYPES To test unknown genotype and find out if the organism is homozygous recessive, we could just see the characteristic if it has positive recessive trait as it only appear if the organism is homozygous for that trait. But what if the organism shows dominant trait? Test Cross This is crossing individual of unknown genotype with homozygous recessive individual If the individual is homozygous dominant The offsprings all show dominant trait and all heterozygous. This can be worked out using Punnett square.
17.4 INCOMPLETE DOMINANCE, CO-DOMINANCE AND MULTIPLE ALLELES Incomplete dominance occurs when both alleles in gene pair is not dominant over another as both exert repective effects so that phenotype of the organism is between those of their parents. Example: when red snapdragon crossed with white snapdragon Let R to be red snapdragon allele and W as white snapdragon allele. Since there is no dominance relationship, both alleles are represented by capital letters. P phenotype pure-breeding red pure-breeding white genotype RR WW gametes
F1 genotype phenotype
F1 self-pollinate to produce F2 gametes
Heterozygous R W
Heterozygous Pure-bred red snapdragon is crossed with pure-bred white snapdragon. It produces F1 generation of all pink flowers. F1 is self pollinated to produce F2 of red, white and pink snapdragons in ratio 1:2:1
Co-dominance is when both genes in heterozygous pair are equally expressed. Multiple alleles is when a gene exists in 2 or more alleles. Multiple alleles in rabbit fur Let C as allele for full fur colour a c as allele for albinism ch as allele for combined fur colour as in Himalayan Through breeding experiments, it’s found that C is dominant over ca and ch, while ch a a is dominant over c . c is recessive to the other ones. In other words: Allelic combinations Phenotype CC, Cca, Cch Full fur colour chch, chca Combined fur colour a a cc Albino Co-dominance in multiple alleles in ABO blood system A B O O The allele for A, B and O blood groups are I , I and I respectively. I is recessive A B while I and I are co-dominant over each other, creating blood type AB. Humans posess 2 ABO alleles, one from each parent. Allelic combinations Blood types Inheritance module IAIA A Homozygous Dominant IAIO A Heterozygous Dominant IAIB AB Co-dominant IBIB B Homozygous Dominant IB IO B Heterozygous Dominant IOIO O Homozygous Recessive 17.5 IT’S A BOY! (OR A GIRL?) A human has 23 pairs of chromosomes, one pair as sex chromosome and the other 22 are autosomes. The sex chromosomes determines gender of individual. One X chromosome is received by either gender from mother while the other chromosome from the father might be Y to be a boy or X to be a girl. Therefore, a boy has sex chromosomes pair of XY while girl has XX. During pregnancy, to find out gender of fetus is carried out during.
Diagram: Parent phenotype genotype MEIOSIS gametes X
female XX Y
Offspring genotype XX XX XY XY phenotype female female male male RATIO 1 : 1 Therefore the possibility is half total number of offspring will be male and other half is female in the ratio 1:1. 17.6 MUTATION Mutation: sudden change in gene structure/chromosome number, may be inheritable. Mutagens: mutagenic agents from external agents which speeds up rate of mutation. E.g.: UV rays; alpha, beta and gamma radiations; formalin, LSD
Albinism This is caused by absence of pigments in skin, eyes and hair due to recessive mutation caused by recessive albino allele. The hair and skin will be white while the eyes will be red of blood vessel colour.
17.7 VARIATION 17.8 GENETIC ENGINEERING
Sickle-cell anaemia This is due to slight chemical structural change in DNA. The sickle-cell allele is recessive hence it expresses itself only in homozygous recessive condition. The mutated gene produces HbS, similar to HbA, but different in one amino acid.
CHAPTER 18 – ORGANISMS AND THEIR ENVIRONMENT
HbS clump together forcing the disc shaped RBC into longer sickle-shaped RBC which breaks more easily causing anaemia. Clumping reduces efficiency of oxygencarrying property of haemoglobin. Heterozygous individuals have a dominant normal allele and a recessive sickle-cell allele and will have fewer sickle-shaped RBC, enhancing survival probability. These individuals are called carriers as they can pass the recessive allele to their offsprings without showing sickle-cell anaemia symptoms. Trisomy 21 (Down’s syndrome) – Mistakes while dividing Down’s syndrome is a disorder due to mutation in chromosome number. There is an extra copy of chromosome 21, which makes it consisting of 3 chromosomes in that sequence. Usually, there are only 2 chromosome 21, making homologous pair. Since it has 3 chromosome 21, it’s known as trisomy 21. This mutation occurs during meiosis in ovary. The ovary receives 2 copies of chromosome-21 from the mother instead of being haploid that when the ovary fuse with the sperm, each sperm also contain chromosome-21 – but single from the father, ends up of creating 3 chromosome-21. The possibility of this happening increases with age of the mother. The baby may have these traits: - Slanted eyes, flat round face, short stature - Heart defects, respiratory infections - Mild to moderate mental disability - Poor muscle development and stunted growth, leading to death at young age