biology spm chapter 6 form 4

CHAPTER 6

NUTRITION

What is Nutrition?  The

entire process by which organism obtain energy from food for growth, maintenance and repair of damaged tissues  Nutrient – the substances that are required for the nourishment of an organism

6.1 Type of Nutrition Two

main types: 1. Autotrophic 2. Heterotrophic

1. Autotrophic A

process in which organisms synthesise organic substances from inorganic substances  Autotroph = Auto – self, trophos – feed (organism which can make their own food)  The source of energy for synthesising food can be either light energy or chemical energy.

 The

synthesis of food using light energy – photosynthesis (photo – light)  Photoautotroph – organisms which produce organic molecules from carbon dioxide and water using sunlight as a source of energy  Example: green plants

 The

synthesis of food using chemical energy – chemosynthesis (chemo – chemical)  Chemoautotroph – organisms which synthesise organic compound by oxidising inorganic compound (hydrogen sulphide and ammonia)  Example: certain bacteria (Nitrosomonas sp. and Nitrobacter sp.)

2. Heterotrophic A

type of nutrition in which organism obtain energy through the intake and digestion of organic substances.  Heterotroph =Hetero – other, trophos – feed (organism that cannot synthesis their own nutrients but obtain the nutrients from other organisms)

They

may practice a) Holozioc nutrition, b) Saprophytism c) Parasitism

a) Holozoic nutrition - holo –like, zoon – animal - The organism feeds by ingesting solid organic matter which is subsequently digested and absorbed into their bodies - Examples: humans, herbivores, carnivores and some carnivorous pitcher plants and Venus fly-traps

b) Saprophytism - The organism called saprophytes - Feed on dead and decaying organic matter - Digest their food externally before absorbing the nutrients into their bodies - Examples: bacteria, fungi

c) Parasitism - The organism called parasite - Obtain nutrient from living on (ectoparasites) or in (endoparasites) the body of another living organism (host) - They absorbs readily digested food from its host - Examples: fleas (ectoparasites), lice, worms (endoparasites), Rafflesia plant

Test Yourself Differentiate between autotrophic and heterotrophic nutrition. A: Autotrophic nutrition – A process in which organisms synthesise organic substances from inorganic substances 1.

Heterotrophic nutrition - A type of nutrition in which organism obtain energy through the intake and digestion of organic substances.

Test Yourself Name two types of autotrophic nutrition. A: Photosynthesis and chemosynthesis 1.

Test Yourself Name three types of heterotrophic nutrition. A: Holozoic nutrition, saprophytism and parasitism 1.

Test Yourself 1.

Name the nutritional habits of the following organisms; a) Pitcher plants A: holozoic nutrition b) Green algae A: photosynthesis d) Tapeworm A: parasitism

Diet fats-sweets group

dairy products group

vegetables group

protein-rich group

fruits group

grain products group

Diet Food Group

Foods in the Group

Grain products

Products made with whole grains or enriched flour.

Fruits and vegetables

Dark green vegetables (broccoli, spinach) and deep yellow vegetables (carrots).

Nutrients Mostly carbohydrates and fibres, Vitamin B, iron and protein. Most carbohydrates and fibre. Various vitamins and minerals

Protein-rich food

Poultry, eggs, fish, red Rich in proteins, Vitamin B and meat, organ meat such as minerals such as magnesium kidneys and liver. Legumes, and zinc. nuts and seeds.

Dairy products

Milk and milk products such Protein, Vitamins A, B and B2. as yoghurt and cheese. Main source of calcium.

Fats-sweets food

Candy, pastries, salad dressing, coffee and cooking oil.

Supplies fats and sugar. Low in nutrient value.

Balanced Diet

Diet

A balanced diet is a diet which supplies all the essential nutrients in the correct proportions.  A balanced diet must contain enough: 





  

Protein to provide all the essential amino acids for growth and repair for the body Energy-food to meet the energy requirements of the individual Minerals and vitamins to maintain good health Roughage or dietary fibre to stimulate peristalsis Water to aid the chemical reactions in the body

 Basal

metabolic rate and physical activity determine energy needs.  Basal metabolic rate varies with sex, age and state of health of a person.

Diet

Factors affecting the daily energy requirement of the Human body 1.climate

2.body size

3.age

~living in colder,less humid countries would result in a tendency to actually lose more energy to a person’s surrounding. ~this is due to the body needing more energy to regulate its body temperature. ~those living in hot,wet areas do not use as much energy to maintain their body temperature. ~people living in cold temperature regions would actually have a much higher basal metabolic rate than people living in the tropics. ~the difference in body size also contributes to a person’s basal metabolism. ~it is estimated that people with a larger build would have a higher basal metabolic rate than another person with a smaller build. ~growing children usually have higher basal metabolism rates than older people simply because of the fact they are growing. ~for growth to take place,increased energy is also needed. ~adults tend to have a decresing basal metabolic rate throughout their lives.

4.gender

5.health

~men normally have higher heat production than woman of the same size and age,because men usually have less fatty tissue in their body. ~fat healps to conserve heat,and thus,men with less fat would lose heat a a quicker rate than women. ~the result in men having a higher basal metabolic rate than women.

~the function of the thyroid galand is to control the metabolic rate by secreting a hormone known as thyroxin. ~an underactive thyroid gland would result in insufficient number of the hormone being created,thereby causing a lower metabolic rate in the person. ~an overactive thyroid,however,may produced too many of these hormones,thereby speeding up the metabolic rate. 6.occupation ~a person who is very active and does heavy labour is only moderately active.

Energy value in food samples carbohydrates , fats and protein are our main supplier of energy.  the same amount of these foods store different amount of energy.  the amount of stored energy in food is found by burning a known mass of the food to heat a certain amount of water in a food calorimeter.  the amount of heat released from the burning of a fixed mass of food is equal to the amount of stored energy in the food.  this is known as its energy value. 

Malnutrition •Kwashiorkor •Marasmus •Cardiovascular

diseases •Rickets

KWASHIORKOR Do you know what Kwashiorkor is??? Kwashiorkor is a form of

malnutrition caused by inadequate protein intake in the presence of fair to good energy (total calories) intake.

KWASHIORKOR What are the symptoms? •Failure to gain weight and failure of linear growth •Irritability •Lethargy or apathy •Decreased muscle mass •Swelling (edema) •Large belly that stick out (protrudes) •Diarrhea •Dermatitis •Hair changes -- hair colour may change, often lightening or becoming reddish, thin, or brittle •increased and more severe infections due to damaged immune system •Shock (late stage) •Coma (late stage)

Marasmus Marasmus is… a form of severe protein-energy malnutrition characterised by energy deficiency A child with marasmus looks emaciated and the body weight may reduce to less than 80% of the normal weight for that height. Marasmus occurrence increases prior to age 1 whereas Kwashiorkor occurrence increases after

18 months.

Symptoms??  dry

skin, loose skin folds hanging over the glutei, axillae, etc  Drastic loss of adipose tissue from normal areas of fat deposits like buttocks and thighs  pigmented and depigmented hair  flaky paint appearance of skin due to peeling.

Cardiovascular Diseases What Are They?? A collection of diseases and conditions affecting : •The heart (cardio) •Blood vessels (vascular) – arteries, veins, and capillaries

Cardiovascular Diseases Artery Disease – a disease of the arteries that supply the heart muscles with blood

 Coronary

 Heart

attack – a sudden heart failure

– the sudden death of brain cells when blood supply to the blood cells is cut off.

 Stroke

blood pressure – the excessive force of blood pumping through the blood

 High

Rickets Apa itu Rickets (What is Rickets)? Rickets is a softening of the bones in children potentially leading to fractures and deformity. Rickets is among the most frequent childhood diseases in many developing countries. The predominant cause is a vitamin D deficiency, but lack of adequate calcium in the diet may also lead to rickets.

Symptoms of   



    

Rickets

Bone pain or tenderness dental problems muscle weakness ( rickety myopathy or "floppy baby syndrome") increased tendency for fractures (easily broken bones), Skeletal deformity Growth disturbance Hypocalcaemia (low level of calcium in the blood), and Tetany (uncontrolled muscle spasms all over the body). Craniotabes (soft skull)

The Digestiv e System

Which parts of the body are involved in digestion?

The Digestive System

• Consists of the alimentary canal and the glands and organs associated with it. • The alimentary canal is like a tube that extends from the mouth to the anus. • Most of its length is coiled in the abdominal cavity.

Which parts of the body are involved in digestion?

mouth teeth

The Digestive System salivary gland pharynx

oesophagus

stomach

liver Gall bladder

pancreas pyloric sphincter

duodenum ileum ascending colon caecum appendix

descending colon rectum anus

The Digestive System Mouth Food enters the body through the mouth.  The mouth leads to the buccal cavity. 

The Digestive System Mouth

What do you find in the mouth?:

Teeth: chewing action (mastication) breaks down mout h large pieces of food into smaller pieces. This increases surface area to volume ratio of the food for enzyme action. teeth  Salivary glands: secrete saliva into the mouth via ducts.  Tongue: helps to mix food with saliva. Taste buds Process of nutrition?? help one to identify and 

salivary gland

The Digestive System Pharynx Connects the buccal cavity to the oesophagus and larynx (voice box).  Leads to the trachea.  Both food and air must pass through the pharynx then they enter the body.  Air will pass to the trachea, while food will go into the 

pharynx air

glottis trachea (windpipe)

larynx (voicebox) oesophagus

The Digestive System Pharynx

The epiglottis is above the larynx, and it prevents food from going the wrong way.  During swallowing, the larynx moves up and the epiglottis moves downwards so epiglottis that the epiglottis glottis larynx covers the larynx. (voice-box)  If food or water enters trachea (windpipe) the trachea, it induces coughing to force the food/water particles out and prevent 

pharynx food particles

oesophagus

The Digestive System Oesophagus Also known as the gullet.  A narrow, muscular tube.  Passes through the thorax (chest) and the diaphragm to join the stomach. 

The Digestive System Oesophagus 

Made up of 2 layers of muscles, present from the oesophagus to the rectum:  Longitudinal

muscles

(outer layer)  Circular muscles (inner layer) 

circular muscles

These muscles are antagonistic muscles – when one contracts, longitudin the other relaxes al muscles

Part of the gut wa

The Digestive System Oesophagus The muscles cause peristalsis – rhythmic, wave-like contractions of the gut walls.  It helps to move food circular along the gut while muscles mixing the food with digestive juices. 

longitudin al muscles

Part of the gut wa

Which parts of the body are involved in digestion?

mouth teeth

oesophagus

The Digestive System

salivary gland

The Digestive System Oesophagus

PERISTALSIS 



When circular muscles contract, longitudinal muscles relax. The gut wall constricts (becomes narrower and longer). Food is squeezed or pushed forward. When longitudinal muscles contract, circular muscles relax. The gut wallwall dilates (becomes dilates to wider and shorter). This widens for allowthe foodlumen to circular muscle food to enter. enter longitudinal muscles

food mass

wall constricts to push food

The Digestive System Oesophagus

PERISTALSIS 



When circular muscles contract, longitudinal muscles relax. The gut wall constricts (becomes narrower and longer). Food is squeezed or pushed forward. When longitudinal muscles contract, circular muscles relax. The gut wall dilates (becomes wider and shorter). This widens the lumen for food to enter.

Process of nutrition??

The Digestive System Stomach The stomach is a distensible (muscular) bag.  The muscles of the stomach wall are thick and well-developed.  When fully stretched, it sends signals to the brain to indicate that it is full. 

The Digestive System Stomach The stomach wall has many pits which lead to gastric glands.  They secrete gastric juices into the What is stomach. 

one enzyme found in gastric juice?

pits

The System WhereDigestive else can we findStomach  Thecircular stomach stores food for a few hours. It muscles? digests food to become chyme.  Food stays in the stomach because of the pyloric sphincter – a ring of circular muscle located between the stomach and duodenum. Contracts: stomach exit closes Process of nutrition??  Relaxes: stomach exit 

The Digestive System – Small Intestine  Consists

of 3 parts:

 Duodenumprogres  Jejunum  Ileum

sively more coiled

The Digestive System – Small Intestine  Wall

of small intestine has 2 functions:  Contains

glands which secrete intestinal juice. It contains digestive enzymes.  Wall is adapted to absorb digested food products and water. Process of nutrition??

The Digestive System – Large Intestine large intestine

 The

large intestine is about 1.5 m long  Shorter

and wider than the small intestine

 Consists

of 2 parts:

 Colon  Rectum

colon rectum small intestine

The Digestive System – Large Intestine  Only

undigested food enters the colon.  It absorbs water and mineral salts from the food.  No digestion occurs colon in the colon.

The Digestive System – Large Intestine  The

rectum temporarily stores faeces.  When it contracts, faeces is expelled through the anus. rectum

The Digestive System – Large Intestine Between the small and large intestines lie the caecum and appendix.  The caecum has no function in humans.  The appendix contains bacteria that are useful to the body. 

caecum

Process of nutrition??

appendix

Which parts of the body are involved in digestion?

The Digestive System

Which parts of the body are involved in digestion?

mouth teeth

The Digestive System salivary gland pharynx

oesophagus

stomach

liver Gall bladder

pancreas pyloric sphincter

duodenum ileum ascending colon caecum appendix

descending colon rectum anus

The Digestive System Liver The largest internal organ in the body  There are 3 important blood vessels attached to the liver: 

Hepatic vein  Hepatic artery  Hepatic portal vein 

The Digestive System Liver 

It is also the largest gland in the Why body. 



liver

Secretes alkaline? bile into the duodenum

Properties of bile: Alkaline  Greenish-yellow  Contains bile salts and bile pigments  Produced in the liver, stored in the gall bladder 

gall bladder

bile duct

The Digestive System Liver 

liver

Functions of bile: Neutralize acid in chyme  Activate intestinal enzymes  Speed up fat digestion  Gives faeces its colour 



When the gall bladder contracts, bile is secreted into the duodenum via the bile duct.

Process of nutrition??

gall bladder

bile duct

The Digestive System Pancreas Connected to the duodenum via the pancreatic duct  Secretes pancreatic juice which contains digestive enzymes.  Also secretes hormones which control blood glucose level. 

Process of nutrition??

What is Digestion?

Definition of Digestion

Digestion is the process by which the body breaks down carbohydrates, fats and proteins into simpler substances that cells can absorb and use.

Physical digestion The mechanical break up of food into small particles.

Chemical digestion The breaking down of large molecules in food into small, soluble molecules which can be absorbed.

Chemical digestion involves hydrolysis catalyzed by digestive

What is Digestion?

Physical Digestion

• Physical digestion breaks down food into smaller particles. • Purpose: to increase surface area to volume ratio of the food to aid enzyme action. • Food substances are not chemically changed during physical digestion. chewing / mastication • Where does physical digestion occur?

– In the mouth peristalsis – Along the alimentary canal – Physical emulsification digestion of fats in the small intestine

What is Digestion?

EMULSIFICATION

Physical Digestion

• Fats do not dissolve in water – they tend to clump together. • This reduces the surface area for enzymes to work, slowing down fat digestion. • Bile molecules place themselves in between the fat and water – half the molecule is hydrophilic, half is hydrophobic. • This prevents the fat from clumping together. • Surface area of fat molecules

Picture taken from http://www.colorado.edu/eeb/web_resources/carto ons/bile.html

What is Digestion?

Chemical Digestion

• Breaking down of large molecules in food (starch, protein, fats) into small soluble molecules which can be absorbed. • Hydrolytic reactions – catalysed by ENZYMES

• Three groups of enzymes: Carbohydrases

Lipases

Proteases

• Chemical digestion occurs mainly in 3 parts of the alimentary canal: – Mouth, stomach, small intestine

What is Digestion?

Chemical Digestion

In the mouth... • Food in the mouth stimulates the salivary glands to secrete saliva. • Saliva is mixed with food. Mucin in saliva softens the food. • Salivary amylase is found in saliva: – Digests starch

to maltose

• The optimum pH of salivary amylase is pH 7. – The pH of saliva is neutral.

• The tongue rolls the food into small, slippery, round masses called boli (singular: bolus). • The boli are swallowed and passed down into the oesophagus.

What is Digestion?

Chemical Digestion

In the stomach...  The presence of food in the stomach stimulates the gastric glands to secrete gastric juice into the stomach.  Gastric juice contains 3 substances: – Hydrochloric acid – Pepsinogen – Prorennin

Chemical Digestion

What is Digestion?

In the stomach... Action of Pepsin  Pepsinogen is activated to pepsin by hydrochloric acid.  Pepsin then digests protein to polypeptides. hydrochloric pepsinog pepsi acid

en

protein s

n

pepsin

polypeptid es

Chemical Digestion

What is Digestion?

In the stomach... Action of Rennin  Prorennin is activated to rennin by hydrochloric acid.  Rennin curdles milk proteins by converting soluble protein caseinogen into insoluble casein.

– Soluble caseinogen would pass through the stomach as easily as water and not be hydrochloric prorenni renni digested. acid – Insoluble n n remain in the stomach to casein can rennin be digested.

caseinog en casein

casei n

pepsin

polypeptid es

What is Digestion?

Chemical Digestion

In the stomach... Purpose of Hydrochloric Acid denaturing

 Stops the activity of salivary amylase by pepsin it rennin

 Activates pepsinogen and prorennin to form and respectively  Provides acidic medium for the action of pepsin and rennin  Kills harmful microorganisms in food

What is Digestion?

Chemical Digestion

In the small intestine...  When chyme enters the small intestine, it stimulates 3 glands: – Intestinal glands secrete intestinal juice, which contains enzymes sucrase, maltase, intestinal lipase, lactase, enterokinase, SMILEE! and erepsin. – Pancreas secretes pancreatic juice, which ALT contains pancreatic amylase, pancreatic lipase, and trypsinogen. – Gall bladder releases bile. It does not contain enzyme

What is Digestion?

In the small intestine...

 All 3 fluids are alkaline:

Chemical Digestion

– Neutralize acidic chyme – Provide suitable pH for the action of pancreatic and intestinal enzymes

Chemical Digestion

What is Digestion?

In the small intestine... Carbohydrate digestion starc h

pancreatic amylase

maltos e

maltase

lactose

lactase

sucros e

sucrase

gluco se glucose + galactose glucose + fructose

Chemical Digestion

What is Digestion?

In the small intestine... Protein digestion enterokinas trypsinog trypsi e

en

proteins polypeptid es

n

trypsin erepsin

polypeptid es amino acids

Chemical Digestion

What is Digestion?

In the small intestine... Fat digestion f ats

lipase

fatty acids + glycerol

Recall: What process speeds up fat digestion in the small intestine?

Digestive Enzymes

What is Digestion?

small intestine

mouth

Carbohydrate digestion star ch

salivary amylase

maltose

pancreatic starc amylase maltose maltase h lactose

lactase

sucros sucrase e

glucos e glucose + galactose glucose + fructose

Digestive Enzymes

What is Digestion?

small intestine

stomac h

Protein digestion hydrochloric prorenni renni acid n n rennin

caseinog en casein

pepsin

casei n polypeptid es

enterokinas trypsinog trypsi e en n trypsin

proteins

polypeptid es

erepsin

polypeptid es amino acids

What happens to food after digestion?

Absorption

• Where does absorption occur?  In the small intestine and large intestine

• What nutrients are being absorbed?  Simple sugars  Amino acids  Fatty acids and glycerols  Water and mineral salts

What happens to food after digestion?

Absorption

How does absorption take place in the small intestine? • Glucose and amino diffusioacids: – Absorbed by nactive into blood capillaries of transport the villi. – Absorbed by when there is lower concentration of digested food substancesdiffusio in the small intestine than in the blood capillaries. n • Fatty acids and glycerol: – Absorbed by small into the epithelium colon – Combine to form fat globules which enter the intestine lacteals

What happens to food after digestion?

Absorption: Small Intestine

Adaptations of the Small Intestine for Absorption • The rate of absorption of digested food substances depends on 3 factors: 1. Surface area 2. The thickness of cell membranes 4. Concentration gradient

What happens to food after digestion?

Absorption: Small Intestine

1. Surface Area • The surface area of the small intestine is increased for absorption in 4 ways: 1. Inner walls have folds 2. The surface of the folds are lined with numerous villi (singular: villus), which are minute finger-like projections. 3. The epithelial cells of the villi have numerous microvilli. 4. The small intestine is long, providing large surface area and ample time for absorption.

What happens to food after digestion?

Absorption: Small Intestine

What happens to food after digestion?

Absorption: Small Intestine

What happens to food after digestion?

Absorption: Small Intestine

2. Thickness of Cell Membranes • The villi have very thin membranes: the epithelium is only one-cell thick. 3. Concentration Gradient • In each villus is a lacteal (lymphatic capillary) surrounded by blood capillaries. • The lacteal continually transports fats away sugars from the villus, while the blood capillaries amino transports and away. acids • This maintains the concentration gradient needed for the absorption of food substances.

What happens to food after digestion?

Egestion

• Some food substances cannot be digested and remain unabsorbed in the large intestine. • These are stored temporarily in the rectum. • When the anus rectum is full, they are discharged as faeces through the . • This process is known as egestion or defecation.

What happens to food after digestion?

Transport and Assimilation

Transport of Simple Sugars • After absorption, the blood in the villi is rich in sugars. • Blood capillaries unite to form the hepatic portal vein. • The hepatic portal vein transports sugars to the liver.

What happens to food after digestion?

Transport and Assimilation

Assimilation of Simple Sugars • In the liver, most sugars are converted to glycogen and stored. • Glucose leaves the liver and is distributed around the body by the bloodstream. – Used during respiration to provide energy for cells.

• Excess glucose is returned to the liver – Hormone insulin (produced by Islets of Langerhan in the pancreas) stimulates the liver to convert glucose to glycogen for storage. – When more glucose is required, the liver will

What happens to food after digestion?

Transport and Assimilation

Transport and Assimilation of Amino Acids • Amino acids pass through the liver before they are transported to the rest of the body. • How are amino acids used? – Converted to protoplasm by cells, used for growth and repair of body parts – Used to form enzymes and hormones

• Excess amino acids are deaminated.

What happens to food after digestion?

Functions of the Liver

The Liver has 7 Functions 2.Regulation of blood glucose concentration 3.Production of bile 4.Protein synthesis 5.Iron storage 6.Deamination of amino acids 7.Detoxification 8.Heat production

What happens to food after digestion?

Functions of the Liver

1. Regulation of Blood Glucose Concentration • Blood normally contains about 70-90 mg of glucose per 100 cm3 of blood. • After a meal: – Amount of glucose in the blood rises – Stimulates Islets of Langerhans in the pancreas to secrete insulin into the bloodstream – Insulin is transported to the liver. – Insulin stimulates liver to convert excess glucose to glycogen for storage. What about – Blood leaving the liver contains a constant

What happens to food after digestion?

Functions of the Liver

1. Regulation of Blood Glucose Concentration • When body cells need glucose: – Glucose level in the blood drops. – Islets of Langerhan are stimulated to secrete hormone glucagon. – Glucagon stimulates liver to convert stored glycogen to glucose. – Glucose enters the blood; blood glucose level returns to normal.

What happens to food after digestion?

Functions of the Liver

1. Regulation of Blood Glucose Concentration • If we have not eaten for a long time: – Glucose level in the blood drops below average. – Blood that is low in glucose reaches the hypothalamus in the brain. – Brain sends signals to the stomach. – This causes strong contractions and we feel hunger pangs. – After eating, the blood glucose level rises. The hypothalamus signals to the stomach to stop contracting.

What happens to food after digestion?

Functions of the Liver

1. Regulation of Blood Glucose Concentration high blood glucose concentratio n

pancreas secretes insulin

pancreas secretes glucagon

low blood glucose concentrati on

converts converts glucose to glycogen to glycogen glucose normal blood glucose

concentration

What happens to food after digestion?

Functions of the Liver

2. Production of Bile gall • The liver produces bile which is stored in the before use. bladd emulsifica of fats. • Bileer is used in the tion

3. Protein Synthesis • Blood plasma contains amino acids from the diet. • The liver synthesizes these amino acids to form proteins, e.g.: – Albumins, globulins, fibrinogen (for blood clotting)

What happens to food after digestion?

Functions of the Liver

4. Iron Storage • Red blood cells contain a iron, which is involved in the transportation of oxygen around the body. • These cells become worn out after some time. • They are destroyed in the spleen, a gland near the liver. • Haemoglobin from red blood cells is brought to the liver. • Haemoglobin is broken down, forming iron and bile.

What happens to food after digestion?

Functions of the Liver

5. Deamination of Amino Acids • Excess amino acids are transported to the liver. • The amino groups are removed and converted to urea. • Urea leaves the body in urine. • The remains of the amino glycogen acid are converted into glucose. • Excess glucose is converted to .

What happens to food after digestion?

Functions of the Liver

6. Detoxification • This is the process of converting harmful substances into harmless ones. • Breaks down alcohol to acetaldehyde by the action of alcohol dehydrogenase • Acetaldehyde can be broken down to compounds which can be used in respiration. • Excessive alcohol consumption stimulates acid secretion in the stomach, increasing the risk of gastric ulcers.

What happens to food after digestion?

Functions of the Liver

6. Detoxification • Prolonged alcohol use can lead to cirrhosis of the liver. – Liver cells are being destroyed and replaced with fibrous tissue – Cells are less able to function – Can lead to liver failure and death

What happens to food after digestion?

Functions of the Liver

7. Heat Production • There are many chemical reactions taking place in the liver. • Heat is produced from these reactions. • The heat is distributed by the blood to other parts other body. • Helps to maintain body temperature.

Constipation  Bowel

Evaluating Eating Habits

movements are difficult and do not occur often enough.  It is caused by a lack of exercise, emotional distress or misuse of laxatives, and/or a diet low in dietary fibres.  Due to constipation, abdominal pressure causes blood vessels in the rectum to enlarge, producing haemorrhoids.

Eating Disorders

Evaluating Eating Habits

Both anorexics and bulimics have a constant fear of being fat and fear rejection 



Anorexia nervosa is characterised by constant dieting, rapid weight loss and feeling too fat in spite of the weight loss. Bulimia is characterised by eating too much food through vomiting or the use of laxatives; tend to gain weight easily and live in constant fear of becoming obese. Bulimics often have mouth and throat problems due to repeating vomiting.

Photosynthesis

Photosynthesis The

synthesis of organic compounds From the splitting of water (photolysis) in the light dependent reaction And from the reduction of carbon dioxide in the light independent reaction

Photosynthesis LIGHT

H2O

ATP

2H+

Oxygen

Carbohydrate

CO2

Leaf structure  The

leaf is the main site for photosynthesis in plants  It has several special features which help it carry out this role;  Flattened

shape – increasing surface

area  Thin – so that gases can diffuse quickly  A vascular system – to supply water & take away the products  Stomata – To allow gas exchange  Chloroplast containing cells – to

Leaf structure Cuticle Upper epidermis Palisade

Vascular tissue Spongy mesophyll Lower epidermis Air space Stoma Guard cell

Palisade cell structure Chloroplast

Cellulose cell wall

Cell surface membrane

Cytoplasm

Vacuole Tonoplast Starch grain Cytoplasm Nucleus

Chloroplast structure

Chloroplast structure Oil droplet Ribosomes

Thylakoid membranes

Granum

Stroma DNA Starch grain

Intergranal membrane

Factors Affecting Photosynthesis Light Intensity

Concentration Of Carbon Dioxide

Temperature

Water Supply

LIGHT INTENSITY Light is essential during the light reaction of photosynthesis. When the concentration of carbon dioxide and temperature are controlled at constant level, the rate of photosynthesis is directly proportional to light intensity up to a certain point.

Rate of photosynthesis

Light intensity

Light intensity

Concentration of carbon dioxide 

Carbon dioxide is needed in the dark reaction as a raw material used in the synthesis of glucose if there is no other factors limiting photosynthesis and increase in the concentration of carbon dioxide results in an increase in the rate of photosynthesis.

 At

a very high light intensity, the rate of photosynthesis slows down because the pigment chlorophyll is damaged by ultraviolet rays.

Rate of photosynthesis

Carbon dioxide concentration 1% CO2

0.035% CO2

Light intensity 

WATER SUPPLY Water is needed for photosynthesis, however water is rarely the limiting factor in photosynthesis because the amount of water required is small. If water is not supplied, wilting occurs and the stomata is closed.This prevents the diffusion of carbon dioxide into the leaves.As a result the rate of photosynthesis decreases as the lower concentration of carbon dioxide becomes the limiting factor.

Temperature The dark reaction of photosynthesis is catalysed by the photosynthetic enzyme and therefore changes in temperature will affect the rate of photosynthesis. Generally, an increase of 10 degree Celsius in the surrounding temperature will doubled the rate of photosynthesis. The optimum temperature for most of the plants are between 25-30 degree celcius. However, when the temperature is too high the photosynthetic enzyme are destroyed and photosynthesis stops altogether.

Rate of photosynthesis

Temperature

25ºC Increasing KE Enzymes denatured

Temperature

Carring attitude towards plants… THE NEED TO TAKE CARE OF PLANTS.  Sustains life d)

Green plans produce and generates the supply of oxygen that all living things need.



Air quality

f)

h)

Plants influence the quality of the air that we breathe. Plants stop the movement of dust and pollutants. Plants reduce the greenhouse effect caused by burning of fossil fuels by absorbing and removing large amounts of carbon dioxide from the atmoshere.



Climate

j)

The type of plant cover influences regional climates. The destruction of forest causes drought and turns fertile land into desert.

g)

k)

 Water b)

c)

quality

Forests are important in maintaining healthy watercatchment areas. Forest hold sil in place,and filtering sediments from water flowing into streams,rivers and lakes.

 Control e)

f)

Plants and trees help to protect the soil from erosion caused by heavy rains. Uncontrolled felling of trees and clearing of plants and clearing of plants can cause landslides.

 Fish h)

of erosion

and wildlife habitat

Plants provide the necessary habitats for wildlife and fish populations.

 Ecosystem b)

c)

Humans,plants and animals all live together supporting each other. Each species serves an important role in the ecosystem.

 Food e)

Humans use about 3000 species of plants as food.

 Medicine g)

h)

Plants have been providing humans with medicines thoughout human history. About 80% of all medicinal drugsoriginate from wild plants and there are many important drugs yet to be discovered from plants.

 Industrial b) c) d)

products

We use fibres from plants to provide clothing. We build our houses and furniture using wood from plants. We produce fuel products are made from plants,palm oil bodies,soy diesel and ethanol made from corn.

 Recreation f)

Our forests provide many recreational activities like hiking,fishing,hunting,nature observation and ecotourism.

 Aesthetics h)

We use plants to enchance the beauty of our homes,gardens and roads which are important for us to seek peace,rest and beauty from nature.

TECHNOLOGICAL DEVELOPMENT IN FOOD PROCESSING

Food

processing is the process of preparing food to make it more attractive, more palatable and to last longer

Food

has to be processed so that it can withstand long periods of transportation and storage

One

of the main purpose of food processing is to preserve food by overcoming the factors that cause food spoilage

 Food

spoilage is caused by :

*the action of microorganism in food, especially decomposing bacteria and fungi which act on carbohydrates and proteins in food to produce carbon dioxide, water, ammonia, hydrogen sulphide and other organic substances. The presence of these substances spoil the food and sometimes make it toxic

The

oxidation of food due to the oxygen reacting with enzymes and chemical released by the cells in the food. Oily food can also become rancid, smell and taste different as a result of oxidation. Rancid food is harmful to the body

 Food

has to be processed : *to extend their lifespan so that they can be stored for future use *to avoid wastage *to prevent the spread of diseases due to contamination of food, which can cause food poisoning

*to ensure there will be the

continuous supply of food for the population *to increase their commercial value *to prevent the bacteria and fungal decay *so that they can withstand long periods of transportation and storage *so that food can be supplied to the local or global market all year round in good condition

To

diversify the uses of food substances. For example , milk has been processed to produce a variety of dairy products such as cheese, yogurt, ice cream, butter and chocolates



RELATING THE FOOD PROCESSING METHODS WITH FACTORS CAUSING FOOD SPOILAGE Microorganisms require nutrients,water,oxygen and a

suitable temperature for optimal growth and reproduction



Microorganisms can only survive in condition with optimum pH and solute concentrations as these will not destroy them



Hence,food can be preserved by destroying the microorganisms present in the food or by stopping their activities



A few methods of processing and preserving food that have been practised since the early days are cooking,fermentation and drying of food

COOKING  Cooking

at high temperatures or boiling for at least five minutes  Heating food to high temperatures can kill microorganisms and denature the enzymes that cause the breakdown of food.  Certain bacterial spores may also be killed. However toxins produced by bacteria are not

FERMENTATION PROCESS Yeast is added to fruit juices or other food substances.  Fermentation produces ethanol which at high concentrations, stops the activity of bacteria that causes food spoilage.  The ethanol produces also has a great commercial value.  E.g. Fruit juices and tapai. 

DRYING  Drying

under the hot sun, in hot air or in the oven.  Drying removes water from food. This prevents microorganisms from growing as microorganisms cannot live without water.  The enzymatic activity in food also stops.  The ultraviolet rays from the sun also kill bacteria and many other harmful microorganisms.

PICKLING FOOD Food

is soaked in an acidic solution such as vinegar. Most organisms cannot lives in low pH conditions. E.g. Chillies, ginger, onions and mangoes

TREATING FOOD WITH SALT AND SUGAR Food

is soaked in a concentrated salt solution or boiled with sugar. Microorganisms lose water through osmosis in a hypertonic solution. E.g. Meat, vegetables and ducks’ eggs

Milk is preserved by pasteurisation to destroy bacteria which cause diseases such as those which cause tuberculosis and typhoid.  In this process,milk is heated to  a) 63 for 30 minutes  b) 72 for 15 seconds  and then rapidly cooled to below 10 



 



While maintaining the nutrient content The purpose of pasteurisation is to kill microorganisms and natural flavour of the milk Nutrient like vitamin B are not destroyed. Pasteurisation is unable to kill all types of bacteria.Therefore,pasteurised milk needs to be stored in the refrigerator because of its short shelf life.This is to prevent those microorganism active again. Fruit juices and soup can also preserved using this method.

Canning uses the heat sterilisation method to kill microorganism and their spores.  The food is packed in cans and steamed at a high temperature and pressure to drive out all the air.  The cans containing food are then sealed while the food is being cooled.  The airtight containers all the vacuum created within the cans prevent the growth of microorganisms. 

Pathogens and food-spoiling bacteria are destroyed and the enzymes in the food are inactivated.  Canning keeps food sterile for long periods hence,the shelf life of canned food is usually longer although the cans may eventually corrode.  However,if the food is not thoroughly cooked,there is a danger contamination by spores of Clostridium botulinum. 

This bacteria can survive in food which is mildly heated and stored at room temperature.Under these conditions,the bacteria produce a toxin which can kill human at very low concentrations.  Consequently,because canned food needs to be thoroughly cooked,it is low in quality. 

Refrigeration is a common method used by household to prevent food spoilage.  Food stored at temperatures below 0 can remain fresh for a long period of time.  Meat,fish and meat products can be preserved this way.  The extremly low temperatures prevent growth of microorganisms or germination of spores because enzymatic reactions stop at low temperatures. 

The End!!! Bubye..