Short Notes Form 4 Biology (Chapter 1-4)

Plasma membrane

⇝ semi-permeable ⇝ regulates the movement of substance

Cytoplasm

biochemical reactions and living process occurs

Cell wall

mechanical strength and support plant cells

Vacuoles

plant elongation

Nucleus

controls the activities of the cell

Mitochondria

release energy and sites for cellular respiration

Ribosomes

sites for protein synthesis

Endoplasmic reticulum

Smooth ER ⇝synthesize lipids Rough ER ⇝ transport proteins

Golgi apparatus

processing, packaging and transport centre

Lysosomes

digestive compartments in a cell

Centrioles (animal cell)

cell division

Chloroplasts

captures energy for photosynthesis

UNICELLULAR

non-organelles

CELL COMPONENTS

CHAPTER 2: CELL STRUCTURE AND CELL ORGANISATION

    

(Amoeba sp.)

Amoeba live in freshwater Constantly changing shape in response to stimuli Use pseudopodium (false feet) for movement and feeding Cytoplasm is 2 layers, inner (endoplasm) and outer (ectoplasm) Pseudopodia also used for eating, surrounding food (phagocytosis), packaging it in a food vacuole and digests it with lysozyme (lysosome enzyme)  Exchange of substances through plasma membrane Os moregul a ti on by diffusion –  Water goes into the cell by osmosis and fills the Regul a te wa ter contractile vacuole, when full, blows out the water from time to time(osmoregulation)  Amoeba sp. reproduces by binary fission, but produces spores when cannot do binary fission MULTICELLULAR 1. Cells grow, change shape and differentiate in multicellular organisms. 2. Mature cells carry out different functions, like different medical specialists are experts in their field, like a cardiologist in the heart, the neurologist in the brain, etc. 3. They undergo specialization to carry out their functions more efficiently. 4. Organisation is in this form:

Cell

Tissue

Organ

System

Multicellular Organism

5. Cells that carry out a function are grouped into tissues. 6. Different tissues that carry out a function are grouped into an organ. 7. Several organs that contribute to one section of an organism’s functions (circulatory, 8.

muscular) are grouped into a system. Several systems make up an organism.

ANIMALS There are 4 main types of tissue in an animal:

Tissues in animals

Muscle tissues (movement) Epithelial

tissues protection, secretion and absorption

⇝Smooth muscle (intestine, blood vessels, urinary and reproductive tract) ⇝ Skeletal muscle (arms and legs)

⇝ Cardiac muscle (heart walls)

Connective tissues (bind structure, provide support and protection) - Tendons -Ligaments - Cartilage - Bones - Blood Fat cells

PLANTS Two main types of tissue in plants:  Meristematic tissue o Consists of small cells with thin walls, large nuclei, dense cytoplasm and no vacuoles o Young, actively dividing cells, undifferentiated, located at root tips and shoot buds  Permanent tissue o Differentiated/partly differentiated mature tissues o Three types of permanent tissue:  Epidermal tissue  Ground tissue (parenchyma, collenchyma, sclerenchyma)  Vascular tissue ( xylem tissue, phloem tissue)  

Nerve tissues (transmit nerve impulses, control and coordiante body activities) - neurons →dendrites and axons

Tissues work together to perform a specific function. These are called organs. Examples are lungs, heart, kidneys, brain etc. Example: The skin:  Consists of various tissues joined together  2 main layers, the epidermis and the dermis  Epidermis is made of epithelial tissue, which constantly divides  Dermis is made of connective, nerve, epithelial and muscle tissue  Blood is supplied through blood capillary network  Nerve endings are scattered throughout the skin, transmit impulses to nervous system  Epithelial cells produce hair follicles, sweat glands and oil glands

  

   

Organs in plants are leaf, stem, root and flower. Systems are root and shoot systems. o Root system – all plant roots. o Shoot system – stem, leaf, bud, flower and fruit. Stem, branch for support system. Leaf for photosynthesis. Flowers for pollination.

Internal environment consists of blood plasma, interstitial fluid and lymph. Physical factors include temperature, blood pressure and osmotic pressure. Chemical factors include pH, salt and sugar content. Homeostasis is maintenance of constant internal environment for optimal cell performance. Any change in the internal environment will cause homeostasis to kick in and work to cancel the change. This is governed by the negative feedback mechanism.

CHAPTER 3: MOVEMENT OF SUBSTANCE ACROSS THE PLASMA MEMBRANE

The structure of the plasma membrane (fluid mosaic model)  Function: regulates the exchange of Hydrophilic head substance between the content of a cell and the external environment  A polar head is attracted to water Hydrophobic tails  A pair of non- fatty acid tails is repelled by water The pl asma membrane is generally described as s emipermeable or selectively permeable because it only l ets certa i n substances through.

Wa ter s oluble s ubstances such as gl ucose and amino a cids and ions need to aid by ca rrier protein.

Lipid-soluble molecules (A,D,E,K, glycerol) Water Small uncharged molecules (O 2 and CO 2 )

Differences between Passive Transport and Active Transport PT (osmosis, facilitated and simple AT diffusion) Does not require energy Require energy from cell respiration Substances move with concentration Substances move against concentration gradient gradient Will continue until an equilibrium is Process leads to accumulation or reached elimination of the substance from the cell

Osmosis The movement of water molecules from region of their higher concentration to a region of their lower concentration through a semipermeable membrane.

Wa ter molecules can move across pl a sma membrane.

Molecules that can move freely across the plasma membrane by simple diffusion

Movement of substance across the plasma membrane

Molecules that cannot move freely across the plasma membrane and require the aid of transport protein (pore proteins and carrier protein) Water-soluble molecules (glucose, amino acids) + + 2+ Inorganic ions ( K , Na , Ca )

Simple diffusion The movement of particles (molecules or solutes) within a gas or a liquid from a region of high concentration to a region of lower concentration.

Facilitated diffusion The movement of hydrophilic molecules or ions across the plasma membrane with the help of transport proteins.

Active transport The movement of particles across the plasma membrane against the concentration gradient, that is from a region of low concentration to a region of high concentration.

Isotonic

⇝ water diffuses into and out of the cell at equal rate ⇝ no net movement of water

Normal cell shape

Hypertonic

⇝ water diffuses out of the cell by osmosis ⇝ the cell shrinks

Crenation

Hypotonic

Isotonic •Solutions with equal solute concentration

Solutions

Hypotonic

Hypertonic •Solution with a higher solute concentration

Hypotonic •Solution with lower solute concentration

ANIMAL CELLS Observation Discussion ⇝ water diffuses into the cell by osmosis ⇝the cell swell up and eventually burst

Turgid

Isotonic

⇝ Water diffuses into and out of the cell at equal rates.

Normal cell shape

Hypertonic

⇝ Water diffuses out of the large central vacuole by osmosis. ⇝ Both the vacuole and cytoplasm lose water to surroundings and shrink. ⇝ The plasma membrane pulls away from the cell

⇝Plasmolysis. ⇝The plant cell becomes flaccid and less turgid.

Condition

Haemolysis

PLANT CELLS ⇝ Water diffuses into the large central vacuole by osmosis. ⇝ The large central vacuole expands, causing the cell to swell.

CHAPTER 4: CHEMICAL COMPOSITION OF THE CELL

CHEMICAL COMPOSITION OF THE CELL Chemical compounds (more than two elements)

Elements (one atom)

Organic (√ Carbon and hydrogen)

Inorganic (x carbon) (eg: water)

The Effects and Applications Of Osmosis In Everyday Life 1. Wilting of plants  Problems can arise if chemical fertilisers are added in excess to the soil.  The soil solution becomes hypertonic to the cell sap of the root hair cells.  Water moves out of the plant by osmosis.  When flaccidity spreads throughout the plant, wilting occurs. 2.

Preservation of foods  Food can be preserved by using salt or sugar.  When salt or sugar is added to the food, it creates a hypotonic condition for the microorganisms that spoil the food.  Water passes out from the microorganisms into the concentrated solution. This results in slower growth of the microorganisms or even death.

Carbohydrates

Lipids

Monosaccharides

Fats

Disaccharides

Oils

Polysaccharides

Proteins

Nucleic acid

Enzymes

Waxes

Phospholipids

Steroids

Carbohydrates (C,H,O)

ORGANIC COMPOUNDS 1. Primary source of energy 2. Monosaccharides (Glucose, Fructose, Galactose) a. Reducing sugars 3. Disaccharides ( Maltose, Sucrose, Lactose) a. Joined together through condensation b. Break down by adding water (hydrolysis) c. Maltose & lactose ( reducing sugar)

Lipids (C,H,O)

Proteins (C,H,O,N)

Nucleic acids (DNA and RNA)

Water

Sucrose (non-reducing sugar) 4. Polysaccharides ( Starch, Cellulose, Glycogen) 1. Fats and Oils a. 1 glycerol: 3 fatty acids (saturated or unsaturated) 2. Waxes 3. Phospholipids (plasma membrane) 4. Steroids a. Include cholesterol and hormones (progesterone, testosterone, oestrogen) 1. Made up of one or more polypeptides (monomers: amino acids – Essential and non-essential) 2. Broken down into amino acids by hydrolysis 3. Protein structures: Primary, Secondary, Tertiary, Quaternary 1. Store genetic information) 2. Basic units ( nucleotides) a. Nitrogenous base b. Pentose sugar c. Phosphate group INORGANIC COMPOUNDS 1. A polar molecule 2. Functions: a. Medium for biochemical reactions b. Solvent c. Transport medium d. Providing support and moisture e. Maintain body temperature f. Lubrication g. Maintaining osmotic balance and turgidity h. High surface tension and cohesion

ENZYMES: ∆ Metabolism (anabolism and catabolism) ∆ Consists of intracellular and extracellular ∆ Biological catalysts ∆ Proteins ∆ Naming: -ase ∆ Uses: o Food processing o Tenderising meat o Detergent manufacturing

General charateristic

Bind with substrate to produce product Not changed or destroyed

Highly specific Needed in small amounts Metabolic reactions: Reversible

The activities can be slowed down or inhibited Require cofactors to function

Mechanism (Lock and Key)

Factors affecting the activity of enzymes

pH ⇝ Optimum pH (enzymatic reaction rate is the fastest) ⇝ Changing in pH, changing the charges on active site causing reducing the ability of both molecules to bind

Temperature, ° C ⇝ Low ° C, slow reaction ⇝ ↑the temperature every 10° C, the reaction is doubled until the optimum temperature is reached ⇝ Max ° C will causing the enzyme to denatured Substrate concentration, [subs] ⇝ Low [subs], rate of reaction increases with the [subs] ⇝ Increase [subs], more products are formed, increase rate of reaction ⇝ Constant rate, enzyme is saturated, all active sites are filled up Enzyme concentration, [enzyme] ⇝ reaction rate is directyly proportion to the [enzyme] until maximum rate is achieved