6093 Bio Syllabus Notes

Requirement I: Cells and Chemistry of Life Structure and function of: Cell Wall Cell Membrane Cytoplasm Nucleus Vacuole Chloroplasts Cell wall (Made up of cellulose and FULLY permeable) - Gives plant cells a fixed shape - Provides structural support and protection Cell Membrane (Made up of lipids and proteins) - PARTIALLY permeable - Control movement of substance in and out of cell Cytoplasm (Jelly like fluid containing water, salt, and protein) - Contains organelles that perform specific jobs within a cell for a particular function Nucleus (Surrounded by nuclear membrane) - Controls cell activities like cell growth and repair of worn out parts - Essential for cell division as chromosomes contains DNA that has genetic information and instructions for cell activities Vacuole -> Store substances within the cell Plant -> Large and central, Contains cell sap (dissolved sugars, mineral salts, and amino acids) Animal -> Small and temporary, Contains water and food substances

Chloroplast - Contains chlorophyll which is essential for photosynthesis Structure and function of: Ribosomes Golgi Body RER SER Ribosomes (Made of rRNA proteins) Attached to RER -> Synthesises protein that’s transported out of cell Lies freely -> Synthesis proteins that are used within the cel RER (Continuous with nuclear membrane) - Modifies & packages protein made by ribosomes into vesicles to the Golgi Body for secretion out of the cell Golgi Body 1) Chemically modifies substances made by ER 2) Stores and packages substances in vesicles for secretion out of the cell SER (More tubular) 1) Synthesis of fats and steroids (sex hormones in mammals) 2) Detoxification Compare structure of animal and plant cell Large central vacuole vs Small temporary vacuole Chloroplast vs no chloroplast Cell wall vs no cell wall

How are red blood cells adapted to their functions? 1) Contains many haemoglobin -> Transports O 2 by temporarily binding to it to form oxyhaemoglobin 2) No nucleus -> More haemoglobin -> ↑↑ O 2 - carrying capacity 3) Biconcave shape -> ↑↑ SA-V Ratio -> ↑↑ O 2 and CO 2 diffusion in and out of cell 4) Flexible -> Turns bell-shaped to pass through narrow capillaries -> Ensures O 2 can be delivered to every tissue in the body How are muscle cells adapted to their functions? 1) Many mitochondria -> ↑↑ rate of aerobic respiration -> Release large amounts of energy for contraction of muscle cells 2) Many nuclei -> ↑↑ protein synthesis 3) Stores glycogen -> Converted to glucose for immediate energy supply How are root hair cells adapted to their function? 1) Elongated shape -> ↑↑ SA-V ratio -> ↑↑ cell membrane surface -> ↑↑ Water and mineral salts uptake 2) Numerous mitochondria -> release energy for active transport of mineral salts and ions 3) Thin cell wall -> Allow substances to move across it quickly

Define diffusion and osmosis Diffusion is the net movement of substances down a concentration gradient. Osmosis is the net movement of water molecules down a WP gradient through a partially permeable membrane. **** Continues until concentration / WP in both regions is the same What is the role of diffusion? (in nutrient uptake and gaseous exchange in both humans and animals) Plant (gas exchange) Diffusion of carbon dioxide into cell through diffusion through the cell membrane and diffusion of oxygen out of the cell through diffusion in the cell membrane Animals Nutrients, water and oxygen enter by diffusion through the cell membrane and metabolic waste substances like carbon dioxide are removed from the cell via diffusion in the cell membrane. 4 factors that affect rate of diffusion 1) Surface area-to-volume ratio 2) Diffusion distance (less time to move through shorter distances) 3) Concentration gradient 4) Temperature

Investigate and describe the effect of osmosis on plants and animal tissues Animal cells : Crenation -> Cell ↓ in size, membrane forms little spikes as the cell shrinks and dehydrates -> cell death Haemolysis -> Cell expands, bursts and dies (reason: no cell wall) Plant cells: Plasmolysis -> water molecules diffuse out of cell sap via osmosis -> decreases in size, becomes flaccid -> cytoplasm and cell membrane shrink away from the cell wall Turgor Pressure -> water molecules diffuse into cell sap via osmosis -> expands -> cell wall prevents overexpansion of cell membrane by exerting an opposing pressure -> fully turgid -> prevents further water entry Importance of turgor pressure 1) Supports the shape of soft tissues in plants 2) Keeps herbaceous plants firm and upright 3) Regulates opening and closing of stomata ( turgid -> open ) Define WP Measure of tendency of water to move from one place to another Define active transport It is the diffusion of substances against a concentration gradient. It uses energy released from aerobic respiration in the mitochondria. 2 examples of active transport 1) Uptake of mineral salts and ions in the root hair cells 2) Uptake of glucose by cells in the villi

Proportion of H and O in carbs and fats Carbohydrates -> Hydrogen and oxygen in fixed ratio of 2 to 1 Fats -> NOT a fixed ratio -> Usually has much LESS OXYGEN than hydrogen Main role of carbohydrates 1) Substrate of respiration -> Provides immediate source of energy for cell activities 2) Converted to amino acids and fats 3) Forms supporting structures (eg. cell walls) Main role of proteins 1 mark answer: Growth and repair of cells - Synthesis of new cytoplasm for growth and repair of worn out cells - Synthesis of enzymes and some hormones - Formation of antibodies to combat disease Main role of fats 1) Insulating material that prevents excessive heat loss 2) Source of long term energy storage due to higher energy value 3) Solvent for fat soluble vitamins and hormones 4) Reduces water loss from the skin surface

Important notes for food tests Reducing sugar -> equal volume, boiling water bath for 2-3 min Protein -> equal volume, shake, let it stand ** Ethanol emulsion Liquid food solution -> add it dropwise to ethanol solution Solid food -> Crush -> add ethanol -> decant -> add that to water Why is glycogen and starch suitable for storage? (4m) 1) Insoluble in water -> Do not change WP of cells 2) Large molecules -> Cannot diffuse through cell membrane -> Not lost from cell 3) Easily broken down to glucose (eg. for tissue respiration) 4) Compact shape -> Occupy less shape than individual glucose molecules Explain the mode of action of an enzyme 1) Specific enzyme has specific three dimensional shape with a depression called the active site 2) Only substrate with 3-D shape complementary to active site can fit, forming an enzyme-substrate complex 3) Enzyme is the lock and substrate is like a