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B4 The Processes of Life Year 11 Revision Cells • All living things made up of cells • MRS GREN • Movement, Reproduction, Sense, Growth, Respiration, Excretion, Nutrition • All reactions in organisms catalysed by enzymes Making Enzymes • Fermenters used to grow bacteria so their enzymes can be harvested. • Contain a nutrient solution • Conditions such as pH, temperature and oxygen levels carefully controlled for optimum values. • Food, textiles industries and biological washing powders Enzymes • Chemical reactions in cells rely on catalysts • Proteins, made up of long chains of amino acids which fold into different shapes • Sequence of amino acids determined by instructions in a gene Lock and Key Model • Some enzymes break down larger molecules into smaller ones, others join molecules together • Molecules must fit into enzyme’s active site Why do we need them? • At 37oC, chemical reactions would happen too slowly to keep you alive • If you increased the temperature, you would damage cells, would need more food to fuel respiration • 80% energy keeps body warm Temperature • At low temps, enzyme reactions increase if the temp is increased • Above certain temperatures, enzyme becomes denatured • Active site shape changed, no longer works • All enzymes have an optimum temperature pH • Proteins can also be damaged by acids and alkalis. • Shape will change is bonds are affected • Substrate no longer able to fit – denatured • Every enzyme has an optimum pH Graphs Examples of Enzymes Enzyme What it does Optimum pH Salivary amylase Breaks down starch to sugar (maltose) Breaks down proteins into short chains of amino acids 4.8 Breaks down hydrogen peroxide into water and oxygen 7.6 Pepsin Catalase 2.0 Photosynthesis • Capturing energy from sunlight, used to make molecules for growth – sugars, starch, enzymes and chlorophyll. • These molecules feed others in the food chain Equation • light • 6CO2 + 6H2O C6H12O6 + 6O2 • chlorophyll • Glucose is made up of CHO so is a carbohydrate • Photosynthesis takes place in chloroplasts. Contain chlorophyll which absorbs light and uses the energy to start photosynthesis • Energy from light splits water molecules into H and O atoms. The H is combined with CO2 from the air to make glucose. O is released as a waste product • Glucose and Starch • Glucose can be converted into starch for storage or cellulose to make new cell walls. Both are polymers of glucose • Glucose can also be built up into fats, proteins and chlorophyll • Glucose molecules are broken down by respiration, releasing energy to power chemical reactions in cells Diffusion • Molecules of liquids and gases move around randomly, collide with each other and spread out. • The y move from areas of high to low concentration • Passive process Stomata • Underside of leaf contains thousands of tiny holes • Allow carbon dioxide in and oxygen out Osmosis • Special type of diffusion • Move water molecules in and out of cells across a partially permeable membrane • Water moves from area of high concentration to area of low concentration of water molecules • Drives uptake of water • Lack of water - wilting Storage • Glucose made by photosynthesis • Glucose transported from leaves together cells where is stored until it is needed for respiration. Water would move to this area unless stored as starch • Insoluble starch grains Need Nitrogen! • Proteins are long chains of amino acids • Nitrogen needs to be combined with carbon, hydrogen and oxygen from glucose made in photosynthesis • Absorbed from soil as nitrate ions • Absorbed by root hair cells What else do plants need? • Magnesium to make chlorophyll • Phosphates to make DNA • Proteins are needed to build cells and make enzymes, so nitrates are needed in the highest quantities • Fertilisers contain minerals such as phosphates and nitrates Active Transport • Nitrate ions are at a higher concentration inside the root cells, compared to the surrounding soil • Diffusion should move ions out into soil. • Plants use active transport to overcome this • Cells use energy from respiration to transport molecules across the membrane Yields • The amount of product a farmer has to sell • Limiting factors of photosynthesis – temperature, light intensity, carbon dioxide, water and chlorophyll • Stomata may close to conserve water, but stops carbon dioxide entering the leaf Habitats • Plants need different amounts of light, water and minerals. • Factors such as soil pH, temperature, light intensity and the availability of water can be measured. • Samples are taken to get a picture of what the habitat is like Measurements • Quadrats (identification keys; percentage growth) • Random (removes bias) • Transect (how species change across landscapes) • Light meters Aerobic Respiration • Cells need constant supply of energy for chemical reactions • Glucose from food reacts with oxygen • Reactions release energy from the glucose • C6H12O6 + 6O2 6CO2 + 6H20 (energy) Where does it occur? • Mitochondria – contains the enzymes for aerobic respiration • Energy made used to make polymers – starch, cellulose, proteins, fats and oils Anaerobic Respiration • Short bursts of intense energy • Doesn’t use oxygen • • • • • Glucose lactic acid (+ energy) Releases less energy Lactic acid is toxic Parts of plants; seeds; micro-organisms Useful anaerobic respiration • Glucose Ethanol + Carbon Dioxide (energy) • Bacteria and yeast can be used in bread, cheese, yoghurts, alcoholic drinks and vinegar. Yeast and Bacteria Products • Bioethanol – vehicle engines (made from sugars in plant material such as beet, maize and wheat) • Fermentation – yeast convert sugars Biofuels • Land may be used for growing fuel instead of food • Forests may be cut down • New research using algae hopefully will end the need to use food crops Biogas • From animal waste or manure • Bacteria break down the manure and produce methane gas • Made in biodigester