#### Understanding the Processes of Life: Cells and Enzymes for Year 11 Revision

1. B4 The Processes of Life Year 11 Revision

2. Cells • All living things made up of cells • MRS GREN • Movement, Reproduction, Sense, Growth, Respiration, Excretion, Nutrition • All reactions in organisms catalysed by enzymes

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. Graphs

10. Examples of Enzymes

11. Photosynthesis • Capturing energy from sunlight, used to make molecules for growth – sugars, starch, enzymes and chlorophyll. • These molecules feed others in the food chain

12. 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

13. 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

14. 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

15. Stomata • Underside of leaf contains thousands of tiny holes • Allow carbon dioxide in and oxygen out

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. Measurements • Quadrats (identification keys; percentage growth) • Random (removes bias) • Transect (how species change across landscapes) • Light meters

24. 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)

25. Where does it occur? • Mitochondria – contains the enzymes for aerobic respiration • Energy made used to make polymers – starch, cellulose, proteins, fats and oils

26. 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

27. Useful anaerobic respiration • Glucose Ethanol + Carbon Dioxide (energy) • Bacteria and yeast can be used in bread, cheese, yoghurts, alcoholic drinks and vinegar.

28. Yeast and Bacteria

29. Products • Bioethanol – vehicle engines (made from sugars in plant material such as beet, maize and wheat) • Fermentation – yeast convert sugars

30. 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

31. Biogas • From animal waste or manure • Bacteria break down the manure and produce methane gas • Made in biodigester