1. B4 The Processes of Life

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. 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

4. Lock and Key Model
Some enzymes break down larger molecules into smaller ones, others join molecules together
Substrates must fit into enzyme’s active site
Enzyme specificity

5. 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

6. 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

7. 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

8. Graphs

9. Examples of Enzymes Enzyme What it does Optimum pH Salivary amylase
Breaks down starch to sugar (maltose)
4.8
Pepsin
Breaks down proteins into short chains of amino acids
2.0
Catalase
Breaks down hydrogen peroxide into water and oxygen
7.6

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

11. 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

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. Diffusion
Molecules of liquids and gases move around randomly, collide with each other and spread out.
They move from areas of high to low concentration
Passive process – doesn’t use energy

14. 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

15. 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
Passive process

16. 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

17. 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

18. 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

19. Yields The amount of product a farmer has to sell
Limiting factors of photosynthesis – temperature, light intensity, carbon dioxide, water and chlorophyll
Can alter factors to optimise photosynthesis rate

20. 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

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

22. Aerobic Respiration
Cells need constant supply of energy for chemical reactions
Glucose from food reacts with oxygen
Reactions release energy from the glucose
C6H12O6 + 6O CO2 + 6H20 (energy)

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

24. Anaerobic Respiration
Short bursts of intense energy
Doesn’t use oxygen
Occurs in cytoplasm
Glucose lactic acid
(+ energy)
Releases less energy
Lactic acid is toxic
Parts of plants; seeds; micro-organisms

25. Useful anaerobic respiration
In yeast:
Glucose Ethanol + Carbon Dioxide (energy)
In bacteria:
Glucose lactic acid (energy)
Can also use anaerobic respiration of bacteria to produce biogas
Use organic waste which bacteria break down under anaerobic conditions to produce methane gas
Bacteria and yeast can be used in bread, cheese, yoghurts, alcoholic drinks and vinegar.

26. Yeast and Bacteria

27. 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

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