Revision lesson on enzymes

1. Revision lesson on enzymes AQA Unit 2 Additional Biology

2. What are enzymes and what do they do? Enzymes are- • Protein molecules (made up of amino acids) • Biological catalysts (Increase the speed of chemical reactions) • Specific (Each one catalyses one particular reaction) • Reusable (Can be used again and again) • Affected by temperature and pH. • Found in animals, plants and microorganisms.

3. 2 main types of enzymes • Catabolic enzymes which (break down) large molecules into smaller molecules e.g. digestion of starch by the enzyme amylase into glucose. • Anabolic enzymes which (build up) small molecules to form larger molecules e.g. production of glucose during photosynthesis from carbon dioxide, water and light.

4. Enzymes and activation energy • Chemical reactions take place when particles collide with enough energy. • The minimum amount of energy required is called the activation energy. • Enzymes lower the amount of activation energy required, so the reaction can proceed at a greater rate.

5. Structure of an enzyme molecule • Enzymes are proteins made up on long chains of amino acids. • These long chains fold to produce a special shape which is vital for the enzyme‘s function. Active Site

6. How enzymes work

7. Step-by-step • Shape of the enzyme’s active site is complimentary to the shape of one particular substrate. • The two bind together to form an enzyme-substrate complex. • The reaction between them take place rapidly. • The products are released from the enzyme’s active site. • Complete Qu 1-8 on your worksheet.

8. Factors affecting enzyme action - Temperature • Enzymes work faster as the temperature increases up to 40oC, but are eventually denatured at about 60oC. • This is because the shape of the active site is lost.

9. Factors affecting enzyme action – pH • Each enzyme works best at a particular pH. This is known as the optimum pH. • Extremes of pH will cause the active site to denature. Answer Qu 8- 11 on your worksheet

10. Enzymes in digestion • Enzymes break down large insoluble food molecules into smaller, soluble ones which can be absorbed through the small intestine wall to enter the bloodstream. • Different parts of the digestive tract have different pH conditions to enable different enzymes to work.

11. The main groups of digestive enzymes • Lipase enzymes digest fatty substrates. • Protease enzymes digest protein substrates. • Carbohydrase enzymes digest carbohydrate substrates.

13. The action of bile • It’s produced by the liver and is stored in the gall bladder which, squirts it into the small intestine. • It’s alkaline to neutralise acidic chyme coming from stomach. • It emulsifies fats to break them into smaller droplets which increases the surface area for lipase enzymes to work.

14. Commercial use of enzymes Complete Qu 12- 17on worksheet.