1. ENZYMES NAME: CHEBET MILTON CONTACT: miltonchebs2000@yahoo.commiltonchebs2000@yahoo.com Subject: Biology Topic: Nutrition

2. Learning objectives Define enzymes Classify enzymes Describe the mode of enzyme action (lock and key hypothesis) Do the mouse mischief exercises at the end using the given mice

3. Introduction to Enzymes What are enzymes biological catalysts, protein in nature which speed up and control the rate of chemical reaction in living organisms Classification of enzymes – Intracellular enzymes. – Extracellular enzymes.

4. Enzyme Action Learning objective: to describe different models for enzyme action and to investigate factors which control the rate of an enzyme reaction More free powerpoints at www.worldofteaching.com

5. Lock and Key

6. However certain substances can bind to the enzyme at sites other than the Active site and modify its activity (inhibitors/co-factors) Idea that the enzyme is flexible

7. Induced Fit

8. Enzyme reactions enzyme + substrateenzyme-substrate complex

9. Enzyme reactions enzyme + substrateenzyme-substrate complex E +S ES

10. Enzyme reactions enzyme + product enzyme-substrate complex E +PES enzyme + substrateenzyme-substrate complex E +S ES

11. Enzyme activity How fast an enzyme is working Rate of Reaction

12. Enzyme activity How fast an enzyme is working Rate of Reaction Rate of Reaction = Amount of substrate changed (or amount product formed) in a given period of time.

13. Rate of Reaction Enzyme activity Variable you are looking at

14. Enzyme activity Four Variables

15. Factors affecting Enzyme activity Four Variables Temperature pH Enzyme Concentration Substrate Concentration

16. Rate of Reaction Temperature

17. Rate of Reaction Temperature 0203050104060

18. Rate of Reaction Temperature 0203050104060 40 o C - denatures 5- 40 o C Increase in Activity <5 o C - inactive

19. Effect of heat on enzyme activity If you heat the protein above its optimal temperature bonds break meaning the protein loses it secondary and tertiary structure

20. Effect of heat on enzyme activity Denaturing the protein

21. Effect of heat on enzyme activity Denaturing the protein ACTIVE SITE CHANGES SHAPE SO SUBSTRATE NO LONGER FITS Even if temperature lowered – enzyme can’t regain its correct shape

22. Rate of Reaction pH

23. Rate of Reaction pH 1 342 5 6 789

24. Rate of Reaction pH 1 342 5 6 789 Narrow pH optima

25. Rate of Reaction pH 1 342 5 6 789 Narrow pH optima WHY?

26. Rate of Reaction pH 1 342 5 6 789 Narrow pH optima Disrupt Ionic bonds - Structure Effect charged residues at active site

27. Rate of Reaction Enzyme Concentration

28. Rate of Reaction Enzyme Concentration

29. Rate of Reaction Substrate Concentration

30. Rate of Reaction Substrate Concentration

31. Rate of Reaction Substrate Concentration Active sites full- maximum turnover

32. In this mischief exercise your are required to Highlight a word in the green (right hand) column and drag it into a middle box corresponding