1. Enzyme Action Learning objective: to describe different models for enzyme action and to investigate factors which control the rate of an enzyme reaction 18 th October

2. Lock and Key Active Site

3. YES ….this is an enzyme molecule --- VERY COMPLEX BUT …..it only is shaped for ONE SUBSTRATE enzyme animation

4. Exceptions to Lock and Key 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

5. Induced Fit

6. Enzyme reactions enzyme + substrateenzyme-substrate complex

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

8. Enzyme reactions enzyme + product enzyme-substrate complex E +PES enzyme + substrateenzyme-substrate complex E +S ES Catabolic – breaking apart

9. THERE ARE ALSO ENZYMES that BUILD substrates as well as take substrates apart as you have seen … Anabolic - building up / combining

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

11. 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.

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

13. Enzyme activity Four Variables

14. Enzyme activity Four Variables Temperature pH Enzyme Concentration Substrate Concentration

15. Rate of Reaction Temperature

16. Rate of Reaction Temperature 0203050104060

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

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

19. Effect of heat on enzyme activty Denaturing the protein

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

21. Rate of Reaction pH

22. Rate of Reaction pH 1 342 5 6 789

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

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

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

26. Rate of Reaction Enzyme Concentration

27. Rate of Reaction Enzyme Concentration

28. Rate of Reaction Substrate Concentration

29. Rate of Reaction Substrate Concentration

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