Enzymes

1. What are they? Enzymes Why do we need them? Name some examples ?

2. Enzymes Globular proteins that catalyse chemical reactions in living organisms

3. Enzymes Globular proteins that catalyse chemical reactions in living organisms Properties Specific Increase rate of the reaction Unchanged at the end of the reaction

4. Enzymes Need them because... Reactions too slow to maintain life Can’t increase temperatures/pressure in cells (fatal)

5. Enzymes Are Proteins The enzyme binds to the substrates by its active site The active site is a pocket formed by the folding of the protein where the substrates bind.

6. Enzymes Are Proteins The enzyme binds to the substrates by its active site The active site is a pocket formed by the folding of the protein where the substrates bind.

7. Active site The active site involves a small number of key residues that actually bind thesubstrates The rest of the protein structure is needed to maintain these residues in position

8. Lock and Key

9. Enzyme reactions enzyme + substrate enzyme-substrate complex

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

11. Enzyme reactions enzyme + substrate enzyme-substrate complex E +S ES enzyme + product enzyme-substrate complex ES E +P

12. How do enzymes work?

13. An Example

14. An Example Sucrose + H2O Glucose + Fructose

15. An Example Substrates Sucrose + H2O Glucose + Fructose Products

16. For a reaction to occur the sucrose and water would have to collide with enough energy to break and form bonds This is the activation energy

17. Sucrose + H2O Glucose + Fructose + + Substrates Products

18. Energy Progress of reaction

19. Energy Substrates Progress of reaction

20. Energy Substrates Products Progress of reaction

21. High energy intermediate Energy Substrates Products Progress of reaction

22. High energy intermediate Activation energy Energy Substrates Products Progress of reaction

23. The minimum amount of energy needed to start the reaction, leading to the formation of a high energy intermediate = The Activation energy

24. High energy intermediate Activation energy Enzymes reduce the height of the energy barrier Energy Substrates Products Progress of reaction

25. 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.

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

27. Temperature 5- 40oC Increase in Activity 40oC - denatures Rate of Reaction 0 10 20 30 40 50 60 <5oC - inactive

28. 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

29. 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

30. pH Narrow pH optima Disrupt Ionic bonds - Structure Rate of Reaction Effect charged residues at active site 1 5 7 8 9 2 3 4 6

31. Enzyme Concentration Rate of Reaction Enzyme Concentration

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

33. What is digestion? Breaking down large, insoluble molecules into smaller, soluble molecules that can be absorbed through the wall of the small intestine What breaks down the large molecules? Digestive enzymes made by specialised cells inside glands

34. Some enzymes are... Amylase Carbohydrates Protease Proteins Lipase Lipids

35. The enzymes break down... Carbohydrates Simple sugars Proteins Amino acids Lipids (fats) Fatty acids + glycerol Digestion animation

36. What does bile do? • Bile is produced in the liver and stored in the gall bladder. • The enzymes in the small intestine need an alkaline pH to work best, so bile passes into the small intestine and neutralizes acid from the stomach. • Bile also emulsifies fat droplets to increase their surface area

37. Why do you think there is acid in the stomach? • Kills bacteria in food – protects us • Denatures proteins – makes digestion easier • Activates stomach enzymes – these only work in acidic conditions • Ever wondered why PEPSIN (stomach enzyme) doesn’t digest our own stomach? • Pepsin is inactive when first made and is only activated by HCL to start digesting proteins.

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