1. Enzymes Learning objective: to examine what enzymes are and describe how they work.

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

3. Enzymes Globular proteins that catalyse chemical reactions in living organisms Properties

4. Enzymes Globular proteins that catalyse chemical reactions in living organisms Properties Specific

5. Enzymes Globular proteins that catalyse chemical reactions in living organisms Properties Specific Increase rate of the reaction

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

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

8. Enzymes Globular proteins that catalyse chemical reactions in living organisms Properties Specific Increase rate of the reaction Unchanged at the end of the reaction Need them Reactions too slow to maintain life Can’t increase temperatures/pressure in cells (fatal)

9. 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.

10. 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.

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

12. How do enzymes work?

13. An Example

14. Sucrose + H 2 O Glucose + Fructose

15. An Example Sucrose + H 2 O Glucose + Fructose Substrates Products

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

17. 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

18. Sucrose + H 2 OGlucose + Fructose + + SubstratesProducts

19. Energy Progress of reaction

20. Energy Progress of reaction Substrates

21. Energy Progress of reaction Substrates Products

22. Energy Progress of reaction Substrates Products High energy intermediate

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

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

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

26. Questions 1.Write a definition for the following:Active Site Substrate Products 2. Explain how the structure of the protein is linked to its ability to act as an enzyme? 3. How does heating a mixture increase the chance that a chemical reaction Will occur? Why can’t this approach be used in cells? 4. Write a paragraph in your own words describing how enzymes act as catalysts by lowering activation energy. Read page 165-66