Enzymes

1. 16th October Enzymes Learning objective: to examine what enzymes are and describe how they work.

2. What are they? Enzymes 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 Specific Properties

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

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

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

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 + H2O Glucose + Fructose + + Substrates Products

19. Energy Progress of reaction

20. Energy Substrates Progress of reaction

21. Energy Substrates Products Progress of reaction

22. High energy intermediate Energy Substrates Products Progress of reaction

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

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

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

26. Questions Read page 57-60 • 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.

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