HOW ENZYMES FUNCTION

1. HOW ENZYMES FUNCTION

2. 5.14 Activation Energy • Activation energy (EA): Energy available to break bonds and form new ones • Although there is a lot of potential energy in biological molecules, such as carbohydrates, it is not released spontaneously

3. Reaction without enzyme EA without enzyme EA with enzyme Reactants Energy Net change in energy (the same) Reaction with enzyme Products Progress of the reaction

4. 5.14 Enzymes- Purpose • Purpose: to lower the Energy of Activation Ea • Enzymes are proteins and specific in shape • If shape changes the enzyme will not function b/c substrate is specific for active site

5. 5.15 Enzymes- Specific Structure • Enzymes have unique three-dimensional shapes • As a result of its shape, the enzyme has an active site where the enzyme interacts with the enzyme’s substrate • Consequently, the substrate’s chemistry is altered to form the product of the enzyme reaction

6. Substrate Active site Enzyme Enzyme-substrate complex

7. Enzyme available with empty active site 1 Active site Enzyme (sucrase)

8. Enzyme available with empty active site 1 Active site Substrate (sucrose) Substrate binds to enzyme with induced fit 2 Enzyme (sucrase)

9. Enzyme available with empty active site 1 Active site Substrate (sucrose) Substrate binds to enzyme with induced fit 2 Enzyme (sucrase) Substrate is converted to products 3

10. Enzyme available with empty active site 1 Active site Substrate (sucrose) Substrate binds to enzyme with induced fit 2 Enzyme (sucrase) Glucose Fructose Products are released 4 Substrate is converted to products 3

11. 5.15 Enzymes- Environmental Conditions • Enzymes require certain environmental conditions • Temperature is very important • human enzymes function best at 37ºC, or body temperature • High temperature will denature (change the shape of) human enzymes • Enzymes also require a pH • around neutral for best results

12. 5.15 Enzymes- Environmental Conditions

13. 5.15 Enzymes- Cofactors • Some enzymes require non-protein helpers • Cofactors are inorganic, such as zinc, iron, or copper • Coenzymes are organic molecules and are often vitamins

14. 5.16 Enzymes- Inhibitors • Competitive inhibitors bind to the active site of an enzyme, competing with the substrate • Noncompetitive inhibitors bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective • Examples of inhibitors include toxins, poisons, pesticides, and antibiotics • BOTH type inhibit enzyme activity!

15. Substrate Active site Enzyme Normal binding of substrate Competitive inhibitor Noncompetitive inhibitor Enzyme inhibition

16. 5.16 Enzyme Inhibitors • Is inhibition reversible?

17. Covalent bonds form between Enzyme and Inhibitor!

18. 5.16 Enzyme Inhibitors • Enzyme inhibitors are important in regulating cell metabolism • Feedback inhibition: when the product of a reaction can serve as an inhibitor of one enzyme in the same reaction • The more product formed, the greater the inhibition = regulation of the reaction

19. 5.16 Enzyme Inhibitors • What would happen if they did not produce feedback inhibitors??

20. 5.16 Enzyme Inhibitors • There would be chaos in the cell! • Too many chemical reactions!