3. Control METABOLISM Metabolic reactions can be controlled and sped up by enzymes that lower the activation energy needed. –metabolic reactions would be too slow to occur if no enzymes were present!

4. Properties of Enzymes 1.Proteins 2.Catalysts 3.Reusable 4.Substrate specific 5.Sensitive to temperature 6.Sensitive to pH

5. Enzymes remain unchanged! Enzymes are not used up Reaction end’s when there is NO more substrate Synthesis or Decomposition reactions Before After

6. substrate enzyme active site substrate Mechanism of enzyme action Each enzyme has an active site Active site is the place where the substrate binds with the enzyme

7. enzyme Action of enzyme in synthesis substrate enzyme- substrate complex product

8. enzyme Action of enzyme in decomposition substrate enzyme- substrate complex product

9. Lock and key hypothesis Enzyme Substrate

10. Lock and key hypothesis SHAPES DON’T MATCH

11. Lock & Key Model One enzyme for every substrate for every substrate unique fit Enzyme Substrate

12. Enzymes are temperature dependent…... Most work best at body temperature 37oC Denatured at high temperatures Inactive at low temperature Temperature o C

13. Effect of pH on enzyme activity Optimum pH : the pH value at which the enzyme has the highest activity (fastest rate of reaction) Different enzymes may have different optimum pH’s pH of substrate higher or lower than optimum pH, it can denature the enzyme making it ineffective.

14. Enzyme Lab Enzyme: catalase Source: liver, potato, apple etc Substrate: H 2 O 2 Hydrogen peroxide is toxic in cells 2H 2 O 2 +catalase  2 H 2 O + O 2  2 H 2 O + O 2 Enzymes end in ‘ase’

15. TA TA!