1. Enzyme s

2. The Need for Enzymes Many important exergonic rxns require more E A than cells can provide Other rxns require specific collision angles, slowing rxn rate

3. Lowering E A Enzymes lower E A to a level that’s safe and attainable

4. Catalysis 1. Enzyme binds substrate(s) at active site 2. Enzyme changes shape to separate or combine molecules 3. Enzyme reverts to original shape

5. Specificity Enzymes are substrate specific –3-D shape makes enzymes specialized –An enzyme binds substrate(s) at active site ActiveSite

6. Rate of Rxns As [substrate] ↑, Rate ↑ [substrate] Rate EnzymeSaturation

7. Rate of Rxns Temperature –As temp ↑, collisions are more frequent (rate ↑) –At high temps, h-bonds break, changing enzyme shape (rate ↓) Temperature Rate Denaturation Optimal Range

8. Rate of Rxns

10. Enzyme Regulation Molecules bind to enzymes to alter their functions Activation –Cofactors Nonprotein helpers Coenzymes – Organic cofactors –Cooperativity Substrate = Activator

11. Enzyme Regulation Active Site Allosteric Site Inhibition –Competitive Blocks active site –Noncompetitive Changes enzyme shape Changes enzyme shape

12. Enzyme Regulation Feedback Inhibition –Product inhibits enzyme