1. Enzymes

2. Enzymes-definition  Act as catalysts, lowering activation energy needed for reactions-speed up reaction.  Substrate binds to enzyme’s active site- lock and key.

3. Enzymes Speed Biochemical Reactions Enzymes are biological catalysts – substances that speed a reaction without being altered in the reaction. Most enzymes are proteins, some are RNA. Enzymes are essential for life. Model of the surface of an enzyme.

4. Enzymes Lower a Reaction’s Activation Energy

5. Enzyme Action

6. The Fit Between Enzyme and Substrate is Critical and Precise Hexokinase, an enzyme (blue), binding its substrate, glucose (yellow).

7. The active site of an enzyme is where substrate is bound. Many Enzymes Work by Altering the Shape of Their Substrates

8. The synthesis of biological molecules often requires many enzyme- catalyzed steps. The entire set of steps is a metabolic pathway. Metabolic Pathways

9. Enzyme Activity is Often Regulated Feedback inhibition - a common form of enzyme regulation in which the product inhibits the enzyme.