1. ENZYMES

2. Enzymes are Catalysts
Catalytic proteins: change the rate of reactions w/o being consumed
Enzymes speed up reactions by lowering the activation energy
Activation energy (free energy of activation) = the E required to break bonds
Activation E must be reached for reaction to progress

3. What’s going on? Substrate: enzyme reactant
Active site: pocket or groove on enzyme that binds to substrate
Induced fit model
Substrate fits into the enzyme which wraps around it

5. How does it work? Enzymes lower AE by:
Bring together in proper orientation
Physical stress- bending or stretching of chemical bonds
Increased reactivity due to environment (charge, pH, etc. within active site)
Activity of substrate directly w/ enzyme

6. Effects on Enzyme Activity
Temperature pH
Cofactors: inorganic, nonprotein helpers; ex.: zinc, iron, copper
Coenzymes: organic helpers; ex.: vitamins

7. Enzyme Inhibitors Irreversible (covalent); reversible (weak bonds)
Competitive: competes for active site (reversible); mimics the substrate
Noncompetitive: bind to another part of enzyme (allosteric site) altering its conformation (shape)
poisons, toxins, antibiotics

8. Allosteric Regulation
Not all chemical processes occur at the same time
Enzymes can be activated when needed and inhibited when they’re not
Allosteric activators and inhibitors bind to turn the enzyme complex on or off
Cooperativity- substrate must be bound to activate enzyme

9. Feedback Inhibition
End product of reaction binds to allosteric site of enzyme to stop further production
Like a thermostat