Lecture Notes: Properties of Enzymes

Key Properties of Enzymes

• Catalysis of Biological Reactions: Enzymes speed up the rate of chemical reactions in the body.
• Equilibrium: Enzymes decrease the time needed for a reaction to reach equilibrium but do not change the equilibrium itself.
  • Energy of Products and Reactants: Enzymes do not change the energy levels of products and reactants at equilibrium.

Energy Diagram and Reaction Mechanics

• Elementary Reaction: Example provided with reactants A-B and C, and products B-C and A.
• Gibbs Free Energy Diagram:
  • Y-Axis: Gibbs free energy
  • X-Axis: Reaction progress
  • Exergonic Reaction: Negative ΔG indicating free energy release and spontaneity.
  • Transition State: Highest energy point in the reaction where bonds are partially broken and formed.

Enzyme Effect on Reactions

• Enzymes do not alter the Gibbs free energy of reactants or products.
• Enzymes lower the activation energy by stabilizing the transition state.
• Active Site: Specific region where substrates bind to form enzyme-substrate complex.
• Stabilization: Active site stabilizes partially broken/forming bonds, lowering activation energy and increasing reaction rate.

Maximum Velocity of Enzymes

• Definition: Maximum rate at which enzymes operate when all active sites are filled.
  • Example: 100 enzymes with active sites filled by 100 substrate molecules.
• Enzyme Activity: Increases with substrate concentration until reaching maximum velocity.
  • Graph Representation:
    • Y-Axis: Enzyme activity/velocity
    • X-Axis: Substrate concentration
    • Dashed line represents maximum enzyme velocity.
• Conclusion: Maximum velocity occurs when all active sites are occupied by substrates.

Next Lecture

• Focus on how the active site stabilizes the transition state.
• Exploration of the active site function and substrate binding.