Enzyme Activity and Reaction Rates

Key Factors Affecting Enzyme Rates

1. Substrate Concentration

   • At low concentrations, many enzymes are inactive due to lack of substrates.
   • At high concentrations, enzymes are saturated, and extra substrates wait for free enzymes.
   • Enzyme activity plateaus as substrate concentration increases.

2. Temperature

   • Enzymes are most active within an optimal temperature range.
   • Low temperatures result in fewer enzyme-substrate interactions due to low kinetic energy.
   • Increasing temperature increases interactions until enzymes denature at high temperatures, decreasing activity.

3. pH Level

   • Enzymes operate best within a specific pH range.
   • pH affects the enzyme's secondary and tertiary structures by altering ionizable side chains and prosthetic groups.
   • Incorrect pH can break bonds holding enzyme structures, affecting the active site and activity.

Cellular Control on Enzymatic Activity

• Cells can regulate enzyme activity through post-translational modifications like phosphorylation and glycosylation.
• Different enzymes are produced in different organs and managed for specific cellular functions.
• Example: Digestive enzymes in the stomach are not found in the brain.

Modulators of Enzymatic Activity

• Activators: Increase enzymatic activity.
• Inhibitors: Decrease enzymatic activity, interacting reversibly or irreversibly.
  • Reversible Inhibitors
    • Competitive: Compete with substrates for the active site.
    • Non-Competitive: Bind to allosteric sites on free or substrate-bound enzymes, altering enzyme activity.
    • Uncompetitive: Bind only to enzyme-substrate complexes, preventing product release and reducing activity.

Conclusion

• Enzyme activity is a finely-tuned process influenced by several factors, including substrate concentration, temperature, and pH.
• Cells further modulate enzyme functions through various mechanisms to meet metabolic needs.