Enzymes and Factors Affecting Their Activity

Enzymes

• Definition: Biological catalysts that speed up the rate of biological reactions.

• Composition: Enzymes are proteins with a complex three-dimensional shape.

Active Site and Substrate

• Substrate: The molecule that the enzyme acts on.

• Active Site: The specific region of the enzyme where the substrate binds.

• Complementarity: The shape of the substrate must be complementary to the enzyme's active site.

• Enzyme-Substrate Complex: Formed when the substrate binds to the enzyme's active site.

  • Lock and Key Hypothesis: Classical model where the active site is seen as a rigid structure fitting a specific substrate.

  • Induced Fit Hypothesis: Modern view where the active site changes shape to better fit the substrate upon binding.

Factors Affecting Enzyme Activity

• Temperature: Increasing temperature enhances reaction rates.

  • Every 10 degrees Celsius increase doubles the kinetic energy and reaction rate.

  • Optimum Temperature: When reached, can lead to denaturation of enzymes if exceeded.

• pH Level: Changes in pH can influence enzyme function.

• Catalysts: Adding more catalysts can increase the speed of reactions.

• Kinetic Energy: Higher temperature increases the kinetic energy of molecules, causing more frequent successful collisions between active sites and substrates.

Denaturation

• Definition: Loss of enzyme specificity and functionality due to extreme conditions (e.g., high temperature, extreme pH).

• Effect: Denatured enzymes can no longer bind substrates effectively, ceasing their catalytic action.