Enzyme action

• Importance of enzymes

  • Biological catalysts
  • Globular proteins that interact with substrate molecules - React at faster rates without a harsh environment
• Reactions catalysed by enzymes:

  • Anabolic (Building up) reactions
  • Catabolic (Breaking down)
  • Digestion of food
• Factors affecting reactions:

  • Temp
  • Pressure
  • pH
• Enzymes only increase rate of reaction up to Vmax
• Activation energy - The energy that is supplied for most reactions to start
• Activation energy lowered - Enzymes help molecules collide successfully
• LAK Hypothesis:

  • Active site - Shape that is complementary to the shape of a specific substrate molecules
  • Enzyme-substrate complex - Substrate bound to active site
  • Enzyme-product complex - Substrate react when bound forming products
• LAK hypothesis:

  1. Substrate is held that the right atom-groups are close enough to react
  2. R-groups in active site also interact with substrate - Temporary bonds formed
  3. Strain places on bonds within substrate
• Induced fit hypothesis - Suggests active site of enzyme changes shape slightly as substrate enters
• IF hypothesis:

  1. Initial reaction with enzyme and substrate is weak
  2. Weak interactions quickly induce changes in the enzymes specific 3d tertiary structure strengthening binding
  3. Strain placed on substrate molecule
  4. Bonds within substrate weakened
  5. Activation energy lowered
• Intracellular enzymes - Enzymes that act within a cell
• Example of intracellular enzymes:

  Hydrogen peroxide - Toxic product of metabolic reactions - Catalase breaks HP down to oxygen and water before accumulation
• Extracellular enzymes - Enzymes that are released from cells to break down large nutrients into smaller molecules through digestion outside the cell