enzymes

• models of enzyme action:

  lock and key model, induced fit model
• lock and key model:

  • active site and substrate are complementary in shape forming an enzyme-substrate complex
• induced fit model:

  • once the substrate binds, the active site slightly changes shape so the substrate is tightly fit with the enzyme
• factors affecting enzyme action:

  • temperature
  • pH
  • inhibitors (competitive & competitive)
  • enzyme/substrate conc.
• effect of temperature when its low:

  • not enough kinetic energy for successful collisions
• effect of temperature when its high:

  • enzymes denature as bonds are broken
  • active site changes shape, no longer complementary
• effect of pH when its low:

  • enzymes denature as theres too many H+ ions that interfere with the charges of the active site and the bonds break
• effect of pH when its high

  • enzymes denature as theres too many OH- ions that interfere with the charges of the active site and the bonds break
• effect of competitive inhibitors:

  • inhibitor consists of the same shape of the substrate so it binds to the active site preventing the substrate to binds, no enzyme-substrate complex is formed
• effect of non-competitive inhibitors:

  • binds to the allosteric side (away from the active site) , causes the tertiary structure to change so substrate can no longer bind
• effect of enzyme/substrate conc when its low

  • reaction is slower so less collisions occur
• effect of enzyme/substrate conc when its high

  • insufficent number of enzymes
  • becomes all saturated as all active sites are in use