Enzymes

• Competitive inhibition:

  • inhibitors bear similar conformation and charge to the substrate, competes for active sites
  • reduces the availability of active sites to substrates, reduces rate of reaction
  • can be overcome by by increasing substrate concentration, increases chance of substrate binding instead of inhibitor, can reach same maximum rate of reaction
• Non-competitive inhibition

  • inhibitor binds to site other than the active site and alters the 3D conformation of enzyme active site, no longer complementary in shape and charge to substrate
  • cannot be overcome
• Binding of an allosteric inhibitor:

  • Binding of inhibitor to the allosteric site stabilised the inactive conformation, 3D conformation and charge is changed
  • Active site is no longer complementary to substrate, substrate cannot bind
• binding of allosteric activator:

  • stabilised the active conformation , induces conformational change, easier to accept subsequent substrates
  • rate of reaction increases
• end product inhibition:

  • pathway inhibited by binding of end produce to an enzyme that acts early in the pathway
  • prevents cell from wasting resources in producing excess of end product
• Lock and key hypothesis:

  • enzyme is lock, substrate is key
  • substrate fits perfectly in active site of enzyme
• induced fit hypothesis:

  • substrate induces a change in conformation in active site such that the active site is more precise fit for the substrate