Enzymes

• Define an enzyme

  A protein that acts as a biological catalyst to increase the rate of reaction by lowering the activation energy
• Describe how the shape of the active site is determined.

  It is determined by the position of hydrogen, ionic bonds and disulphide bridges in the tertiary structure
• Describe the induced fit model

  -Active site and substrate are not initially complementary

  -Active site changes shape to fit the substrate

  -This strains bonds in substrate, lowering the activation energy
• Describe a competitive inhibitor

  -The inhibitor has a similar shape to the substrate

  -It is complementary to the active site so binds

  -This blocks the substrate

  -This reduces the rate of enzyme-substrate complexes

  • It can be overcome by increasing the substrate concentration
• Describe a non-competitive inhibitor

  -The inhibitor binds to the allosteric site

  -This alters the hydrogen and ionic bonds, changing the active site shape

  -The active site is no longer complementary to the substrate