Competitive inhibition

• what is competitive inhibition?

  reduction of the rate of an enzyme-controlled reaction by a molecule or ion that has a complimentary shape to the active site, similar to the substrate, and binds to the active site, preventing the substrate from binding
• whats an example of competitive inhibition?

  • in the mitochondrial matrix, a reaction in the Krebs cycle is catalysed by the enzyme succinic dehydrogenase
  • malonic acid has a similar shape to succinic acid so they compete for the active site of succinic dehydrogenase
• what happens when you increase the concentration of the substrate in the competitive inhibition of malonic and succinic acid?

  increasing the concentration of the substrate (succinic acid) reduces the effect of the inhibitor because the more substrate molecules present, the greater the chance of binding to active sites, leaving fewer available fr the inhibitor
• what happens if you increase the inhibitor concentration in the competitive inhibition of malonic and succinic acid?

  if the inhibitor concentration increases, it binds to more active sites and so the reaction rate is slower
• what is this a diagram of?

  competitive inhibition

  
• when does end-product inhibition occur?

  when a product of a series of reactions inhibits an enzyme that acts earlier in the series so it slows down the whole sequence of reactions - this is an important way of controlling cell metabolism
• is the competitive inhibitor permanently or temporarily bound to the active site?

  temporarily
• what happens when a competitive inhibitor leaves the active site?

  another molecule can take its place - this can be a substrate or inhibitor, depending on their relative concentrations
• how is the rate of reaction affected by the concentration of competitive inhibitor?

  as the concentration of competitive inhibitor increases, the rate of reaction decreases
• what does this graph show?

  the effect of a non-competitive inhibitor, competitive inhibitor and no inhibitor

  
• if a competitive inhibitor is reversible, what can it do?

  it can bind to and unbind from the active site