Rate: Inhibitor Concentration (Cambridge (CIE) A Level Biology): Revision Note

Rate: inhibitor concentration

• There are two types of inhibitors:

  • Competitive inhibitors have a similar shape to that of the substrate molecules

    • This means they compete with the substrate for the active site

  • Non-competitive inhibitors bind to the enzyme at an alternative site, altering the shape of the active site

    • This prevents the substrate from binding to it

• Both types of inhibitors slow down or stop enzyme activity

• Increasing the concentration of an inhibitor reduces the rate of reaction

  • Eventually, if inhibitor concentration continues to be increased, the reaction will stop completely

• For competitive inhibitors, countering the increase in inhibitor concentration by increasing the substrate concentration can increase the rate of reaction once more

  • This is because more substrate molecules mean they are more likely to collide with enzymes and form enzyme-substrate complexes before the inhibitor can bind

• For non-competitive inhibitors, increasing the substrate concentration cannot increase the rate of reaction once more

  • This is because the shape of the active site of the enzyme remains changed, so enzyme-substrate complexes are still unable to form despite the high number of substrate molecules present