1.8 - Factors affecting enzyme action

• 5 main factors that can affect enzyme action ?

  Temperature, pH, enzyme concentration, substrate concentration, con of competitive and non-competitive inhibitors
• What’s the pH of a solution ?


  A measure of its hydrogen ion concentration
• What’s an enzymes optimum pH ?


  The pH at which it works fastest
• How to calculate the pH of a solution ?


  -log10(H+)
• What pH is a solution with a H+ ion concentration of 1x10^-9


  pH 9
• What 2 ways can changing pH reduce enzyme activity ?

  Can alter the charges on amino acids that make up the active site so no enzyme-substrate complexes can form, or the H+ ions can interrupt the bonding in the active site causing it to change shape
• What affect does a lower pH have compared to a higher one ?

  Lower pH is more acidic so has a higher concentration of H+ ions, so more bonds are interrupted
• Are pH fluctuations usually small ?


  Yes, more likely to reduce an enzymes activity rather than denature it
• What effect does a rise in temp have on an enzyme reaction ?


  Increase KE of molecules, move around more rapidly and collide more frequently, results in more successful collisions so more enzyme-substrate complexes forming so rate increases
• What can too high temperatures do ?

  Can begin to break hydrogen bonds and other bonds in the enzyme, the enzyme and its active site changes shape so it’s no longer complementary
• What happens before the enzyme has fully denatured due to high temperatures ?


  The substrate will fit less easily into the enzyme so the rate of the reaction will just slow
• What does it mean if an enzyme has fully denatured ?


  The enzyme is so disrupted that it stops working all together, denaturation is a permanent change and the enzyme cannot function again
• What happens if the enzyme concentration increase when the substrate is in excess ?


  The rate of the reaction will increase proportionally
• What happens if the substrate is a limiting factor and the enzyme concentration increases ?


  Will have no effect on the rate of reaction, the graph will level off as there’s no change in rate
• What happens if the substrate concentration is increased ?


  The rate of reaction will increase proportionally to the substrate concentration because as there’s more substrate more enzyme-substrate complexes form until all active sites are full (the rate is at maximum Vmax)
• What happens is the substrate is added in excess ?


  The rate will level off