Factors affecting enzymes

• What are the 4 factors affecting enzyme action?


  Temperature, pH, substrate concentration and enzyme concentration
• What happens to the rate of reaction when temperature is increased?

  -rate of reaction increases (up to a certain temperature)

  -the enzyme and substrate have greater kinetic energy

  -this results in more frequent successful collisions (that have the required activation energy)

  -more enzyme-substrate complexes form
• When happens to the rate when temperature is too high?

  -as temperature increases too much, the rate decreases

  -this is because the enzyme becomes denatured

  -at higher temperatures, atoms vibrate. This leads to bonds breaking (e.g. hydrogen bonds) in the active site

  -this means that the shape of the active site is no longer complimentary to the shape of the substrate

  -fewer/no enzyme-substrate complexes form
• Enzymes function over a narrow range of pH. Slight deviations from the optimum cause reversible changes to occur, but larger deviations from the optimum pH causes the enzyme to be denatured. It is the presence of H+ ions (acids) and OH- ions (alkalis) that disrupt the bonding in the active site.
• What happens to the rate of reaction as substrate concentration increases?

  -as substrate concentration increases, rate increases

  -more enzyme-substrate complexes form
• What happens to the rate of reaction as substrate concentration increases if enzymes are limiting?

  -if enzymes are limited, all active sites are occupied

  -so even though there are plenty of substrate molecules, no more enzyme substrate complexes can form
• What happens to the rate of reaction as enzyme concentration increases if the substrate is not limiting?

  -as enzyme concentration increases, rate increases

  -the greater the number of active sites available, the greater the number of enzyme-substrate complexes that will form