Thursday, 17 October 2013

Factors affecting Enzymes


  • Temperature affects the action of enzymes, as higher temperatures increase the rate of reactions as the enzyme and substrate gain kinetic energy, meaning they collide more frequently and successfully.
  • But once the enzyme has passed its optimum temperature, it becomes denatured, as the proteins of the enzyme are broken down by heat, and the active site changes shape and no longer is complementary to the substrate.


  • Most enzymes have evolved to have an optimum pH of 7, or neutral. Some enzymes do however have different optimums, depending on the conditions in which they function, e.g. pepsin in the stomach has a pH of about 2.
  • The closer the pH is to the optimum, the better it will work. But if it is too far either side of the optimum pH, the enzyme can become denatured and the active site could change shape and no longer function

Concentration of enzyme and substrate concentration 

  • Greater concentration causes an increase in the rate of reactions, as there is a greater likelihood of collisions between the enzyme and substrate. 
  • However, the concentration of the other concentration (the one we are keeping constant) starts to become the limiting factor 
  • i.e. when increasing enzyme concentration, the substrate becomes the limiting factor and vice versa