factors affecting enzymes

• temperature

  -as temp increases the rate of activity increases until it reaches it's optimum temp then it decreases.

  -particles move faster+ more frequent, more kinetic energy= higher rate.

  -as temp increases past optimum temp the enzymes denature- the bonds holding the proteins tertiary structure together break so the enzymes active site changes shape so the substrate can no longer fit and the enzyme can no longer function.
• -temperature coefficient Q10 of a reaction= measure of how much the rate of reaction increases with a 10 degree rise in temp.

  • rate of reaction doubles with a 10 degree temp increase.
• Enzyme/substrate concentration 


  -increased concentration= increased number of substrate particles so a higher collision rate with active site of enzymes, so rate increases.

  -it increases up to it's vmax, all of the active sites are occupied by substrate particles, no more enzyme-substrate complexes can be formed.

  -Only way to increase rate is to add more enzymes/substrates or increase the temperature.
• pH 


  -a change in pH= change in hydrogen ion concentration.

  -active site will only be right shape at certain hydrogen ion concentration= optimum pH.

  -when pH becomes more acidic or alkaline, the structure/active site is altered.

  -renaturation= if pH returns to optimum, the protein will resume it's ordinary shape.
• pH- continued

  -when pH is altered more significantly, the structure of the enzyme is irreversibly altered. Active site is no longer complementary, enzyme is denatured= reduces rate of reaction.

  -more hydrogen ions present= less of R-groups are able to interact- leads to bonds breaking and shape of enzymes changing.
• inhibitors 


  = a molecule that prevents enzymes carrying out their normal function.
• competitive inhibition 


  =a molecule or part of a molecule that has a similar shape to the substrate, and can fit into the active site.

  • this blocks the substrate from entering the active site, preventing the enzyme catalysing the reaction.
  • enzymes can't carry all it's function.
  • substrate+ inhibitor compete to bind to the active site
  • reducing the number of substrates binding to the active site, so reduces the rate of reaction.
  • eg: statins, asprin
• Non-competitive inhibitor 


  = an inhibitor bind to the enzyme at location other than the active site= allosteric site.

  • binding of inhibitors causes tertiary structure to change so the active site changes shape.
  • active site no longer has complementary shape, unable to bind with substrate.
  • enzymes can't carry out their function.
  • so will decrease the rate of reaction as more active sites will become unavailable.
  • eg; insectacides, herbicides
• cofactors 


  = inorganic compounds that can bind to the enzyme at the active site.

  • Results in formation of an enzyme-substrate-complex being more likely.
  • eg; chloride ions are need to form the correctly shaped active site in amylase.
• coenzymes 


  = organic molecules, aid formation of enzyme-substrate-complexes.

  • eg; NAD+NADP help transfer H+ ions during respiration and photosynthesis.
• prosthetic groups 


  = also aid formation

  • however they form a permanent group bound to the enzyme.
  • eg; Zn2+ ions form a prosthetic group on carbonic anhydrase