enzymes

• what 4 factors affect enzyme activity?


  temp

  pH

  enzyme conc

  substrate conc
• Why does temperature have an influence on enzyme activity?


  • rise in temp makes the enzyme's molecules vibrate more
  • if the temp goes above a certain level this vibration breaks some of the bonds that hold the enzyme in shape
  • the active site changes shape and the enzyme and substrate no longer fit together
  • At this point the enzyme is denatured - it no longer functions as a catalyst
• what happens if the temp goes above a certain level ?


  This vibration breaks some of the bonds that hold the enzyme in shape
• What do all enzymes have regarding pH?


  an optimum pH value
• what is the optimum ph foer most human enzymes?


  7 (neutral) but there are exceptions
• what is the optimum pHfor peptin?


  2 which is useful because it is found in the stomach
• what happens above and below the optimum pH?


  the H+ and OH- ions found in acids and alkalis can mess up the ionic bonds and hydrogen bonds that hold the enzymes tertiary structure in place

  this makes the active site change shape so the enzyme is denatured
• how does increasing enzyme concentration increase rate of reaction?

  The more enzyme molecules there are in a solution the more likely a substrate molecule is to COLLIDE with one and form an enzyme-substrate complex
• what happens if the amount of substrate is limited?


  there comes a point when there is more than enough enzyme molecules to deal with all the available substrate, so adding more enzyme has no further effect
• how does substrate concentration affect the rate of reaction:?


  affects the rate of reaction UP TO A POINT
• Why is it that the higher the substrate concentration, the faster the reaction?


  more substrate molecules means a collision between substrate and enzyme is more likely and so more active sites will be used

  • this is only true up until a SATURATION POINT though
• what happens after the saturation point (substrate conc)?


  After that there are so many substrate molecules that the enzymes have about as much as they can cope with (all the active sites are full) and adding more makes no difference
• When does substrate concentration decrease?


  Substrate concentration decreases with time during a reaction (unless more substrate is added to the reaction mixture) so if no other variables are changed, the rate of reaction will decrease over time too

  This makes the initial rate of reaction the highest rate of reaction
• what can happen to enzyme activity?


  enzyme activity can be inhibited
• What can enzyme activity be prevented by?


  enzyme inhibitors
• what are enzyme inhibitors?


  molecules that bind to the enzyme that they inhibit
• what can inhibition be?


  competitive or non-competitive