Effect of concentration on enzyme action

• what is the definition of 'limiting factor'?

  a variable that limits the rate of a process, if all other conditions are kept constant, increasing this variable will increase the rate of process
• describe the effect of changing substrate concentration on a graph

  • as graph line increases in gradient, substrate concentration is a limiting factor, but when it platos the substrate concentration is no longer a limiting factor and now temp or enzyme concentration is now the main limiting factor
• what are the effects of changing enzyme concentration on a graph?

  • as the graph line increases in gradient, enzyme concentration is the limiting factor, but when it platos the enzyme concentration is no longer a limiting factor, some other factors (substrate concentration) is now the main limiting factor
• explain what happens when you change the enzyme concentration in a reaction?

  • if there is no enzyme, then no enzyme-substrate complexes can form so the reaction cannot proceed
  • as the enzyme concentration increases, more active sites become available, more enzyme-substrate complexes can form, so more products form and the reaction rate increases
  • eventually all the substrate molecules are occupying active sites, so increasing the enzyme concentration will not cause any further increase in reaction rate
• why are enzymes usually maintained at low concentration inside cells?

  • to control the rate of reaction - easier control
  • enzymes can catalyse reactions very quickly and are reusable, so only very small amounts are needed in cells