• The greater the substrate concentration, the higher the rate of reaction:
  • As the number of substrate molecules increases, the likelihood of enzyme-substrate complex formation increases
  • If the enzyme concentration remains fixed but the amount of substrate is increased past a certain point, however, all available active sites eventually become saturated and any further increase in substrate concentration will not increase the reaction rate
  • When the active sites of the enzymes are all full, any substrate molecules that are added have nowhere to bind in order to form an enzyme-substrate complex

   

• For this reason, in the graph below there is a linear increase in reaction rate as substrate is added, which then plateaus when all active sites become occupied

The effect of substrate concentration on the rate of an enzyme-catalysed reaction