Limiting Factors Affecting Enzymes: Substrate Concentration (AQA A Level Biology): Revision Note

The effect of substrate concentration

• 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 to form an enzyme-substrate complex

• 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