Rate: Enzyme Concentration (Cambridge (CIE) AS Biology): Revision Note
Exam code: 9700
Rate: enzyme concentration
Enzyme concentration affects the rate of reaction
The higher the enzyme concentration in a reaction mixture:
The greater the number of active sites available
The greater the likelihood of enzyme-substrate complex formation
As long as there is sufficient substrate available, the initial rate of reaction increases linearly with enzyme concentration
If the amount of substrate is limited, at a certain point any further increase in enzyme concentration will not increase the reaction rate as the amount of substrate becomes a limiting factor
Examiner Tips and Tricks
Always mention substrate availability when explaining the effect of increasing enzyme concentration.
A common mistake is to say that “more enzymes always increase the rate” — but this is only true while there is enough substrate present. In exams, you should state that if substrate becomes limiting, the rate will level off even if enzyme concentration keeps increasing.
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