BRAINCAKEEffect of Enzyme Concentration
If the substrate concentration and all other conditions are kept constant, changing the enzyme concentration changes the number of active sites available.
With substrate in excess: increasing enzyme concentration means more active sites, so more enzyme-substrate complexes form per second and the rate increases. Because there is always plenty of substrate, the rate is directly proportional to enzyme concentration, and the graph of initial rate against enzyme concentration is a straight line through the origin. Doubling the enzyme concentration doubles the initial rate.
With a limited amount of substrate: at high enzyme concentrations there are more active sites than substrate molecules can fill. Substrate concentration becomes the limiting factor, and the rate levels off; adding more enzyme has no further effect.
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Key terms in this lesson
- limiting factor
- A factor that, when in shortest supply, directly controls the rate of a process, even if other factors are increased.
- gene expression
- The process by which the information in a gene is used to make a functional product, such as a protein.
More in Enzymes
- Measuring Rate of Reaction
- Effect of Substrate Concentration
- Effect of Temperature
- Effect of pH
- Reversible and Irreversible Inhibition
- Competitive Inhibition
- Non-competitive Inhibition
- End-Product Inhibition
All 14 lessons in Enzymes · All Edexcel AS-level Biology topics