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The conditions under which a particular enzyme is most active are called the optimum conditions. When an enzyme is most active the rate of the biological reaction it catalyses is highest.

The bacterium Thermus aquaticus lives in hot springs. Its enzymes have an optimum temperature of around 70^oC.

Effect of temperature on enzyme activity

You can investigate the effect of temperature on enzyme activity in the lab. Watch this video to see the correct procedure for an experiment showing how temperature affects the action of catalase on hydrogen peroxide.

Temperature is a measure of how much kinetic energy molecules have.

Description

As the temperature is increased enzyme activity increases to a maximum value at the optimum temperature (around 37^oC for most human enzymes). As the temperature is increased above the optimum temperature enzyme activity decreases.

Explanation

At low temperatures enzyme activity is low because the enzyme and substrate molecules have less kinetic energy so there are fewer collisions between them.

At the optimum temperature, the kinetic energy in the substrate and enzyme molecules is ideal for the maximum number of collisions.

At high temperatures the shape of the enzyme is altered so that it is no longer complementary to its specific substrate. This effect can be permanent and irreversible and is called denaturation.

The diagram below shows what happens to an enzyme when denaturation occurs.