B3 - More on Enzymes

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Enzymes like it warm not not too hot

Changing temperature changes the rate of a enzyme-catalysed reaction

The higher the temperature, the quicker the reaction at first. This is because more heat means the enzymes and substrate have more energy, this means there is a higher collision rate

Lower temperatures have the opposite effect

However, if it gets too hot, some of the bonds which hold the enzyme together will break

This means that the enzyme loses its shape, and its active site doesn't fit into its substrate anymore. This means that it can't catalyse the reaction and the reaction stops - the enzyme can't function

The enzyme is now said to have to be denatured. Its change in shape is irreversible

Each enzyme has its own optimum temperature when the reaction is at its fastest. This is the temperature just before it gets too hot and starts to denature. The optimum temperature for most human enzymes is 37 degrees

Enzymes like the right pH too

The pH also has an effect on enzymes too

If the pH is too high or low it interferes with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzyme

All enzymes have an optimum pH that they work best at, it's often neutral at pH 7, but not always. Some enzymes like pepsin work at pH 2 which means it's well suited to the acidic conditiond

Q10 values show how he rate of reaction changes with temperature

The Q10 value for a reaction shows how much the rate of reaction changes when the temperature changes (raised by 10 degrees)

It can be calculated using the equation rate at higher temperature/rate at lower temperature

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