L4 - Enzymes and Temperature

objectives

• Explain the effect of changes in temperature and pH on enzyme activity
• Examples of enzymes include Proteases, lipases, amylases and their functions

Factors Affecting Enzyme Activity

For an enzyme to work, it must:

1. Collide with its substrate.

2. Have an active site which fits the substrate

All factors that affect the rate of enzymes, will affect one or both of the above.

You need to know about the effects of temperature and pH

Explaining Enzyme Activity with Temperature

Explaining the Temperature Graph

An initial rising curve

Peak at optimum temperature = 37^oC

A sharp decreasing curve

At first, why does the rate of reaction of enzyme increase as temperature increases?

• more kinetic energy so more movement of enzyme and substrate molecules
• more likely for them to collide and react.

Why does the rate of reaction of enzyme decline after a certain temperature?

• At higher temperatures the active site begins to change shape
• Enzyme is denatured

Denaturing

Enzymes are proteins and their functioning is dependent on their shape, particularly the shape of the active site.

When temperature is increased beyond the optimum, bonds within the enzyme start to break. The active site changes shape and the substrate can no longer fit. The enzyme is denatured. This is irreversible.