What is an enzyme and what effect does temperature have on enzyme activity? (6 marks)

An enzyme is a globular protein that acts as a biological catalyst.  They work by reducing the activation energy of chemical reactions, which increases the rate of reactions.

All enzymes have an optimum temperature.  

The rate of reaction increases as temperature increases, up to the optimum temperature.  This is because both the enzyme and substrate molecules have more kinetic energy so move around faster and are more likely to collide.  A collision creates an enzyme substrate complex, which triggers the catalytic effect.  

As temperature rises above the optimum temperature the particles with the molecule vibrate more energetically, which cause the bonds to break.  This means that the active site changes shape and the enzyme becomes denatured.  Enzyme substrate complexes can no longer form and the catalytic effect is lost.