Describe the theory of enzyme action.

Enzymes are biological catalysts that speed up the rate of biological reactions. The enzyme active site and the substrate are complimentary in shape. This allows the substrate to bind to the active site of the enzyme forming an enzyme-substrate complex. The enzyme then catalyses the reaction which releases the breakdown products. Enzymes can be used to catalyse further reactions. The action of enzymes can be described as the 'lock and key model' - each enzyme is specific in that it will only catalyse a reaction with its normal substrate. For example, only the substrate starch will fit into the active site of amylase.