Enzymes are macromolecules that are critical for growth, cell processes, and digesting. Most are proteins and they usually have the suffix -ase.

A catalyst is an enzyme that will increase the rate of a reaction without changing its structure. However, reactions will still occur without the presence of an enzyme. It increases the rate by decreasing the activation energy. Activation energy is the minimum amount of energy required to start a reaction.

Enzymes have a specific shape and structure for their substrate. They can build up or break down and their activity is dependent on factors such as pH and temperature. Within a certain range of temperature and pH, the enzyme will have optimal activity. However, the further you get from this range, the greater the enzyme will be denatured and lose its function.

Enzymes have a specific active and binding site for a particular substrate. The substrate binds to the active site and is transformed into a product under ideal conditions (pH, temperature, co-enzyme).