Coenzymes and cofactors

Cofactors are molecules that bind to enzymes alongside the substrate in order for the reaction to occur. An example of a cofactor is chloride ions, which is a cofactor for amylase. Chloride ions bind to the amylase and allow it to break down starch.

Another type of cofactor is a coenzyme. Coenzymes are large, organic molecules that temporarily bind to the enzyme to allow a reaction to occur. For example, NAD is a coenzyme used by enzymes involved in respiration. Coenzymes often come from vitamins.

Cofactors normally do not bind permanently to the enzyme.

Cofactors that do bind permanently to the enzyme are called prosthetic groups. An example of a prosthetic group are zinc ions for carbonic anhydrase.