Organic compounds that work with enzymes to speed up biological processes such as digestion. A coenzyme may be a vitamin, or contain one, or to be manufactured in the body from one. For example, coenzyme A - used in the metabolism of carbohydrates and fats - contains pantothetic acid, a B vitamin.

Substances needed by some enzymes to catalyze reactions (e.g. vitamins).

organic molecules that act as cofactors, such as NAD and FAD.