Vitamin B1   thiamine A coenzyme in the catabolism of sugars and amino acids.
Vitamin B2   riboflavin A precursor of cofactors called FAD and FMN, which are needed for flavoprotein enzyme reactions, including activation of other vitamins
Vitamin B3   niacin (nicotinic acid), nicotinamide riboside A precursor of coenzymes called NAD and NADP, which are needed in many metabolic processes.
Vitamin B5   pantothenic acid A precursor of coenzyme A and therefore needed to metabolize many molecules.
Vitamin B6   pyridoxine, pyridoxal, pyridoxamine A coenzyme in many enzymatic reactions in metabolism.
Vitamin B7   biotin A coenzyme for carboxylase enzymes, needed for synthesis of fatty acids and in gluconeogenesis.
Vitamin B9   folate A precursor needed to make, repair, and methylate DNA; a cofactor in various reactions; especially important in aiding rapid cell division and growth, such as in infancy and pregnancy. Synthetic folate is known as folic acid.
Vitamin B12   various cobalamins; commonly cyanocobalamin or methylcobalamin in vitamin supplements A coenzyme involved in the metabolism of every cell of the human body, especially affecting DNA synthesis and regulation, but also fatty acid metabolism and amino acid metabolism.