Vitamins B1, B2, B3, and B5 are important cofactors for enzymes involved in cellular metabolism. Vitamin B1 or thiamine is a cofactor for enzymes in carbohydrate metabolism. Vitamin B2 or riboflavin is a precursor for FAD and FMN which are electron carriers in the electron transport chain and metabolic pathways like the citric acid cycle. Vitamin B3 or niacin is needed to make NAD+, which is used in glycolysis and the electron transport chain. Vitamin B5 or pantothenic acid is needed to make Coenzyme A, which is involved in acetyl group transfers in metabolic pathways.

2. Vitamin B1 - Thiamine
Thiamine
Some uses:
Cofactor for several enzymes (a precursor for thiamine pyrophosphate, one of the
cofactors used by the pyruvate decarboxylase complex (PDC).
Also, a cofactor for branched chain a-keto dehydrogenase.
Found in a wide variety of foods, including meat, grains. Deficiency causes
beriberi (muscle atrophy, neurological problems).

3. Vitamin B2 - riboflavin
FAD flavin adenine dinucleotide.
FAD is a cofactor for pyruvate
dehydrogenase complex (PDC), and
succinate dehydrogenase in TCA cycle.
Riboflavin is a precursor for
FAD and FMN.
FMN - Flavin
mononucleotide
FMN is an electron carrier in the
electron transport chain.

4. Vitamin B3 - nicotinic acid
(a precursor for NAD).
Also known as niacin.
nicotinic acid
NAD+ is needed for glycolysis, NADH gets oxidized in electron transport chain,
etc.

5. Vitamin B5 - pantothenic acid (needed for making CoA)
pantothenic acid
Coenzyme A
We get pantothenic acid in our diet as CoA, which must be broken down to
pantothenic acid to be absorbed in intestine. We then use the pantothenic acid
in making our own CoA.