What are the active forms of riboflavin?

Riboflavin, also known as vitamin B2, is essential for various biological functions and exists primarily in two active forms: flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). FMN is derived from riboflavin through phosphorylation, while FAD is formed when AMP is added to FMN. Both FMN and FAD serve as cofactors in numerous enzymatic reactions, particularly those involved in redox reactions and energy metabolism.

For example, FAD acts as a cofactor for several dehydrogenases, playing a crucial role in the electron transport chain. FMN also participates in the same processes. This dual functionality highlights the importance of riboflavin in energy production, carbohydrate metabolism, and the metabolism of fats and proteins.

The other choices listed do not relate to riboflavin. NAD and NADH are derived from niacin (vitamin B3) and are involved in oxidation-reduction reactions but do not have any direct association with riboflavin. Coenzyme A and HMG-CoA are involved in fatty acid metabolism and the synthesis of cholesterol, respectively, but they are synthesized from pantothenic acid (vitamin B5). Lastly, th