Which vitamin is a constituent of two redox coenzymes?

Which vitamin is a constituent of two redox coenzymes?

• A. Vitamin A
• B. Vitamin B2
• C. Vitamin B6
• D. Vitamin C

Answer: (B)

Riboflavin (vitamin B2) is the source of two redox-active cofactors: flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). These cofactors shuttle electrons in many dehydrogenase reactions across metabolism, including the citric acid cycle (for example, succinate dehydrogenase uses FAD) and fatty acid beta-oxidation, as well as handoffs to the electron transport chain. Because one vitamin gives rise to two distinct redox cofactors, it stands out as the constituent of two redox coenzymes. The other vitamins listed do not form two such cofactors: Vitamin A primarily supports vision and gene regulation; Vitamin C acts as an antioxidant and enzyme cofactor in certain hydroxylation reactions but isn’t a redox coenzyme in two forms; Vitamin B6 functions as pyridoxal phosphate in amino acid metabolism, not as a redox coenzyme.

Riboflavin (vitamin B2) is the source of two redox-active cofactors: flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). These cofactors shuttle electrons in many dehydrogenase reactions across metabolism, including the citric acid cycle (for example, succinate dehydrogenase uses FAD) and fatty acid beta-oxidation, as well as handoffs to the electron transport chain. Because one vitamin gives rise to two distinct redox cofactors, it stands out as the constituent of two redox coenzymes. The other vitamins listed do not form two such cofactors: Vitamin A primarily supports vision and gene regulation; Vitamin C acts as an antioxidant and enzyme cofactor in certain hydroxylation reactions but isn’t a redox coenzyme in two forms; Vitamin B6 functions as pyridoxal phosphate in amino acid metabolism, not as a redox coenzyme.