What best describes the function of cobalamin (vitamin B12)?

What best describes the function of cobalamin (vitamin B12)?

• A. Antioxidant properties
• B. Coenzyme used for absorption
• C. Hormonal regulation
• D. Energy production in mitochondria

Answer: (B)

Vitamin B12 functions as a coenzyme in essential metabolic reactions. It cofactors two key enzymes: methionine synthase, which remethylates homocysteine to methionine, and methylmalonyl-CoA mutase, which converts methylmalonyl-CoA to succinyl-CoA. These reactions support DNA synthesis, myelin formation, and integration of certain nutrient intermediates into the TCA cycle, linking to energy metabolism. Among the options, describing B12 as a coenzyme best captures its primary role; the other choices describe properties that aren’t its defining function. Note that absorption involves intrinsic factor and the ileum, not a direct coenzyme role.

Vitamin B12 functions as a coenzyme in essential metabolic reactions. It cofactors two key enzymes: methionine synthase, which remethylates homocysteine to methionine, and methylmalonyl-CoA mutase, which converts methylmalonyl-CoA to succinyl-CoA. These reactions support DNA synthesis, myelin formation, and integration of certain nutrient intermediates into the TCA cycle, linking to energy metabolism. Among the options, describing B12 as a coenzyme best captures its primary role; the other choices describe properties that aren’t its defining function. Note that absorption involves intrinsic factor and the ileum, not a direct coenzyme role.