What is the main function of Cobalamin (B12) in the body?

Cobalamin, or vitamin B12, plays a crucial role in the formation of red blood cells. This vitamin is essential for the synthesis of DNA during the production of red blood cells, which take place in the bone marrow. A deficiency in cobalamin can lead to megaloblastic anemia, where red blood cells become large and inefficient, disrupting the oxygen-carrying capacity of the blood. Additionally, B12 is involved in the proper functioning and development of brain and nerve cells, further highlighting its significance beyond just red blood cell formation.

The option regarding carbohydrate metabolism pertains more to other vitamins like B1 (thiamine) and B6 (pyridoxine), which are directly involved in processes that convert carbohydrates into energy. Similarly, protein metabolism primarily involves other B vitamins, such as B6, which plays a key role in amino acid metabolism. For fat metabolism, while some B vitamins contribute indirectly, they do not play as central a role in fat metabolism as they do in red blood cell formation. Thus, cobalamin's primary and most notable function is indeed in the formation of red blood cells.