Question

Which of the following statements about vitamin $B_{12}$ is false?
A. It has a cobalt atom
B. It also exists in plants
C. It is present in rain water
D. It is needed by human body in very small amounts

Answer 1

Hint: Vitamin $B_{12}$ is essential for the synthesis of DNA and RBC. It is not synthesised by our body and needs to be supplemented either through animal sources or through supplements.

Complete Answer:
- Vitamin $B_{12}$ is known as cobalamin. It is a water soluble protein and is involved in cellular metabolism.
Structure- It contains cobalt at the centre of a corrin ring.
- Source: Certain bacteria and archaea produce Vitamin $B_{12}$. As $B_{12}$ is highly water soluble it can be found in rainwater and other water sources. It is taken indirectly by herbivores through plants. These bacteria enter the gut and produce vitamin $B_{12}$ in the organism. Animal sources like meat, fish, milk and other dairy products are rich in vitamin $B_{12}$. Human body requires around 2.4mcg of vitamin $B_{12}$.

Function: It acts as a cofactor in DNA synthesis, fatty acid and amino acid metabolism.
- It is important in the normal functioning of the nervous system.
- It helps in development and maturation of RBCs in the bone marrow.
According to the given question, the statement A, C, D is correct.

Thus the correct answer is (B).

Note: Vitamin $B_{12}$ helps to protect against cancer. It is also taken orally in pernicious anaemia. Its deficiency can cause severe damage to the brain and nervous system.