Question

Cobalt is a constituent of

• A. Folic acid
• B. Vitamin B 12
• C. Niacin
• D. Biotin

Hint:

Cobalamin = Cobalt + Vitamin.
It's the only "Metallo-vitamin."
For legumes, no Cobalt means no Nitrogen fixation!

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks to identify the biological molecule or vitamin that contains the transition metal element Cobalt as a central structural component.
Detailed Explanation:

• Structure of Vitamin $B_{12$:}
Vitamin $B_{12}$ is also known as Cobalamin.
Its chemical structure features a central Cobalt ion coordinated within a "corrin" ring (similar to the porphyrin ring in heme or the chlorin ring in chlorophyll).
It is the only vitamin that contains a metal ion.

• Biological Importance:
In humans, Vitamin $B_{12}$ is essential for the normal functioning of the brain and nervous system, and for the formation of red blood cells.
In agriculture and soil science, Cobalt is a "beneficial" element. It is essential for the nitrogen-fixing bacteria (like Rhizobium) that live in the root nodules of legumes. These bacteria need Cobalt to synthesize $B_{12}$ to function properly.

• Analyzing Other Options:
Folic acid ($B_9$): Primarily made of carbon, hydrogen, nitrogen, and oxygen.
Niacin ($B_3$): A simple organic compound derived from pyridine.
Biotin ($B_7$): A heterocyclic, sulfur-containing vitamin.

• Sources:
Vitamin $B_{12}$ is synthesized only by certain bacteria and archaea. Animals get it by eating these microbes or their products. Plants do not require or contain $B_{12}$ unless they are in symbiosis with nitrogen-fixing bacteria.

Step 3: Final Answer:
Cobalt is a fundamental constituent of Vitamin $B_{12}$ (Cobalamin).