Question

Elements associated with nitrogenase enzyme in biological nitrogen fixation
(A). Molybdenum
(B). Iron
(C). Copper
(D). Nickel

Choose the correct answer from the options given below:

• A. (A), (B) and (D) only.
• B. (A) and (B) only.
• C. (A), (B), (C) and (D).
• D. (B), (C) and (D) only.

Hint:

A molybdenum deficiency in legumes can indirectly cause nitrogen deficiency symptoms because the nitrogenase enzyme cannot function without the molybdenum cofactor.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The nitrogenase enzyme complex catalyzes biological nitrogen fixation, reducing atmospheric dinitrogen (\(\text{N}_2\)) to ammonia (\(\text{NH}_3\)).

Step 2: Detailed Explanation:
The nitrogenase enzyme is a highly conserved two-protein complex:
The Fe-protein (dinitrogenase reductase) contains iron-sulfur clusters and serves as an obligate electron donor.
The MoFe-protein (dinitrogenase) contains a unique molybdenum-iron cofactor (\(\text{FeMo-co}\)) at its active site where dinitrogen is bound and reduced.
Therefore, Molybdenum (A) and Iron (B) are the two primary essential transition metal elements associated with the active nitrogenase enzyme complex.

Step 3: Final Answer:
Hence, the correct option is (B), containing (A) and (B) only.