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:

Mo, Fe, and Ni are essential for nitrogenase enzyme activity in nitrogen fixation.

Answer 1

The Correct Option is A

Nitrogenase, the key enzyme in nitrogen fixation, is a metalloenzyme that requires molybdenum and iron. Nickel also supports some bacterial strains. Copper, though essential for other enzymes, is not directly involved in nitrogenase activity.

Answer 2

Looking at nitrogenase's molecular structure: The nitrogenase enzyme complex has two component proteins - the MoFe protein (dinitrogenase), which contains molybdenum and iron in its cofactor where nitrogen reduction occurs, and the Fe protein (dinitrogenase reductase), which supplies electrons using iron alone.
Many nitrogen-fixing bacteria also carry an associated nickel-iron hydrogenase that recycles the hydrogen gas produced as a by-product of nitrogen fixation, linking nickel to the overall nitrogenase system.
Copper is not part of this enzyme complex at all, so molybdenum, iron and nickel are the elements associated with nitrogenase.