Question

In biological nitrogen fixation conversion of dinitrogen molecule into ammonia is carried out by enzyme.

• A. Hydrogenase
• B. Dehydrogenase
• C. Nitrogenase
• D. Nitrate reductase

Hint:

Directly associate the process {Nitrogen fixation} with the enzyme {Nitrogenase}. The names are directly linked, making it an easy-to-remember pair.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Biological nitrogen fixation is the process by which atmospheric nitrogen gas (\(N_2\)), which is largely inert, is converted into ammonia (\(NH_3\)), a form of nitrogen that can be readily used by plants. This vital process is carried out by certain microorganisms. The question asks for the specific enzyme that catalyzes this conversion.
Step 2: Detailed Explanation:
Hydrogenase: An enzyme that catalyzes the reversible oxidation of molecular hydrogen (\(H_2\)). It is often associated with nitrogen fixation to recycle \(H_2\) produced as a byproduct, but it doesn't act on \(N_2\).
Dehydrogenase: A broad class of enzymes that oxidize a substrate by transferring one or more hydrides (\(H^-\)) to an acceptor, usually NAD\(^+\)/NADP\(^+\) or a flavin coenzyme. They are involved in respiration, not directly in nitrogen fixation.
Nitrogenase: This is the key enzyme complex responsible for biological nitrogen fixation. It breaks the strong triple bond of the dinitrogen molecule and reduces it to ammonia. This enzyme is found only in prokaryotes (bacteria and archaea).
Nitrate reductase: An enzyme that catalyzes the reduction of nitrate (\(NO_3^-\)) to nitrite (\(NO_2^-\)), a step in nitrogen assimilation by plants and bacteria, but not nitrogen fixation.
Step 3: Final Answer:
The enzyme that converts dinitrogen into ammonia is Nitrogenase.