Which element is a constituent of **nitrogenase enzyme** (catalyses biological N₂ fixation)?
ACalcium
BMolybdenum (and iron) — Mo–Fe cofactor
CSodium
DSilicon
Answer & Solution
Correct answer: B. Molybdenum (and iron) — Mo–Fe cofactor
Nitrogenase has a complex iron–molybdenum cofactor (FeMoCo). Mo and Fe are essential micronutrients; their deficiency cripples N fixation in legumes/Rhizobium. Plants of pulses and free-living N-fixers like Azotobacter need Mo.
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