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GATE 2026 BT – Question 17

General Biology · Microbiology: Microbial growth and nutrition, operons (lac, trp, ara), nitrogen fixation · 1 mark · Multiple choice

In nitrogen fixation, to reduce nitrogen to ammonia, which one of the following shows the correct order of electron flow?

  1. Ferredoxin $\rightarrow$ reductase $\rightarrow$ nitrogenase
  2. NADH $\rightarrow$ reductase $\rightarrow$ nitrogenase
  3. Ferredoxin $\rightarrow$ nitrogenase $\rightarrow$ reductase
  4. Reductase $\rightarrow$ NADH $\rightarrow$ nitrogenase

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Correct answer: (A) Ferredoxin $\rightarrow$ reductase $\rightarrow$ nitrogenase

Explanation

Electrons come from reduced ferredoxin (or flavodoxin) to the Fe protein (the nitrogenase reductase), which passes them on to the MoFe protein (nitrogenase) that reduces $N_2$ to $NH_3$.