Question

How many ATP molecules are needed to produce $4$ moles of $N{H}_3$ without release of the $H_2$ during symbiotic $N_2$ fixation by Rhizobium leguminosarum ________________.

• A. $32$
• B. $24$
• C. $16$
• D. $12$

Answer 1

The correct option is A $32$

Biological nitrogen fixation can be represented by the following equation, in which two moles of ammonia are produced from one mole of nitrogen gas, at the expense of 16 moles of ATP and a supply of electrons and protons.

N${}_2$ + 8H+ + 8e- + 16 ATP$\to$ 2NH${}_3$ + H${}_2$ + 16ADP + 16 Pi

So, for 4 mole of ammonia, 32 ATP molecules are required.

So, the correct option is '32'.