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Botany Question 21 – AP-EAMCET 2025

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No. of ATP, protons and electrons required for formation of 6NH3 molecules in biological nitrogen fixation

Understand the overall stoichiometry of the nitrogenase enzyme complex in converting atmospheric nitrogen to ammonia.

Step 1: Recall the overall reaction for biological nitrogen fixation✦ Active

The overall balanced equation for biological nitrogen fixation, catalyzed by the nitrogenase enzyme complex, for the formation of two molecules of ammonia (NH3) is:

N2+8e−+8H++16ATP→2NH3+H2+16ADP+16Pi
💡 Teacher's Secret Hint

Remember that the equation typically shows the formation of 2NH3 from one N2 molecule.

Step 2: Determine requirements for 2 molecules of NH3○ Expand

From the balanced equation, for the formation of 2NH3 molecules, the requirements are:

- ATP: 16 molecules

- Protons (H+): 8 ions

- Electrons (e−): 8 electrons

Step 3: Calculate requirements for 1 molecule of NH3○ Expand

To find the requirements for one molecule of NH3, divide the values for 2NH3 by 2:

- ATP: 16/2=8 molecules

- Protons (H+): 8/2=4 ions

- Electrons (e−): 8/2=4 electrons

💡 Teacher's Secret Hint

Ensure you divide all three components (ATP, protons, electrons) by 2 consistently.

Step 4: Calculate requirements for 6 molecules of NH3○ Expand

The question asks for the requirements for 6NH3 molecules. Multiply the requirements for 1NH3 by 6:

- ATP: 8×6=48 molecules

- Protons (H+): 4×6=24 ions

- Electrons (e−): 4×6=24 electrons

Thus, the number of ATP, protons, and electrons required for the formation of 6NH3 molecules is 48, 24, and 24, respectively.

💡 Teacher's Secret Hint

Pay attention to the order requested in the question: ATP, protons, and then electrons.

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