How may ATP molecules are needed to produce 4 molecules of NH3 during symbiotic N2 fixation by Rhizobium leguminosarum in root Nodule ?

Options

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

Answer

To determine how many ATP molecules are needed to produce 4 molecules of NH3 during symbiotic nitrogen fixation by Rhizobium leguminosarum in root nodules, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Reaction**:
The nitrogen fixation reaction can be summarized as:
\[ N_2 + 8H^+ + 8e^- + 16 ATP \rightarrow 2 NH_3 + H_2 + 16 ADP + 16 P_i \]
This equation indicates that 16 ATP molecules are required to produce 2 molecules of NH3.

2. **Calculate ATP for 2 NH3**:
From the equation, we see that 16 ATP is needed to produce 2 NH3 molecules.

3. **Determine ATP for 4 NH3**:
Since we need to produce 4 NH3 molecules, we can set up a proportion based on the ATP required for 2 NH3:
\[ \text{If } 2 \text{ NH3 requires } 16 \text{ ATP, then } 4 \text{ NH3 requires } X \text{ ATP.} \]
This can be expressed mathematically as:
\[ \frac{2 \text{ NH3}}{16 \text{ ATP}} = \frac{4 \text{ NH3}}{X \text{ ATP}} \]

4. **Cross-Multiply and Solve for X**:
Cross-multiplying gives:
\[ 2X = 4 \times 16 \]
Simplifying this:
\[ 2X = 64 \]
Dividing both sides by 2:
\[ X = 32 \]

5. **Conclusion**:
Therefore, the total number of ATP molecules needed to produce 4 molecules of NH3 is **32 ATP**.

### Final Answer:
**32 ATP molecules are needed to produce 4 molecules of NH3.**

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