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 Process**: Biological nitrogen fixation is the process where atmospheric nitrogen (N2) is converted into ammonia (NH3) by certain bacteria, including Rhizobium leguminosarum.

2. **Write the Chemical Equation**: The general equation for biological nitrogen fixation can be represented as:
\[ N_2 + 8H^+ + 8e^- + 16 ATP \rightarrow 2 NH_3 + H_2 + 16 ADP + 16 P_i \]
This equation shows that 2 molecules of NH3 are produced from 16 ATP.

3. **Calculate ATP for 2 NH3**: From the equation, we see that to produce 2 molecules of NH3, 16 ATP are required.

4. **Determine ATP for 4 NH3**: Since we need to produce 4 molecules of NH3, we can set up a proportion:
\[ \text{For 2 NH3: 16 ATP} \\ \text{For 4 NH3: } x \text{ ATP} \]
To find \( x \):
\[ x = 16 \times 2 = 32 \text{ ATP} \]

5. **Conclusion**: Therefore, to produce 4 molecules of NH3, a total of 32 ATP molecules are required.

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