How many ATP are required to form one molecule of ammonia by nitrogen fixation through Rhizobium?

Options

A. 16 ATP
B. 20 ATP
C. 8 ATP
D. 4 ATP

Answer

To determine how many ATP molecules are required to form one molecule of ammonia through nitrogen fixation by Rhizobium, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Nitrogen Fixation**:
- Nitrogen fixation is the process by which atmospheric nitrogen (N₂) is converted into ammonia (NH₃) by certain bacteria, including Rhizobium, which has a symbiotic relationship with leguminous plants.

2. **Chemical Reaction**:
- The overall reaction for nitrogen fixation can be summarized as:
\[ N_2 + 8e^- + 8H^+ + 16 ATP \rightarrow 2 NH_3 + 16 ADP + 16 P_i \]
- In this reaction, atmospheric nitrogen combines with electrons and protons in the presence of ATP to produce ammonia.

3. **ATP Requirement for Ammonia Production**:
- From the reaction, we can see that to produce 2 molecules of ammonia (NH₃), 16 ATP molecules are consumed.

4. **Calculating ATP for One Molecule of Ammonia**:
- Since 16 ATP are required for 2 ammonia molecules, we can calculate the ATP needed for just 1 ammonia molecule by dividing the total ATP by 2:
\[ \text{ATP for 1 NH}_3 = \frac{16 \text{ ATP}}{2} = 8 \text{ ATP} \]

5. **Conclusion**:
- Therefore, to form one molecule of ammonia through nitrogen fixation by Rhizobium, **8 ATP molecules are required**.

### Final Answer:
**8 ATP molecules are required to form one molecule of ammonia by nitrogen fixation through Rhizobium.**

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