The number of ATP required in excess to assimilate atmospheric `CO_2` to four molecules of triose phosphates in `C_2` plants as compared to `C_3` plants is

Options

A. 60
B. 24
C. 30
D. 12

Answer

To solve the question regarding the number of ATP required in excess to assimilate atmospheric CO2 to four molecules of triose phosphates in C2 plants compared to C3 plants, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Process**:
- Photosynthesis involves the fixation of CO2 to produce triose phosphates, which are important for the synthesis of carbohydrates.
- C3 plants use the Calvin cycle for CO2 fixation, while C2 plants (also known as C4 plants) have a different mechanism that involves an additional step.

2. **Identifying the ATP Requirement**:
- In C3 plants, the process of converting CO2 into triose phosphates requires a certain amount of ATP.
- In C2 (C4) plants, the process is more complex and requires additional energy, specifically in the form of ATP.

3. **Calculating Excess ATP in C2 Plants**:
- It is known that C2 plants require more ATP than C3 plants for the same amount of CO2 fixation.
- For the assimilation of atmospheric CO2 to form four molecules of triose phosphates, C2 plants require an excess of 24 ATP compared to C3 plants.

4. **Conclusion**:
- Therefore, the number of ATP required in excess for C2 plants compared to C3 plants to assimilate atmospheric CO2 to four molecules of triose phosphates is **24 ATP**.

### Final Answer:
The number of ATP required in excess to assimilate atmospheric CO2 to four molecules of triose phosphates in C2 plants as compared to C3 plants is **24**.

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