Choose the correct statement for the fixation of one `CO_(2)` molecule

Options

A. 3 ATP & 2 NADPH are required through calvin cycle
B. 5 ATP & 2 NADPH are required through Hatch & stack cycle
C. Photochemical reactions are involved in photolysis of water & phosphorylation of ADP into ATP
D. all of the above

Answer

To answer the question regarding the fixation of one CO₂ molecule in the Calvin cycle (C3 cycle), we can break down the process into several steps:

### Step-by-Step Solution:

1. **Understanding the Calvin Cycle**: The Calvin cycle consists of three main stages: carboxylation, reduction, and regeneration. It is crucial to know that this cycle occurs in the chloroplasts of plant cells.

2. **Carboxylation**: The first step involves the enzyme Rubisco (Ribulose bisphosphate carboxylase/oxygenase) catalyzing the reaction between carbon dioxide (CO₂) and ribulose bisphosphate (RuBP). This reaction produces two molecules of 3-phosphoglycerate (3-PGA).

3. **Reduction Phase**: In the second step, the 3-PGA molecules undergo reduction. This process requires energy and reducing power, which is provided by ATP and NADPH. Specifically, one ATP and one NADPH are used per molecule of 3-PGA to convert it into glyceraldehyde-3-phosphate (G3P), a three-carbon sugar.

4. **Regeneration of RuBP**: The final step of the cycle is the regeneration of RuBP, which is essential for the cycle to continue. This step also requires ATP. For every three CO₂ molecules fixed, three RuBP molecules are regenerated, using a total of three ATP molecules.

5. **Overall Requirement**: For the fixation of one CO₂ molecule, the Calvin cycle requires a total of:
- 3 molecules of ATP
- 2 molecules of NADPH

### Conclusion:
The correct statement regarding the fixation of one CO₂ molecule is that it requires **3 molecules of ATP and 2 molecules of NADPH**.

---