Reduction of 1 `CO_(2)` in `C_(3)` plants requires

Options

A. 3ATP
B. 5ATP
C. 8ATP
D. 12ATP

Answer

To answer the question regarding the reduction of 1 CO₂ in C₃ plants, we need to understand the Calvin Cycle, which is the process involved in photosynthesis in these plants.

### Step-by-Step Solution:

1. **Understanding the Calvin Cycle**: The Calvin Cycle, also known as the dark reaction or light-independent reaction, occurs in the mesophyll cells of C₃ plants. It consists of three main stages: fixation, reduction, and regeneration.

2. **Fixation of CO₂**: In the first step, CO₂ is fixed into a 5-carbon sugar (ribulose bisphosphate, RuBP) by the enzyme ribulose bisphosphate carboxylase/oxygenase (RuBisCO), producing a 6-carbon intermediate that quickly splits into two 3-carbon molecules (3-phosphoglycerate, 3-PGA).

3. **Reduction Phase**: In the second step, the 3-PGA molecules undergo reduction. This step requires energy in the form of ATP and reducing power in the form of NADPH. For the reduction of one molecule of CO₂, 3 ATP and 2 NADPH are required.

4. **Regeneration of RuBP**: After the reduction phase, the final step involves the regeneration of RuBP, which allows the cycle to continue. This step also requires ATP.

5. **Total Requirements for One CO₂**: Therefore, to reduce one molecule of CO₂ in the Calvin Cycle, the total requirements are:
- **ATP**: 3 molecules
- **NADPH**: 2 molecules

### Final Answer:
The reduction of 1 CO₂ in C₃ plants requires **3 ATP and 2 NADPH**.

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