In `C_(3)` cycle the regeneration of RuBP from glyceraldehyde-3-phosphate requires

Options

A. ATP molecule
B. NADPH
C. `CO_(2)`
D. Both (1) and (2)

Answer

To answer the question about what is required for the regeneration of RuBP from glyceraldehyde-3-phosphate in the C3 cycle, we can break down the process step by step:

### Step-by-Step Solution:

1. **Understanding the C3 Cycle**: The C3 cycle, also known as the Calvin cycle, is a crucial process in photosynthesis that occurs in the chloroplasts of plant cells. It consists of three main stages: carboxylation, reduction, and regeneration.

2. **Carboxylation Phase**: In the first step, carbon dioxide (CO2) is fixed by the enzyme RuBisCO to ribulose 1,5-bisphosphate (RuBP), resulting in the formation of 3-phosphoglycerate (PGA).

3. **Reduction Phase**: In the second step, PGA is converted into glyceraldehyde-3-phosphate (G3P) using ATP and NADPH produced during the light-dependent reactions of photosynthesis. This is where the energy and reducing power are provided.

4. **Regeneration Phase**: The third step involves the regeneration of RuBP from G3P. This is essential for the cycle to continue, as RuBP is needed to fix more CO2.

5. **Requirement for Regeneration**: During the regeneration of RuBP from G3P, one molecule of ATP is utilized. This ATP is necessary to convert G3P back into RuBP, allowing the cycle to proceed.

6. **Conclusion**: Therefore, the regeneration of RuBP from glyceraldehyde-3-phosphate requires ATP.

### Final Answer:
The regeneration of RuBP from glyceraldehyde-3-phosphate in the C3 cycle requires **one molecule of ATP**.

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