The first stable product of `CO_(2)` fixation in Calvin cycle is

Options

A. PGA
B. OAA
C. DHAP
D. RuBP

Answer

**Step-by-Step Solution:**

1. **Understanding the Calvin Cycle**: The Calvin cycle is a series of biochemical reactions that take place in the stroma of chloroplasts in photosynthetic organisms. It is responsible for fixing carbon dioxide (CO2) from the atmosphere into organic molecules.

2. **Identifying the Stages of the Calvin Cycle**: The Calvin cycle consists of three main stages:
- Carboxylation
- Reduction
- Regeneration

3. **Carboxylation Stage**: In the first stage, CO2 is fixed. The enzyme Ribulose-1,5-bisphosphate carboxylase/oxygenase (commonly known as Rubisco) catalyzes the reaction between CO2 and Ribulose-1,5-bisphosphate (RUBP), which is the CO2 acceptor.

4. **Formation of the First Stable Product**: The reaction produces a 6-carbon intermediate that quickly splits into two molecules of 3-phosphoglycerate (PGA), which is the first stable product of CO2 fixation in the Calvin cycle.

5. **Conclusion**: Therefore, the first stable product of CO2 fixation in the Calvin cycle is 3-phosphoglycerate (PGA).

**Final Answer**: The first stable product of CO2 fixation in the Calvin cycle is 3-phosphoglycerate (PGA).

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