3-PGA is first stable product in

Options

A. carbon reduction cycle
B. OAA
C. malic acid
D. PEP

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the first stable product in a specific metabolic pathway. Here, we need to identify which cycle produces 3-PGA as its first stable product.

2. **Identifying the Pathways**: The options provided include:
- Carbon reduction cycle
- Oxaloacetic acid (OAA)
- Malic acid
- Phosphoenolpyruvate (PEP)

3. **Analyzing Each Option**:
- **Carbon Reduction Cycle**: This refers to the Calvin cycle, which is part of photosynthesis. In this cycle, the first stable product formed after carbon fixation is 3-phosphoglycerate (3-PGA). Thus, this option is likely correct.
- **Oxaloacetic Acid (OAA)**: OAA is a four-carbon compound that is a stable product in the C4 photosynthetic pathway. Since the question is about a three-carbon compound, this option is incorrect.
- **Malic Acid**: Malic acid is also a four-carbon compound and is associated with the C4 cycle. Therefore, this option is also incorrect.
- **Phosphoenolpyruvate (PEP)**: PEP is an intermediate compound in glycolysis and is not directly related to the stable products of the Calvin cycle. Hence, this option is incorrect.

4. **Conclusion**: Based on the analysis, the correct answer is that 3-PGA is the first stable product in the carbon reduction cycle (Calvin cycle).

**Final Answer**: 3-PGA is the first stable product in the carbon reduction cycle.

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