When `CO_(2)` is added to PEP. The first stabel product synthesised is

Options

A. pyruvate
B. glyceraldehyde-3-phosphate
C. phosphoglycerate
D. oxaloacetate

Explanation

To solve the question "When CO₂ is added to PEP, the first stable product synthesized is," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Context**: The question is related to the process of photosynthesis, specifically in C4 plants. In these plants, carbon dioxide (CO₂) is fixed in a unique way compared to C3 plants.

2. **Identify the Initial Reactants**: The reactants in this process are CO₂ (carbon dioxide) and PEP (phosphoenolpyruvate), which is a 3-carbon compound.

3. **Recognize the Reaction**: When CO₂ is added to PEP, it undergoes a carboxylation reaction, which is facilitated by the enzyme PEP carboxylase.

4. **Determine the Product**: The product of this reaction is oxaloacetate, which is a 4-carbon compound. This compound is the first stable product formed in the C4 pathway.

5. **Eliminate Other Options**:
- Pyruvate is produced later in glycolysis and is not the first stable product in this context.
- Glyceraldehyde 3-phosphate is also an intermediate in glycolysis and not the initial product of CO₂ fixation.
- Phosphoglycerate is another intermediate in glycolysis and does not relate to the initial fixation of CO₂ with PEP.

6. **Conclude the Answer**: Therefore, the correct answer to the question is oxaloacetate.

### Final Answer:
The first stable product synthesized when CO₂ is added to PEP is **oxaloacetate**.

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