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

Options

A. Pyruvate
B. Glyceraldehyde-3-phosphate
C. Phosphoglycerate
D. Oxaloacetate

Answer

To solve the question, "When CO₂ is added to PEP, the first stable product synthesized is:", we need to understand the biochemical process involved. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the Reaction Context
- The reaction in question occurs in C4 plants, which utilize a specific pathway for carbon fixation known as the C4 pathway.

### Step 2: Understand the Role of PEP
- Phosphoenolpyruvate (PEP) is a 3-carbon compound that acts as a substrate in this reaction.

### Step 3: Identify the Enzyme Involved
- The enzyme responsible for catalyzing the reaction between CO₂ and PEP is called phosphoenolpyruvate carboxylase (PEP carboxylase). This enzyme is present in the mesophyll cells of C4 plants.

### Step 4: Describe the Reaction
- When CO₂ is added to PEP, the enzyme PEP carboxylase facilitates the reaction, converting PEP into a 4-carbon compound.

### Step 5: Identify the First Stable Product
- The first stable product formed from this reaction is oxaloacetic acid (also known as oxaloacetate). This compound is a 4-carbon molecule, which is the result of the carboxylation of PEP.

### Conclusion
- Therefore, when CO₂ is added to PEP, the first stable product synthesized is **oxaloacetic acid (oxaloacetate)**.

### Final Answer
- The correct option is **oxaloacetic acid**.

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