Carbon in carbon dioxide is radioactively labelled. The product in which radioactive carbon can be traced in `C_(3)` plants is

Options

A. `PEP`
B. `RuBP`
C. `PGAL`
D. `PGA`.

Answer

To solve the question regarding the radioactive carbon in carbon dioxide and its tracing in C3 plants, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the C3 Cycle**: The C3 cycle, also known as the Calvin cycle, is the primary pathway for carbon fixation in C3 plants. It is called the C3 cycle because the first stable product formed is a three-carbon compound.

2. **Identify Key Components**: The main components involved in the C3 cycle include carbon dioxide (CO2) and ribulose 1,5-bisphosphate (RuBP). When CO2 enters the cycle, it combines with RuBP.

3. **Formation of the First Product**: The reaction between CO2 and RuBP leads to the formation of two molecules of phosphoglyceric acid (PGA), which is a three-carbon compound. This is the first stable product of the C3 cycle.

4. **Radioactive Labeling**: Since the question specifies that the carbon in carbon dioxide is radioactively labeled, we need to determine where this radioactive carbon would be traced in the cycle.

5. **Tracing the Radioactive Carbon**: As CO2 is fixed into the cycle, the radioactive carbon from the labeled CO2 will be incorporated into the PGA. Therefore, the product in which the radioactive carbon can be traced is phosphoglyceric acid (PGA).

6. **Conclusion**: Based on the above reasoning, the correct answer to the question is that the product in which radioactive carbon can be traced in C3 plants is **PGA (phosphoglyceric acid)**.

### Final Answer:
The product in which radioactive carbon can be traced in C3 plants is **PGA (phosphoglyceric acid)**.

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