Common product formed due to the activity of transketolase enzyme during `C_3` cycle

Options

A. Ribulose - 5 - phosphate
B. Ribose - 5 - phosphate
C. Xylulose - 5 - phosphate
D. Fructose - 5 - phosphate

Answer

### Step-by-Step Solution

1. **Understanding the C3 Cycle**: The C3 cycle, also known as the Calvin cycle, is a series of biochemical reactions that take place in the chloroplasts of photosynthetic organisms. It is responsible for fixing carbon dioxide and synthesizing glucose.

2. **Role of Transketolase**: Transketolase is an enzyme that plays a crucial role in the C3 cycle. It catalyzes the transfer of two-carbon units (ketolase activity) between sugars, which is essential for the regeneration of ribulose bisphosphate (RuBP).

3. **Identifying the Substrates**: During the regeneration phase, transketolase acts on fructose 6-phosphate (F6P) and glyceraldehyde 3-phosphate (G3P). The enzyme facilitates the conversion of these substrates into different sugar phosphates.

4. **Formation of Erythrose 4-Phosphate**: When transketolase acts on fructose 6-phosphate, it removes two carbons, resulting in the formation of erythrose 4-phosphate. This is a key intermediate in the cycle.

5. **Formation of Xylulose 5-Phosphate**: The two-carbon units that are removed from fructose 6-phosphate are then added to glyceraldehyde 3-phosphate, leading to the formation of xylulose 5-phosphate.

6. **Conclusion**: Therefore, the common product formed due to the activity of the transketolase enzyme during the C3 cycle is xylulose 5-phosphate.

### Final Answer
The common product formed due to the activity of transketolase enzyme during the C3 cycle is **xylulose 5-phosphate**.

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