The four carbon compound formed during the regeneration of RUBP in Calvin cycle

Options

A. Sedoheptulose phosphate
B. Xylulose phosphate
C. Erythrose phosphate
D. Ribose phosphate

Answer

### Step-by-Step Solution:

1. **Understanding the Calvin Cycle**: The Calvin cycle is a series of biochemical reactions that take place in the chloroplasts of photosynthetic organisms. It is responsible for the fixation of carbon dioxide and the regeneration of ribulose bisphosphate (RuBP).

2. **Identifying the Regeneration Phase**: In the Calvin cycle, after carbon fixation, the cycle goes through a regeneration phase where RuBP is regenerated to continue the cycle. This phase is crucial for the continuation of the cycle.

3. **Recognizing the Compounds Involved**: During the regeneration of RuBP, various intermediates are formed. One of the key intermediates is a 4-carbon compound.

4. **Identifying the 4-Carbon Compound**: Among the options provided (pseudo-Heptylose phosphate, Xylulose phosphate, Erythrose phosphate, and ribulose phosphate), we need to identify which one is a 4-carbon compound formed during the regeneration of RuBP.

5. **Analyzing Each Option**:
- **Pseudo-Heptylose phosphate**: Not a common compound in the Calvin cycle.
- **Xylulose phosphate**: This is a 5-carbon compound and not formed during the regeneration of RuBP.
- **Erythrose phosphate**: This is a 4-carbon compound and is formed during the regeneration phase.
- **Ribulose phosphate**: This is a 5-carbon compound and not the answer.

6. **Conclusion**: The correct answer is **Erythrose phosphate**, which is the 4-carbon compound formed during the regeneration of RuBP in the Calvin cycle.

### Final Answer:
**Erythrose phosphate (Option C)** is the 4-carbon compound formed during the regeneration of RuBP in the Calvin cycle.

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