Number of G-3-P and DHAP molecules required to regenerate 6 molecules of RuBP in Calvin cycle respectively are

Options

A. 4,6
B. 6,4
C. 6,6
D. 4,4

Answer

To determine the number of G-3-P (glyceraldehyde 3-phosphate) and DHAP (dihydroxyacetone phosphate) molecules required to regenerate 6 molecules of RuBP (ribulose bisphosphate) in the Calvin cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Calvin Cycle**: The Calvin cycle is a series of biochemical reactions that occur in the stroma of chloroplasts in photosynthetic organisms. It is responsible for fixing carbon dioxide and synthesizing glucose.

2. **Identify the Role of RuBP**: RuBP is the starting molecule in the Calvin cycle. It reacts with carbon dioxide to form 3-phosphoglycerate (3-PGA).

3. **Conversion of G3P to RuBP**: Each molecule of RuBP is regenerated from G3P. Specifically, for every 1 molecule of RuBP, 1 molecule of G3P is required. Therefore, to regenerate 6 molecules of RuBP, we need 6 molecules of G3P.

\[ \text{G3P required} = 6 \text{ molecules of RuBP} \Rightarrow 6 \text{ molecules of G3P} \]

4. **Understanding the Formation of DHAP**: DHAP is formed alongside G3P during the reduction phase of the Calvin cycle. For every 2 molecules of G3P produced, 1 molecule of DHAP is formed.

5. **Calculate the Required DHAP**: Since we need 6 molecules of G3P, we can calculate the number of DHAP molecules produced. For every 2 G3P, 1 DHAP is produced. Therefore, for 6 G3P:

\[ \text{DHAP required} = \frac{6 \text{ G3P}}{2} = 3 \text{ molecules of DHAP} \]

6. **Final Summary**: To regenerate 6 molecules of RuBP, we need:
- 6 molecules of G3P
- 3 molecules of DHAP

### Final Answer:
- **G3P required**: 6 molecules
- **DHAP required**: 3 molecules