How many Calvin cycles are involved in the synthesis of one glucose molecule by photosynthesis?

Options

A. 3
B. 1
C. 4
D. 6

Explanation

To determine how many Calvin cycles are involved in the synthesis of one glucose molecule by photosynthesis, we can follow these steps:

### Step-by-Step Solution:

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

2. **Stages of the Calvin Cycle**: The Calvin cycle consists of three main stages:
- **Carboxylation**: The process where carbon dioxide is fixed.
- **Reduction**: The stage where energy is used to convert the fixed carbon into a carbohydrate.
- **Regeneration**: The stage where the cycle is regenerated to continue the process.

3. **Carbon Atoms in Glucose**: A glucose molecule (C6H12O6) contains six carbon atoms. Therefore, to synthesize one glucose molecule, six carbon atoms need to be fixed.

4. **Carbon Fixation per Cycle**: Each turn of the Calvin cycle fixes one carbon atom (from one molecule of CO2).

5. **Calculating the Number of Cycles**: Since six carbon atoms are required to form one glucose molecule and each cycle fixes one carbon atom, we need a total of six turns of the Calvin cycle to produce one glucose molecule.

6. **Conclusion**: Therefore, the number of Calvin cycles involved in the synthesis of one glucose molecule is **6**.

### Final Answer:
**6 Calvin cycles are involved in the synthesis of one glucose molecule by photosynthesis.**

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