How many full turns of the Calvin cycle are required to make one molecule of glucose

Options

A. one
B. two
C. four
D. six

Answer

To determine how many full turns of the Calvin cycle are required to make one molecule of glucose, 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 plants. It is also known as the light-independent reactions or dark reactions of photosynthesis.

2. **Identify the Steps of the Calvin Cycle**: The Calvin cycle consists of three main steps:
- **Fixation**: Carbon dioxide is fixed into a stable intermediate.
- **Reduction**: The fixed carbon is reduced to form carbohydrates.
- **Regeneration**: The cycle regenerates ribulose bisphosphate (RuBP) to continue the cycle.

3. **Carbon Requirement for Glucose**: A glucose molecule (C6H12O6) contains six carbon atoms.

4. **Carbon Produced per Turn**: Each full turn of the Calvin cycle produces one carbon atom.

5. **Calculate Full Turns Needed**: Since one turn of the Calvin cycle yields one carbon atom, to produce one molecule of glucose (which requires six carbon atoms), we need:
\[ \text{Number of turns} = \text{Number of carbons in glucose} = 6 \]

6. **Conclusion**: Therefore, to synthesize one molecule of glucose, six full turns of the Calvin cycle are required.

### Final Answer:
**Six full turns of the Calvin cycle are required to make one molecule of glucose.**

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