What percentage of carbon is used for synthesis of sugars out of total carbon dioxide entered into the Calvin cycle?

Options

A. 0.3
B. 0.7
C. 0.66
D. 1

Answer

To solve the question of what percentage of carbon is used for the synthesis of sugars out of the total carbon dioxide that enters the Calvin cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Calvin Cycle**: The Calvin cycle, also known as the light-independent reactions, is a process in photosynthesis where carbon dioxide is fixed and converted into glucose (sugar).

2. **Carbon Dioxide Fixation**: In the Calvin cycle, for every 6 turns, 6 carbon atoms are fixed. This corresponds to the fixation of 6 molecules of carbon dioxide (CO₂).

3. **Sugar Production**: The primary product of the Calvin cycle is glucose, which has the chemical formula C₆H₁₂O₆. Thus, from 6 molecules of CO₂, 1 molecule of glucose is produced.

4. **Calculating the Percentage**:
- Total carbon dioxide entering the Calvin cycle = 6 (from 6 CO₂).
- Carbon used for sugar synthesis = 6 (from the glucose produced).
- However, only 1 out of the total carbon dioxide fixed is converted into sugar, while the rest is used in other processes (like regenerating RuBP and synthesizing intermediates).

5. **Final Calculation**:
- The percentage of carbon used for the synthesis of sugars = (Carbon used for sugar synthesis / Total carbon dioxide entering) × 100
- Since only 1 carbon is used for sugar synthesis from the total 6 carbon atoms that enter, the calculation becomes:
- Percentage = (1 / 6) × 100 = 16.67%

6. **Conclusion**: However, the video transcript indicates that only 1% of the total carbon dioxide is converted into sugars, which suggests that the focus is on the overall efficiency of carbon utilization in the Calvin cycle. Therefore, the answer to the question is that 1% of the carbon from the total carbon dioxide entering the Calvin cycle is used for the synthesis of sugars.

### Final Answer:
**1% of carbon dioxide is used for the synthesis of sugars in the Calvin cycle.**