Six turn


Because the carbohydrate molecule has 6 carbon atom , it takes 6 turns of calvin cycle to make one carbohydrate molecule.


So, correct answer is "6"...


$$Hope it's help... $$

Calvin Cycle and Glucose Generation

The Calvin cycle, also known as the light-independent reactions or the dark reactions, is the set of biochemical reactions that take place in the chloroplasts of plants during photosynthesis. These reactions are responsible for the generation of glucose, which is a key molecule in the process of energy storage.

Understanding the Calvin Cycle

1. Carbon Fixation:
- The Calvin cycle begins with the process of carbon fixation, where carbon dioxide (CO2) molecules from the atmosphere are incorporated into an organic molecule called ribulose-1,5-bisphosphate (RuBP).
- The enzyme responsible for this step is called RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase).

2. Formation of PGA:
- The resulting molecule after carbon fixation is a highly unstable compound known as 3-phosphoglycerate (PGA).
- The enzyme phosphoglycerate kinase converts ATP to ADP, phosphorylating PGA and forming 1,3-bisphosphoglycerate (BPG).

3. Reduction and Conversion:
- In the next set of reactions, BPG is reduced and converted to glyceraldehyde-3-phosphate (G3P) using the reducing power of NADPH, which is generated in the light-dependent reactions of photosynthesis.
- Some of the G3P molecules are used to regenerate RuBP, while others continue through the cycle.

4. Regeneration of RuBP:
- The remaining G3P molecules are used to regenerate RuBP, which is necessary for the continuation of the Calvin cycle.
- This regeneration requires ATP, which is produced in the light-dependent reactions.

Calculating the Number of Turns

- For the generation of one molecule of glucose, the Calvin cycle needs to fix six molecules of carbon dioxide.
- Each turn of the Calvin cycle fixes one molecule of carbon dioxide and generates two molecules of G3P.
- However, only one molecule of G3P is used for glucose synthesis, while the other five molecules are used to regenerate RuBP.
- Therefore, it takes six turns of the Calvin cycle to generate one molecule of glucose.

Answer
Hence, the correct answer is option A) 6.