Final answer:
The Calvin-Benson cycle needs to turn six times to produce one molecule of glucose, with each turn incorporating one CO2 molecule and using energy from ATP and NADPH.
Step-by-step explanation:
To produce one molecule of glucose, the Calvin-Benson cycle needs to turn six times. Each turn fixes one molecule of carbon dioxide (CO2), and since glucose has six carbon atoms, six CO2 molecules must be incorporated to produce one glucose molecule. The cycle operates in three stages: carbon fixation, reduction, and regeneration of RuBP. It is in the reduction stage where ATP and NADPH are used to convert 3-PGA to GA3P, and after six turns, two GA3P molecules combine to form one glucose molecule.
In summary, the Calvin cycle utilizes energy from ATP and NADPH (12 ATP and 12 NADPH in the reduction step, and 6 ATP in the regeneration step) to fix carbon and produce GA3P, eventually leading to the formation of glucose.