For each molecule of glucose produced during the carbon fixation reactions of photosynthesis, how many RuBP molecules, CO₂ molecules, and G3P molecules are involved in the steps of the Calvin cycle?

To produce one glucose molecule in photosynthesis, 12 RuBP molecules, 6 CO₂ molecules, and 12 G3P molecules are involved in the Calvin cycle, with six cycles needed to fix enough carbon.

Explanation:

For each molecule of glucose produced during the carbon fixation reactions of photosynthesis, 12 molecules of ribulose-1,5-bisphosphate (RuBP) are required, because the Calvin cycle has to go around six times to produce a six-carbon glucose molecule. Photosynthesis also involves the fixation of 6 carbon dioxide (CO₂) molecules, as one CO₂ molecule is fixed per cycle. In terms of glyceraldehyde-3-phosphate (G3P) molecules, three full cycles of the Calvin cycle yield one G3P that can leave the cycle to contribute to the formation of glucose, while the other G3Ps are used to regenerate RuBP. Therefore, to create the equivalent of one full glucose molecule, it takes six cycles, which corresponds to 6 CO₂ molecules fixed, 12 G3P molecules (two of which leave the cycle), and 12 molecules of regenerated RuBP.