Q. Find the number of ATP required in the reduction step of the C3 cycle if the cycle is involved in the formation of one sucrose molecule.

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Solution:

Calvin cycle consists of three steps, carboxylation, reduction, and regeneration. For a reduction of 6 molecules of carbon dioxide to form one glucose molecule, 12 ATP molecules are required. Sucrose, commonly named cane and beet sugar is a disaccharide with the combination of the monosaccharides glucose and fructose with the formula C12H22O11. The ATP molecule required in reduction step of the Calvin cycle is 24. Here, 6 ATP is required for 3 carbon sugar. In sucrose 12 carbon is present. So, 6 x 4=24 ATP. Hence, the correct answer is 24.