Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Six turns of the Calvin cycle are required to synthesize one molecule of glucose. Reason (R): The regeneration of RuBP during the Calvin cycle requires two ATP molecules for every molecule of CO₂ fixed. In the light of the above statements, choose the most appropriate answer from the options given

Step-by-step solution

Assertion (A) is correct because one turn of the Calvin cycle fixes one molecule of CO₂ . Since glucose is a six-carbon sugar ( C₆H₁₂O₆ ), six turns of the cycle are required to synthesize one molecule of glucose. Reason (R) is incorrect because the regeneration of the CO₂ acceptor molecule (RuBP) requires only one ATP molecule for phosphorylation per molecule of CO₂ fixed, not two. It is the reduction step that requires two ATP molecules per CO₂ fixed. Therefore, Assertion is correct but Reason is not correct. Ans