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How many ATP and NADPH₂ are required for the synthesis of one molecule of glucose in the Calvin cycle?

(a) 12 ATP and 16 NADPH₂ Your answer
(b) 12 ATP and 12 NADPH₂ Your answer
(c) 18 ATP and 16 NADPH₂ Your answer
(d) 18 ATP and 12 NADPH₂ Correct

Your answer: Correct answer: (d)

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Explanation

Why (d) is correct

Making one glucose needs 6 turns of the Calvin cycle. Each turn (one CO₂) uses 3 ATP and 2 NADPH, so the total is 18 ATP and 12 NADPH.

Why the other options are wrong

(a) · your answer The figures are wrong: it is 18 ATP (6 x 3) and 12 NADPH (6 x 2).
(b) · your answer 12 ATP is too few; regeneration of RuBP needs an extra 6 ATP.
(c) · your answer 16 NADPH is wrong; 6 turns x 2 NADPH = 12.

NCERT point: In: 6 CO₂, 18 ATP, 12 NADPH. Out: 1 glucose, 18 ADP, 12 NADP⁺.

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