ATP and NADPH Requirements in Calvin Cycle — NEET Biology
✅ Asked in NEET 2026How many ATP and NADPH molecules are required to make one molecule of glucose through the Calvin pathway?
How many ATP and NADPH molecules are required to make one molecule of glucose through the Calvin pathway?
(NEET 2024) How many molecules of ATP and NADPH are required for every molecule of CO₂ fixed in the Calvin cycle?
(NEET 2024) How many molecules of ATP and NADPH are required, respectively, for fixation of every CO₂ molecule entering the Calvin cycle?
How many ATP and NADPH₂ are required for the synthesis of one molecule of glucose during Calvin cycle? (NEET 2023)
Answer & NCERT explanation
Correct answer: A — 18 ATP and 12 NADPH
Each Calvin cycle turn fixes 1 CO2 using 3 ATP and 2 NADPH. To make one glucose (6 carbons), 6 turns are needed: 6x3 = 18 ATP and 6x2 = 12 NADPH.
Read more NCERT concept on the PYQ
Hence for every CO₂ molecule entering the Calvin cycle, 3 molecules of ATP and 2 of NADPH are required. It is probably to meet this difference in number of ATP and NADPH used in the dark reaction that the cyclic phosphorylation takes place.
For every one CO₂ molecule fixed in the Calvin cycle, exactly 3 ATP and 2 NADPH molecules are consumed. The NTA tests whether students can recall these specific stoichiometric ratios and understand why more ATP than NADPH is needed. Students commonly confuse the numbers or forget that cyclic photophosphorylation specifically occurs to generate the extra ATP molecules required. The key to remembering: 3 ATP per CO₂ (not 2), and 2 NADPH per CO₂. This imbalance explains why cyclic photophosphorylation is essential—it produces additional ATP without generating NADPH, balancing the energy requirements of the dark reaction.
What does NCERT say about Hence for every CO?
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