Light & Dark Reactions of Photosynthesis — NEET Biology
✅ Asked in NEET 2024We learnt that the products of light reaction are ATP, NADPH and O₂. Of these O₂ diffuses out of the chloroplast while ATP and NADPH are used to drive the processes leading to the synthesis of food, more accurately, sugars. This is the biosynthetic phase of photosynthesis. This process does not directly depend on the presence of light but is dependent on the products of the light reaction, i.e., ATP and NADPH, besides CO₂ and H₂O. You may wonder how this could be verified; it is simple: immediately after light becomes unavailable, the biosynthetic process continues for some time, and then stops. If then, light is made available, the synthesis starts again.
NTA tests whether students understand that O₂ is a product of light reaction that diffuses out, while ATP and NADPH are used in the dark reaction (Calvin cycle) to synthesize glucose. The common mistake is confusing which reaction depends on light directly—students often think the biosynthetic phase needs light, but it actually depends only on ATP and NADPH from the light reaction. The trap: NEET questions ask why the dark reaction continues briefly after light is removed (due to residual ATP/NADPH) and stops later (when those molecules deplete). Remember: Light reaction is light-dependent; dark reaction is light-independent but ATP/NADPH dependent.
This paragraph was tested 3 times in NEET.
(NEET 2024) Which one of the following products diffuses out of chloroplast during photosynthesis?
(NEET 2024) Which of the following are required for the dark reaction of photosynthesis? A. Light B. Chlorophyll C. CO₂ D. ATP E. NADPH
Which of the following is not a product of light reaction of photosynthesis? (NEET 2018)
Through deep analysis of NEET and NTA, 88 of 90 questions from the NEET 2026 paper were matched straight from the MedicNEET Biology question bank.
88/90MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.