Cyclic Photophosphorylation & PS I — NEET Biology
✅ Asked in NEET 2023Which of the following statements is incorrect? (NEET 2023)
Which of the following statements is incorrect? (NEET 2023)
Which of the following statements is incorrect? (NEET 2021)
Answer & NCERT explanation
Correct answer: B — Cyclic photophosphorylation involves both PS I and PS II
This is identical to question 7. Cyclic photophosphorylation involves only PS I, not both photosystems. As stated in NCERT, cyclic process uses only photosystem I where electrons circulate back to the same photosystem generating ATP but not NADPH. Non-cyclic photophosphorylation requires both PS I and PS II to produce both ATP and NADPH.
Read more NCERT concept on the PYQ
When only PS I is functional, the electron is circulated within the photosystem and the phosphorylation occurs due to cyclic flow of electrons. A possible location where this could be happening is in the stroma lamellae. While the membrane or lamellae of the grana have both PS I and PS II the stroma lamellae membranes lack PS II as well as NADP reductase enzyme. The excited electron does not pass on to NADP+ but is cycled back to the PS I complex through the electron transport chain. The cyclic flow hence, results only in the synthesis of ATP, but not of NADPH + H+. Cyclic photophosphorylation also occurs when only light of wavelengths beyond 680 nm are available for excitation.
In cyclic photophosphorylation, only PS I operates and electrons cycle back to PS I instead of moving to NADP+, producing only ATP—not NADPH. This occurs in stroma lamellae lacking PS II and NADP reductase. Students often confuse it with non-cyclic photophosphorylation (which uses both PS I and PS II to make both ATP and NADPH). Remember: cyclic = PS I only = ATP only; non-cyclic = both photosystems = ATP + NADPH. NTA tests whether you distinguish between these pathways and understand which products each makes.
What does NCERT say about When only PS I?
Has this concept appeared in NEET?
Which chapter is this from?
Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.
176/180MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.