Water Splitting & Proton Accumulation — NEET Biology
✅ Asked in NEET 2022Identify the correct statements regarding chemiosmotic hypothesis: (NEET 2022 Phase 2) (a) Splitting of the water molecule takes place on the inner side of the membrane. (b) Protons accumulate within the lumen of the thylakoids. (c) Primary acceptor of electron transfers the electrons to an electron carrier. (d) NADP reductase enzyme is located on the stroma side of the membrane. (e) Protons increase in number in stroma.
Identify the correct statements regarding chemiosmotic hypothesis: (NEET 2022 Phase 2) (a) Splitting of the water molecule takes place on the inner side of the membrane. (b) Protons accumulate within the lumen of the thylakoids. (c) Primary acceptor of electron transfers the electrons to an electron carrier. (d) NADP reductase enzyme is located on the stroma side of the membrane. (e) Protons increase in number in stroma.
Answer & NCERT explanation
Correct answer: C — , (b) and (d)
Correct statements are: water splitting occurs on inner side (lumen side), protons accumulate in thylakoid lumen, and NADP reductase is on stroma side. According to NCERT chemiosmotic theory, water splits at PS II releasing protons into lumen, creating gradient. NADP reductase on stroma side reduces NADP+ using electrons. Protons decrease in stroma, not increase.
Read more NCERT concept on the PYQ
Since splitting of the water molecule takes place on the inner side of the membrane, the protons or hydrogen ions that are produced by the splitting of water accumulate within the lumen of the thylakoids.
During light reactions in photosynthesis, water molecules split inside the thylakoid lumen (not outside), releasing protons (H⁺ ions) and oxygen. These protons accumulate specifically in the thylakoid lumen, creating a proton gradient across the thylakoid membrane. Many students mistakenly think water splitting happens in the stroma or that protons are equally distributed everywhere. The critical point to remember: the location of water splitting (inner membrane side) directly causes proton concentration inside the thylakoid lumen, which drives ATP synthesis. NTA tests this because understanding compartmentalization and ion gradients is fundamental to photosynthesis mechanisms.
What does NCERT say about Since splitting water molecule?
Has this concept appeared in NEET?
Which chapter is this from?
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.