Q23.The rate of oxygen production is enhanced when there is operation of
(A) Cyclic photophosphorylation
(B) Non-Cyclic photophosphorylation
(C) Both Cyclic and Non-cyclic photophosphorylation
(D) Oxidative phosphorylation
The correct answer is (B) Non-Cyclic photophosphorylation. Non-cyclic photophosphorylation involves both photosystems I and II, where water splitting (photolysis) releases oxygen as a byproduct, directly enhancing oxygen production rates.​
This process generates both ATP and NADPH while evolving Oâ‚‚, unlike other pathways.
Option Analysis
Cyclic photophosphorylation:Â Involves only photosystem I, with electrons cycling back to produce ATP but no NADPH or oxygen evolution, as water photolysis doesn’t occur.
Non-Cyclic photophosphorylation:Â Uses both photosystems I and II; electrons from water pass linearly through the chain, producing ATP, NADPH, and oxygen via PSII-mediated water splitting.
Both Cyclic and Non-cyclic photophosphorylation: Cyclic contributes no oxygen, so combining doesn’t enhance Oâ‚‚ production beyond non-cyclic alone.​
Oxidative phosphorylation: Mitochondrial ATP synthesis via electron transport; consumes oxygen as the terminal acceptor, not producing it.​
Non-cyclic photophosphorylation enhances the rate of oxygen production through water photolysis at photosystem II, making it essential for atmospheric O₂ generation. This light-dependent reaction powers photosynthesis globally.
Process Details
Cyclic photophosphorylation cycles electrons around PSI for ATP only—no O₂ released. Non-cyclic photophosphorylation drives linear flow, splitting H₂O to yield O₂, ATP, and NADPH. Oxidative phosphorylation occurs in respiration, reducing O₂.
Comparison Table
| Process | Oxygen Production | Key Products |
|---|---|---|
| Cyclic photophosphorylation | None ​ | ATP only |
| Non-cyclic photophosphorylation | Enhanced via photolysis ​ | ATP, NADPH, O₂ |
| Both cyclic/non-cyclic | Only from non-cyclic ​ | Balanced ATP/NADPH |
| Oxidative phosphorylation | Consumes O₂ ​ | ATP (respiration) |


