During non-cyclic photophosphorylation, what is the primary role of the oxygen-evolving complex (OEC) associated with Photosystem II?
Answer and explanation
Correct answer: C. Splitting water into protons, electrons, and molecular oxygen at the luminal side of the thylakoid membrane
- Step 1: Photosystem II contains a water-splitting complex (OEC) containing a manganese cluster () and chloride ions.
- Step 2: The complex is situated on the inner (luminal) surface of the thylakoid membrane.
- Step 3: It oxidizes water: , supplying replacement electrons to the photo-oxidized reaction center P680+.
Answer
Splitting water into protons, electrons, and molecular oxygen at the luminal side of the thylakoid membrane
Why not the others: 'Reducing NADP+ to NADPH...' is catalyzed by ferredoxin-NADP+ reductase (FNR) on the stromal side; 'Pumping protons directly from the stroma...' is mediated by plastoquinone and the cytochrome b6f complex, not the OEC; 'Transferring electrons directly from plastocyanin...' describes the reduction of P700+ by plastocyanin, which operates downstream of PS II.
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