- A An iron-sulfur cluster that shuttles electrons toward plastoquinone
- B A manganese cluster (Mn4CaO5) that oxidizes water to release O2
- C A copper-containing center analogous to that found in plastocyanin
- D A zinc-finger motif that stabilizes the reaction center protein scaffold
Correct answer: B. A manganese cluster (Mn4CaO5) that oxidizes water to release O2
Explanation: OEC (oxygen-evolving complex) contains a Mn4CaO5 cluster. It cycles through 5 S-states (S0-S4). At S4, two water molecules are oxidized to release O2, 4H+ and 4e-.
Concept context
Light reactions, the Calvin cycle, C3/C4/CAM pathways, photorespiration, and factors affecting the rate of photosynthesis. One of the highest-yield NEET chapters.