In light-dependent reactions of photosynthesis, what is the initial electron donor that undergoes photolysis to release oxygen gas?
Answer and explanation
Correct answer: A. water molecules (H2O)
- Step 1: Photosystem II splits water (2 H2O -> 4 H+ + 4 e- + O2) to replenish electrons excited by sunlight, releasing O2 as a byproduct. Answer: water molecules (H2O). Why not the others: CO2 is fixed during the light-independent Calvin cycle, not split for electrons.
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