Photosynthesis source of oxygen: Identify the molecule that provides the O₂ released. Full question: During photosynthesis, the oxygen gas (O₂) evolved comes from which reactant molecule? Choose the correct option.
General Knowledge
Biology
Difficulty: Easy
Choose an option
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AWater (H₂O)
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BCarbon dioxide (CO₂)
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CGlucose (C₆H₁₂O₆)
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DChlorophyll
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EOxygen dissolved in cytoplasm
Answer
Correct Answer: Water (H₂O)
Explanation
Given data
- Target: Identify the source of released O₂ in photosynthesis.
Concept / ApproachIn the light reactions, water undergoes photolysis at photosystem II, producing electrons, protons, and O₂. Isotopic tracing (using H18₂O) shows that the oxygen comes from water, not CO₂.
Key reaction fragment2 H₂O → O₂ + 4H⁺ + 4e⁻ (driven by light energy)
Final AnswerWater (H₂O).