What happens to the oxygen released from splitting water?

• A. It is used to synthesize CO2
• B. It remains in the leaf as peroxide
• C. Either used in respiration OR released to the atmosphere
• D. It forms glucose directly

Answer: (C)

Oxygen produced in photosynthesis comes from splitting water during the light-dependent reactions. When water is split, O2 is formed and released as a gas from the leaf. This oxygen isn’t used to build CO2 or to form glucose directly; glucose is created later from CO2 in the Calvin cycle. In plant cells, some of the produced O2 is used in respiration to generate ATP, while the rest diffuses out into the atmosphere. So the oxygen released from splitting water can either be used in respiration or released to the atmosphere.