- A Oxygen evolved in photosynthesis is derived from carbon dioxide rather than from water as generally observed in typical laboratory settings
- B Isolated chloroplasts can evolve oxygen from water in the presence of a suitable electron acceptor, even without CO2 fixation
- C Carbon dioxide fixation can occur in complete darkness if sufficient ATP is supplied externally under normal conditions
- D Chlorophyll molecules can directly fix CO2 into a 3-carbon compound without any enzyme involvement under usual circumstances
Correct answer: B. Isolated chloroplasts can evolve oxygen from water in the presence of a suitable electron acceptor, even without CO2 fixation
Explanation: Robert Hill demonstrated that isolated chloroplasts, supplied with an artificial electron acceptor, could evolve oxygen from water even in the absence of CO2, showing that O2 evolution (water splitting) is independent of CO2 fixation.
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.