Answer: Isolated chloroplasts can evolve oxygen from water in the presence of a suitable electron acceptor, even without CO 2 fixation.
- 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 CO<sub>2</sub> 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 CO<sub>2</sub> 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 CO<sub>2</sub> fixation
Explanation: Robert Hill demonstrated that isolated chloroplasts, supplied with an artificial electron acceptor, could evolve oxygen from water even in the absence of CO<sub>2</sub>, showing that O<sub>2</sub> evolution (water splitting) is independent of CO<sub>2</sub> fixation.
Simplified photosynthesis diagram: light energy, CO2, and H2O enter the leaf and are converted in the chloroplast into glucose and O2.
Concept context
Light reactions, the Calvin cycle, C 3 /C 4 /CAM pathways, photorespiration, and factors affecting the rate of photosynthesis. One of the highest-yield NEET chapters.