Answer :
Answer:
The correct answer will be option-D
Explanation:
The process of photosynthesis release oxygen from the plant which is used by the organism on earth during cellular respiration.
The oxygen released by the plants is formed through the splitting of water molecules as a result of the transfer of electrons through the electron transport chain in the thylakoid membrane during the light-dependent reaction.
Since the released oxygen is the result of the light-dependent reaction and not the light-independent reaction or Calvin cycle where heavy oxygen isotope is utilized in the cycle.
Thus, option-D is the correct answer.
Final answer:
Given CO2 with heavy oxygen (18O), the photosynthesizing green algae will include the 18O in all the organic molecules produced, such as RuBP, sugars, and PGA. However, the O2 released by the algae will not contain the 18O as it originates from water.
Explanation:
If photosynthesizing green algae are provided with CO2 containing heavy oxygen (18O), later analysis will show that all of the following molecules produced by the algae contain 18O, EXCEPT for the oxygen (O2) released by them. This is due to the fact that in photosynthesis, the heavy oxygen is integrated into the organic molecules produced, such as RuBP, sugars produced by the Calvin cycle, and PGA. However, the O2 released comes from water rather than from the CO2 molecule.
The process starts with the fixation of CO2 into organic molecules via the enzyme RuBisCO, where RuBP (ribulose bisphosphate) reacts with CO2 to form an intermediate compound, which eventually becomes 3-phosphoglyceric acid (3-PGA). These molecules now contain the heavy oxygen atom. The 3-PGA is then reduced, using electrons supplied by NADPH, to produce glyceraldehyde 3-phosphate (G3P), which can further be used to synthesize glucose. The last stage is the regeneration of RuBP, which would again be ready to fix another CO2 molecule.
So, in this process, the heavy oxygen (18O) present in the CO2 would be found in the RuBP regenerated, the sugars (like glucose) produced by the Calvin cycle, and the PGA produced in the Calvin cycle, but will not be part of the O2 released by the algae.
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