Answer :
The molecule that does not contain heavy oxygen (^18^O) after photosynthesis in green algae is O_2 released by them. This is because O_2 originates from water in the light-dependent reactions, not from the CO_2 provided for the Calvin cycle. Therefore, the correct option is D
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 O2 released by them. This is because the 18O from the CO2 is incorporated into the Calvin cycle and ends up in the carbohydrate products and intermediate molecules such as ribulose bisphosphate (RuBP), 3-phosphoglyceric acid (PGA), and sugars produced through the Calvin cycle (like G3P, which eventually forms glucose).
During the light-dependent reactions of photosynthesis, the water molecule is split in a process called photolysis, and this is where the O2 released comes from. The oxygen that is released as a byproduct of photosynthesis is derived from the water molecules, not from the carbon dioxide; therefore, it would not contain the heavy oxygen 18O if the algae were only provided with 18O through CO2.
The molecule that does not contain heavy oxygen (^18^O) after photosynthesis in green algae is O_2 released by them. This is because O_2 originates from water in the light-dependent reactions, not from the CO_2 provided for the Calvin cycle. Therefore, the correct option is D
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 O2 released by them. This is because the 18O from the CO2 is incorporated into the Calvin cycle and ends up in the carbohydrate products and intermediate molecules such as ribulose bisphosphate (RuBP), 3-phosphoglyceric acid (PGA), and sugars produced through the Calvin cycle (like G3P, which eventually forms glucose).
During the light-dependent reactions of photosynthesis, the water molecule is split in a process called photolysis, and this is where the O2 released comes from. The oxygen that is released as a byproduct of photosynthesis is derived from the water molecules, not from the carbon dioxide; therefore, it would not contain the heavy oxygen 18O if the algae were only provided with 18O through CO2.