If photosynthesizing green algae are provided with CO₂ containing heavy oxygen (18O), subsequent analysis will show that 18O first appears in which of the following molecules produced by the algae?

Question

Quizplus · Accepted Answer

The heavy oxygen (18O) will first appear in the molecule 3-phosphoglycerate. This is because in the first step of the Calvin cycle, the enzyme rubisco catalyzes the carboxylation of RuBP with CO₂ to form 2 molecules of 3-phosphoglycerate, and the oxygen in CO₂ becomes incorporated into the organic molecule. Therefore, any 18O in the CO₂ will be first incorporated into 3-phosphoglycerate.

If Photosynthesizing Green Algae Are Provided with CO₂ Containing Heavy