From where does the oxygen in glucose come in photosynthesis?

Question

Is it carbon dioxide or water? I'm talking about the oxygen present in glucose and not the oxygen that is released after photolysis of water.

Answer 1

The oxygen in the glucose molecule comes from the carbon dioxide, which is used in the Calvin Cycle. As you mentioned, the oxygen in water is broken down in the non-cyclic phosphorylation process to obtain an electron which can be used in the photosystem I and II to form ATP and NADPH.