Question

In an experiment regarding photosynthesis, the oxygen of co 2 and h 2 o is labelled as 16o and 18o, respectively. The oxygen evolved during photosynthesis would be labelled as

Answer 1

First we have the water broken into components by light.

2H2O →  4e- + 4H+ + O2

This is followed by:

CO2 + 4e- + 4H+ → CH2O + H2O

Then ATP production and the fixation of carbon in the plant.

So the free oxygen comes from the water, not the CO2.