# Which gas molecule is given off as a waste product during the light dependent reactions?

Oxygen, $\text{O"_2}$
During the light dependent reactions of photosynthesis, water is split into $\text{O"_2}$ and ${\text{H}}^{+}$. The oxygen is excreted and the hydrogen ion combines with NADP to form NADPH, which will be used in the Calvin cycle (light independent reactions).