Question

Through the use of oxygen isotope 18 (heavy oxygen), scientists have found that the oxygen released during photosynthesis comes from molecules of

Answer 1

Ruben and Kamen traced the route of oxygen through photosynthesis using an isotope of oxygen. An alga was given heavy oxygen in the form of either water or carbon dioxide and it was found that the isotope given in H${}_2$O was invariably found in the resulting O${}_2$.