Question

During photosynthesis, an oxygen molecule comes from water. This was proved by

• A. Ruben and Kamen
• B. Hill
• C. Warburg
• D. Black man

Answer 1

Answer: (A)

Ruben and Kamen

Oxygen is released during photosynthesis by the process of photolysis in which the water is broken down into proton, electron and oxygen in the presence of sunlight. The atmospheric oxygen contains the oxygen atoms which are O${}^{16}$. Ruben conducted an experiment by labelling the oxygen of water with O${}^{18}$. The oxygen evolved during photolysis contained O${}^{18}$. He also prepared a source of carbon dioxide that was enriched in O${}^{18}$. The oxygen evolved was not comprised of labelled O${}^{18}$ isotope. So, it was proved that oxygen evolved was from water molecules not carbon dioxide.

So, the correct answer is option A.