Question

The oxygen produced during photosynthesis comes from photolysis of water was first time proved by
A. Ruben and Kamen
B. Robert Mayer
C. Malvin Calvin
D. Blackman

Answer 1

Hint: Photosynthesis is a physicochemical process by which the plants use light energy to drive the synthesis of an organic compound. Photosynthesis is important due to two reasons first it is the primary source of food on earth. It is also responsible for the release of oxygen into the atmosphere by green plants.

Step by step answer:
1. Photosynthesis is completed into steps or stages.
2. First is the light reaction which directly uses the light energy and also synthesises ATP and NADPH.
3. The product of light reactions are used in the dark reaction. Which is used in the second stage of
photosynthesis for the enzymatic reaction synthesis of sugar which in turn forms starch.
4. Photolysis of water is a part of the light-dependent reaction of the photosynthesis process.
5. In the photolysis of water oxygen is released from the water molecule which was first
experimentally proved by Ruben and Kamen.
6. By the use of radioactive isotopes they found that oxygen comes from water.
So, the correct answer is ( A )
Additional information :
1. As we know that the photosynthesis occurs in the mesophyll cells in the leaves that have a large
number of chloroplasts.
2. Within the chloroplast there is a membrane system consisting of grana, stroma lamina, and the
matrix stroma.
3. Grana region of the chloroplast is where the light reaction occurs.
4. Stroma region of the chloroplast is the region where the dark reaction occurs.

Note: Dark reaction is not that it is independent of light . As a dark reaction is not directly
dependent on light but depending on the products obtained by the light reaction.