Question

Which statement is correct for given reaction for photosynthesis?

$2H_{2}A+C{O}_2\stackrel{light}{\to }2A+C{H}_{2}O+H_{2}O$

• A. $H$ donor is oxidisable substrate
• B. $O_2$ evolve from $H_{2}O$ if reducible compound is $H_{2}O$
• C. Glucose gain its oxygen from $H_{2}O$
• D. Both A and C
  

Answer 1

The correct option is A $H$ donor is oxidisable substrate

The light reaction of the photosynthesis starts when the chlorophyll loses its electron after absorbing the light. In order to maintain the continuity of the reaction, there is a requirement of an oxidizable substance that can donate its electron to the chlorophyll. Water acts as the electron donor through a process called photolysis of water. In this process, the oxygen is also released as a by-product.

A. In the given equation H donor is an oxidizable substrate that happens to be water.

B. O${}_2$ is evolved from water but it is not reducible compound.

C. Glucose in oxygen comes from the carbon dioxide and not water. The oxygen from water is released as a by-product of the reaction.

Hence, the correct answer is 'H donor is oxidizable substrate'.