Question

Photooxidation of water results in the formation of
A. $H^{+}$, $O_{2}$, ATP
B. $H^{+}$, $O_{2}$, e-, ATP
C. $H^{+}$, $O_{2}$, e-
D. None of the above

Answer 1

Hint: Photosynthesis is the synthesis of carbohydrates or food from sunlight, water and carbon dioxide by the green plants. It is an endergonic and anabolic process in which the light energy is changed into chemical energy by plants. During this process photooxidation of water occurs.

Complete answer: During the light reaction, light is trapped by photosynthetic pigments present in the quantasomes of grana thylakoids. The light-harvesting complexes are made up of hundreds of pigments bounded by proteins.
Each photosystem has a different reaction centre that contains a special chlorophyll-a molecule. It also has hundreds of other pigment molecules that make up the light-harvesting system called antennae which absorb light of shorter wavelengths to make the photosynthesis more efficient.
The reaction centre is different for both the photosystems I and II.
PS-I - The reaction centre or the chlorophyll-a has a peak of absorption at a wavelength of 700 nm.
PS-II- The reaction centre has a peak of absorption at 680 nm.
The photosystem-II has a small complex of proteins attached to it called the oxygen evolving complex. It oxidizes water into oxygen, H+ and electrons. So molecular oxygen is evolved by PS-II. In PS-I molecular oxygen is not evolved.
So, the correct answer is “Option C”.

Note: The process of photosynthesis has two phases- light phase and the dark phase. The light phase includes steps like absorption of light, splitting of water, the release of oxygen and the formation of high energy chemical intermediates i.e. ATP and NADPH. Dark phase uses the products of light reaction for carbon fixation.