Question

Assertion :The splitting of water is associated with PS II Reason: Water is split into $H^{+},O_2$ and electrons

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

The phenomenon of breaking up of water into hydrogen in the illuminated chloroplast is called photoysis or photocatalytic splitting of water. Light energy, an oxygen evolving complex (OEC) and an electron carrier $Y_2$ are required. The complex has four Mn ions. Light energised changes in Mn ($M{n}^{2+},M{n}^3,M{n}^{4+}$) removes electrons from $O{H}^{-}$ component of water forming oxygen. Liberation of $O_2$ also requires two other ions, $C{a}^{2+}+$ and $C{l}^{-}$ Electron carrier $Y_2$ transfers the released electrons to $P_{680}$ (It is a component of a protein connected wiith $P_{680}$ Centre).
$4H_{2}O\rightleftharpoons 4H^{+}+4O{H}^{-}$
$4O{H}^{-}\underset{M{n}^{2+},C{a}^{2+},C{l}^{-}}{\overset{oxygenevolvingcomplex}{\to }}2H_{2}O+O_2\uparrow +4e^{-}$
The electrons released during photolysis of water are picked up by $P_{680}$ photocentre of photosystem II. So the correct answer is 'Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion'.