Question

All of the following statements are incorrect for non-cyclic electron transport system, except:

• A. Electron transport between PS -II to PS-I produces ATP by substrate level phosphorylation.
• B. In PS-II, the oxidation of two water molecules produces four electrons, four protons, $\&$ a single $O_2$.
• C. Water is oxidized & electrons are released by PS-I.
• D. PS - II reduces $NAD{P}^{+}$to $NADPH$.

Answer 1

Answer: (B)

Photophosphorylation (discovered by Arnon) is of two types- cyclic and non-cyclic phosphorylation. Non cyclic photophosphorylation involves the participation of both PS I and PS II. The first step is photo-oxidation of water resulting in splitting of water into $H^{+},e^{-}$and release of $O_2$. It involves sequence of electron transfer where $NAD{P}^{+}$is reduced by PS-I, PS-I is reduced by PS-II and PS-II is reduced by water so that the electro transport is non-cyclic.