Question

Non-cyclic photophosphorylation is performed by:
(1) dark reaction
(2) PS-I
(3) only PS-I
(4) PS-II

• A. 1,2 and 3 are correct
• B. 1 and 2 are correct
• C. 2 and 4 are correct
• D. 1 and 3 are correct

Answer 1

Answer: (C)

Non-cyclic photophosphorylation is carried out in collaboration of both photosystems-I and II. Electrons released during photolysis of water are picked up by photocentre of PS-II called $P_{680}$. The same is extruded out when the photocentre absorbs light energy $(hv.)$ The extruded electron has an energy equivalent to $23kcal/mole$. It passes through ' a series of electron carriers-Phaeophytin, $PQ$ cytochrome $b-f$ complex and plastocyanin. while passing over cytochrome complex, the electron loses sufficient energy for the synthesis of ATP. The electron is handed over to photocentre $P_{700}$ of PS-I (One) by plastocyanin.