Question

1. Explain how the oxidation of water and PQH2 during the light reactions contributes to the formation of ATP.

Answer 1

Oxidation of water by PSII generate O₂ H⁺ and e^-

Oxidation of PQH₂ to PQ generate H⁺ and e^-

The e^- (electron) produced during oxidation of water is transferred to PQ to form PQH₂ and further the e^- (electrons) produced during oxidation of PQH₂ to PQ is transferred to b₆f which is further transferred to PSI. During the oxidation of water the H⁺ ion are produced within the thylakoid lumen and when the PQH₂ oxidized to PQ it releases 2 H⁺ within the lumen. Due to this H⁺ ion concentration increases within the thylakoid lumen leading to production of electrochemical proton gradient. This electrochemical proton gradient generate proton motive force across the thylakoid membrane, which is released by passing the H⁺ ion to the stroma through ATP synthase leading to the formation of ATP.

The PSII i.e. Photosystem II is associated with the formation of oxygen by splitting of water. The oxygen atom of O₂ gas comes from water.

ATO Light synthone. WAS STROMA Lihat are con AOPERIT (bot THY LAICOID MEMBRANE SPUTTING WATGR BU PSI Lumen