Talk about the cyclic chain first step (Light absorption and its effects)

Photosystem I can operate independently of photosystem II. The molecules of the P700 reaction center absorb light, the excited electron moves to a primary acceptor molecule that transfers its additional electron to a secondary acceptor and so on along the electron transport chain. Finally, the electrons return to the reaction center of photosystem I. This transfer of electrons is coupled to a proton pump from the outside to the inside of the thylakoid membrane creating a proton motive force capable of producing ATP from ADP and Pi. This ATP synthesis in chloroplast due to light is called phosphorylation.