Electron in photosynthesis

Fig. 29. Diagram of an electrode for simulating successive transfer of energy and electron in photosynthesis processes. [From Fromherz and Arden (1980).]...

The oxidation of water by photosystem II to produce oxygen is the ultimate source of electrons in photosynthesis. These electrons are subsequently passed from photosystem II to photosystem I by the electron transport chain. The electrons from water are needed to fill the hole that is left when the absorption of one photon of light leads to donation of an electron from photosystem II to the electron transport chain. 

Reflect and Apply Why do we describe the path of electrons in photosynthesis as starting in photosystem II and ending in photosystem I In other words, why is the nomenclature backward ... 

It is well established that the path of electrons in photosynthesis goes from photosystem II to photosystem I. The reason for the nomenclature is that photosystem I is easier to isolate than photosystem II and was studied more extensively at an earlier date. 

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