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Electron transport chain refers to the light driven reactions of photosynthesis. They were first formulated in 1939 by Robert Hill.
The two photosystems are connected in series with each other by the components of electron transport system. The reaction centres become so excited that they escape high energy electron (e-) which move to nearby electron acceptor molecules. The electrons move through two pathways - non-cyclic and cyclic. The non-cyclic electron transport system involves participation of both PS-II and PS-I, whereas cyclic electron transport chain involves only PS-I.
Non-cyclic Electron Transport System
The light energy of specific wavelengths is absorbed by chlorophylls and accessory pigments of PS-II. These pigments transfer their absorbed energy to PS-II reaction centre - P
680 (chlo 680). This centre become photo excited and exudes an electron with a gain of energy (23 K Cal/mol).
The electron is immediately accepted by the primary acceptor quinone. The reaction centre comes to ground state by getting an electron from photo-oxidation of water. (The overall process involving conversion of light energy into chemical form is called quantum conversion).
