Overall, light energy drives a flow of electrons along a system of carriers from H2O to NADP+. The carriers are bound to the membrane between reaction centres. Though their precise arrangement is not known, the carriers seem to be organized so that the electron flow cause H+ to move from the stroma to the space within the thylakoids. The resulting difference in H+ concentration across the membrane represents a store of energy that is though to drive he formation of ATP. According to current ideas, the enzymes that form ATP are bound to the thalakoid membrane and are arranged so that the formation of ATP release H+ to the stroma and OH- to the space with in the thylakoid. The OH- combines with H+ to form H2O. These events would decrease the H+ difference across the membrane, “discharging the battery” to form ATP. Electrons move spontaneously along the electron transport chain because each carrier in the chain has a greater tendency to capture and hold electron than the carrier before it.
Photosynthesis which requires the energy of sunlight by the green chlorophyll pigment for the manufacture of carbonhydrate, carbondioxide and H2O. Van Neil propose a general equation for photosynthesis as follows: CO2
H2O + 2A
The hydrogen donator H2A can be H2O, H2S, H2 or any other substance capable of donating hydrogen to CO2 in the process of photosynthesis.
Classic experiments performed by Blackman in 1920 laid the basis that the reaction of photosynthesis were of two types, those requiring light (the light reaction or the photochemical) and those which would proceed in its absence (the dark reaction or the chemical). This separation of photosynthesis was later amplified by the work of Emerson and Arnold (1932) who showed that the light and dark reactions could to separated in time. Cells of the unicellular green alga...
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