# Overview of Chemiosmotic hypothesis

Abstract: An important part of photosynthesis is chemiosmotic theory or hypothesis . We have already learn electron transport chain. When the electron passes from it , it then releases energy and this energy used for the synthesis of ATP. Here I simply discuss the matter but the original phenomenon is quite complicated let's draw a thylakoid. It is an outer membrane and an inner membrane. The cavity is known as lumen. The water splitting complex is present in the the inner membrane .

Thylakoid 

On the bottom of PS II there is chlorophyll reaction center and the top is primarily electron acceptor and then electron is going to pass from PS II to PS I through cytochrome . When the sunlight fall on PS II then the electron are activated and now electron pair is passing through cytochrome and finally go to the PS I  this electron is going to higher level to lower level. It release energy at the cytochrome. It reveals that energy when the electron transport the electron from Pq to Pc . The cytochrome accept a pair of proton from stroma and pass the proton in the lumen using the energy from stroma .

The water splitting complex is activated to replace the electrons to PS II .

It releases 3 things .....

1. A pair of electrons.

2. A pair of protons

3.1/2 O2 

1/2 O2 is released in lumen and diffused from it.

Now if u see , there are one pair of protons is pumped by cytochrome and H2O splitting complex also produced a pair of protons so here protons gradient is higher than stroma . protons comes out in Stroma by integral protein and extrinsic protein complex (F0-F1) . F0 - F1 particle acting as a channel for proton that they can go from higher concentrations to lower . F0 helps  facilitated diffusion of protons. When protons enter in F0 then it releases energy , which is used by F1 particle to add an inorganic phosphate to ADP and make ATP . 

The electron pair  is going to PSI and then this pair of electron will go to NADP  and the enzyme NADP reductase is going to help in formation of production reducing power and then proton is required. 

NADP +2 proton in the presence of NADP REDUCTASE produce NADPH2 . The light reaction take place in thylakoid but the dark reaction is takes place in stroma.

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