What is photosystem ? Which is the pigment that acts as reaction centre ? Describe the interaction of photosystem I and photosystem II.
Photosystem : It is a group of pigment molecules and electron acceptors which take part in oxidation and reduction reaction in photosynthesis for producing ATP and NADPH.
Reaction Centre : Chla molecules act as reaction centres. The Chla of speacial types form different reaction centres like P680 in PS II and P700 in PS I.
Interaction of PS I and PS II :
PS I and PS II are interlinked in following two
Ist way : P680 reaction centre of PS II takes energy from sunlight. Then, it emits electron which pass through number of electron acceptors and then go to P700, a reaction centre of PSI.
IInd way : The P700 takes energy from sunlight via harvesting molecule and its electron is emitted. This electron passes through primary acceptor x and then to ferrodoxin and after this to NADP reductase.
During photolysis of H2O, the H2O splits into H+ and OH–. The OH– changes into H2O, O2 and electrons are released which go to P680 molecule. The H+ goes to NADP reductase which combines NADP, H+ and e– form assimilatory power called NADPH