LIGHT REACTION
It is also called hill reaction or primary photo chemical reaction.it takes in the presence of light in grana portion of chloroplast.in light reaction,assimilatory power NADPH2 and ATP is formed and oxygen is evolved.it involves following process:
Photo excitation of chlorophyll-a : a molecule of chlorophyll -a receives light energy in the form of photon and chlorophyll-a becomes activated. in this state ,chlorophyll-a release one electron and develop a +ve charge on it.the released electron contains extra amount of energy, and part of which is utilised to split out water and other part is utilised in formation of atp.
photolysis of water : during this process,water molecules split into H+and OH- ion in presence of light and chlorophyll. OH- ion reunite to form water molecule and O2 is evolved.the ionised chlorophyll is brought back to ground state with help of electron made available hrough photolysis of water.
photophospho relation : in this process,light energy is converted into chemical energy in the form of ATP.the energy released by excited chlorophyll-a is used in formation of ATP from ADP and phosphoric acid.
the photo phospho relation takes place in two steps :
Non-cyclic:
in this process,movement of electron is unidirectional. it starts from ps2. the electron donated by ps2 pass through plastoquinone,cytochromeb6,cytochrome f ,plastocyanin and finally accepted by ps1.the electron given out by ps1 are taken up by primary acceptor and ultimately passes on to NADP. the electron combines with hydrogen ion and reduces NADP into NADPH2.the NADPH2 is utilised for reduction of Co2 into glucose.during this entire process,ATP SYNTHESIS occurs between cytochromeb6 and cytochrome f, oxygen is evolved and NADPH2 is formed.
Cyclic : in this process,the initial donar and final acceptor of electron is same i.e chlorophyll-a of ps1.hence the movement of electron is cyclic.in this cycle,ps1 receives light energy,becomes acticated and expels electrons.the electron are taken up by ferredoxin. the electrons are returned back to ps1 through cytochrome b6,cytochrome f and plastocyanin. in this process, 2 ATP molecule is formed per electron transfer,water is not splitted and oxygen is not evolved.
It is also called hill reaction or primary photo chemical reaction.it takes in the presence of light in grana portion of chloroplast.in light reaction,assimilatory power NADPH2 and ATP is formed and oxygen is evolved.it involves following process:
Photo excitation of chlorophyll-a : a molecule of chlorophyll -a receives light energy in the form of photon and chlorophyll-a becomes activated. in this state ,chlorophyll-a release one electron and develop a +ve charge on it.the released electron contains extra amount of energy, and part of which is utilised to split out water and other part is utilised in formation of atp.
photolysis of water : during this process,water molecules split into H+and OH- ion in presence of light and chlorophyll. OH- ion reunite to form water molecule and O2 is evolved.the ionised chlorophyll is brought back to ground state with help of electron made available hrough photolysis of water.
photophospho relation : in this process,light energy is converted into chemical energy in the form of ATP.the energy released by excited chlorophyll-a is used in formation of ATP from ADP and phosphoric acid.
the photo phospho relation takes place in two steps :
Non-cyclic:
in this process,movement of electron is unidirectional. it starts from ps2. the electron donated by ps2 pass through plastoquinone,cytochromeb6,cytochrome f ,plastocyanin and finally accepted by ps1.the electron given out by ps1 are taken up by primary acceptor and ultimately passes on to NADP. the electron combines with hydrogen ion and reduces NADP into NADPH2.the NADPH2 is utilised for reduction of Co2 into glucose.during this entire process,ATP SYNTHESIS occurs between cytochromeb6 and cytochrome f, oxygen is evolved and NADPH2 is formed.
Cyclic : in this process,the initial donar and final acceptor of electron is same i.e chlorophyll-a of ps1.hence the movement of electron is cyclic.in this cycle,ps1 receives light energy,becomes acticated and expels electrons.the electron are taken up by ferredoxin. the electrons are returned back to ps1 through cytochrome b6,cytochrome f and plastocyanin. in this process, 2 ATP molecule is formed per electron transfer,water is not splitted and oxygen is not evolved.
hey great work
ReplyDelete