Light Dependent Reaction: series of Oxidation Reduction Reactions • Reactants • Water • NADP+ • Light • PURPOSE: • Split (oxidize) the Water Molecule-removes H+ • Produce ATP for Calvin Cycle • Reduce NADP+ to NADPH-carries H+ to Calvin Cycle • Products • Oxygen • ATP • NADPH
Light Dependent Reaction 1.Photon of light strikes chlorophyll molecules 2.Chl loses electrons (oxidized) at the reaction center chl -> chl+ + electrons 3.Excited electrons are captured by primary receptor(-reduced) 4. Photolysis and oxidation of water molecule in thylakoid membrane H2O -> 2H+ + electrons + O (joins another O) waste product 5. Electrons from H2O reduce chl+ (chl+ + electrons -> chl) • Chemiosmosis produces ATP as electrons are moved from one receptor to another, releasing energy in the process 7. Electrons reduce chl+ in photosystem I which lost electrons when chl was ecited by photons of light 8. Primary acceptor captures electrons and passes them to NAPD+ 9. NADP+ (reduced) + electrons + H = NADPH 10. NADPH is formed in stroma where the H will be used to produce glucose
Photophosphorylation(Chemiosmosis-producing ATP) 1. H+ ions accumulate in stroma after photolysis of water 2. Electrons move along electron transport chain in thylakoid membrane-release energy to pump H+ into thylakoid • High concentration of H+ in thylakoid causes pH to drop(pH=5); pH=8 in stroma.This creates a concntration gradient from thylakoid to stroma.
Chemiosmosis continued 4. H+ move along gradient through ATP synthetase (in thylakoid membrane) into the stroma • Energy released by moving H+ is captured by ADP and P to produce ATP molecules • ATP is used to power the Light Independent Reaction
Non cyclic photophosphorylation • Produces ATP • Reduces NADP+ to NADPH • Involves PS I and II • P680 and P700 nm • Photolysis of water
Cyclic Photophosphorylation • Produces ATP only • No photolysis of H2O • Involves PS I only • P700 nm • Evolutionary Remnant • Only photosystem in early prokaryotes-used to make ATP, not sugars
Light Independent Reaction • Occurs in absence or presence of light • Carbon Fixation-conversion of an inorganic form of carbon to an organic form • Occurs in the Stroma • Also referred to as the Calvin Cycle-cyclical
NEEDED Carbon Dioxide RuBP Provides energy reducing power to make Organic Compounds: carbohydrates,amino acids, etc ATP -> ADP + P NADPH ->NADP+ + H PRODUCED RuBP Triose Phosphate 6 turns of the Calvin Cycle makes 1 molecule of glucose ADP NADP+ Participants in the Light Independent Reaction