BOLOGY 107 Lecture 14 Outline of Last Lecture I Enzyme Regulation II Redox Reactions III Biological Energetics a Photosynthesis b Light c Light reactions Outline of Current Lecture IV Light Reactions a Linear electron flow b Geometry of the reaction c ATP production V Calvin Cycle a Phases Current Lecture Light Reactions 1 Photosystems a Photosystem II PSII i Absorbs light to a maximum of 680 nm b Photosystem I PSI i Absorbs light to a maximum of 700 nm 2 Linear electron flow a Initial light absorbed by PSII b Excited electrons are passed to the primary acceptor and to the quinone c Electrons are extracted from water to restore the reaction center complex creates O2 and 2H d Electrons pass down the electron transport chain e Protons are passed across the membrane indirectly generate ATP f Energy from light excites electrons in PSI they are passed to the electron receptor ferredoxin g These electrons are replaced by the electrons from PSII h Electrons from PSI passed through second electron transport chain i NADP is reduced to NADPH These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 3 Geometry of the reaction a Water electrons are stripped in the thylakoid space b Electrons are passed to the matrix side by PSII c The reduced plastoquinone picks up H ions from the matrix side d The re oxidized plastoquinone releases H ions into the thylakoid space e Electrons passed to PSI in the thylakoid space f Electrons passed to the matrix by PSI g NADP reduced in the matrix 4 Cyclic electron flow a If all NADP is used the activated ferredoxin electrons are passed to the first electron transport chain to pump more ATP only involves the PSI 5 ATP production a Uses the proton gradient loose H ions from water b ATP synthase used to facilitate diffusion outside the membrane i Multi protein complex in the thylakiod membrane ii Catalytic domain uses ADP and P to create ATP iii Converts potential energy gradient to kinetic energy movement to chemical energy ATP Calvin Cycle a Occurs in stroma b Uses ATP NADPH and CO2 c Forms glyceraldehydes 3 phosphate G3P i Building block for sugars used 1 Phases a Carbon fixation i CO2 attached to RuBP 3x by rubisco ii Results in 3 6 C sugars 1 Unstable splits into 6 3 C sugars spontaneously b Reduction i 3 C sugars phosphorylated by ATP 1 Reduced by NADPH ii 1 G3P leaves 5 stay c Regeneration i 5 3 C sugars rearranged to 3 5 C sugars 1 Phosphate added from ATP ii 3 5 C RuBPs formed d In total 1 G3P made for every 3 CO2 6 NADPH 3 RuBP and 9 ATP e G3P transported outside to cytoplasm i Used for glucose sucrose etc
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