BOLOGY 107 Lecture 14Outline of Last Lecture I. Enzyme RegulationII. Redox ReactionsIII. Biological Energeticsa. Photosynthesis b. Light c. Light reactions Outline of Current Lecture IV. Light Reactionsa. Linear electron flowb. Geometry of the reactionc. ATP production V. Calvin Cyclea. PhasesCurrent LectureLight Reactions1) Photosystems a) Photosystem II (PSII)i) Absorbs light to a maximum of 680 nmb) Photosystem I (PSI)i) Absorbs light to a maximum of 700 nm 2) Linear electron flowa) Initial light absorbed by PSIIb) Excited electrons are passed to the primary acceptor and to the quinonec) Electrons are extracted from water to restore the reaction center complex, creates O2 and 2H+d) Electrons pass down the electron transport chaine) Protons are passed across the membrane, indirectly generate ATPf) Energy from light excites electrons in PSI, they are passed to the electron receptor ferredoxing) These electrons are replaced by the electrons from PSIIh) Electrons from PSI passed through second electron transport chaini) NADP+ is reduced to NADPHThese 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 spaceb) Electrons are passed to the matrix side by PSIIc) The reduced plastoquinone picks up H+ ions from the matrix sided) The re-oxidized plastoquinone releases H+ ions into the thylakoid spacee) Electrons passed to PSI in the thylakoid spacef) Electrons passed to the matrix by PSIg) NADP+ reduced in the matrix4) Cyclic electron flowa) If all NADP+ is used, the activated ferredoxin electrons are passed to the first electron transport chain to pump more ATP, only involves the PSI5) ATP productiona) Uses the proton gradient (loose H+ ions from water)b) ATP synthase used to facilitate diffusion outside the membranei) Multi-protein complex in the thylakiod membraneii) Catalytic domain uses ADP and P to create ATPiii) Converts potential energy (gradient) to kinetic energy (movement) to chemical energy (ATP)Calvin Cyclea) Occurs in stromab) Uses ATP, NADPH, and CO2c) Forms glyceraldehydes-3-phosphate (G3P)i) Building block for sugars used1) Phases a) Carbon fixationi) CO2 attached to RuBP (3x) by rubiscoii) Results in 3 6-C sugars(1) Unstable, splits into 6 3-C sugars spontaneouslyb) Reduction i) 3-C sugars phosphorylated by ATP(1) Reduced by NADPHii) 1 G3P leaves, 5 stayc) Regeneration i) 5 3-C sugars rearranged to 3 5-C sugars(1) Phosphate added from ATPii) 3 5-C RuBPs formedd) In total, 1 G3P made for every 3 CO2, 6 NADPH, 3 RuBP, and 9 ATPe) G3P transported outside to cytoplasmi) Used for glucose, sucrose,
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