lecture 9 - Photosynthesis Section II Diversity of vascular...

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Photosynthesis
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Section II Diversity of vascular plants, photosynthesis and respiration Session 7 Bryophytes, Vascular Plants Session 8 Flowering Plants Session 9 Photosynthesis Session 10 C4 photosynthesis and Respiration Session 11 Mineral nutrition Session 12 Plant tissues
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Photosynthesis occurs in the chloroplasts of leaf cells Where does it happen?
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The Phases of Photosynthesis Photosynthesis has two major phases : 1. The absorbance of light and production of chemical forms of energy (light reactions) 2. The fixation and reduction of carbon and other oxidized molecules (dark reactions)
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The Phases of Photosynthesis 1. The light reactions (light harvesting and energy transduction) Requires light Very similar in all photosynthetic organisms Catalyzed by protein complexes embedded in the thylakoid membrane. Figs. 7-10 and 7-12 of the Raven et al. textbook. Phases: a. Light harvesting in the antennae complex b. Energy transfer to reaction centers of the photosystems c. Water-splitting and electron donation (O 2 production) d. Electron transport from PSII to PSI, with proton pumping e. Electron transport from PSI to NADP + , forming NADPH f. ATP synthesis by chemiosmosis
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The Phases of Photosynthesis 2. Carbon-fixation and reduction (dark reactions) Occurs in the stroma Occurs in the dark if ATP and NADPH are added artificially Catalyzed by soluble proteins in the stroma or cytosol Figs. 7-11 and 7-20 in the Raven et al. text Phases: a. Ribulose-1,5 bisphosphate (RuBP) carboxylation by RuBP carboxylase/oxygenase (Rubisco), forming PGA b. PGA reduction to triose phosphates c. RuBP regeneration in the Calvin cycle d. Production of starch and sucrose
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Light absorption Light absorption and transfer to the reaction centers
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Energy flow between the photosystems and to NADP +
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Energy flow between the photosystems and to NADP + Redox potential (volts) +1.0 0.0 -1.0 High Free Energy Low Free Energy This diagram is often called the Z-scheme
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Electron Transport in the Thylakoid Membrane H + X The red X indicates that protons do not directly pass through the cytochrome complex. Protons cross the membrane via oxidation and reduction of quinones
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Photosystem II water-splitting complex Special pair of chlorophyll a (termed P 680 ) Outer antennae (chlorophyll-containing light harvesting protein complex) Inner antennae (chlorophyll protein complex) Bound Plastoquinone A (Q a ) Pheophytin (like chlorophyll, but no magnesium in ring-structure) The Reaction Center Plastoquinone docking site (Q b site) Thylakoid Membrane
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Photosystem I PHOTOSYSTEM II PHOTOSYSTEM I Outer antennae (chlorophyll-containing light harvesting protein complex) Special pair of chlorophyll a (termed P 700 ) Inner antennae Iron-sulfur cluster phylloquinone Chlorophyll a The Reaction Center
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Core Proteins PHOTOSYSTEM II PHOTOSYSTEM I D1 and D2 A1 and A2 At the center of each photosystem are two intertwined proteins to which the special pair chlorophylls, and the initial electron transport intermediates are bound.
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Interchain and Terminal Electron Transporters Cytochrome b 6 /f Plastocyanin Ferredoxin NADP reductase Mobile Plastoquinone
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This note was uploaded on 06/21/2011 for the course BIO BIO251 taught by Professor Busch during the Fall '11 term at University of Toronto.

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lecture 9 - Photosynthesis Section II Diversity of vascular...

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