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Photosynthesis

Photosynthesis. Photosynthesis in Nature The pathways of Photosynthesis 6CO 2 + 12H 2 O C 6 H 12 O 6 + 6H 2 O + 6O 2. Photosynthesis in nature. Producers are plants and other autotrophs Key organelle- chloroplast Location hierarchy plant leaf mesophyll cell

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Photosynthesis

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  1. Photosynthesis Photosynthesis in Nature The pathways of Photosynthesis 6CO2 + 12H2OC6H12O6 + 6H2O + 6O2

  2. Photosynthesis in nature • Producers are plants and other autotrophs • Key organelle- chloroplast • Location hierarchy plant leaf mesophyll cell chloroplast thylakoid memb. stroma

  3. Chloroplast Ultrastructure • 4-7 μm • 3 functional compartments 1) intermembrane space 2) thylakoid lumen 3) stroma

  4. The Nature of Sunlight • Electromagnetic energy-wave & particle • Photosynthesis uses visible light • Red and violet most efficient • Green reflected?

  5. Role of Pigment Molecules • Substances that absorb visible light • Chlorophyll a-most important • Accessory pigments chlorophyll b and carotenoids • Organized into photosystems y y

  6. Photosystems: light-harvesting complexes of the thylakiod membrane • Antenna complex-contains ch. a, ch. b and carotenoids • Reaction center chlorophyll-a single specialized ch. a • Primary electron acceptor-traps e- released from the reaction center

  7. Photosynthetic Unit • Photosystem I- ch. a-known as P700 • Photosystem II- ch. a-known as P680 • P700 and P680 identical, but associated with a different protein • Thousands of photosynthetic units/chloroplast

  8. The Pathway of Photosynthesis • The light reactions (thylakoid) 1) noncylic electron flow 2) cyclic electron flow • The Calvin cycle (stroma)

  9. The Light Reactions • Incorporates photolysis and chemiosmosis • Occurs in the thylakoid membrane and lumen • Produces ATP and NADPH

  10. Photolysis • 2H2O4H+ + 4e- + O2 • Occurs in the lumen • Source of e- for the ETC • Oxygen is a byproduct

  11. Linear Electron Flow (Noncyclic electron Flow) • Produces NADPH • Produces O2 • Occurs in the thylakoid membrane • Moves e- from water to NADP

  12. Cyclic Electron Flow • Simplest pathway • Uses photosystem I • Generates ATP only • Electron starts and ends in chlorophyll a • Function: to continue to produce ATP when NADP is in excess

  13. Photosynthesis Source of H+ and e- is water Light provides the energy ATP synthase ETC present Proton motive force Cellular Respiration Source of H+ and e- is food Chemical bonds from food provide the energy ATP synthase ETC present Proton motive force Photosynthesis vs. Cellular Respiration (chemiosmosis)

  14. Calvin Cycle • Three phases 1) Carbon Fixation 2) Reduction 3) Regeneration of RuBP

  15. Photorespiration, C4 Plants, and CAM Plants • Photorespiration-evolutionary relic • Role of Rubisco • CAM plants-specially adapted for arid environments, stomates open at night • C4 plants-anatomical and chemical adaptations for dry climates

  16. Videos and Websites • http://vcell.ndsu.nodak.edu/animations/photosystemII/index.htm • http://nobelprize.org/nobel_prizes/chemistry/laureates/1988/illpres/highlights.html • http://www.johnkyrk.com/photosynthesis.html • http://www4.utsouthwestern.edu/goodmanlab/vi/spectrophotometer.htm

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