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Photosynthesis - PowerPoint PPT Presentation

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Photosynthesis
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  1. Photosynthesis

  2. Photosynthesis • Process that traps light energy & uses it for carbohydrate synthesis. • Phototrophs - both plants and bacteria

  3. C. 2 major processes 1. light rxns (light-dep. rxns): protons from H2O make ATP from ADP and Pi & electrons from H2O reduce NADP+ to NADPH. a. H2O is split H goes to dark rxn

  4. b. ATP: adenosine triphosphate c. ADP: adenosine diphosphate d. NADP+ : nicotinamide adenine dinucleotide phosphate e. NADPH: reduced nicotinamide adenine dinucleotide phosphate

  5. 2.Dark rxns (light-independent rxns): uses NADPH & ATP in carbon update. a. meaning: C from CO2 & H comes from light rxn FCHO

  6. 3. Both can occur during daylight 4. Overall chemical equation: 6H2O + 6CO2 C6H12O6 + 6O2 light

  7. II. Chloroplast

  8. A. Thylakoid Membrane 1. highly folded membrane network a. highly permeable to CO2

  9. 2. Site of light dependent rxn that produce NADPH & ATP

  10. B. Stroma 1. Aqueous matrix 2. enzymes that catalyze reduction of CO2 to CHO 3. site of dark rxn

  11. C. Lumen 1. aqueous space within thylakoid membrane 2. ATP synthesis

  12. D. Grana 1. thylakoid membrane folded into flattened vesicles & stacked

  13. Parts of the chloroplasts Stroma (fluid) Grana- stacks of Thy. Membrane Thylakoid Membrane: sac that contains chlorophyll Lumen (fluid)

  14. E. Chlorophyll 1. Chl a & Chl b 2. absorbs light in violet/blue to orange/red region 3. Reflects green

  15. F. Accessory pigments 1. carotenoids: yellow - brown 2. phycobilins a. phycoerythrin: red b. phycocyanin: blue

  16. III.Light –Dependent Rxns (p. 233) A. Sunlight excites chlorophyll via antenna complexes B. Passes energy to electron C. Electron pass down Electron Transport Chain (ETC) – twice

  17. As electrons “fall” lose energy • a. Energy trapped in ATP • D. Electron passed to carrier molecule – NADP+ • E. Combine with H ion from H20 – NADPH

  18. F. Photosystems 1. Electrons which are excited by a photon of light have one of four fates: a. fall to normal state releasing energy as heat

  19. b. fall to normal state releasing energy as fluorescent light c. transfer energy to another pigment molecule d. oxidation/reduction rxn or a separation of charge

  20. 2. Photosystem II a. located in grana & unstacked region b. splits molecules of H2O into 1/2 O2, 2H, and 2 electrons– photolysis

  21. c. chemiosmosis theory: electrons are transported down the ETC, some of the energy released is used to pump protons across the thylakoid membrane from the stroma of the chloroplast to the thylakoid interior space producing a proton gradient or proton motive force

  22. d. ATP made from ADP + Pi

  23. 3. Photosystem I a. unstacked region of T.M. b. electron falls down ETC & combines with 2H+ from the surrounding medium and NADP+ to produce NADPH + H+.

  24. 4. Z – scheme: PII & PI

  25. IV. Light independent rnxs A. Use CO2 to make glucose B. Stroma C. Calvin Cycle (p. 235) 1. Melvin Calvin

  26. 2. one of last molecule is 1st in rxn 3. 6 rounds to get 1 glucose a. CO2 ≠ C6H12O6

  27. D. 5 Steps 1. carbon fixation 2. PGA formation 3. Use of ATP & NADPH 4. Glucose production 5. ATP & PGAL replenish RuBP (ribulose biphosphate)

  28. E. Drawing & description p. 235 animation