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Photosynthesis -.pptx

  1. 1. Bellringer Without fail, I forget to water my plants. My house’s temperature (electric heat = dry) is kept at 72o F. Explain, using your botannical vocabulary, why my house plants shriveled up and died over the winter.
  2. 2. Set up lab, lecture, finish lab • Today’s goal: – Define pigment. – Explain why plants are green. – Give examples of the accessory pigments and explain their role in photosynthesis.
  3. 3. All you ever wanted to know about photosynthesis Part One
  4. 4. • Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water AN OVERVIEW OF PHOTOSYNTHESIS Carbon dioxide Water Glucose Oxygen gas PHOTOSYNTHESIS
  5. 5. Energy can be transformed from one form to another FREE ENERGY (available for work) vs. HEAT (not available for work)
  7. 7. • Almost all plants are photosynthetic autotrophs, as are some bacteria and protists – Autotrophs generate their own organic matter through photosynthesis – Sunlight energy is transformed to energy stored in the form of chemical bonds (a) Mosses, ferns, and flowering plants (b) Kelp (c) Euglena (d) Cyanobacteria THE BASICS OF PHOTOSYNTHESIS
  8. 8. Ingredients and Components 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2
  9. 9. Food Chain
  10. 10. THE FOOD WEB
  11. 11. WHY ARE PLANTS GREEN? It's not that easy bein' green Having to spend each day the color of the leaves When I think it could be nicer being red or yellow or gold Or something much more colorful like that… Kermit the Frog
  12. 12. Electromagnetic Spectrum and Visible Light Gamma rays X-rays UV Infrared & Microwaves Radio waves Visible light Wavelength (nm)
  13. 13. Sunlight • Form of energy (photons) • Measured in wavelengths • Sun radiates full spectrum, atmosphere screens out most, allows primarily only visible light through (380-750 nm) • Amount of energy is inversely related to the wavelength of light
  14. 14. Different wavelengths of visible light are seen by the human eye as different colors. Gamma rays X-rays UV Infrared Micro- waves Radio waves Visible light Wavelength (nm)
  15. 15. Pigment • Substances that absorb visible light • Different pigments absorb light of different wavelengths • Color we see is the color most reflected or transmitted by the pigment
  16. 16. Sunlight minus absorbed wavelengths or colors equals the apparent color of an object. The feathers of male cardinals are loaded with carotenoid pigments. These pigments absorb some wavelengths of light and reflect others.
  17. 17. Why are plants green? Transmitted light
  18. 18. Chlorophyll a •Chl a has a methyl group •Chl b has a carbonyl group Porphyrin ring delocalized e- Phytol tail
  19. 19. Spectrophotometer
  21. 21. Predict: action spectrum • Measure photosynthetic output against the various wavelengths of light…
  22. 22. Action spectrum
  23. 23. So chlorophyll isn’t the whole story here…
  24. 24. The Pigments • Chlorophyll a: blue-green; only pigment that can participate directly in photosynthesis Accessory (antennae) pigments - absorb light and transfer it to chlorophyll a: • Chlorophyll b: yellow-green • Carotenoids: various shades of yellow and orange • Xanthophylls: purples • Anthocyanin: yellow
  25. 25. Fall colors
  26. 26. So what? • Demonstration!
  27. 27. Electron Excitation
  28. 28. Excited state e Heat Light Photon Light (fluorescence) Chlorophyll molecule Ground state 2 (a) Absorption of a photon (b) fluorescence of isolated chlorophyll in solution Excitation of chlorophyll in a chloroplast e
  29. 29. Okay…still, so what?
  30. 30. Primary electron acceptor Primary electron acceptor Photons PHOTOSYSTEM I PHOTOSYSTEM II Energy for synthesis of by chemiosmosis Noncyclic Photophosphorylation • Photosystem II regains electrons by splitting water, leaving O2 gas as a by-product
  31. 31. Parts of the chloroplast • Thylakoids: flattened sac, pigments of photosynthesis located in their membranes • Grana: stacks of thylakoids (literally, “stacks of coins”) • Stroma: interior portion
  32. 32. • The location and structure of chloroplasts LEAF CROSS SECTION MESOPHYLL CELL LEAF Chloroplast Mesophyll CHLOROPLAST Intermembrane space Outer membrane Inner membrane Thylakoid compartment Thylakoid Stroma Granum Stroma Grana
  34. 34. • The Calvin cycle makes sugar from carbon dioxide – ATP generated by the light reactions provides the energy for sugar synthesis – The NADPH produced by the light reactions provides the electrons for the reduction of carbon dioxide to glucose Light Chloroplast Light reactions Calvin cycle NADP ADP + P • The light reactions convert solar energy to chemical energy – Produce ATP & NADPH AN OVERVIEW OF PHOTOSYNTHESIS
  35. 35. Review of photosynthesis… • The reactants: CO2 and H2O • Driving the reaction: sunlight • Products: Glucose and O2 • Sunlight captured by pigments (chlorophylls and others) • Pigments located in the chloroplasts
  36. 36. • Chloroplasts absorb light energy and convert it to chemical energy Light Reflected light Absorbed light Transmitted light Chloroplast
  37. 37. What is a pigment? Substance that absorbs visible light Different pigments absorb light of different wavelengths Arranged into clusters called photosystems (more on that later!)
  38. 38. Chloroplasts: Sites of Photosynthesis • Photosynthesis – Occurs in chloroplasts, organelles in certain plants – All green plant parts have chloroplasts and carry out photosynthesis • The leaves have the most chloroplasts • The green color comes from chlorophyll in the chloroplasts • The pigments absorb light energy
  39. 39. Photosystems • In the membrane of the thylakoid • Contains several hundred molecules of chlorophyll a and b along with accessory pigments • Named by the wavelength of light they absorb (P680 and P700)
  40. 40. Why have photosystems? To harvest light over a larger surface area and larger portion of the spectrum than any single pigment could harvest.
  41. 41. Primary electron acceptor Photon Reaction center PHOTOSYSTEM Pigment molecules of antenna Molecular Game of “Hot Potato”
  42. 42. Water-splitting photosystem NADPH-producing photosystem ATP mill • Two types of photosystems cooperate in the light reactions
  43. 43. Primary electron acceptor Primary electron acceptor Photons PHOTOSYSTEM I PHOTOSYSTEM II Energy for synthesis of by chemiosmosis Noncyclic Photophosphorylation • Photosystem II regains electrons by splitting water, leaving O2 gas as a by-product
  44. 44. • The O2 liberated by photosynthesis is made from the oxygen in water (H+ and e-) Plants produce O2 gas by splitting H2O
  45. 45. 2 H + 1/2 Water-splitting photosystem Reaction- center chlorophyll Light Primary electron acceptor Energy to make Primary electron acceptor Primary electron acceptor NADPH-producing photosystem Light NADP 1 2 3 How the Light Reactions Generate ATP and NADPH
  46. 46. • Two connected photosystems collect photons of light and transfer the energy to chlorophyll electrons • The excited electrons are passed from the primary electron acceptor to electron transport chains – Their energy ends up in ATP and NADPH In the light reactions, electron transport chains generate ATP, NADPH, & O2
  47. 47. • The electron transport chains are arranged with the photosystems in the thylakoid membranes and pump H+ through that membrane – The flow of H+ back through the membrane is harnessed by ATP synthase to make ATP – In the stroma, the H+ ions combine with NADP+ to form NADPH Chemiosmosis powers ATP synthesis in the light reactions
  48. 48. • The production of ATP by chemiosmosis in photosynthesis Thylakoid compartment (high H+) Thylakoid membrane Stroma (low H+) Light Antenna molecules Light ELECTRON TRANSPORT CHAIN PHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE
  49. 49. Cyclic Pathway
  50. 50. • A Photosynthesis Road Map Chloroplast Light Stack of thylakoids ADP + P NADP Stroma Light reactions Calvin cycle Sugar used for  Cellular respiration  Cellulose  Starch  Other organic compounds
  51. 51. Join me, on the dark side of photosynthesis
  52. 52. overview
  53. 53. Redox reactions • Reduction: gains electrons (escorted by hyrdrogens) • Oxidation: loses electrons
  54. 54. • ATP is a limiting factor: more is used by calvin cycle • Need a way to fill deficit
  55. 55. Cyclic Photophosphorylation • Process for ATP generation associated with some Photosynthetic Bacteria • Reaction Center => 700 nm
  56. 56. Review: Photosynthesis uses light energy to make food molecules Light Chloroplast Photosystem II Electron transport chains Photosystem I CALVIN CYCLE Stroma LIGHT REACTIONS CALVIN CYCLE Cellular respiration Cellulose Starch Other organic compounds • A summary of the chemical processes of photosynthesis
  57. 57. It's not that easy bein' green… but it is essential for life on earth!
  58. 58. Balancing Act
  59. 59. climate
  60. 60. photorespiration
  61. 61. Adaptations C4 Plants: spatial separation CAM Photosynthesis: temporal separation