Se ha denunciado esta presentación.
Utilizamos tu perfil de LinkedIn y tus datos de actividad para personalizar los anuncios y mostrarte publicidad más relevante. Puedes cambiar tus preferencias de publicidad en cualquier momento.

Chapter 10 (5)

4.826 visualizaciones

Publicado el

Publicado en: Tecnología
  • Inicia sesión para ver los comentarios

Chapter 10 (5)

  1. 1. Chapter 10 notes Photosynthesis
  2. 2. Photosynthesis In Nature <ul><li>All life acquires organic compounds for energy and carbon skeletons by one of two ways </li></ul><ul><li>- Autotrophs : ( autos = self, trophos = feed) </li></ul><ul><li>- they sustain themselves w/out eating other organisms </li></ul>
  3. 3. Photosynthesis In Nature <ul><li>- plants are photoautotrophs because they use light as a source of energy </li></ul><ul><li>- Heterotrophs : ( hetero = other, different) </li></ul><ul><li>- live on compounds produced by other organisms </li></ul><ul><li>Heterotrophs are dependent on photoautotrophs for food and oxygen </li></ul>
  4. 4. Photosynthesis In Nature <ul><li>Chloroplasts are the site of photosynthesis in plants </li></ul><ul><li>All green parts of plants have chloroplasts </li></ul><ul><li>- color is from chlorophyll , the green pigment in the chloroplasts </li></ul><ul><li>- chloroplasts are mainly found in the mesophyll , interior tissue of the leaf </li></ul>
  5. 6. Photosynthesis In Nature <ul><li>- CO 2 enters/O 2 leaves the leaf through pores called stomata </li></ul><ul><li>- water is absorbed through the roots </li></ul><ul><li>6CO 2 +6H 2 O+light  C 6 H 12 O 6 +6O 2 </li></ul>
  6. 7. Pathways of Photosynthesis <ul><li>The oxygen produced from photosynthesis comes from the spliting of water, not CO 2 </li></ul><ul><li>- use of oxygen-18 to trace pathway </li></ul><ul><li>Hydrogen is extracted from water to make sugar </li></ul><ul><li>- O 2 is a waste product </li></ul>
  7. 8. Pathways of Photosynthesis
  8. 9. Pathways of Photosynthesis <ul><li>Photosynthesis is made of two processes, each containing several steps </li></ul><ul><li>1) Light reaction (AKA light harvesting reaction, light dependent reaction) </li></ul><ul><li>2) Calvin cycle (AKA dark reaction, carbon fixation reaction) </li></ul>
  9. 10. Pathways of Photosynthesis <ul><li>The light rxn. converts solar energy to chemical energy; occurs in the thylokoid membrane </li></ul><ul><li>- light absorbed drives a transfer of e- and hydrogen to an acceptor, NADP + </li></ul><ul><li>- NADP + is reduced to NADPH </li></ul><ul><li>- ATP is generated from ADP through photophosphorylation </li></ul>
  10. 11. Pathways of Photosynthesis <ul><li>The Calvin cycle stores the chemical energy in the form of sugar; occurs in the stroma </li></ul><ul><li>- CO 2 is incorporated w/ other molecules in the chloroplast through carbon fixation </li></ul><ul><li>- fixed carbon is reduced to carbohydrates </li></ul>
  11. 16. Pathways of Photosynthesis <ul><li>Light is a form of energy known as electromagnetic energy; travels in waves </li></ul><ul><li>- wavelength is the distance between crests of electromagnetic waves </li></ul><ul><li>- electromagnetic spectrum : the entire range of radiation </li></ul>
  12. 17. Pathways of Photosynthesis <ul><li>Visible light is the band that ranges from 380 to 750 nm in wavelength </li></ul><ul><li>- detected as colors by the human eye </li></ul><ul><li>The amount of energy is inversely related to the wavelength </li></ul><ul><li>- shorter the wavelength, greater the energy </li></ul>
  13. 19. Pathways of Photosynthesis <ul><li>In the chloroplasts light is absorbed mainly by chlorophyll a . </li></ul><ul><li>- blue and red light is primarily absorbed </li></ul><ul><li>- green is the least absorbent color </li></ul><ul><li>Chlorophyll b absorbs light at slightly different wavelengths </li></ul>
  14. 20. Pathways of Photosynthesis
  15. 21. Pathways of Photosynthesis <ul><li>Chloroplasts also contain accessory pigments, carotenoids </li></ul><ul><li>- may broaden the spectrum of colors that can drive photosynthesis </li></ul><ul><li>- act in photoprotection : they absorb excessive light that might damage chlorophyll </li></ul>
  16. 22. Pathways of Photosynthesis <ul><li>Light Dependent Reaction </li></ul><ul><li>Inside the thylakoid, chlorophyll is organized w/ proteins into photosystems </li></ul><ul><li>- light gathering “antenna complex” </li></ul><ul><li>Two types of photosystems </li></ul><ul><li>- PS II, PS I </li></ul>
  17. 23. Pathways of Photosynthesis <ul><li>PS II = P680 </li></ul><ul><li>- best at absorbing light w/ a wavelength of 680 nm </li></ul><ul><li>PS I = P700 </li></ul><ul><li>- best at absorbing light w/ a wavelength of 700 nm </li></ul>
  18. 24. Pathways of Photosynthesis <ul><li>Light drives the synthesis of ATP and NADPH by energizing e- in the photosystems </li></ul><ul><li>Two possible routes for e- flow </li></ul><ul><li>- cyclic </li></ul><ul><li>- noncyclic </li></ul>
  19. 25. Pathways of Photosynthesis <ul><li>Noncyclic electron flow : </li></ul><ul><li>- predominant route </li></ul><ul><li>1) P680 absorbs light, and splits a water molecule </li></ul><ul><li>2) e- absorb the energy and then cascade down an ETC from PS II to PS I </li></ul><ul><li>3) ATP is formed by noncyclic photophosphorylaton </li></ul>
  20. 26. Pathways of Photosynthesis <ul><li>4) P700 absorbs more light to reenergize the e- so it can pass down another ETC </li></ul><ul><li>5) NADP + is the final e- accepter as it is reduced to NADPH (through redox rxns.) </li></ul>
  21. 27. Pathways of Photosynthesis
  22. 28. Pathways of Photosynthesis
  23. 29. Pathways of Photosynthesis
  24. 30. Pathways of Photosynthesis
  25. 31. Pathways of Photosynthesis
  26. 32. Pathways of Photosynthesis <ul><li>Cyclic electron flow: </li></ul><ul><li>- uses PS I, but not PS II </li></ul><ul><li>- makes ATP, but not NADPH or oxygen </li></ul><ul><li>- cyclic photophosphorylation </li></ul><ul><li>- because the Calvin cycle uses more ATP than NADPH, cyclic e- flow makes up the difference </li></ul>
  27. 33. Pathways of Photosynthesis
  28. 34. Pathways of Photosynthesis <ul><li>Chloroplasts and mitochondria both generate ATP through chemiosmosis </li></ul><ul><li>- both ETC’s pump protons across the membrane during the redox rxns. (transforms redox energy into proton motive force) </li></ul><ul><li>- both use ATP synthase to couple diffusion to phosphorylation </li></ul>
  29. 35. Pathways of Photosynthesis <ul><li>Differences between oxidative phosphorylation and photophosphorylaton </li></ul><ul><li>- in mitochondria, high energy e- are from food </li></ul><ul><li>- in chlorplasts, photosystems capture light energy to drive e- transfer </li></ul>
  30. 36. Pathways of Photosynthesis <ul><li>Difference in the spatial organization </li></ul><ul><li>- mitochondria: the inner membrane pumps protons from the matrix to the innermembrane space </li></ul><ul><li>- chloroplasts: thylakoid pumps protons to the thylakoid space from the stroma </li></ul>
  31. 37. Pathways of Photosynthesis
  32. 38. Pathways of Photosynthesis
  33. 39. Pathways of Photosynthesis <ul><li>Calvin Cycle </li></ul><ul><li>- uses ATP and NADPH to incorporate CO 2 into sugar (does not make glucose but a 3 carbon sugar called G3P ) </li></ul><ul><li>- 3 steps to the Calvin cycle </li></ul>
  34. 40. Pathways of Photosynthesis <ul><li>Step 1: Carbon fixation </li></ul><ul><li>- CO 2 is attached to RuBP (rxn. is catalyzed by rubisco ) </li></ul><ul><li>- a 6-carbon intermediate is created  splits into 2 3-carbon molecules </li></ul><ul><li>Step 2: Reduction </li></ul><ul><li>- ATP and NADPH are used to transform the molecule into G3P </li></ul>
  35. 41. Pathways of Photosynthesis <ul><li>- for every three molecules of CO 2 , there are 6 molecules of G3P; only 1 is a net gain </li></ul><ul><li>Step 3: Regeneration of RuBP </li></ul><ul><li>- the remaining 5 molecule of G3P are reconverted back into RuBP to continue the Calvin cycle </li></ul>
  36. 42. Pathways of Photosynthesis <ul><li>In hot, dry environments, plants have adapted to maximize photosynthesis, while limiting water loss (transpiration) </li></ul><ul><li>Most plants will close the stomata to prevent water loss, but this limits CO 2 intake </li></ul>
  37. 43. Pathways of Photosynthesis
  38. 44. Pathways of Photosynthesis <ul><li>In most plants, carbon fixation leads to a 3-carbon compound; these plants are called C 3 plants </li></ul><ul><li>- ex. rice, wheat, soy </li></ul><ul><li>- in hot weather, the stomata close which deprives the plant of CO 2 ; rubisco can accept O 2 instead of CO 2 </li></ul>
  39. 45. Pathways of Photosynthesis <ul><li>- when oxygen binds to rubisco, photorespiration occurs, not photosynthesis </li></ul><ul><li>- process break the resulting compound down into CO 2 </li></ul><ul><li>- photorespiration does not make ATP (like cellular respiration) nor food (like photosynthesis) </li></ul>
  40. 46. Pathways of Photosynthesis <ul><li>Plants have adapted by developing C 4 photosynthesis and CAM </li></ul><ul><li>C 4 plants preface the Calvin cycle w/ an alternate mode of carbon fixation </li></ul><ul><li>- ex. Sugarcane, corn, grasses </li></ul><ul><li>- form a 4-carbon compound as its first product </li></ul>
  41. 47. Pathways of Photosynthesis <ul><li>In C 4 plants there are 2 types of photosynthetic cells </li></ul><ul><li>- Bundle-sheath cells are arranged into tightly packed sheaths around the veins; mesophyll cells are more loosely arranged </li></ul>
  42. 48. Pathways of Photosynthesis <ul><li>Step 1: In the mesophyll cells, PEP carboxylase adds CO 2 to PEP (phosphoenolpyruvate); has a high affinity for CO 2 ; forms the 4-carbon product </li></ul><ul><li>Step 2: 4-carbon compounds move from mesophyll cells to the bundle-sheath </li></ul>
  43. 49. Pathways of Photosynthesis <ul><li>Step 3: Within the bundle-sheath, the 4-carbon compound releases CO 2 which then is combined via rubisco </li></ul><ul><li>The mesophyll cells pump CO 2 into the bundle-sheath so the [CO 2 ] is high enough for rubisco to accept CO 2 and not oxygen </li></ul>
  44. 50. Pathways of Photosynthesis
  45. 51. Pathways of Photosynthesis <ul><li>CAM plants open their stomata at night, but keep them closed during the day </li></ul><ul><li>- found in succulent plants </li></ul><ul><li>- at night the CO 2 is incorporated into other organic acids; this mode of carbon fixation is called crassulacean acid metabolism ( CAM ) </li></ul>
  46. 52. Pathways of Photosynthesis <ul><li>The mesophyll cells of CAM plants store the acids in their vacuoles until they are needed the following day </li></ul><ul><li>C 4 and cam are similar in that CO 2 is first incorporated into an intermediate before entering the Calvin cycle </li></ul><ul><li>However, C 4 plants have a spatial separation of steps, while CAM is temporal </li></ul>
  47. 53. Pathways of Photosynthesis