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Recognize the importance of photosynthesis for our survival;
Identify the reactants and products of photosynthesis;
To draw the absorption and action spectrum of photosynthesis
Explain and illustrate the two phases of photosynthesis.

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  • Action spectrum of photosynthesis shows wavelengths used for light dependent reactions. Different colours are different wavlengths. The green region is not used, so green light is reflected and seen.
  • Photosynthesis

    1. 1.  Why are plants so important? Why are plants green? Which are the main pigments in a plant? What plants produce? Which materials are used to poduce organic materials? What do they release during this process? What is the name of this process?
    2. 2. Aim: to introduce the students to the processof photosynthesisObjectives: Recognize the importance of photosynthesis for our survival; Identify the reactants and products of photosynthesis;To draw the absorption and action spectrum ofphotosynthesisExplain and illustrate the two phases of photosynthesis.
    3. 3. Light Energy Harvested by Plants & Other Photosynthetic Autotrophs
    4. 4. What is photosynthesis? Photosynthesis is the process by which autotrophicorganisms use light energy to make sugar and oxygen gas from carbon dioxide and water
    5. 5. Photosynthesis in Overview In this process plants and other autotrophs store the energy of sunlight into sugars. Requires sunlight, water, and carbon dioxide. Overall equation: 6 CO2 + 6 H20  C6H12O6 + 6 O2
    6. 6. Where does photosynthesis take place? Occurs in theleaves of plants in organelles called chloroplasts.
    7. 7. Leaf
    8. 8. The location and structure of chloroplasts Chloroplast LEAF CROSS SECTION MESOPHYLL CELL LEAF Mesophyll CHLOROPLAST Intermembrane space Outer membrane Granum Inner membrane Grana Stroma Thylakoid Stroma Thylakoid compartment
    9. 9. Chloroplast Structure Have 2 membranes  A “bi-bilayer!” The inner membrane is called the thylakoid. The thylakoid is folded and looks like stacks of coins called granum (grana singular). The stroma is the space surrounding the granum
    10. 10. Why are plants green?
    11. 11. Why are plants green?Different wavelengths of visible light are seen by the human eye as different colors. Gamma Micro- Radio X-rays UV Infrared rays waves waves Visible light Wavelength (nm)
    12. 12. The feathers of male cardinalsare loaded with carotenoidpigments. These pigmentsabsorb some wavelengths oflight and reflect others. Sunlight minus absorbed wavelengths or colors equals the apparent color of an object.
    13. 13. Why are plants green? Transmitted light
    14. 14. Why are plants green? Plant Cells have Green Chloroplasts The thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments (i.e., chlorophylls, carotenoids).
    15. 15. THE COLOR OF LIGHT SEEN IS THE COLOR NOT ABSORBED Chloroplasts absorb light energy and convert it to chemical Light Reflected light energy Absorbed light Transmitted Chloroplast light
    16. 16. During fall what causes pigments to change colour?
    17. 17. Fall Colours In addition to the chlorophyll pigments, there are other pigments present. During the fall, the green chlorophyll pigments are greatly reduced revealing the other pigments (carotenoids and xantophylls)
    18. 18. Pigments Chlorophyll A is the most important photosynthetic pigment. Other pigments called antenna or accessory pigments are also present in the leaf.  Chlorophyll B  Carotenoids (orange / red)  Xanthophylls (yellow / brown) These pigments are embedded in the membranes of the chloroplast in groups called photosystems.
    19. 19. Different pigments absorb light differently
    20. 20. Chlorophyll in the chloroplasts Chlorophyll molecules are embedded in the thylakoid membrane Act like a light “antenna” These molecules can absorb sunlight energy.
    21. 21. Photosystem• Reaction centre (chlorophyll a & electron acceptor)• Light-harvesting complex (pigment molecules bounded to proteins)
    22. 22. Harvesting lightThere are two types ofreaction centre:  Photosystem I is arranged around a chlorophyll a molecule with absorption peak of 700 nm.  Photosystem II is arranged around a chlorophyll a molecule with absorption peak of 680 nm.
    23. 23. Photosynthesis occurs in 2 phases: The light reactions convert solar energy Light Chloroplast to chemical energy NADP  Produce ATP & ADP NADPH +P Calvin Light cycle reactions• The Calvin cycle makes sugar from carbon dioxide – The ATP and NADPH are used to assemble sugars and other organic compounds
    24. 24. Excitation of chlorophyllin a chloroplast Loss of energy due to heat causes the photons of light to be less energetic. e Excited 2 state Less energy translates into longer wavelength.Fluorescene Heat Transition toward the red end of the visible spectrum. Light Light (fluorescence) Photon Ground state Chlorophyll molecule (a) Absorption of a photon (b) fluorescence of isolated chlorophyll in solution
    25. 25. 1. Light Reaction (Electron Flow)  Occurs in the Thylakoid membranes  During the light reaction, there are two possible routes for electron flow. A. Noncyclic Electron Flow B. Cyclic Electron Flow
    26. 26. B. Noncyclic Electron Flow Occurs in the thylakoid membrane Uses PS II and PS I P680 rxn center (PSII) - chlorophyll a P700 rxn center (PS I) - chlorophyll a Uses Electron Transport Chain (ETC) Generates O2, ATP and NADPH
    27. 27. Noncyclic Photophosphorylation Photosystem II regains electrons by splitting water, leaving O2 gas as a by-product Primary electron acceptor Primary electron acceptor Photons Energy for synthesis of PHOTOSYSTEM I PHOTOSYSTEM II by chemiosmosis
    28. 28.  Two types of photosystems cooperate in the light reactions ATP mill Water-splitting NADPH-producing photosystem photosystem
    29. 29. In the light reactions, electron transport chains generate ATP, NADPH, & O2 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
    30. 30. B. Noncyclic Electron Flow ADP + P  ATP (photophosphorylation) NADP+ + H  NADPH (source of energized electrons) Oxygen comes from the splitting of H2O, not CO2 H 2O  1/2 O2 + 2H+
    31. 31. A. Cyclic Electron Flow Occurs in the thylakoid membrane. Uses Photosystem I only P700 reaction center- chlorophyll a Uses Electron Transport Chain (ETC) Generates ATP only ADP + P ATP
    32. 32. A. Cyclic Electron FlowReaction Center => 700 nm 2e- 2e- 2e- 2e-
    33. 33. The Hill reaction Hill placed cells of the green alga Chlorella into water containing the heavy isotope 18O He was able to show that the Oxigen given off in photosynthesis was na isotope 18O which must have come from water.
    34. 34. When Hill repeated the experiment with CO2 containing the heavy18O instead, the oxygen given off was normal 16O Photolysis H2O + Energy  ½ O2 + 2H+ + 2e-
    35. 35. The production of ATP by chemiosmosis in photosynthesisThylakoidcompartment(high H+) Light LightThylakoidmembrane Antenna moleculesStroma ELECTRON TRANSPORT(low H+) CHAIN PHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE
    36. 36. Chemiosmosis powers ATP synthesis in the light reactions The electron transport chains are arranged with the photosystems in the thylakoid membranes and pump H+ into the thylakoid space  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 Video
    37. 37. Calvin Cycle Calvin Cycle (light-independent) occur in the stroma:  Carbon fixation  Carbon dioxide is “fixed” into the sugar glucose.  ATP and NADPH molecules created during the light reactions power the production of this glucose.
    38. 38. The Calvin Cycle
    39. 39. Carbon Fixation: (3) CO2 molecules enter Rubisco attaches the Co2 to RuBP The 6C product immediately splits into 2x glycerate 3- phosphate
    40. 40. Reduction 6 ATP and 6 NADPH used Some of the triose phosphatemolecule are linked to formGlucose phosphate
    41. 41. Regenerate RuBP Use 3 more ATPVideo
    42. 42. The light-independent stage CO2 combines with a five-carbon compound, ribulose biphospate (RuBP) The unstablr 6-carbon compound breaks down to form 2 molecules of 3-carbon glycerate 3-phosphate ATP is used to phosphorylate the 2 molecules of GP forming 2 molecules of glycerate biphosphate
    43. 43. The light-independent stage NADPH reduces each molecule of glycerate biphosphate to glyceraldehyde 3-phosphate (GALP) For every six molecules of GALP formed, five are used in a series of reactions to regerate RuBP. One of six GALP molecules is converted to glucose and other carbohydrates, aminoa cids and lipids
    44. 44.  A Photosynthesis Road Map Chloroplast Light Stroma Stack of NADP thylakoids ADP +P Light Calvin reactions cycle Sugar used for  Cellular respiration  Cellulose  Starch  Other organic compoundsVideoVideo Video
    45. 45.  37Rrw1vEsw&feature=related ture=related eature=related ture=related ure=related wmwx88&feature=related