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  1. 1. The Biology of Photosynthesis
  2. 2. An Overview of Photosynthesis <ul><li>This presentation will focus on: </li></ul><ul><li>The importance of autotrophs </li></ul><ul><li>An overview of photosynthesis </li></ul><ul><li>Leaf and chloroplast structure and function </li></ul><ul><li>The electromagnetic spectrum </li></ul><ul><li>Pigment function and variety </li></ul><ul><li>The Light Reactions </li></ul><ul><li>The Calvin Cycle </li></ul>
  3. 3. The Importance of Autotrophs
  4. 4. The Importance of Autotrophs
  5. 5. The Importance of Autotrophs <ul><li>All organisms require a source of energy </li></ul><ul><li>All organisms require a source of carbon compounds </li></ul><ul><li>Provides molecular oxygen for the atmosphere </li></ul>
  6. 6. The Importance of Autotrophs <ul><li>2 Types of Autotrophs: </li></ul><ul><li>Chemotrophs </li></ul><ul><li>Photoautotrophs </li></ul>
  7. 7. An Overview of Photosynthesis 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2
  8. 8. An Overview of Photosynthesis
  9. 9. Leaf Structure and Function <ul><li>Plants are composed of three major organ systems: </li></ul><ul><li>The Root System </li></ul><ul><ul><li>anchors the plant in place </li></ul></ul><ul><ul><li>stores excess sugars </li></ul></ul><ul><ul><li>absorbs water and mineral nutrients </li></ul></ul><ul><li>The Shoot System </li></ul><ul><ul><li>supports the plant body </li></ul></ul><ul><ul><li>provides passageway for nutrients and minerals </li></ul></ul><ul><li>Leaves </li></ul><ul><ul><li>site of photosynthesis (food production) </li></ul></ul>
  10. 10. Leaf Structure and Function <ul><li>Plant organs are made up of 3 types of tissues: </li></ul><ul><li>Dermal </li></ul><ul><ul><li>cells for structure and protection </li></ul></ul><ul><ul><li>secretion of cutin to prevent water loss </li></ul></ul><ul><li>Ground </li></ul><ul><ul><li>photosynthesis </li></ul></ul><ul><ul><li>storage of food and water </li></ul></ul><ul><li>Vascular </li></ul><ul><ul><li>specialized for transport of water and nutrients </li></ul></ul>
  11. 11. Leaf Structure and Function
  12. 12. Leaf Structure and Function
  13. 13. Leaf Structure and Function
  14. 14. Chloroplast Structure and Function
  15. 15. The Electromagnetic Spectrum <ul><li>The ultimate source of energy is the sun </li></ul><ul><li>Solar energy is called electromagnetic radiation </li></ul><ul><li>Travels in waves of photons </li></ul><ul><li>The Electromagnetic spectrum describes the range of energy in solar radiation </li></ul><ul><li>The EM spectrum is measured by wavelength </li></ul>
  16. 16. The Electromagnetic Spectrum
  17. 17. Pigments Pigments are organic molecules that absorb visible light Wavelengths not absorbed are reflected, creating the visible color of an object Wavelengths absorbed cause the excitations of electrons Plants contain a major pigment, chlorophyll a, and accessory pigments like carotenoids and anthocyanins
  18. 18. Pigments
  19. 19. Chlorophyll Structure and Function
  20. 20. Chlorophyll Structure and Function
  21. 21. Review of Major Concepts So Far! Go to Go through the sections called “Overview” and “Strategy/Players”
  22. 22. The Reactions of Photosynthesis <ul><li>The Light Reactions </li></ul><ul><li>Light Dependent </li></ul><ul><li>“ Photo” Division </li></ul><ul><li>Energy Capturing </li></ul><ul><li>The Calvin Cycle </li></ul><ul><li>Light Independent </li></ul><ul><li>“ Synthesis” Division </li></ul><ul><li>Energy Storage </li></ul>                                                                                                                              
  23. 23. The Light Reactions <ul><li>Occur on thylakoid membranes </li></ul><ul><li>Use 2 Photosystems </li></ul><ul><li>PSI (p700) and PSII (p680) </li></ul>                                                                                                                                                                            
  24. 24. Chlorophyll Structure and Function
  25. 25. Click image to see a membrane view of the light reactions                                                                                                                                                                             
  26. 26. Events of the Light Reactions: PSII <ul><li>Sunlight strikes p680 boosting electron to excited state </li></ul><ul><li>High energy electrons passed from primary electron acceptor down electron transport system via oxidation-reduction. These reactions power the active transport of H + from the stroma into the thylakoid space </li></ul><ul><li>H + diffuse back into stroma through ATP synthetase converting ADP + P into ATP </li></ul><ul><li>Electrons from p680 end up at p700. Hole at p680 filled by oxidation of H 2 O into O 2 </li></ul>
  27. 27. Events of the Light Reactions: PSI <ul><li>Sunlight hits p700 boosting electron to excited state </li></ul><ul><li>High energy electrons passed from primary electron acceptor down electron transport system via oxidation-reduction. </li></ul><ul><li>High energy electrons transferred by NADP + reductase to NADP + to form NADPH </li></ul><ul><li>Hole at p700 filled by electrons from p680 </li></ul>
  28. 28. Click image for link to animated overview of noncyclic photophosphorylation                                                                                                                                                                     
  29. 29. Light Reactions Summary Sunlight + H 2 O O 2 + ATP + NADPH ADP, P, and NADP + from Inorganic Nutrient Pool are raw materials Study the following tutorials: You control the light reactions! Biology Project Light RXNs Tutorial Photosynthesis Light RXNs Interactive
  30. 30. The Calvin Cycle Occurs in the Stroma Uses ATP and NADPH from Light Rxns CO 2 is Raw Material
  31. 31. . . .
  32. 32. The Calvin Cycle Phase 1: Carbon Fixation CO 2 comes into the stroma of the chloroplast via the stomata of the leaves.  Rubisco catalyzes the bonding of CO 2 to RuBP to create an unstable 6-carbon molecule that instantly splits into two 3-carbon molecules of 3-PGA. Back to diagram
  33. 33. The Calvin Cycle Phase 2: Reduction ATP phosphorylates each 3-PGA molecule and creates 1,3-bisphosphoglycerate (1,3 DPGA).  NADPH reduces 1,3-bisphosphoglycerate which causes the molecule to become glyceraldehyde-3-phosphate (PGAL). NADPH is oxidized by this process and becomes NADP+. Back to diagram
  34. 34. The Calvin Cycle Phase 3: Regeneration For every six molecules of PGAL created, five molecules continue on to phase 3 while one leaves to be used for organic compounds. ATP is once again needed.  However, this time it phosphorylates G3P to regenerate RuBP after some rearrangement. Back to diagram
  35. 35. The Calvin Cycle <ul><li>Summary of Calvin Cycle </li></ul><ul><li>CO 2 + ATP + NADPH ADP + NADP + + PGAL </li></ul><ul><li>PGAL is rearranged to produce: </li></ul><ul><li>Glucose for cellular respiration </li></ul><ul><li>Fructose in Fruits </li></ul><ul><li>Sucrose for Transport Throughout Plant </li></ul><ul><li>Starch for Storage </li></ul>Study the following tutorials: The 3 Phases Animated Calvin Cycle Tutorial at Biology Project Photosynthesis Dark RXNs Interactive
  36. 36. Alternate Mechanisms of Photosynthesis <ul><li>Plants fight water loss and dehydration </li></ul><ul><ul><li>Close stoma to prevent water loss </li></ul></ul><ul><ul><li>Closed stoma mean no input of CO 2 into leaf </li></ul></ul><ul><ul><li>Light reactions continue to produce O 2 </li></ul></ul><ul><li>Photorespiration </li></ul><ul><ul><li>When O 2 concentration increases, rubisco adds O 2 to the Calvin Cycle instead of CO 2 </li></ul></ul>
  37. 37. Alternate Mechanisms of Photosynthesis <ul><li>Photorespiration </li></ul><ul><ul><li>Occurs on bright, hot, dry days when stoma close </li></ul></ul><ul><ul><li>Consumes O 2 </li></ul></ul><ul><ul><li>Releases CO 2 </li></ul></ul><ul><ul><li>Unlike cellular respiration, generates no ATP </li></ul></ul><ul><ul><li>Unlike photosynthesis, generates no food </li></ul></ul><ul><ul><li>Actually decrease rate of photosynthetic output </li></ul></ul>
  38. 38. Alternate Mechanisms of Photosynthesis Mechanisms to fight photorespiration: C4 and CAM pathways Incorporate CO 2 into organic acids first, then release it into the Calvin Cycle
  39. 39. Alternate Mechanisms of Photosynthesis <ul><li>PEP Carboxylase accepts CO 2 in mesophyll cells </li></ul><ul><li>A 4C intermediate carries the CO 2 into the bundle-sheath cells </li></ul><ul><li>This maintains a high concentration of CO2 in the bundle sheath to avoid photorespiration </li></ul>