AP Bio Ch 10, part 1


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AP Bio Ch 10, part 1

  1. 1. PHOTOSYNTHESIS The Process That Feeds the Biosphere •All organisms either directly or indirectly depend on photosynthesis •Autotrophs- “self-feeders” •Heterotrophs-Consumers Depend on organic Produce organic molecules from compounds produced by CO2 & other inorganic materials other organisms *Plants, algae, & some protists are photoautotrophs, they use light to synthesize glucose
  2. 2. All heterotrophs depend on autotrophs for food and the oxygen that’s a biproduct of photosynthesis
  3. 3. Photosynthsis Converts Light Energy to Chemical Energy of Food Which organelle is responsible for photosynthesis?? Chloroplasts What is the chemical energy that autotrophs produce?? Glucose What are the raw materials that go into photosynthesis? What are the products? 6CO2 + 6H2O + Light Energy C6H12O6 + 6O2 Which plant organ is the primary site of photosynthesis? Leaves
  4. 4. Anatomy of the Leaf & Its Chloroplasts
  5. 5. How do we know what we know about photosynthesis?? Tracking Atoms: The overall chemical reaction of photosynthesis is the reverse of cell respiration, but the process of photosynthesis is NOT the reverse of cell respiration: What’s the equation for cell respiration? C6H12O6 + 6O2  6CO2 + 6H2O + ATP energy What’s the equation for photosynthesis? 6CO2 + 6H2O + light energy  C6H12O6 + 6O2 If you don’t already hav e these equa tions memo rized, write them down and commit the m to memo ry!!
  6. 6. Relationship Between Cell Respiration & Photosynthesis Heat Sunlight Photosynthesis Cellular respiration
  7. 7. Photosynthesis Equation in its Simplest Form: CO2 + H2O  [CH2O] + O2 General formula for a carbohydrate
  8. 8. The Splitting of Water Before the 1930’s, it was widely believed that the O2 produced by plants is a result of the splitting of CO2 during photosynthesis Thanks to C.B. van Niel & others, we now know that the O2 produced is a result of the splitting of a water molecule during photosynthesis: Van Niel’s Experimental Results Sulfur bacteria: CO2 + 2H2S  [CH2O] + H2O + 2S Plants: CO2 + 2H2O  [CH2O] + H2O + General: CO2 + 2H2X  [CH2O] + H2O + 2X O2 Conclusion: photosynthetic organisms require a hydrogen source which is split during photosynthesis
  9. 9. Later Tests Using Oxygen-18 Isotope Markers Confirmed the Same…. Exp #1: When the oxygen in water is labeled… CO2 + 2H2O  [CH2O] + H2O + O2 Exp #2: When the oxygen in carbon dioxide is labeled… CO2 + 2H2O  [CH2O] + H2O + O2
  10. 10. Tracking Atoms Through Photosynthesis….
  11. 11. Quick Think • With someone near you, discuss: where does the oxygen released from plants during photosynthesis come from and how did scientists determine this? • Be prepared to share your ideas.
  12. 12. Photosynthesis as a Redox Process Cell Resp Photosynthesis Employs redox reactions Employs redox reactions e-Gain orpotential lose Lose? energy as they move down ETC By-product = H?O 2 e- Gain orpotential gain Lose? energyrequires energy from light By-product = O2 ?
  13. 13. Photosynthesis Overview Go to your diagrams
  14. 14. Two Stages of Photosynthesis: Light Reactions & Calvin Cycle Light Reactions: •Light is absorbed by chlorophyll •Energy from the light splits H2O •H from water reduces NADP+ (an e- acceptor) to NADPH •Chemiosmosis makes ATP from ADP. This process is known as photophosphorylation •Products of light reactions: Energy = ATP & NADPH By-product = O2 Occurs in thylakoid
  15. 15. Two Stages of Photosynthesis: Light Reactions & Calvin Cycle The Calvin Cycle: Occurs in stroma •CO2 from atmosphere enters chloroplast & is incorporated into organic molecules = carbon fixation •NADPH from the light rxns reduces the fixed carbon (by donating H) to carbohydrate; ATP from light rxns is required for this step •Product of Calvin Cycle: glucose
  16. 16. The Light Reactions of Photosynthesis
  17. 17. The Light Reactions Convert Solar Energy to the Chemical Energy of ATP & NADPH The Nature of Sunlight (electromagnetic energy): •Light has properties of both waves & particles (photons) •Visible light is the part of the EMS that drives photosynthesis •The shorter the wavelength, the higher the energy
  18. 18. Photosynthetic Pigments are Light Receptors •Pigments like chlorophyll either absorb, transmit, or reflect light •The wavelength of light that is reflected is the color that we detect with our eyes •Which wavelength (color) of Light is least effective for Photosynthesis?? Green
  19. 19. These accessory pigments allow chloroplasts to take advantage of a broader spectrum
  20. 20. Quick Think • With someone near you discuss: Why are plants green? • Be prepared to share your thoughts
  21. 21. Excitation of Chlorophyll by Light •Energy from a photon of light raises a pigment molecule’s e- from ground state to an unstable excited state •When the e- drops back down to its ground state, energy is emitted in the form of heat & light •Chloroplasts in plants don’t fluoresce because the excited eis passed to an e- acceptor rather than dropping back down to ground state Go to your diagrams
  22. 22. A photosystem is a bundle of pigment molecules and proteins •Photosystems act as an antenna for light Made of 2 chlorophyll a molecules & a primary eacceptor Special because they can use light to boost an e- to the next energy level…light energy has now been converted to chemical energy
  23. 23. The thylakoid has 2 photosystems: PS I & PS II Chlorophyll a molecules that best absorb light at 680 nm & 700 nm respectively
  24. 24. Noncyclic Electron Flow: PS I & PS II work together to use light to make ATP & NADPH during the light reactions During the light reactions, e- may flow in either a cyclic or noncyclic manner: Noncyclic flow of e- plastocyanin plastoquinone
  25. 25. Noncyclic Electron Flow: PS I & PS II work together to use light to make ATP & NADPH during the light reactions Noncyclic flow of eAnimation of steps: http://www.cst.cmich.edu/users/baile1re/bio101fall/enzphoto/photoanima.htm# http://www.stolaf.edu/people/giannini/flashanimat/metabolism/photosynthesis.swf http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter10/animations. Go to your diagrams
  26. 26. Quick Think • With someone near you, summarize the steps of noncyclic electron flow in the light reactions
  27. 27. Cyclic Electron Flow: uses PS I but not PS II During the light reactions, e- may flow in either a cyclic or noncyclic manner: •Only ATP is produced, not NADPH •Noncyclic e- flow Cyclic e- Flow produces NADPH & ATP •BUT the Calvin cycle uses more ATP •SO Cyclic e- flow is used to keep up with the ATP demand so that the Go to your Calvin cycle doesn’t diagrams
  28. 28. Quick Think • With someone near you, discuss the differences between noncyclic and cyclic electron flow
  29. 29. Comparing Chemiosmosis in Mitochondria and Chloroplasts
  30. 30. Comparing Chemiosmosis in Chloroplasts & Mitochondria Similarities In both organelles, the ETC pumps H+ ions from an area of low concentration to an area of higher concentration. The diffusion of H+ through ATP synthase drives ATP synthesis
  31. 31. Comparing Chemiosmosis in Chloroplasts & Mitochondria Differences •In mitochondria chemical energy from food is transferred to ATP & NADH. •In Chloroplasts light energy is transfered to ATP & NADPH • H+ diffuse across inner membrane to matrix in the mitochondrion •H+ diffuse out of the thylakoid & into the stroma of the chloroplast.