3.8 8.2 Photosynthesis PPT

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  • Photosynthesis title, definition and equation.
  • Chloroplast: colour TEM, parts and functions.
  • Why does a leaf look green?
  • 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.
  • Absorption spectrum of chlorophyll a vs action spectrum of photosynthesis. Chlorophyll b is used to ‘fill the gaps’ in the action spectrum.
  • Photolysis of water produces high-energy electrons, H+ protons and oxygen.
  • Protons are pumped into stroma using energy from electrons
  • Photosystem I is activated
  • Non-cyclic phosphorylation produces ATP.
  • Reduction of NADP+ by ferredoxin.
  • Calvin cycle overview.
  • Calvin cycle animation links.
  • Team analogy for the limiting factors theory. Time to vote off the weakest link.
  • CO2 affects rate of photosynthesis. CO2 is the substrate in carbon fixation (Calvin cycle) – rubisco is the enzyme.
  • Light intensity affects rate of photosynthesis.
  • Temperature affects the rate of photosynthesis. Remember enzyme theory. Enzymes used in respiration: rubisco is the main one. ATP synthase can also be denatured.
  • Explain the effects of limiting each of the three factors on the process of photosynthesis. It’s not enough to just say “it slows down.”
  • This graph suggests that CO2 is more important than temperature. Why?
  • Iron is limiting – seeding algae with iron stimulates algal blooms. Iron is used in ferroxidase – responsible for reduction of NADP+ in the light dependent reactions. Results with CO2 were short-term. Levels dropped in the immediate area, but the seeding is too expensive to work. Pros: possible reduced CO2 levels, algal blooms provide food for grazers and thus fisheries. Cons: large blooms block light to lower levels, may cause eutrophication; Diatoms block gills of some species; iron seeding may encourage blooms of toxic algae; who owns the ocean?
  • 3.8 8.2 Photosynthesis PPT

    1. 1. Topics 3.8 + 8.2 Photosynthesis<br />IB Biology<br />
    2. 2.
    3. 3. Leaves <br />Green tissue in the interior of the leaf (mesophyll) = contains chloroplasts<br />CO2 enters the leaf and O2 exits through the stoma<br />Stomata =bottom of leaf<br />
    4. 4. Chloroplasts<br />similar to mitochondria<br />outer and inner membrane<br />membranous sacs: THYLAKOIDS<br />thylakoids = concentrated in stacks called GRANA<br />thylakoids: contain chlorophyll (capture light)<br />filled with fluid: STROMA (where sugars are made from CO2 )<br />
    5. 5. Overview<br />
    6. 6. Electromagnetic Spectrum<br />
    7. 7.
    8. 8.
    9. 9.
    10. 10. The 2 stages of Photosynthesis<br />Light Dependent Reactions:<br />convert light energy to chemical energy (ATP + NADPH) and produce oxygen gas as a waste product<br />Light Independent Reactions (Calvin Cycle):<br />make sugar using carbon dioxide and the energy-containing products of the light-reactions (ATP + NADPH) <br />
    11. 11. Light Dependent Reaction<br />Light can be..<br />Absorbed<br />Reflected<br />Transmitted<br />Occurs in thylakoids<br />Chlorophyll A and B = main photosynthetic pigments (also carotenes, anthocyanins)<br />
    12. 12. Light Dependent Reaction<br />Light energy is used to split water. <br />H + is released = used by ATP Synthase to produce ATP<br />NADP + is reduced to NADPH+<br />ATP and NADPH = used in light independent reactions<br />O2 = waste product<br />
    13. 13. Photosystems<br />Photosystem: place in thylakoid where light is harvested<br />Photon is absorbed by a pigment molecule = electrons gain energy<br />Excited electron is passed to a neighboring molecule - the primary acceptor<br />
    14. 14. Photosystems I & II work together<br />Both photosystems absorb light<br />Electron Transport Chain= electrons go down an energy hill = lose energy at each step - this energy is stored in ATP or NADPH<br />Electrons released from PSI is replaced by electrons coming from PSII<br />
    15. 15.
    16. 16.
    17. 17.
    18. 18. Chemiosmosis/Photophosphorylation<br />
    19. 19.
    20. 20. Role of Water<br />The light energy is used to split water molecules (photolysis)<br />H2O -> H+ + O + e-<br /><ul><li>The electrons allow reduction of NADP+ / replace those leaving photosystem II
    21. 21. H + flow allows ATP production
    22. 22. The O2 is released and leaves the plant through the stoma </li></li></ul><li>Mechanical Analogy for Making ATP<br />As electrons skip down the ETC, ATP are generated.<br />
    23. 23. Animations<br />http://www.youtube.com/watch?v=hj_WKgnL6MI<br />
    24. 24. Light Independent Reaction (Calvin Cycle)<br />Glucose phosphate is produced = stored as starch<br />CO2 , ATP and NADPH are used<br />
    25. 25.
    26. 26. Simple Calvin Cycle animations: <br />
    27. 27. Summary<br />Light dependent reaction<br />Light independent reaction<br />
    28. 28.
    29. 29.
    30. 30. plateau<br />CO2 is a substrate in an enyme-catalysed light-dependent reaction. <br />At low CO2 concentration, rate is positively correlated with concentration<br />
    31. 31. plateau<br />At low light intensity, rate of photosynthesis is proportional to light intensity. <br />
    32. 32. Optimum temperature<br />Increased temp. gives increased energy and increased rate of photosynthesis<br />Above the optimum temp., enzymes are denatured and rate drops steeply. <br />
    33. 33.
    34. 34. What are the conditions of each of these trials? <br />Rate of photosynthesis<br />Light intensity<br />

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