Photosynthesis<br />
Electron Micrograph of a Chloroplast<br />
Photosynthesis<br />Photosynthesis consists of light-dependent and light independent  reactions<br />*Should not be called...
Light-Dependent Reactions<br />The thylakoid membrane is populated by two types of photosystems<br />Photosystem II (PS II...
Photosystem II<br />The starting point for light-dependent reactions of photosynthesis<br />Electron acceptor for Photosys...
Photosystem II<br />Two photons of light are absorbed causing the production of one reduced plastoquinone<br />One of the ...
Photosystem II - Photolysis<br />Photoloysis- the splitting of water <br />Generates oxygen in photosynthesis as a waste p...
General Formula- Photosystem II<br />2H2O  O2 + 4H+ + 4e-<br />
Photosystem I<br />The useful product of Photosystem I is NADPH the reduced form of NADP+<br />Chlorophylls absorb light e...
Photosystem I<br />That electron travels through the chain of carriers in Photosystem I<br />Passed to ferredoxin<br />Two...
Electron Transport Chain<br />Links Photosystem II and Photosystem I<br />Electrons excited in Phtosystem II are passed al...
Cyclic Photophosphorylation<br />As electrons flow back along the electron transport chain from Photosystem II to Photosys...
Photophosphorylation and Chemiosmosis<br />Photophosphorylation- the production of ATP, using energy from light<br />Due t...
Light- Independent Reactions<br />First carbohydrate produced is triose phosphate<br />Two triose phosphate molecules comb...
Light- Independent Reactions<br />The conversion of 3- carbon sugars (triose phosphate) to the 5- carbon sugar (ribulose p...
Plant absorb all visible light except for green, which is reflected<br />
Bibliography<br />http://www.agri.huji.ac.il/~zacha/images/chloroplast.jpg<br />http://www.marietta.edu/~spilatrs/biol103/...
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Photosynthesis Part 2

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Photosynthesis Part 2

  1. 1. Photosynthesis<br />
  2. 2. Electron Micrograph of a Chloroplast<br />
  3. 3. Photosynthesis<br />Photosynthesis consists of light-dependent and light independent reactions<br />*Should not be called “light” and “dark” reactions<br />
  4. 4. Light-Dependent Reactions<br />The thylakoid membrane is populated by two types of photosystems<br />Photosystem II (PS II)<br />Photosystem I (PS I)<br />
  5. 5. Photosystem II<br />The starting point for light-dependent reactions of photosynthesis<br />Electron acceptor for Photosystem II is called plastoquinone (hydrophobic)<br />Collects two electrons from Photosystem II and relocates then to another position in the thylakoid membrane <br />
  6. 6. Photosystem II<br />Two photons of light are absorbed causing the production of one reduced plastoquinone<br />One of the chlorophylls looses two electrons<br />Process is repeated to reduce another plastoquinone and have a total of four lost electrons<br />Due to the oxidising agent this produces, nearest water molecules split and give up electrons to replace the lost electrons.<br />
  7. 7. Photosystem II - Photolysis<br />Photoloysis- the splitting of water <br />Generates oxygen in photosynthesis as a waste product<br />The energy gathered from Photosystem II drives all the reactions of photosynthesis<br />
  8. 8. General Formula- Photosystem II<br />2H2O  O2 + 4H+ + 4e-<br />
  9. 9. Photosystem I<br />The useful product of Photosystem I is NADPH the reduced form of NADP+<br />Chlorophylls absorb light energy and pass the energy to two chlorophyll molecules at the reaction center<br />Raises electron in one of the chlorophylls to a high energy level (photoactivation)<br />
  10. 10. Photosystem I<br />That electron travels through the chain of carriers in Photosystem I<br />Passed to ferredoxin<br />Two molecules of the reduced ferredoxin are used to reduce NADP+ to form NADPH + H+<br />Electron that was passsed to the chain of electron carriers is replaced by an electron carried by plastocyanin<br />
  11. 11. Electron Transport Chain<br />Links Photosystem II and Photosystem I<br />Electrons excited in Phtosystem II are passed along the chain of carriers to plasocyanin, which gives the electrons to Photosystem I<br />
  12. 12. Cyclic Photophosphorylation<br />As electrons flow back along the electron transport chain from Photosystem II to Photosystem I, they cause pumping of protons, which allows ATP production<br />
  13. 13. Photophosphorylation and Chemiosmosis<br />Photophosphorylation- the production of ATP, using energy from light<br />Due to non-cyclic photophosphorylation, a concentration gradient of protons develops across the thylakoid membrane (potential energy)<br />Energy released by protons passing down their concentration gradient produces ATP from ADP- Chemiosmosis<br />
  14. 14. Light- Independent Reactions<br />First carbohydrate produced is triose phosphate<br />Two triose phosphate molecules combine to from hexose phosphate<br />Hexosephospahte can combine by condensation reactions to form starch<br />Some triose phosphate in the chloroplast are used to regenerate RuBP<br />
  15. 15. Light- Independent Reactions<br />The conversion of 3- carbon sugars (triose phosphate) to the 5- carbon sugar (ribulose phosphate) requires three ATP<br />
  16. 16. Plant absorb all visible light except for green, which is reflected<br />
  17. 17. Bibliography<br />http://www.agri.huji.ac.il/~zacha/images/chloroplast.jpg<br />http://www.marietta.edu/~spilatrs/biol103/photolab/PScncpt1.gif<br />

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