Photosystem II: Difference between revisions

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Emily Forschler, Eran Hodis, Jaime Prilusky, Ilan Samish, David Canner, Eric Martz, Karl Oberholser, Michal Harel, Alexander Berchansky, Joel L. Sussman

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 <scene name='Photosystem_II/Chlorophyll_green/1'>Chlorophyll</scene> surround Photosystem II and capture energy from sunlight, exciting electrons.  Chlorophyll are highly conjugated and absorb visible light, along with accessory light harvesting pigments such as <scene name='Photosystem_II/Betacarotene/1'>beta carotene</scene>. Beta carotene absorbs visible light of other wavelengths and also protects Photosystem II by destroying reactive oxygen species that result from this photoexcitation.  [[Image:b-car.svg.png|b-car.svg.png|thumb|right|400px|structure of beta carotene]]  Electrons are passed from chlorophyll to <scene name='Photosystem_II/Pheophytin_purple/3'>pheophytin</scene>.  Pheophytin are very similar to chlorophyll except they  contain 2 H<sup>+</sup> instead of a Mg<sup>2+</sup> ion.  From the pheophytin, electrons transferred to <scene name='Photosystem_II/Quinone_pink/3'>plastoquinones</scene>, which are reduced.  Between each pair of quinones, an iron, in red, helps to transfer the electron. These plastoquinones eventually move to a plastoquinone pool which travels to another large protein subunit, cytochrome b <sub>6</sub>/ f.  Eventually these electrons reduce NADP<sup>+</sup> to NADPH.  Here the <scene name='Photosystem_II/Electron_pathway/1'>electron pathway</scene> through Photosystem II is shown, with '''<FONT COLOR="#F87217">beta-carotenes</FONT>''', '''<FONT COLOR="#571B7e">pheophytins</FONT>''', '''<FONT COLOR="#E42217">iron</FONT>''' and '''<FONT COLOR="#F535AA">plasotoquinones</FONT>'''.
 [[Image:plastoquinone.jpg|thumb|300px|right|reduced plastoquinone]]
 ==Oxygen Evolution==
-Another important facet of photosystem II is its ability to oxidize water to oxygen with its <scene name='Photosystem_II/Oxygen_evolving_centers/5'>oxygen evolving centers</scene>.  These <scene name='Photosystem_II/Oxygen_evolving_centers/3'>centers</scene> were shown to be cubane-like Mn<sub>3</sub>CaO<sub>4</sub>cluster linked to a fourth Mn by a mono-μ-oxo bridge. [1]  Purple represents manganese, red represents oxygen and green is for calcium.  Oxidation of water to leaves 2 H <sup>+</sup> on the lumenal side of the membrane, helping to establish the proton gradient essential for ATP synthesis in the CF<sub>1</sub>CF<sub>0</sub>-ATP sythase protein.
+Another important facet of photosystem II is its ability to oxidize water to oxygen with its <scene name='Photosystem_II/Oxygen_evolving_centers/5'>oxygen evolving centers</scene>.  These <scene name='Photosystem_II/Oxygen_evolving_centers/8'>centers</scene> were shown to be cubane-like Mn<sub>3</sub>CaO<sub>4</sub>cluster linked to a fourth Mn by a mono-μ-oxo bridge. [1]  Purple represents manganese, red represents oxygen and green is for calcium.  Oxidation of water to leaves 2 H <sup>+</sup> on the lumenal side of the membrane, helping to establish the proton gradient essential for ATP synthesis in the CF<sub>1</sub>CF<sub>0</sub>-ATP sythase protein.
 ==References==