Photosystem II: Difference between revisions
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< | <StructureSection load='3a0b' size='400' frame='true' align='right' caption='Photosystem II, [[3a0b]]' scene='' > | ||
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==Electron Transfer== | ==Electron Transfer== | ||
[[Image:Chlorophyll_a.svg.png|thumb|170px|left|structure of chlorophyll ''a'']] | |||
<scene name='Photosystem_II/Chlorophyll_green/4'>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/3'>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. Electrons are passed from chlorophyll to <scene name='Photosystem_II/Pheophytin_purple/5'>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/5'>plastoquinones</scene>, which are reduced. Located between each pair of quinones, an iron 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. The <scene name='Photosystem_II/Electron_pathway/3'>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>'''. | |||
==Oxygen Evolution== | ==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/11'>oxygen evolving centers</scene>. These centers are <scene name='Photosystem_II/Single_oxygen_evolving/1'>cubane-like</scene> structures with 3 '''<FONT COLOR="#8D38C9">manganese</FONT>''', 4 '''<FONT COLOR="#C11B17">oxygen</FONT>''' and a '''<FONT COLOR="#59E817">calcium</FONT>''' linked to a fourth manganese<ref>PMID: 14764885</ref>. Oxidation of water 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/11'>oxygen evolving centers</scene>. These centers are <scene name='Photosystem_II/Single_oxygen_evolving/1'>cubane-like</scene> structures with 3 '''<FONT COLOR="#8D38C9">manganese</FONT>''', 4 '''<FONT COLOR="#C11B17">oxygen</FONT>''' and a '''<FONT COLOR="#59E817">calcium</FONT>''' linked to a fourth manganese<ref>PMID: 14764885</ref>. Oxidation of water 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. | ||
[[Image:b-car.svg.png|b-car.svg.png|thumb|left|400px|structure of beta carotene]] | |||
[[Image:plastoquinone.jpg|thumb|300px|left|reduced plastoquinone]] | |||
</StructureSection> | |||
==3D structures of photosystem II== | ==3D structures of photosystem II== | ||
