Chapter 9: Photophosphorylation

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Chapter 9 Photophosphorylation Capture energy
from sunlight Simple systems such as
bacteriorhodpsin, may have been the first to
create charge separating membranes, possibly
predating respirative electron transport Basic
Idea
Not unlike redox reactions
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A More Useful Rxn
hn, photon
Ground state
Excited state
ADP P ? ATP OR NADP e- ? NADPH
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Photosystems in Order of Likely Evolutionary
Appearance Anoxygenic, no O2 produced 1.) OR
Bacteriorhodopsin-like 2.) Oxygenic, leading to
the production of O2, requires larger energy
gaps and more reactions Bacteriorhodopsin-li
ke --- Conformational cycling of a
protein-carotenoid pair --- Driven by
carotenoid photon absorption --- Pumps protons
across the cytoplasmic membrane --- pmf drives
ATPsynthase --- A one protein light driven
proton pump
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Light Driven Confromational Cycling in Carotenoid
pigment of Bacteriorhodopsin --- Shifts Base
Reaction
Light Driven Rxn
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More Complicated Schemes Anoxygenic
Photosynthesis Purple Non-Sulfur
Bacteria Purple Sulfur Bacteria Green Sulfur
Bacteria
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Cyanobacterial Photosynthesis
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Racker Experiment