MadSci Network: Biochemistry |
In photosynthetic electron transport, every facilitating protein compound on the thylakoid can not accept electron (be reduced) unless it just lost(excited, be oxidized) one of its own. So the excited electron from one compound may not be the exact same one that just accepted. This is also the case in cyclic electron transport: The electron back to P700 may not be the same original one from P700. So the process is like: PSI pigments are excited by one photon and cause the excitation and removement of an electron from P700. Then oxidized P700 can receive one electron from reduced PC and form reduced P700. Electrons from reduced PSI now can move to mobile ferrodoxins (this movement and all the following "movement" and "transport" are due to the oxidation-reduction process), from there to cytb6 complex and plastoquinone. The full reduction of plastoquinone takes two protons from stroma side of thylakoid (not from PSII) besides accepted electrons. These two protons will be moved to thylacoid lumen in later transport, thus facilitate the ATP synthesis; and the electrons will be transported via Fe-S, cytf and PC, then back to PSI. So you are right, the electrons will go to another "hole", but another electron will be removed later from the "hole" thus form a electron transport chain.
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