BIOL 2P03 Lecture Notes - Lecture 7: Electric Motor, Atp Synthase, Reduction Potential

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Lecture 7 ETC
The ‘electron transport system’ – a closer look
Redox potentials and electron transport chains
Respiratory complexes – functions and organization
Proton gradients and ATP synthesis
Redox potentials in the electron transport system
Denition of ‘redox potential’ (from Wikipedia, honestly):
a measure of the tendency of a chemical species to acquire electrons and
thereby be reduced.
measured in millivolts (mV).
the more positive the potential, the greater the molecule’s a*nity for
electrons and therefore its tendency to be reduced
NADH and FADH2 are electron donors, initiating series of redox reactions
terminating in reduction of oxygen to make water
And there are two highly mobile
electron shuttles
associated with the ETS:
(1) Coenzyme Q: Highly lipophilic; abundant in the inner membrane Accepts
electrons from complexes I and II; donates them to complex III
(2) Cytochrome C
A small heme protein (~12 kDa)
Peripheral protein, associated with outer lea8et of inner membrane
Moves electrons from complex III to complex IV
How the ETS (or ETC) is organized within the inner membrane
Although the ‘electron transport system’ is usually represented as a chain the
links in the chain (i.e. the respiratory complexes) are actually organized into
supercomplexes – associations between the respiratory complexes
Data from cryoelectron microscopy and blue native electrophoresis suggest the
following arrangement of ATP synthases:
2 x ATP synthases
2 x ATP/ADP exchanger
2 x P - transporter
= two ‘ATP synthasomes’
Oxidative phosphorylation – summary
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