Oxidative phosphorylation
occurs in the mitochondria
• The energy stored in a H+ gradient across a membrane couples the redox reactions of the ETC to ATP synthesis
• The H+ gradient is referred to as a proton-motive force, emphasizing its capacity to do work
The figure is found at http://www.grossmont.net/cmilgrim/Bio220/Outline/ECB2Figures&Tables_Ed2- Ed1/Chapter14_13/REDOX_POTENTIALS_ElectronTransportChain_Fig14-21.htm(December 2006)
Gibbs energy
„G“
Redox potential „E“
↑ reducing properties
↑ oxidizing properties
Electron carriers
Complexes I and II feed the ubiquinone pool
NADH-ubiquinone oxidoreductase
Complex III
(ubiquinol-cytochrome c oxidoreductase)
• Uses the transfer of electrons from QH2 to cytochrome c to
“transport” four protons
• Cyt bc1 complex:
10-11 subunits cyt b
cyt c
Fe-S protein (Rieske protein)
• Myxathiazol binds to Fe-S protein
• Antimycin A
Complex IV (cytochrome oxidase)
• Cytochrome oxidase passes electrons
from cytochrome c through a series of heme groups and Cu ions to O
2,
reducing it to H
2O
4 Cyt c (reduced) + 8H+ (N side) + O2 =>
4 cyt c (oxidized) + 4H+ (P side) + 2H2O
The figure is found at http://plaza.ufl.edu/tmullins/BCH3023/cell%20respiration.html (December 2006)
ATP synthase
inner mitochondrial membrane
The figure is found at http://departments.oxy.edu/biology/Franck/Bio222/Lectures/March23_lecture_shuttles.htm(December 2006)
Uncoupling proteins
(UCP)
= separate RCH from ATP
synthesis
(the synthesis is interrupted)
energy from H+ gradient is released
as a heat
