inside

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inside
outside
outside
inside
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Which way do the electrons flow?
oxidized species ne- ? reduced species or
reduced species ? oxidized species ne-
2H 2e- ? H2 or H2 ? 2H 2e-
From Lehninger Principles of Biochemistry
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Electrochemistry review

• High Eo' indicates a strong tendency to be
  reduced
• Nernst equation ?Go' -nF?Eo'
• ?Eo' Eo'(acceptor) - Eo'(donor)
• Electrons are donated by the half reaction with
  the more negative reduction potential and are
  accepted by the reaction with the more positive
  reduction potential
• ?Eo' positive, ?Go' negative
• If a given reaction is written so the reverse is
  true, then the ?Eo' will be a negative number and
  ?Go' will be positive

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Why do the electrons flow through the electron
transport chain?
Most oxidizing Most reducing
From Lehninger Principles of Biochemistry
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From Lehninger Principles of Biochemistry
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From Lehninger Principles of Biochemistry
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The sequence of electron transport
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Electron Transport
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From Lehninger Principles of Biochemistry
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Complex I NADH to Coenzyme Q Complex II
Succinate to Coenzyme Q Complex IIICoenzyme Q to
Cytochrome c Complex IV Cytochrome c to O2
SDH is on the matrix side of the IMS
From Lehninger Principles of Biochemistry
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NADH dehydrogenase aka NADH-Coenzyme Q reductase
o
NADH 2e- donor FMN
1 or 2 e- donor Fe-S clusters 1 e- donor

• Estimated mass of this complex 850 kD
• Involves more than 30 polypeptide chains
• One molecule of FMN
• As many as 7 Fe-S clusters (2Fe-2S 4Fe-4S)
• Precise mechanism of this complex is unknown

From Lehninger Principles of Biochemistry
12
Complex I
o
r
o
r
o
r
o
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From Lehninger Principles of Biochemistry
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Complex III structure (half of the functional
dimer)
From Lehninger Principles of Biochemistry
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From Lehninger Principles of Biochemistry
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Electron Transport
From Lehninger Principles of Biochemistry
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Cytochrome c
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From Lehninger Principles of Biochemistry
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Core of Complex IV is comprised of 3 subunits
Subunit II
CuA (2 Cu)
Subunit III
CuB
Subunit I
heme a, heme a3, and CuB
From Lehninger Principles of Biochemistry
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O2 4 H 4 cyt c (Fe2) ? 2 H2O 4 cyt c
(Fe3)
From Lehninger Principles of Biochemistry
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From Lehninger Principles of Biochemistry
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Determining the sequence of electron carriers
using inhibitors of electron transfer
Those that are reduced are blue.
Those that stay oxidized are pink
From Lehninger Principles of Biochemistry
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Coupling of electron transfer and ATP synthesis
in isolated mitochondria
Dinitrophenol causes dissipation of the proton
gradient and thus uncouples.
Inhibits ATP Synthase
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Determining the sequence of electron carriers
using inhibitors of electron transfer
Those that are reduced are blue.
Those that stay oxidized are pink
From Lehninger Principles of Biochemistry
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The proton gradient drives the release of ATP
from the enzyme surface
ATP is stabilized by binding to enzyme. Free
energy required for its release is provided by
proton-motive force.
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Model of ATP Synthase complex
????????????? ?3?3???
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Binding-change model for ATP synthase
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From Lehninger Principles of Biochemistry
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From Lehninger Principles of Biochemistry
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Regulation of the ATP-producing pathways
From Lehninger Principles of Biochemistry
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Model of ATP Synthase complex
????????????? ?3?3???
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Website for animations of ATP Synthase
http//www.biologie.uni-osnabrueck.de/Biophysik/Ju
nge/overheads.html