What is the Electron Transport Chain?

NADH and FADH2 from
glycolysis, pyruvate oxidation
and the citric acid cycle are
used as the source of energy to
pump protons (hydrogen ions)
out of the mitochondrial matrix
into the intermembrane space
of the mitochondria.
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The Electron Transport Chain
The electron transport chain uses electrons temporarily stored in
NADH and FADH2 to reduce a series of membrane associated
protein complexes which use the released energy to pump protons
out of the mitochondrial matrix. The energy stored in the
concentration gradient created is known as the proton motive force
and it is subsequently used to power the conversion of ADP to ATP.
This chemiosmotic production of ATP is powered by protons
diffusing back down the gradient through ATP Synthase.
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Inner
Mitochondrial
Membrane
Outer
Mitochondrial
Membrane
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Intermembrane Space
cc
IV
Q
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III
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Mitochondrial
Matrix
II
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Four proteins complexes and one
lipid are involved in electron transport:
(I) NADH-Q reductase
(II) Succinate dehydrogenase
(Q) Ubiquinone
(III) Cytochrome c reductase
(cc) Cytochrome c
(IV) Cytochrome c oxidase
Note: In prokaryotic cells, electron transport occurs on the cell membrane.
Attribution-Noncommercial 3.0 United States
+
Oxygen (O2)
is used as the
final electron
acceptor. This is
why we need to
breath oxygen!
Water is produced
as a byproduct of
the electron
transport chain.
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ATP Synthase uses
the proton motive force to
generate ATP from ADP as
protons move down the
concentration gradient
established by the electron
transport chain.
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