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CASE FILES: BIOCHEMISTRY
B IO C H E M IS T R Y PE A R L S
The electron transport chain (ETC) or electron transport system
(ETS) is located on the inner membrane of the mitochondrion
and is responsible for the harnessing of free energy. The chain
consists of a series of carriers arranged along the inner membrane
of mitochondria that transport electrons from NADH and reduced
flavin carriers to molecular oxygen.
Energy is released as electrons travel from more reduced (more neg-
ative reduction potential,
E
'0)
to more oxidized (more positive
E'0)
carriers to drive the phosphorylation of ADP to ATP.
The components of the electron transport chain have various cofactors,
which form vital complexes.
The disruption of various complexes may interfere with the ETC,
leading to inability to manufacture ATP.
The energy gained from electron transfer is used to drive protons out
of the inner mitochondrial matrix to the cytosol, establishing a
gradient of protons. As the protons come back into the matrix via
the ATP synthase complex, ADP is phosphorylated to ATP.
The normal mitochondria produce ATP as they transport electrons to
oxygen; any interference with ATP synthesis or translocation
across the mitochondrial membrane will inhibit electron transfer.
Rotenone binds avidly to the flavoprotein NADH CoQ reductase,
complex I (also called NADH dehydrogenase).
REFERENCES
Davidson VL, Sittman DB. National Medical Series-Biochemistry. Philadelphia,
PA: Harwol, 1994:381-3.
Devlin TM, ed. Textbook of Biochemistry with Clinical Correlations, 5th ed. New
York: Wiley-Liss, 2002:563-82.
Goodman AG, Gilman LS, eds. The Pharmacological basis of Therapeutics, 10th ed.
New York: McGraw-Hill, 2001:1642.
McGilvery RW. Biochemistry: A Functional Approach. Philadelphia, PA: W.B.
Saunders, 1979:397-400.
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