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7/27/2019 The Electron Transport Chain
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7/27/2019 The Electron Transport Chain
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ETC in:
Eukaryotescollection of moleculesembedded in the inner membrane ofmitochondria
Cristae- infoldings of the inner membrane
Prokaryotesfound in the plasma
membrane. Most components are proteins in nature.
Multiprotein complexes(1 to 4)
Contain prosthetic groups
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During electron transportelectron
carriers alternate between reduced and
oxidised. Entry of electron in an EC from uphill
ECreduced
Exit of electron from an EC to downhillECoxidised.
DownhillECmore electronegativethan their uphill EC.
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NADH from glycolysis and krebscycletransfer electrons to Complex 1.
Complex 1flavoprotein, named afterits prosthetic group, flavinmononucleotide(FMN)
Flavoprotein oxidises when passingelectrons to an iron-sulfur protein (Fe-s incomplex 1)
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FADH2reduced product of Citric acid
cycle
Transfers electrons to complex 2 Complex 2lower energy level than
complex 1
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Not a protein
Small and hydrophobic in nature
Individually mobile within the membrane Fe-S group of complex 1 and 2 transfer
their electrons to ubiquinone.
The latter is reduced while the 2complexes return back to their oxidizedstate
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Remaining carriers between ubiquinoneand water.
Protein in nature
Prosthetic groupheme ETC has different kinds of cytochromes,
different proteins with slightly different hemegroups also.
cyta3last cytochrome, gives electrons tofinal acceptorOxygen
A pair of hydrogen ions is also picked up foreach oxygen atom forming water.
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ATP synthaseenzyme that makes ATP fromADP and pi
In eukaryotesfound embedded in the inner
membrane of mitochondria In prokaryotesin plasma membrane ATP synthasemakes use of existing ion
gradient to fund synthesis of ATP Ion gradientH+ gradient across inner
membrane of mitochondrion Chemiosmosiscarrying out cellular work
using energy stored in the form of H+ iongradient across a membrane.
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ATP synthasemultisubunit complex
with four main parts
Each partmultiple polypeptides H+ ions move one by one into binding
sites on one of the parts, resulting in
spinning of the rotor in a way to catalyseATP production
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ETCenergy converter
Makes use of exergonic flow of electrons
to pump H+ into intermembrane space. Protonstendency to flow back
towards the matrix( down its
concentration gradient) The membrane then, offers only one
route or exitATP synthase
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Proton motive forcethe H+ gradient
generated when H+ is pumped into the
intermembrane space. Chemiosmosisan energy coupling
mechanism that uses energy stored inthe form of H+ gradient across amembrane to drive cellular work.
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