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Electron transport chainand oxidative phosphorylation
Group – 3 Shah Sunil and Groups
Respiration
Respiration Involves : Glycolysis,
Krebs cycle, Electron transport and
Oxidative Phosphorylation
INTRODUCTION
Glycolysis :Occurs in the cytoplasm.Breaks glucose into two molecules of pyruvate.
Krebs cycle :occurs in the mitochondrial matrix. degrades pyruvate to carbon dioxide.
Several steps in glycolysis and the Krebs cycle transfer electrons from substrates to NAD+, forming NADH.
NADH passes these electrons to the electron transport chain.
Mitochondria
stage 3rd of respirationOccurs in mitochondria.
Mitochondria
Outer membrane- permeable tosmall moleculesInner membrane-electron transport ATP synthase Cristae increase areaIntegrity required for
coupling ETS to ATP synthesis
Mitochondria
outer membrane relatively permeableinner membrane permeable only to
those things with specific transporters◦Impermeable to NADH and FADH2
◦Permeable to pyruvateCompartmentalization
◦Kreb's and β-oxidation in matrix◦Glycolysis in cytosol
Electron Transport System
Electron Transport Chain – is a collection of molecules embedded in the inner membrane of the mitochondria
◦Most components are proteins
Electron Transport System
Mechanism the cell that converts the energy in NADH and FADH2 into ATP.
Electrons flow along an energy gradient via carriers in one direction from a higher reducing potential to a lower reducing potential
The ultimate acceptor is molecular oxygen.
At the end of the chain electrons are passed to oxygen forming water.
Electron Transport System
An NADH molecule begins the process by “dropping off” its electron at the first electron carrier molecule
ETS
Remember: each component will be reduced when it accepts the electron and oxidized when it passes the electron down to the more electronegative carrier molecule in the chain
H2O
O2
NADH
FADH2
FMN
Fe•S Fe•S
Fe•S
O
FAD
Cyt b
Cyt c1
Cyt c
Cyt a
Cyt a3
2 H + + 12
I
II
III
IV
Multiproteincomplexes
0
10
20
30
40
50
Free e
nerg
y (
G)
rela
tive t
o O
2 (k
cl/m
ol)
Finally the electron is passed to oxygen, which is very electronegative.
The oxygen also picks up 2 H+ ions from the aqueous solution and forms water
H2O
O2
NADH
FADH2
FMN
Fe•S Fe•S
Fe•S
O
FAD
Cyt b
Cyt c1
Cyt c
Cyt a
Cyt a3
2 H + + 12
I
II
III
IV
Multiproteincomplexes
0
10
20
30
40
50
Free e
nerg
y (
G)
rela
tive t
o O
2 (k
cl/m
ol)
ETS
FADH goes through mostly the same processes, except it drops off its electron at a lower point on the ETC
H2O
O2
NADH
FADH2
FMN
Fe•S Fe•S
Fe•S
O
FAD
Cyt b
Cyt c1
Cyt c
Cyt a
Cyt a3
2 H + + 12
I
II
III
IV
Multiproteincomplexes
0
10
20
30
40
50
Free e
nerg
y (
G)
rela
tive t
o O
2 (k
cl/m
ol)
The ETC makes no ATP directly!
The ETC releases energy in a step-wise series of reactions
It powers ATP synthesis via oxidative phosphorylation.
But it needs to be coupled with chemiosmosis to actually make ATP.
Oxidative Phosphorylation
Production of ATP using transfer of electrons for energy
Some ATP is produced by substrate-level phosphorylation during glycolysis and the Krebs cycle, but most comes from oxidative phosphorylation
Oxidative phosphorylation
CONCEPT :
During oxidative phosphorylation, chemiosmosis
couples electron transport to ATP synthesis
Chemiosmosis
The Energy-Coupling MechanismInner membrane of mitochondria has
many protein complexes called ATP synthase◦ATP synthase – enzyme that makes ATP
from ADP and inorganic phosphate
It uses the energy of an existing gradient to do this.
The existing gradient is the difference in H+ ion concentration on opposite sides of the inner membrane of the mitochondria
Oxidative
phosphorylation.
electron transport
and chemiosmosis
Glycolysis
ATP ATP ATP
Inner
Mitochondrial
membrane
H+
H+ H+
H+
H+
ATP P i
Protein complex
of electron
carners
Cyt c
I
II
III
IV
(Carrying electrons
from, food)
NADH+
FADH2
NAD+
FAD+ 2 H+ + 1/2 O2
H2O ADP +
Electron transport chain
Electron transport and pumping of protons (H+),
which create an H+ gradient across the membrane
Chemiosmosis
ATP synthesis powered by the flow
Of H+ back across the membrane
ATP
synthase
Q
Oxidative phosphorylation
Intermembrane
space
Inner
mitochondrial
membrane
Mitochondrial
matrix
Chemiosmosis
Chemiosmosis – the process in which energy stored in the form of a hydrogen ion gradient across a membrane is used to drive cellular work (like the synthesis of ATP)
It is the job of the ETC to create this H+ ion gradient
Oxidativephosphorylation.electron transportand chemiosmosis
Glycolysis
ATP ATP ATP
InnerMitochondrialmembrane
H+
H+H+
H+
H+
ATPP i
Protein complexof electron carners
Cyt c
I
II
III
IV
(Carrying electronsfrom, food)
NADH+
FADH2
NAD+
FAD+ 2 H+ + 1/2 O2
H2OADP +
Electron transport chainElectron transport and pumping of protons (H+),
which create an H+ gradient across the membrane
ChemiosmosisATP synthesis powered by the flowOf H+ back across the membrane
ATPsynthase
Q
Oxidative phosphorylation
Intermembranespace
Innermitochondrialmembrane
Mitochondrialmatrix
H+ ions are pumped into the intermembrane space by the ETC
The H+ ions want to drift back into the matrix.
But they can only come into the matrix easily through ATP synthase channels
A protein complex, ATP synthase, in the cristae actually makes ATP from ADP and Pi.
ATP used the energy of an existing proton gradient to power ATP synthesis.
proton gradient develops between the intermembrane space and the matrix.
Mitochondrial redox carrier
NADH Complex I Q Complex III
Complex II Complex IV
FADH O2
4 Complexes
proteins in specific order Transfers 2 electrons in specific order
◦ Proteins localized in complexes Embedded in membrane Ease of electron transfer
◦ Electrons ultimately reduce oxygen to water 2 H+ + 2 e- + ½ O2 -- H2O
Complex I
Has NADH binding site◦ NADH reductase activity
NADH - NAD+
◦ transfers to electron carriers
◦ NADH (nicotinamide adenine dinucleotide )
Passes them to coenzyme Q ( Ubiquinone )
Also receive electron from complex II
Complex II
succinate ---FAD—ubiquinone◦ Contains coenzyme Q◦ FADH2 binding site
FAD reductase activity FADH2 -- FAD conversion of succinate to
fumerate
Mitochondrial redox carriers
Complex III
ubiquinone - ubiquinone while cytochrome C gets
reduced Also contains cytochromes b NADH generates more energy
than FADH2
Complex IV
reduction of oxygencytochrome oxidaseoxygen ---> water
◦2 H+ + 2 e- + ½ O2 -- 2 H2O
◦transfers e- one at a time to oxygen
ATP Produced
◦The NADH from glycolysis may also yield 3ATP.
Krebs cycle can be used to generate about 2ATP.
Electron transport chain yield 32 ATP.
ATP Produced
About 40% of energy glucose molecule
transferred to ATP during cellular respiration
Makes approximately 38 ATP.
Conclusion /Result
OVERALL yield from
glucose 36-38 ATPs
THANK YOU
GROUP -3SHAH SUNIL KUMARGIRI JEMYTIMILSINA BINODMAJHI INDRAABDHIKINIWARSAMEMOHAMMAD ABDIKALI