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The final piece of the puzzle. Electron transport and Oxidative phosphorylation. Take a deep breath and push on. Major Energy Pathways. Glucose. Glycolysis. Fatty Acids. Acetyl-CoA. Krebs Cycle. 1 FADH 2. 3 NADH. O 2. H 2 O. Galactose Fructose Mannose. Anaerobic. Lactate. - PowerPoint PPT Presentation
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Electron transport and
Oxidative phosphorylation
The final piece of the puzzle
Take a deep breath and push on
Major Energy Pathways
Glycolysis
Oxidative phosphorylation
pyruvate
3 NADH
GlucoseGalactoseFructoseMannose
Fatty Acids
1 FADH2
Lactate
Amino Acids
O2
H2O
Anaerobic
Aerobic
Krebs Cycle
Acetyl-CoA
Electron Transport and Oxidative PhosphorylationElectron Transport and Oxidative Phosphorylation
1. The absolute heart of aerobic metabolism
2. Three Functional Phases
Electron transfer from NADH, FADH2 to O2
Energy preserved as a proton gradient
Proton gradient energy makes ATP
We are making ATP from ADP and Pi by tapping the oxidative energy generated in the transfer of electrons to O2
We are making ATP from ADP and Pi by tapping the oxidative energy generated in the transfer of electrons to O2
Anatomy of Mitochondria
Mitochondria are composed of a dual membrane system:
Outer: Porous to all molecules < 10 kDaInner: Transporter-dependent transport
Inner Membrane Transport in Mitochondria
Densely packed with specific membrane transporters andthe electron-transporting complexes
Table 1: Cytochromes in the Electron Transport System
1. Cytochrome b562 also called bH Complex III Fe2+/Fe3+
2. Cytochrome b566 also called bL Complex III Fe2+/Fe3+
3. Cytochrome b560 Complex II Fe2+/Fe3+
4. Cytochrome c1 Complex III Fe2+/Fe3+
5. Cytochrome c Mobile Fe2+/Fe3+
6. Cytochrome a Complex IV Fe2+/Fe3+ Cu+/Cu2+
7. Cytochrome a3 Complex IV Fe2+/Fe3+ Cu+/Cu2+
Electron TransportThe successive passage of electrons through a series ofmembrane complexes to Oxygen.
NADH FMN CoQ Cyt b Cyt c1 Cyt c Cyt a+a3 O2
Complex I Complex III Complex IV
Strategies p219
Transport Mechanism
NADH
NAD+
FMN
FMNH2 CoQ
CoQH2
Cyt b(Fe3+)
Cyt b(Fe2+)
Cyt c1
(Fe3+)
Cyt c1
(Fe2+)Cyt c(Fe3+)
Cyt c(Fe2+)
Cyt a+a3
(Fe3+)
Cyt a+a3
(Fe2+) O2
H2O
A bucket-brigade
Reduced Oxidized
..
..
..
..
..
..
..
..
-0.32 volts + 0.82 volts
Electron Transport Complexes
• Membranes bound heme proteins or “cytochromes”
• Iron-Sulfur proteins..high reducing potential
• Mobile electron carriers– Coenzyme Q– Cytochrome c
Electron TransportNADH
O2
Complex I
Complex III
Complex IV
-0.32
+0.82
CoQ
Cyto C
Reductive Energy
Oxidative Energy
Complex II
FADH2
H2
Fe2+
H2O
Fe
S
SFe
S
SS
S
Cys
Cys
Cys
Cys 2-
2-
Fe-S 2Fe-2S
Fe
S
ssS
Cys
Cys
Cys
Cys
Iron-Sulfur Centers
n =6-10Oxidized CoQ
CH3H3CO
H3CO ROH
OH
Semiquinone
OCH3H3CO
H3CO R
.
OH
CoQH. CoQH2Quinol Form
Form (2 electrons)(one electron)
(no electrons)
CH3H3CO
H3CO (CH2=CO
O
CH3
CH2)nHisoprenoid units
Coenzyme Q
NADH-CoQ Reductase
FMNFeS
I
CoQ
Succinate-CoQ Reductase
FADFeSCyt b560
II
CoQ-cyto c Reductase
Cyt b562
Cyt b566
FeSCyt c1
III
Cyto c
IVCu2+
Cyt aCyt a3
O2
Mobile
Succinate Fumarate
NADH
Electron TransportComplexes
Energy Time
How does the energy of oxidation translate into free energy?
Go’ = –nFEo’
F = Faraday’s constant = 96,500 J/mol x volt
n = Number of electrons
Eo’ = Standard Reduction Potential at pH 7
E = Eo’ + 0.06 log
[electron acceptor]
[electron donor]
Nernst Equation for one electron transferDetermines E under non-standard state conditions
Textbook p372
E = Eo’ + 0.06 log[electron acceptor]
[electron donor]
pH = pKa + log [proton acceptor]
[proton donor]
E (reduction potential)pH
pKa Eo’ (standard reductionpotential)
Proton Acceptor Electron acceptor (oxidant)(base)
Proton Donor (acid) Electron donor (reductant)
Acid/Base Redox
Donors(Reductants)
Acceptors(Oxidants)
e-
Eo’= Eo’ acceptor - Eo’ donorEo’= Eo’ acceptor - Eo’ donor
Eo’
NADH + H+ + 1/2 O2NAD+ + H2O
NAD+ + 2e + 2H+ NADH + H+ –0.32 volts1/2 O2 + 2e + 2H+ H2O +0.82 volts
To Arrive at equation:
NADH + H+ NAD+ +2e + 2H+ +0.32 volts
1/2 O2 + 2e + 2H+ H2O +0.82 volts
NADH + H+ + 1/2 O2 NAD+ + H2O +1.14 volts
Go’ = –nFEo’ Go’ = –220 kJ/mol
Top reduces bottom
J/CoulombCoulomb/mol
Shuttles
Problem: Cytosolic NADH cannot penetrate the mitochondria
Solution: Pass the electrons to something that canpenetrate the mitochondria membrane
Two Shuttles
Glycerol-PO4
Malate-aspartate
FADH2 2 ATP per NADHc
NADH 3 ATP per NADHc
Mammalian muscle and liver
Insect brain and flight muscle
CH2OH
C=O
CH2OP
CH2OH
HO-C-H
CH2OP
CH2OH
HO-C-H
CH2OP
CH2OH
C=O
CH2OP
Cytosol
Mitochondria
Membranetransporter
Glycerol-PO4
Shuttle
DHAPGlycerol-PO4
Flavoproteindehydrogenase
FADH2FADH2
FAD
2ATP2ATP
NAD+NADHNADH:
:
:
:
COO
HO-C-H
CH2
COO
COO
C=O
CH2
COO
COO
C=O
CH2
COO
COO
HO-C-H
CH2
COO
COO
H3N-C-H
CH2
COO
+
COO
H3N-C-H
CH2
COO
+
Glu-Kg
-Kg Glu
NADHNADH
OAA
Asp
Malate-Aspartate
L-malate
Malatedehydrogenase
Malatedehydrogenase
NAD+
NAD+NADHNADH
3ATP3ATPAminotransferase
Aminotransferase
P457P457
Mitochondria
Cytosol