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ELECTRON TRANSPORT SYSTEM
Recaps
Gycolysis
glucose(C6H12O6) + 2 ADP + 2 Pi + 2 NAD+
2 pyruvic acid(C3H4O3) + 2 ATP + 2 H2O + 2 NADH + 2 H+
Pyruvate dehydrogenase
pyruvic acid + NAD+ + CoASH
acetyl-CoA(C2H3O-CoA) + CO2 + NADH + H+
TCA
acetyl-CoA(C2H3O-CoA) + 3 NAD+ + FAD + GDP + Pi + 2H2O
CoA-SH + 2 CO2 + 3 NADH + 3 H+ + FADH2 + GTP
Overall
Glucose (C6H12O6) + 2 ADP + 2 Pi + 2 NAD+ (cytoplasm)
+ 8 NAD+ + 2 FAD + 2 GDP + 2Pi + 2 H2O (mitochondria)
+ 2 ATP + 2 NADH + 2 H+ (cytoplasm)
+ 6CO2 + 8 NADH + 8 H+ + 2 FADH2 + 2 GTP (mitochondria)
Much of the energy released by oxidation of glucose has
been retained in bonds of reduced NADH and FADH2
Electron transport system
Use oxidation of NADH + H+ and FADH 2 to form ATP
and recycle NAD + and FAD
Mitochondria
Note: outer membrane, inner membrane,
crista, matrix, intermembrane space
Outer membrane permeable to > 1000 daltons
Inner membrane impermeable to І 1 dalton (H+)
Relevant enzymes embedded in the inner
mitochondrial membrane
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Electron transport and ATP synthesis as described in BIS 2A:
reduced donor
(e.g. malate)
oxidized acceptor
(NAD+)
oxidized donor
(e.g. OAA)
reduced acceptor
(NADH + H+)
Why do electrons
flow in this direction?
1/2 O2
H2O
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Mitochondrial electron transport chain:
Electron flow depends on standard reduction
potentials, since concentrations of carriers are ТfixedУ
(except at the beginning and the end).
Complex I: >30 polypeptides, 1 FMN, <7 Fe-S
+
centers, ~850 kD, proton pump pumping 4-6 H /2e
Complex II: 4 polypeptides, 7 Fe-S centers, FAD,
100-140 kD, no proton pump
Complex III: 11 polypeptides, 3 cytochromes, Rieske+
Fe protein, 240 kD, homodimer (500 kD); -2 H in,+ 4
+
H out per 2e
Complex IV: 13 polypeptides, 2 hemes, 2 Cu, 204
+
kD; 2 H /2e
O.
|
OH
|
|
OH
-2H+
-e-
.
O
||
-e-
||
O
||
O
Summary:

NADH and FADH 2 are oxidized by the ETS

Energy released during e- flow is used to
transport H+ across the inner mitochondrial
membrane

The gradient of H+ across the membrane
represents a store of energy (to be used to
make ATP)