1. Requirements for oxidative phosphorylation
Requirements for the production of ATP
1. An ion impermeable membrane
A mechanism for moving protons (H+) across
the membrane to produce an energy-rich
proton gradient
A mechanism to capture the energy made
available as protons move down the proton
gradient

2. Requirements for oxidative phosphorylation
1. An ion impermeable membrane
See Fig 14.6 in Horton

3. A typical representation of an electron transport chain
A typical representation of an electron transport chain. Images from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates ( and WH Freeman ( used with permission.

4. Requirements for oxidative phosphorylation
A mechanism for moving protons (H+) across
the membrane to produce an energy-rich
proton gradient
Electron transport chain 4 2
2H+

5. NMN
AMP
nicotinamide H+ H

6. Isoalloxazine FMNH FMNH2 (semiquinone) (hydroquinone) 2H+ -H+, -e- 2e-1 5
Isoalloxazine
-H+, -e-
2H+
2e- H
FMNH
(semiquinone) H
FMNH2
(hydroquinone)
-H+, -e-

7. H
FADH2

8. + 1 e- - + 1 e-, +2H+ Isoprenoid unit Semiquinone ( Q- ) H
Ubiquinol ( QH2 )

9. Non-heme iron sulfur proteins
(Fe-S clusters)
2S -2Fe
Cys
Cys S S S Fe Fe S S S
Cys
Cys
4S -4Fe S
Cys Fe
Cys S S Fe S Fe S S Fe
Cys
Cys S S

10. Cytochromes Heme-containing proteins
Classified as a, b or c based on absorption spectrum
Electron transport has: a and a3, b566 (bL) and b562 (bH).
and c and c1
carry 1 electron per heme iron
a, a3, b566,,, b562,, and c1 are integral membrane proteins
c is a peripheral membrane protein on outer surface of
inner mitochondrial membrane

11. Heme group in cytochromes
methyl
proprionate
Heme group of Cytochrome b
See fig in Horton

12. Heme group in cytochromes a and c
See fig in Horton

13. ca nm
ba nm
aa nm
See Fig Horton

14. Difference spectra b c a O2
= spectra of experimental– spectra of fully oxidized mito
b c a O2
Normal
Blocked between
Cyt b and c1
a and c fully oxidised
b fully reduced

15. Standard redox potentials of mitochondrial oxidation-reduction
components
Substrate or complex
Eo’ (V)
NADH
-0.32
Complex I
FMN
Fe-S clusters
-0.30
Succinate
+ 0.03
Complex II
FAD
0.0
-0.26 – 0.00
QH2/Q
+0.04
Complex III
Cyt B560
Cyt b566
Cyt c1
+0.28
- 0.1
+ 0.05
+ 0.22
Cytochrome c
+ 0.23
Complex IV
Cyt a
CuA
Cyt a3
CuB
+ 0.21
+ 0.24
+ 0.39
+ 0.34 O2
+ 0.82

16. NADH + H+ + CoQox NADH + CoQH2
Electron transport complexes
Complex I: NADH-Q reductase
DE0' = V
DG = -70 kJ/2e-
Contains at least 34 polypeptides
FMN, 2Fe-2S and 4Fe-4S clusters, tightly bound CoQ
Mr = 880kD
Result: 2 e- from NADH to CoQ
4 H+ from matrix to intermembrane space
NADH + H+ + CoQox NADH + CoQH2
Intermembrane
space
4H+
2H+
QH2
FMNH2
Fe-S
2e-
2e-
FMN Q
4H+
matrix
NAD
NADH + H+

17. Intermembrane space 2 x e- 2e- matrix QH2 Fe-S Q FAD Fumarate + 2H+
Complex II: succinate dehydrogenase/ succinate – Q reductase
DE0' = V
DG = -2.9 kJ/2e-
Contains: FAD, Fe_S
Result: 2 e- from FADH2 to CoQ
No protons translocated
FADH CoQox FADH + CoQH2
Intermembrane
space
FAD
Fe-S Q
QH2
2e-
2 x e-
2H+
succinate
Fumarate +
matrix

18. CoQH2 + 2Cyt c (Fe+3) CoQ + 2Cyt c (Fe+2)
Complex III: Cytochrome C reductase
DE0' = V
DG = --37 kJ/2e-
Contains: Cyt b (bL and bH), Cyt c1, Fe-S protein, several additional proteins
Result: 2 e- from CoQH2 to Cyt c
2 H+ taken up from matrix, 4 H+ to intermembrane space
CoQH2 + 2Cyt c (Fe+3) CoQ + 2Cyt c (Fe+2)
Intermembrane
space
2H+
2 x e- c
4H+
QH2 Q
matrix

19. CoQ cycle C1
Fe-S bL bH C1 C1
Fe-S
Fe-S bL bL bH bH C1
Fe-S bL bH

20. 4Cyt c (Fe+2) + 4 H+ + O2 4Cyt c (Fe+3) + 2 H2O
Complex IV: Cytochrome oxidase
DE0' = V
DG = -110 kJ/2e-
Contains: 10 subunits, Cyt a and Cyt a3, 2 Cu (A , B)
Result: 4 e- from 4 Cyt c to form 2 H2O
4 H+ taken up from matrix, 2 H+ to intermembrane space
4Cyt c (Fe+2) + 4 H+ + O Cyt c (Fe+3) + 2 H2O
Intermembrane
space
a - CuA
1/2O2
2 x e-
2H+ c
a3 - CuB
H2O
matrix

21. Cytochrome oxidase: electron transfer to O2
CuB
Cu2+
Fe3+
OH- a3
Cu2+ .
Fe3+ .
Cu+
Fe2+
Cu2+
Fe3+ O- H
Cu2+
Fe3+ O-
Cu+
Fe3+ O-
See Horton, fig 14.16

22. Electron transport chain
Cplx I
Cplx III
Cyt c
Cyt c
Cplx IV
CoQ
CoQ e-
H2O
NADH + H+ H+ H+
2H+ + ½ O2 H+
NAD
Summary of protons translocated per 2 e-
Complex
Matrix
Intramembrane space I -5 +4
III -2 IV -4 +2 II

24. 1997 Nobel Prize for Chemistry
Paul D. Boyer John E. Walker Jens C. Skou
"for their elucidation of the
enzymatic mechanism underlying
the synthesis of adenosine
triphosphate (ATP)"
"for the first discovery
of an ion-transporting
enzyme,
Na+, K+ -ATPase"

25. ATP synthase
These and the following images can be found at the home page of Boris A. Feniouk
( that contains a wealth of
additional information on ATP synthesis. See also Horton p 450 and 451.

27. Binding-change mechanism
(See page 451 in Horton)
From:

28. For movies and details go to:

29. H+ H+
Cplx I
Cplx III c c
Cplx IV
ATP
synthase
CoQ
CoQ
H2O e- H+ H+ H+
NADH + H+
2H+ + ½ O2
ADP + PO4 H+
ATP
NAD