1. RESPIRATION & COUPLED REACTIONS
© 2016 Paul Billiet ODWS

2. THE ELECTRON TRANSPORT CHAIN (ETC)
Coupling the oxidation of food to the synthesis of ATP Oxidation Is a Loss of electrons (OIL) Reduction Is a Gain of electrons (RIG)
© 2016 Paul Billiet ODWS

3. Natural Electron ACCEPTORS
Pyridine nucleotides
Nicotinamide Adenine Dinucleotide (NAD)
Flavine Adenine Dinucleotide (FAD)
NAD+ + 2H+ + 2e NADH + H+
Reduction
Oxidation
Cytochromes Conjugate proteins which contain a haem group.
The iron atom undergoes redox reactions
Fe3+ + e Fe2+
Reduction
Oxidation
NB The iron atom in the haem group of haemoglobin does not go through a redox reaction Haemoglobin is oxygenated or deoxygenated
© 2016 Paul Billiet ODWS

4. OXIDATIVE PHOSPHORYLATION
A series of REDOX REACTIONS using electron acceptor/donor molecules
coupled to glycolysis and the Krebs cycle
The electron acceptors/donors reduce (when receiving electrons)
And oxidise (when losing electrons) one another along an ELECTROCHEMICAL GRADIENT
Each molecule in the series has a lower REDOX POTENTIAL than the one before.
© 2016 Paul Billiet ODWS

5. Down the chain
If this energy release is > 30.5 kJ mol-1 a mole of ATP can be synthesised from ADP by a coupled reaction
The first molecule in the series is NAD (or FAD), a COENZYME of various DEHYDROGENASE enzymes
[NAD (oxidised)  NADH + H+ (reduced)]
Next come a series of iron containing proteins called CYTOCHROMES.
© 2016 Paul Billiet ODWS

6. +ve Redox potential -ve
Reaction co-ordinate
NAD+
NADH + H+
FAD
FADH2
2e-
G=- 51 kJ
Flavoprotein/Cytochrome b
2e-
 G= kJ
Cytochrome c
Cytochrome a.a3
 G= kJ
2e-
1/2O2 + 2H+
H2O
© 2016 Paul Billiet ODWS

7. The electron transport chain
Electrons are produced by splitting hydrogen atoms taken from the food molecules (H  H+ + e-) by dehydrogenases The last electron acceptor in the series is OXYGEN Thus at the end of the ETC: 2H+ + 2e- + 1/2O2  H2O
© 2016 Paul Billiet ODWS

8. The location of the ETC
The mitochondrial inner membrane of eukaryotes(the plasma membrane of prokaryotes)
Surface area increased by CRISTAE Numbers of cristae = activity of cell
e.g. Liver cell 40 m2 g-1 mitochondria Heart muscle 200 to 250 m2 g-1 mitochondria.
© 2016 Paul Billiet ODWS

9. The importance of the inner membrane
Insect flight muscle x
Open University S Hurry (1965) Murray
Mouse cardiac muscle
Open University S Hurry (1965) Murray
© 2016 Paul Billiet ODWS

10. The Mechanism of Oxidative phosphorylation: THE CHEMIOSMOTIC PUMP
Outer membrane
The Mechanism of Oxidative phosphorylation: THE CHEMIOSMOTIC PUMP
Inner membrane
MATRIX e- H+ H+ H+ O2
2H2O
ADP + Pi H+
ATP synthetase
ATP
Intermembrane space
© 2016 Paul Billiet ODWS

11. Electron tomography used to produce images of active mitochondria.
© 2016 Paul Billiet ODWS

12. The Mechanism: THE CHEMIOSMOTIC PUMP
The ETC creates a concentration gradient by pumping H+ out of the mitochondrial inner matrix
As these H+ diffuse back into the matrix across the inner membrane they drive ATP synthesis.
© 2016 Paul Billiet ODWS

13. THE CHEMIOSMOTIC PUMP IN CHLOROPLASTS
X Open University S Hurry (1965) Murray
X Open University S Hurry (1965) Murray
© 2016 Paul Billiet ODWS

14. Photophosphorylation
NADPH+ + H+
NADP+
Stroma
2H+
2e-
2e-
2e-
2H+
H2O
2H+ + 1/2O2
1/2O2
Thylakoid space
2H+
2H+
Thylakoid membrane
ATP synthetase
ADP + Pi
ATP
2H+
© 2016 Paul Billiet ODWS