Energetics

Respiratory Chain

Respiratory Chain

- Part 1 -

Simplified scheme of the hydrogen and electron transport in a bacterial membrane.

Respiratory Chain

- Part 2 -

Principles ofATP-synthesis by electron transport phosphorylation

Respiratory Chain - Part 3 -

Redoxpotentials of the respiratory chain. The chain starts with NAD as the component with the most negative potential and is terminated by Cytochrome-Oxidase as the component with the most positive potential.

Physiologie Folie 28

Phototrophy

Physiologie Folie 29a

Chemolithotrophy

Physiologie Folie 29b

Chemoorganotrophy

Thermodynamics

Physiologie Folie 30a

∆G∆H∆S

Physiologie Folie 30b

Calculation example:

Using ΔGB°–values the ΔG°–value

and the ΔG°´–value for the

formation of lactic acid from

glucose can be calculated.

This reaction is the

metabolic basis for lactic acid bacteria

Physiologie Folie 30b

Example:glucose 2 lactate + 2 H+

ΔGB° (glucose) = - 917 kJ mol-1ΔGB° (lactate) = - 518 kJ mol-1ΔGB° (H+, pH0) = 0 kJ mol-1ΔGB° (H+, pH7) = - 40 kJ mol-1

for pH = 0:ΔG° = 2 (-518 kJ mol-1) – (- 917 kJ mol-1)

= -119 kJ mol-1

for pH = 7:ΔG° = [2 (-518 kJ mol-1) + 2(-40 kJ mol-1)] – (- 917 kJ mol-1)

= -199 kJ mol-1

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Standard formationenergies

for selected important

compounds (∆GB°

-values)

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Example :

For the formation of lactic acid from glucose

the ΔG–value can be calculated under

physiological conditions as follows:

ΔG = ΔG° + RT ln [C] [D] / [A] [B]

= ΔG° + RT ln q

Physiologie Folie 32

Example:

glucose 2 lactate + 2H+

ΔG = ΔG° + RT ln [C] [D] / [A] [B]= ΔG° + RT ln q

physiological concentrations:glucose = 10-2 mol l-1lactate = 10-2 mol l-1protons = 10-7 mol l-1q = 10-16

ΔG = -119 kJ mol-1 + RT ln 10-16

= -210 kJ mol-1

ΔG° = -119 kJ mol-1

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Stan-dard redox values E0´

Physiologie Folie 33a

„Electron tower“

Physiologie Folie 34

Example :

The oxidation of molecular hydrogen by oxygen is the basis of the energy metabolism of hydrogen bacteria (Knallgasbakterien)

H2 + ½ O2 H2O

ΔG°´ = - 2 x 96,5 kJ V-1 mol-1 x 1,24 V= - 239 kJ mol-1

Using standard values for redox potentials of the reaction partners the free energy of the reaction can be calculated:

2 H+ / H2: E0´ = - 0,42 V½ O2 /H2O : E0´ = 0,82 V

Δ E0´ = 1,24 V

Physiologie Folie 34a

Depen-dence of redox potential on pH or oxidation/reduc-tion ratio

Energy conservation

Physiologie Folie 34b

Energy transfer/storage compounds

Physiologie Folie 34c

Sub-strate phos-phori-lation

Physiologie Folie 34d

High energy phosphate bonds

Physiologie Folie 35

Proton transfer across the membrane

Physiologie Folie 36

Elec-trontrans-fer phosphori-lation

Physiologie Folie 36a

F1F0-ATPase

Respiratory Chain

- Part 1 -

Simplified scheme of the hydrogen and electron transport in a bacterial membrane.

Respiratory Chain

- Part 2 -

Principles ofATP-synthesis by electron transport phosphorylation

Physiologie Folie 37

Electrontrans-portchainandtrophiccondi-tion

Physiologie Folie 37a

Compo-sition ofelectron transport chainversussubstrate type

Physiologie Folie 38a

Electron transfercom-pounds (1)

Physiologie Folie 38e

Electron transfer compounds (2)

Physiologie Folie 38b

Redoxpotential of ETS compounds

Physiologie Folie 38c

Cytochrome structures (heme and substituents)

Physiologie Folie 83d

Model of cytochrome c

Physiologie Folie 39

Top:ETS ofPara-coccusdenitrifi-cansadapts tooxygen

Bottom:ETS andproton trans-location

Physiologie Folie 40

Photo-syn-thesisand protontrans-loca-tion/ATPase

Reversed electron transport

Physiologie Folie 41

Reversedelectrontrans-portfor NADH2formationfrom oxi-dized sub-strates