Electron transport chain

• NADH

• FADH2

• H20

• 26-28 ATP

• redox reactions - protein and non-protein complexes

• inner mitochondrial membrane

electron transport chain - products

• sequential

• enzyme catalysed

Redox reactions - in chain

• carry electrons from one reaction in one cellular compartment to a different reaction in a different compartment

• NADH

• FADH2

• Coenzyme Q

• others

Electron carriers

• loses electrons

oxidised

• gains electrons

Reduction

• electrons passed through H atoms

hydrogen ions

• water soluble

• transfer 2 electrons

• mobile

NAD+ and NAD

• hydrophobic

• present in membranes

• contains vitamin Q

Coenzyme Q

• water soluble

• can transfer one or more electrons

• mobile

FAD (flavin adenine dinucleotide)

• water

• can transfer one or more electrons

• mobile

FMN

• hydrophobic

• present in membrane

• contains vitamin Q

Coenzyme Q

• present on membranes but water soluble

• contain heme

• can be A,B,C,D hemes

Cytochrome proteins (ubiquinone)

• contains iron surrounded by sulphur-containing amino acids

• found in complexes I,II,III

Iron-sulfur proteins

• accepts 2e- as a hydride

• nicotinamide derived from niacin

• niacin derived from tryptophan and diet

NAD+

• reduction

• H+

• +2e

NAD+ to NADH

• oxidation

• H+

• -2e

NADH to NAD+

• semiquinone

FADH

• hydroquinone

FADH2

• ubiquinone

• fully oxidised

Q

• semiquinone

QH

• ubiquinol

QH2

• oxidise NADH back to NAD+

NADHD hydrogenase

• catalyses the transfer of electrons to oxgyen to form water

cytochrome oxidase

• converts ADP to ATP

• high to low concentration

• movement of protons

ATP synthase

• NADH dehydrogenase

• FMN

• Fe-S

Complex 1

• Succinate dehydrogenase

• FAD

• FE-S

Complex 2

• cytochrome C Ubiquinone

• Oxidoreductase

• Heme

• Fe-S

Complex 3

• Cytochrome Oxidase

• Heme

• Cu

Complex 4

• measure the tendency of a chemical species to gain electrons and be reduced

• low reduction potential to high reduction potentials

• Eo - reduction potentials measured in V

• calculate Gibbs free energy

• negative - exergonic (with gradient) and favourable reaction

• positive - endergonic (against gradient) and unfavourable reaction

Reduction potentials

• low to high

• flow of electrons increases

• oxgyen is highest

Reduction potential

• electron transfer and oxidation with ATP synthesis

• Phosphorylation of ADP to ATP - driven by electron transfer to oxgyen

• free energy of electron transport is coupled to the endergonic flow of protons across a proton-impermeable membrane (matrix to intermembrane

• flow of protons down concentration gradient through specific channels - free energy for ATP synthesis

Chemiosmotic hypothesis

• movement of protons

• harnesses negative free energy from accepting protons

Proton motive force

• F0 subunit

• Axle

• F1 subunit

• hexamer

• open form

• loose form

• tight form

• rotattion of axel interconverts the conformation of the alpha/beta subunits sequentially

ATP synthase structure

• electron transport

• ATP synthesis coupled

• electrons dont flow through ETC to oxygen unless ADP is phosphorylated to ATP

• rate oxidative phosphorylation - determine by the need for ATP

• control of rate of oxidative phosphorylation

ATP production

• decrease glycolysis

• decrease acetyl CoA oxidation (citric acid cycle)

• decrease oxidative phosphorylation

high ATP

• increase glycolysis

• increase acetyl CoA oxidation (citric acid cycle)

• increase oxidative phosphorylation

low ATP

• inhibits pyruvate dehyrogenase

High NADH

• no 02 - no proton motive force

• reverse reaction favourable

• mitochondria contains this factor and inhibits ATP synthase activity

Inhibitory factor

• protons can reenter the membrane

• generates heat - thermogenesis

• in adipose tissue

Uncoupling proteins

• Valinomycin - antibiotic

• Carbonyl cyanide 4 - bioenergetics

• 2,4-dinitrophenol - weight loss

Uncoupling chemicals

• Complex 1 - Rotenone, Amytal

• Complex 3 - antimycin

• Complex 4 - cyanide, carbon monoxide, azide

• ATP synthase - oligomycin

Chemical inhibitors