Electron Transport Chain and ATP synthesis by Oxidative Phosphorylation

What is Oxidative Phosphorylation

electrons from NADH and FADH2 are used to reduce molecular oxygen to water

Negative Reduction Potential

the oxidized form of a substance has a lower affinity for electrons than H2 (e.g. NADH is a strong reducing agent and is more likely to donate electrons, less likely to be reduced)

Positive Reduction Potential

the oxidized form of a substance has a higher affinity for electrons than H2 (e.g. O2 is a strong oxidizing agent and is more likely to accept electrons, more likely to be reduced)

Driving force of the electron transport chain

the electron-transfer potential of NADH or FADH2->electrons always flow to components with more positive reduction potentials (a higher electron affinity)

What does FMN stand for

flavin mononucleotide

Complex 1

NADH-Q Oxidoreductase (NADH dehydrogenase)

NADH-Q Oxidoreductase (NADH dehydrogenase) size

46 polypeptide chains (>900 kDa)

NADH-Q Oxidoreductase (NADH dehydrogenase) prosthetic groups

FMN

iron-sulfur clusters

Coenzyme Q states

Ubiquinone

Semiquinone radical

Semiquinone

Ubiquinol

Ubiquinone

Q

fully oxidized form

Semiquinone radical

Q•-

the addition of one electron

Semiquinone

QH•

the addition of one electron and proton

Ubiquinol

QH2

fully reduced form

Complex 2

Succinate-Q reductase (Succinate dehydrogenase)

Succinate-Q reductase (Succinate dehydrogenase) size

4 polypeptide chains (140 kDa)

Succinate-Q reductase (Succinate dehydrogenase) prosthetic groups

FAD

iron-sulfur clusters

Cytochrome b 560 (for anchoring)

Complex 3

Q-Cytochrome c Oxidoreductase (Cytochrome c reductase)

Q-Cytochrome c Oxidoreductase (Cytochrome c reductase) size

11 polypeptide chains (250 kDa)

Q-Cytochrome c Oxidoreductase (Cytochrome c reductase) prosthetic groups

Heme (Cytochrome) bH (b 566) and bL (b 562) Heme (Cytochrome) c and c1

iron-sulfur clusters

Complex 4

Cytochrome c Oxidase

Cytochrome c Oxidase size

13 polypeptide chains (160 kDa)

Cytochrome c Oxidase prosthetic groups

Heme a and a3

Cu-containing proteins Cu A and Cu B