BioChem - Electron Transport Chain

Complex I

NADH Dehydrogenase

Complex II

Succinate Dehydrogenase

Coenzyme Q

n/a

Complex III

Cytochrome bc 1

Cytochrome C

N/A

Complex IV

Cytochrome a+a3

Cytochrome Oxidase

Complex I -

has an FMN prosthetic group and it accepts electrons from NADH+ H+ to become FMNH2

FMNH2 is re-oxidized to FMN to accept more electrons

Complex II -

converts succinate to fumarate

contains FAD as its prosthetic group

Coenzyme Q - 

accepts electrons from the FMNH2 of complex 1 and FADH2 from complex 2

passes its electrons off to complex III

Cytochromes: bc 1, c, and a + a3 - 

Fe atom is reversibly converted from ferric (Fe3+) to ferrous (Fe2+) from accepting and donating electrons

this occurs in all three ^

ATP generation

3

2

1

Flow of a pair of electrons from NADH Dehydrogenase to O2 generates 3 ATP

Flow of a pair of electrons from Succinate Dehydrogenase to O2 generates 2 ATP

Flow of a pair of electron to cytochrome c through the ECT chain to O2 generates 1 ATP

Inhibitors of the ETC

• Antimycin A

• Cyanide, Carbon Monoxide, and Sodium azide

• Amytal and Rotenone

• Antimycin A: inhibits complex III from donating electrons to cytochrome C

• Cyanide, Carbon Monoxide, and Sodium azide: inhibits Complex IV from donating electrons to O2

• Amytal and Rotenone: inhibits complex 1 from donating electrons to Coenzyme Q

Which has a higher redox potential and what does it mean?

NADH or oxygen

Oxygen has a higher redox potential

• meaning its the better electron acceptor

NADH has the lowest redox potential (more negative)

• meaning its the better electron donor