Electron transport chain and oxidative phosphorylation

Complex 1

NADH loses electrons to complex 1 and becomes NAD+

Complex 1 then pumps protons into the intermembrane space from the mitochondrial matrix, establishing a proton gradient

Sends the electrons it gained to CoQ

Complex 2

FADH2 loses electrons to complex 2, becoming FAD+ but this complex does not pump protons into the intermembrane space.

Sends the electrons it gained to CoQ

CoQ

CoQ sends the electrons it gained from complex 1 and 2 to complex 3

Complex 3

Complex 3 receives electrons from CoQ and transfers them to cytochrome c while pumping protons into the intermembrane space, contributing to the proton gradient.

Cytochrome C

Sends electrons it received from complex 3 to complex 4

Complex 4

Receives electrons from cytochrome c and transfers them to oxygen, the final electron acceptor, while helping to pump protons into the intermembrane space.

ATP Synthase

Protons travel from the intermembrane space through ATP Synthase back into the mitochondrial matrix

Using the energy of the proton gradient ADP is phosphorylated to form ATP.