electron transport chain--a series of coupled oxidation reduction reactions

The high energy electrons of NADH and FADH2 are transfered to FMN, UBQ, cytb, cytc1, cytC, cyta, cyta3 and finally end up in water. The proteins (enzymes) that carry out these reactions are located in the inner mitochondrial membrane (except to cytochrome C). As the figure below indicates, each reaction is an exergonic reaction and liberates free energy.