Important findings regarding the structure and function of respiratory cytochromes have been made from the study of these hemeproteins associated to liposomes. These studies contributed to the comprehension of the biological role of these proteins in the electron transfer process, the regulatory mechanisms, the energy transduction mechanisms, the protein sites that interact with mitochondrial membranes and the role played by the non-redox subunits present in the protein complexes of the respiratory chain of eukaryotes. In this chapter, the protocols developed to study cytochrome bc 1 activity in liposomes and the binding of cytochrome c to lipid bilayers is presented . The former protocol was developed to study the mechanism of energy transduction related to the topology of the components of bc 1 complex in the mitochondrial membrane. These studies were done with purified cytochrome bc 1 complexes reconstituted into potassium-loaded vesicles. The latter protocol was developed to study the influence of pH, ΔpH, and ΔΨ on the interaction of cytochrome c with liposomes that mimic the inner mitochondrial membrane.