Schematic representation of a mitochondrion with its functional components and compartments. The OM is the external lipid bilayer that interfaces with the cytosol. The IM encapsulates the matrix and is composed of two functionally distinct regions, the inner boundary membrane (IBM; in close opposition to the OM) and the CM. The CM is the place where the protein complexes from the electron-transport chain (ETC) reside. At the apex of the CM and along the tubular cristae, ATP synthases are allocated. Through these protein complexes, ATP is synthesized in the matrix. ATP is further transported from the matrix through ANTs to the intermembrane space (IMS)—the space between the two membranes—to finally cross the OM at the VDAC into the cytosol.