 Most of the ATP synthesized in the mitochondria will be used for cellular processes in the cytosol ; thus it must be exported from its site of synthesis in the mitochondrial matrix . The inner membrane contains an antiporter , the ADP / ATP translocase , which is an integral membrane protein used to exchange newly synthesized ATP in the matrix for ADP in the intermembrane space . This translocase is driven by the membrane potential , as it results in the movement of about 4 negative charges out of the mitochondrial membrane in exchange for 3 negative charges moved inside . However , it is also necessary to transport phosphate into the mitochondrion ; the phosphate carrier moves a proton in with each phosphate , partially dissipating the proton gradient . 
