Primary and Secondary Proton Pumps

Primary pups differ highly depending upon the energy source used by the membrane. For example, the respiratory chains of mammalian mitochondria act as oxidation-reduction driven proton pumps, which transfer electrons from the NAD+/NADH couple to the O2/H2O couple. The respiratory chain consists of more than 20 discrete carriers of electrons which are mainly grouped into four polypeptide complexes: NADH-ubiquinone oxidoreductase, succinate dehydrogenase, ubiquinol-cytochrome c oxido-reductase and cytochrome c oxidase. Three of these complexes are involved in proton translocation.