F-ATPase, also known as F-Type ATPase, is an ATPase found in bacterial plasma membranes, in mitochondrial inner membranes (in oxidative phosphorylation, where it is known as Complex V), and in chloroplast thylakoid membranes. It uses a proton gradient to drive ATP synthesis by allowing the passive flux of protons across the membrane down their electrochemical gradient and using the energy released by the transport reaction to release newly formed ATP from the active site of F-ATPase. In some bacteria, sodium ions may be used instead of protons. Together with V-ATPases and A-ATPases, F-ATPases belong to superfamily of related ATP synthases. F-ATPase, also known as F-Type ATPase, is an ATPase found in bacterial plasma membranes, in mitochondrial inner membranes (in oxidative phosphorylation, where it is known as Complex V), and in chloroplast thylakoid membranes. It uses a proton gradient to drive ATP synthesis by allowing the passive flux of protons across the membrane down their electrochemical gradient and using the energy released by the transport reaction to release newly formed ATP from the active site of F-ATPase. In some bacteria, sodium ions may be used instead of protons. Together with V-ATPases and A-ATPases, F-ATPases belong to superfamily of related ATP synthases.