An example of anaerobic respiration in E. coli

When exposed to anaerobic conditions, E. coli can use nitrate instead of oxygen as the final electron acceptor in an electron transport chain. This generates an H+ electrochemical gradient that is used to make ATP via chemiosmosis. Note: As shown in this figure, ubiquinone (Q) picks up H+ on one side of the membrane and deposits it on the other side. A similar event happens during aerobic respiration in mitochondria (described in Figure 7.16), except that ubiquinone transfers H+ to cytochrome b?c1, which pumps it into the intermembrane space.