A model of active ion transport is analyzed in which an essential part of the pumps molecule is an ion channel. Ion translocation in the channel is described as a series of jumps between binding sites which are separated by energy barriers. Pumping action results from a transient energy-dependent modification of the barrier structure of the channel and requires only minor conformational changes of the pump molecule. This model is applied to the light-driven proton pump of Halobacterium and to redox-coupled proton pumps in the mitochondrial respiratory chain. Similar considerations may be used to describe ATP-dependent ion transport.