Ion Permeation through Channels Across Biological Membranes

Abstract

Ion channels have three conceptual elements which determine the nature of a channel, namely the gate, the selectivity filter and the unitary conductance.
The gate rules opening and closing of a channel. It's operation is regulated by a set of rate constants which are functions of membrane potential (voltage gated channel), agonist concentration (chemically gated channel) or some other physico-chemical elements (sensory transducing channel).
The selectivity filter determines the ionic species which can permeate through the channel. Because of this property, the channel can have a reversal potential which is strictly determined by the activity ratio of the intra-and the extra-cellular ions selected.
The ionic channel has relatively large unitary conductance in general, resulting in the mass-transportation of ions across the biological membrane.