ABSTRACT
Ion channels are transporters of materials and electrolytes across membranes. The channels also act as communicators between regions on both sides of the membrane. Ion channels are cell membrane-hosted physical structures that help the membrane to be selectively permeable to certain ions. There is one more state that falls in a category of nonparticipants to the gating mechanism. This may be called the tightly closed state, negating the gating mechanism. Voltage-gated ion channels (VGICs) are multisubunit protein complexes in cell membranes that alter conformations in response to changes in channel hosting membrane potential and that the conformational alterations may lead to gating or opening-closing transitions of a transmembrane ion-selective pore. Three major VGIC families distinguished by the cations conducted through them are as follows: sodium channels, potassium channels, and calcium channels. Ligand-gated ion channels are integral membrane proteins containing a pore that allows the regulated flow of selected ions across the plasma membrane.
