What are Ion Channels?
Ion channels are pore-forming membrane proteins that allow the passive transport of ions through hydrophobic core of the membranes of virtually all living cells. They are special enzymes that catalyze the ion transport at high speed, with exquisite specificity and under very tight regulation. The flow of ions down their transmembrane electrochemical gradient changes the net charge of a cell and thereby changes its membrane voltage, which ultimately controls responses specific to cellular context.
Physiological Roles of Ion Channels.
Ion channels are fundamental to cellular existence - from simple bacteria to highly specialized neurons. In unicellular organisms, ion channels help maintain the volume, the homeostasis of inorganic ions and the generation of Ca2+ transients, which are important in many key cellular events, including secretion, gene expression and cell division. In multicellular organisms, ion channels play much more sophisticated roles. They are essential components to generate electrical signals. These electrical signals and the resulting intracellular Ca2+ transients transmit information among cells and tissues over long distance with high speed and fidelity, tightly coordinating distant cellular functions. Therefore, ion channels are important in many physiological processes, including muscle contraction, hormone secretion, sensation and mental processes. If the function of ion channels goes wrong, there can be serious consequences, including life-threatening diseases, such as epilepsy, cardiac arrhythmia, hypertension, cystic fibrosis, diabetes and cancer.