Ion Channels

Ion channels are pore-forming membrane proteins which allow the passage of ions in and out of a cell through the plasma membrane. Hundreds of different types of ion channel have been identified in the membranes of all biological cells.


Ion channels can be classified by different properties, including by the gating mechanism or the ion selectivity of the pore.

Classification by gating mechanism:

  • Voltage-gated ion channels
  • Ligand-gated ion channels (also known as ionotropic receptors)
  • Light-gated ion channels
  • Mechanosensitive ion channels
  • Cyclic nucleotide-gated ion channels
  • Calcium-gated ion channels

Classification by ion selectivity:

  • Calcium
  • Potassium
  • Sodium
  • Chloride
  • Proton
  • Non-selective (let any type of ion pass)
Physiology and Disease

Ion channels are essential for life and play a fundamental role in physiological processes such as muscle contraction and nutrient transport. A multitude of diseases result from the disruption of normal ion channel function. Disorders resulting from a mutation in the gene encoding an ion channel or its regulatory proteins are called channelopathies. Common channelopathies include cystic fibrosis, long QT syndrome and epilepsy. Ion channels are also involved in non-genetic diseases, such as diarrhea, which is mediated by toxicological effects on ion channel function.