Editing Potassium channel (section)

== Function ==
Potassium channels function to conduct potassium ions down their [[electrochemical gradient]], doing so both rapidly (up to the [[diffusion rate]] of K<sup>+</sup> ions in bulk water) and selectively (excluding, most notably, [[sodium]] despite the [[Ionic radius|sub-angstrom]] difference in ionic radius).<ref>{{cite book | vauthors = Lim C, Dudev T |chapter= Roles and Transport of Sodium and Potassium in Plants|publisher= Springer|date= 2016|series= Metal Ions in Life Sciences|volume=16| journal = The Alkali Metal Ions: Their Role in Life| veditors = Sigel A, Sigel H, Sigel RK | title = The Alkali Metal Ions: Their Role for Life |pages= 325–347|doi=10.1007/978-3-319-21756-7_9|pmid= 26860305 |isbn= 978-3-319-21755-0}}</ref> Biologically, these channels act to set or reset the [[resting potential]] in many cells. In excitable cells, such as [[neuron]]s, the delayed counterflow of potassium ions shapes the [[action potential]].

By contributing to the regulation of the [[cardiac action potential]] duration in [[cardiac muscle]], malfunction of potassium channels may cause life-threatening [[Cardiac arrhythmia|arrhythmias]].  Potassium channels may also be involved in maintaining [[vascular tone]].

They also regulate cellular processes such as the secretion of [[hormones]] (''e.g.'', [[insulin]] release from [[beta cell|beta-cells]] in the [[pancreas]]) so their malfunction can lead to diseases (such as [[Diabetes mellitus type 2|diabetes]]).

Some toxins, such as [[dendrotoxin]], are potent because they block potassium channels.<ref>indirectly cited from reference number 3,4,5,6 in {{cite journal | vauthors = Rehm H, Lazdunski M | title = Purification and subunit structure of a putative K+-channel protein identified by its binding properties for dendrotoxin I | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 85 | issue = 13 | pages = 4919–4923 | date = July 1988 | pmid = 2455300 | pmc = 280549 | doi = 10.1073/pnas.85.13.4919 | doi-access = free | bibcode = 1988PNAS...85.4919R }}</ref>