Potassium channel
0Potassium channel, by Wikipedia https://en.wikipedia.org/wiki?curid=1011474 / CC BY SA 3.0
#Ion_channels
#Electrophysiology
#Integral_membrane_proteins
Potassium channel Kv1.
2, structure in a membrane-like environment.
Calculated hydrocarbon boundaries of the lipid bilayer are indicated by red and blue lines.
Potassium channels are the most widely distributed type of ion channel and are found in virtually all living organisms.
They form potassium-selective pores that span cell membranes.
Potassium channels are found in most cell types and control a wide variety of cell functions.
Potassium channels function to conduct potassium ions down their electrochemical gradient, doing so both rapidly （up to the diffusion
rate of K+ ions in bulk water） and selectively （excluding, most notably, sodium despite the sub-angstrom difference in ionic radius）.
Biologically, these channels act to set or reset the resting potential in many cells.
In excitable cells, such as neurons, 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 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-cells in the pancreas） so their malfunction can lead to diseases （such as diabetes）.
Some toxins, such as dendrotoxin, are potent because they block potassium channels.
There are four major classes of potassium channels: The following table contains a comparison of the major classes of potassium channels with representative examples （for a complete list of channels within each class, see the respective class pages）.
For more examples of pharmacological modulators of potassium channels, see potassium channel blocker and potassium channel opener.
Top view of a potassium channel with potassium ions （pu...
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