Sodium potassium ion channel, molecular model. The image shows the potassium channel proteins (green, cyan) and one of the six potassium ions (purple). The four sodium ions are hidden inside the channel. 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.