and close under the regulation of intracellular signals, e.g. G-proteins,
Signalling molecules and their receptors
to allow the flux of solutes (usually inorganic ions) of specific size and
charge. Transport through ion channels is always passive, and ion flow The majority of signalling molecules (ligands) are hydrophilic and so
through an open channel depends only on the ion concentration gradi- cannot cross the plasma membrane of a recipient cell to effect changes