While transporters are mainly responsible for transmembrane transport of metabolites and other substances such as nutrition uptake, ion channels are used for transducing ion-encoded information. Ion channels are fundamentally different from another type of membrane proteins, namely transporters. They function in the plasma membrane, membranes of certain intracellular organelles, and other dynamic systems mediating cooperativities between organelles (Hosaka et al. Ion channels are essential for transmembrane signaling and ionic homeostasis as well as regulating membrane polarization (Yellen 2002). Similarly, ion channels, together with ion-sensing proteins as well as downstream effectors, are equally important, as they constitute basic functional nodes of such information network, perceiving, processing, and transducing signals encoded in ion fluxes (Jan and Jan 1989). Without a properly maintained membrane potential, the cell would lose its essential information network. In fact, together with redox potential and ATP hydrolysis, membrane potential is one of the three major, interchangeable energy forms in all of living cells (Smith and Morowitz 2016). 2012), in addition to other cellular resources used to establish and preserve the network infrastructure. Approximately 1/3–2/3 of cellular energy originating from ATP hydrolysis is consumed to maintain the membrane potential (Howarth et al. In this network, the transmembrane electrochemical potential is the major power source, and a variety of ions can be considered as the information carriers. Together, membrane potential and ion fluxes form an information network for regulation of cellular functions (Roux 1997). Being both a driving force and a result of these ion fluxes, the membrane potential is deeply intertwined with the dynamic distribution of ions across the membrane.
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Information transmission in living cells is encoded through ion fluxes, resulting in complex spatiotemporal concentration patterns of ions.