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The Energetics of Ion Distribution: The Origin of the Resting Electric Potential of Cells
Author(s) -
Veech Richard L.,
Kashiwaya Yoshihiro,
Gates Denise N.,
King M. Todd,
Clarke Kieran
Publication year - 2002
Publication title -
iubmb life
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.132
H-Index - 113
eISSN - 1521-6551
pISSN - 1521-6543
DOI - 10.1080/15216540215678
Subject(s) - atp hydrolysis , ion , chemistry , nernst equation , resting potential , membrane potential , electric potential , ion transporter , valence (chemistry) , energetics , atpase , intracellular , analytical chemistry (journal) , biochemistry , thermodynamics , enzyme , chromatography , electrode , physics , organic chemistry , quantum mechanics , voltage
The relation between the energies of ion movement and ATP hydrolysis is unknown in tissues with widely varying electric potentials. Consequently, we measured the concentration of the nine major inorganic ions in the extra‐ and intracellular phases in heart, liver, and red cells with resting electrical potentials, E N, of ‐86, ‐28, and ‐6 mV, respectively, under six different physiological conditions. We calculated the Nernst electric potential and the energy of ion movement between the phases. We found that the energy of ATP hydrolysis was essentially constant, between ‐54 and ‐58 kJ/mol, in all tissues and conditions. In contrast, as E N decreased, the energies of the Na + and K + gradients decreased, with slopes approximating their valence. The difference between the energies of Na + and K + gradients remained constant at 17 kJ/mol, which is approximately one third of the energy of ATP hydrolysis, demonstrating near‐equilibrium of the Na +/K + ATPase in all tissues under all conditions. All cations, except K +, were pumped out of cells and all anions, except Cl ‐ in liver and red cell, were pumped into cells. We conclude that the energy of ATP was expressed in Na +/K + ATPase and its linked inorganic ion transporters to create a Gibbs‐Donnan near‐equilibrium system, an inherent part of which was the electric potential.