SUMMARY

All eukaryotic animal cells have high extracellular sodium and high intracellular potassium, a reverse of the situation seen outside the cells. A typical cell keeps a resting membrane potential of-70 mV. Potassium ions will tend to flow out of the cell, since their equilibrium potential (-91 mV) is more negative than the transmembrane potential. Sodium ions have a very strong force driving them into the cell, since both the chemical and electrical gradients (equilibrium potential of +64 mV) favor Na+ uptake. The enzymatic manifestation of the sodium pump is the Na+, K+-ATPase. This enzyme, found in all mammalian cell membranes, is necessary for proper cellular function since it helps to preserve the ionic gradients across the cell membrane and thus the membrane potential and osmotic equilibrium of the cell [1]. The enzyme pumps 3Na+ and 2K+ ions against their concentration gradient, at the expense of an ATP molecule. The transport of 3Na+ for 2K+ across the membrane, through the means of the sodium pump, maintains transmembrane gradients for the ions and produces a convenient driving force for the secondary transport of metabolic substrates such as amino acids and glucose. In addition the nonequivalent transport is electrogenic and leads to the generation of a transmembrane electrical potential allowing cells to become excitable. The ATPase family: Sodium pump belongs to the family of P-ATPases along with the sarcoplasmic reticulum and plasma membrane Ca+2 ATPase and H+, K+ ATPase of stomach and colon in vertebrates. P-type ATPase superfamily, differs structurally an