Chemistry · Ch 5 — Alkali and Alkaline Earth Metals
Biological Importance of Sodium and Potassium
Biological Importance of Sodium and Potassium
Monovalent sodium and potassium ions are found in large proportions in biological fluids, where they perform essential functions such as maintaining ion balance and conducting nerve impulses. A typical 70 kg human body contains about 90 g of sodium and 170 g of potassium -- far more than the mere 5 g of iron and 0.06 g of copper it holds.
Sodium ions are located mainly outside the cell -- in blood plasma and the interstitial fluid surrounding cells. From this extracellular position they take part in transmitting nerve signals, regulating the flow of water across cell membranes, and transporting sugars and amino acids into cells.
Although sodium and potassium are chemically very similar, they differ quantitatively in how well they penetrate cell membranes, in their transport mechanisms, and in how effectively they activate enzymes. Potassium ions, correspondingly, are the most abundant cations found within cell fluids, where they activate many enzymes, take part in the oxidation of glucose to produce ATP and, together with sodium, are responsible for transmitting nerve signals. …
What this figure shows. A schematic of a cell membrane showing the Na⁺/K⁺-ATPase pump protein embedded in the lipid bilayer, actively transporting three Na⁺ ions out of the cell and two K⁺ ions into the cell against their concentration gradients (using ATP), maintaining the characteristic high extracellular Na⁺ / high intracellular K⁺ distribution nee …