Biological importance of sodium : Sodium ions are found primarily outside the cells in blood plasma and in the interstitial fluids which surround the cells. These ions participate in the transmission of nerve signals, in regulating the flow of water across cell membranes and in the transport of sugars and amino acids into cells.
Biological importance of potassium : Potassium ions are the most abundant cations within cell fluids, where they activate many enzymes, participate in the oxidation of glucose to produce ATP and with sodium, are responsible for the transmission of nerve signals.
Biological importance of magnesium : All enzymes that utilise ATP in phosphate transfer require magnesium as the cofactor. The main pigment for the absorption of light in plants is chlorophyll which contains magnesium.
Biological importance of calcium : About 99% of body calcium is present in bones and teeth. It also plays important roles in neuromuscular function, maintenance of a regular heartbeat, various aspects of metabolism and blood clotting. The calcium concentration in plasma is maintained by two hormones : calcitonin and parathyroid hormone.