Chemical Symbol: Ca
German: Kalzium
Calcium is a bivalent alkaline earth metal with an atomic number of 20 and a medial atomic weight of ca. 40 g/mol.
About 90% of the calcium pool in human organism is found in bones as a phosphate in the form of hydroxyapatite (Ca5[PO4]3OH). In this way, calcium ensures stability of the skeleton.
Other important roles of calcium - predominantly in its ionised form Ca2+ - cover coagulation and signal transduction within and outside of cells, thus controlling nerval activity, secretion of hormones and muscular contraction.
In serum, about 50% of calcium stock is bound to proteins, the remainder being in form of ions. The relation is influenced by protein concentration and blood-pH. Serum calcium levels raise in state of acidosis and fall in alkalosis.
Calcium is an essential trace element. Daily requirements depend from bone metabolism and amount 800 to 1200 mg per day in adults and at least 1500 mg/day in adolescents, in pregnancy, lactation and postmenopausal period.
Relevant calcium sources are e. g. mild produts, soy, certain vegetables and mineral waters.
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