Nearly all the minerals required by the body are elements of low atomic number, from sodium (11) to selenium (34); the exceptions are molybdenum (42) and iodine (53). In living matter, these elements are present in a number of different states: as inorganic compounds, as free ions in body fluids, or combined with organic compounds (Coultate, 1985).
Approximately 99% of the body's calcium and 85% of its phosphorus are in the hard mineral component of bone. The two elements are combined together to form a compound similar to hydroxyapatite, Ca10(OH)2(PO4)6. Other inorganic elements, such as fluoride (F-), magnesium sodium and potassium are also incorporated into the bone mineral to form the partly amorphous and partly crystalline structure of bone.
In contrast to calcium in the skeleton, the element iron occurs almost entirely as part of co-ordination compounds based on the porphyrin nucleus involved in the transport of oxygen. Several of the other trace elements are also mainly present in biological tissues as organic compounds, such as selenium in the metalloenzyme glutathione peroxidase, and molybdenum in superoxide dismutase.
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