Normal serum concentration range: 0.65–1.05 mmol/L, divided into three fractions: Magnesium naturally exists in three stable isotopes: There are obvious chemical similarities between calcium and magnesium but in cell biology, major differences often prevail ( Table 1).Įighth most abundant element in the crust of the Earthįifth most abundant element in the crust of the Earth dehydrated) ion to the transmembrane transport pathway through the membrane ( Figure 1). Steric constraints for magnesium transporters are also far greater than for any other cation transport system : proteins transporting magnesium are required to recognize the large hydrated cation, strip off its hydration shell and deliver the bare (i.e. For instance, it is almost impossible for magnesium to pass through narrow channels in biological membranes that can be readily traversed by calcium because magnesium, unlike calcium, cannot be easily stripped of its hydration shell. This simple fact explains a lot of magnesium’s peculiarities, including its often antagonistic behaviour to calcium, despite similar chemical reactivity and charge.
Consequently, the ionic radius of dehydrated magnesium is small but biologically relevant.
This difference between the hydrated and the dehydrated state is much more prominent than in sodium (∼25-fold), calcium (∼25-fold) or potassium (4-fold). Its radius is ∼400 times larger than its dehydrated radius. Thus, the hydrated magnesium cation is hard to dehydrate. In the dissolved state, magnesium binds hydration water tighter than calcium, potassium and sodium. Magnesium is a Group 2 (alkaline earth) element within the periodic table and has a relative atomic mass of 24.305 Da, a specific gravity at 20☌ of 1.738, a melting point of 648.8☌ and a boiling point of 1090☌. Traditionally, magnesium salts are used as antacids or laxatives in the form of magnesium hydroxide, magnesium chloride (MgCl 2), magnesium citrate (C 6H 6O 7Mg) or magnesium sulphate (MgSO 4). Magnesium is also used widely for technical and medical applications ranging from alloy production, pyrotechnics and fertilizers to health care. In vertebrates, magnesium is the fourth most abundant cation and is essential, especially within cells, being the second most common intracellular cation after potassium, with both these elements being vital for numerous physiological functions.
In plants, magnesium is the central ion of chlorophyll. Magnesium plays an important role in plants and animals alike. As a result, magnesium is readily available to organisms. Magnesium salts dissolve easily in water and are much more soluble than the respective calcium salts. In the sea, the concentration of magnesium is ∼55 mmol/L and in the Dead Sea-as an extreme example-the concentration is reported to be 198 mmol/L magnesium and has steadily increased over time. The most plentiful source of biologically available magnesium, however, is the hydrosphere (i.e. Dolomite CaMg(CO 3) 2 is, as the name suggests, abundant in the Dolomite mountain range of the Alps. Magnesium is the eighth most common element in the crust of the Earth and is mainly tied up within mineral deposits, for example as magnesite (magnesium carbonate ) and dolomite. Magnesium, physicochemical properties, physiological function, regulation, hypomagnesaemia, hypermagnesaemia Introduction
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