Biological elements, table Group

The first two elements of Group 5A(15), gaseous nonmetallic nitrogen (N) and solid nonmetallic phosphorus (P) have great industrial, environmental, and biological significance. Below these nonmetals are two metalloids, arsenic (As) and antimony (Sb), followed by the sole metal, bismuth (Bi), the last nonradioactive element in the periodic table [Group 5A(15) Family Portrait]. 

Most metals, for which compounds are carcinogenic, are from IV group of Periodic Table of Elements. In biological systems, carcinogenic metals can form stable complexes and biological availability of these complexes determines the carcinogenic potential of various metal compounds. 

Metals in biological systems function in a number of different ways. Group 1 and 2 metals operate as structural elements or in the maintenance of charge and osmotic balance (Table 1.2). Transition metal ions that exist in single oxidation states, such as zinc(II), function as structural elements in superoxide dismutase and zinc fingers, or, as an example from main group +2 ions, as triggers for protein activity—that is, calcium ions in calmodulin or troponin C... 

Blood and blood products constitute a major group of traditional biologies. The main components of blood are the red and white blood eells, along with platelets and the plasma in which these eellular elements are suspended. Whole blood remains in routine therapeutic use, as do red blood cell and platelet coneentrates. A variety of therapeutieally important blood proteins also eontinue to be purified from plasma. These inelude various elotting faetors and immunoglobulins (immunoglobulins will be considered in the next ehapter). Sueh blood produets are summarized in Table 9.1. 

Metals that are potentially biologically active, either therapeutically or toxicologically, may be divided into the following groups, based upon their electron configuration and position in the periodic table of the elements ... 

A further group of biologically available chemical species comprises organic compounds of the trace elements, which may be divided into two groups organic complexes of cations, and metal and non-metal alkyls (Table 3). These species are mainly neutral molecules, in contrast to the ionic species identified in Table 2, and are thought to be taken up as a consequence of their lipid-solubility (Florence et al., 1983). 

The most extensively studied radionuclides with respect to biological incorporation and the contamination of food chains are (37Cs and Sr. The elements Cs and Sr, respectively, belong to groups I and II of the periodic table and as such share common physico-chemical properties with K and Ca. As analogues of these elements 137Cs and Sr are readily incorporated by biological tissues and so, historically, the ex-... 

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