Fig. 5 Classification of elements depending on their role in structure formtion of organic and inorganic compounds

1. Main structure-forming (constituting) elements of simple molecules participating in biochemical processes, interacting with each other and as a result forming macromolecules (biopolymers) of very complex structure, for instance, polysaccharides, proteins, made up of amino acids and nuclear acids. Such elements as H, C, O, N, S, P can be assigned to them. Thus, the element composition of basic proteins is presented: С – 50,6-54,5%; О – 21,5-23,5%; Н – 6,5-7,3%; N – 15-17,6%: S – 0,3 – 2.5%; (LSE, V.3, 1970, p.110). V.I. Vernadskiy suggested terming these elements organogenic. These elements play a significant role in the structure and functions of living matter. Their extraction from the structure of definite compounds is not possible without its destruction. The replacement of one or other components, especially of phosphate groups and sulfur is likely to be supposed.

2. Accompanying structure-forming chemical elements that can be found or not found in the structure of some specific proteins, for example, enzymes as well as pigments, vitamins, hormones.

All these components of LM are in complex relations with each other, sometimes forming complex compounds, for example, lipids and propteins (lipoproteids as a part of protoplasm), proteins and porphyrins, e.g., hemoglobin (chromoproteid) etc.

As a rule, many of them contain metals, e.g. enzymes (metallokoenzymes) or pigments, e.g., porphyrins containing chromophore groups.

To the elements of this group, presumably, one should assign: Mg, Ca, Mn, Fe, Co, Cu, Zn, as well as, probably, V, Cr, Ni, Mo, Cd (Yartsimirskiy К.B., 1976; Inorganic chemistry, 1978 etc.). It is just these elements that most often considered as «life metals» (Williams D, 1975 and others) or essential and conditionally essential elements (Avtsyn А.P. et al, 1991). Their number in structures can be rather changeable as far as they can be absent at all.

In the process of their replacement by other metals or changing their valence the conformation transformation of biopolymers could take place, e.g., transition of hemoglobin into methemoglobin at changes in valence of Fe (Fe⁺²; Fe⁺³) with quite different biochemical and physiological properties.

It should be noted that presence or absence of enzymes containing these or those metals in organisms can depend on both the type of tissue and the environmental conditions (Kirbi R., 2005).

3. Non-structure-forming elements, to which most of chemical elements belong, not included in groups 1 and 2.

Forms of occurrence of elements in LM as well as in solid bodies are diverse. First of all, they can be present in the form of real, colloidal and complex compounds solved in water, the portion of which in LM can range from 60 to 99% of organism weight (Glazovskiy N.F., 2005). V.I. Vernadskiy noted that all organisms are half-liquid, sometimes liquid aqueous systems. Water in its liquid (not-connected) form is necessary for all cellular biochemical reactions though there are some ferments active in waterless environment (Kirbi R., 2005). Water is a basic transporting means of many chemical components. Apart from dissolved components it (cations K⁺, Na⁺, Cа⁺², Mg⁺² etc, anions Cl^-, I^-, Br^- etc.) can contain dissolved gases (О₂, СО₂ etc.), solid dissolved salts. In this respect water of living organisms is very similar to marine water (Horn R., 1972), being quite a dynamic physical-chemical system. V.I. Vernadskiy paid special attention to the interconnection of LM chemical composition and the World Ocean water. In this case, as it follows from the data analysis on plankton composition, the portion of main accompanying structure-forming elements in monocellular animals amounts about 98,1% of the entire mass, whereas the portion of dissolved anions and cations (Cl^-, K⁺, Na⁺) supporting osmolality in cells of LM via the mechanism of «Na pump» reaches 1,9%.

Besides, non-structure-forming elements can occur in adsorbed dissipated state in cellular membranes, blood and lymphatic vessels etc, or is in the form of self mineral formation including micron and nanomicron sizes formed in the process of biochemical reactions in LM.

Hence, at the moment there are a lot of approaches to the classification of chemical elements. Application of this or that is determined by the tasks that stated in definite conditions and for the solution of which each of them is more appropriate.

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