Biogeochemistry
It has been proven that there is a close relationship between the chemical composition of soils and the forms of plants growing on them. Some plants are capable of concentrating certain chemical elements from the environment (soil, water). Thus, the content of Silicon, Phosphorus, and Manganese in plants is approximately 10^3-10^5 times higher than in seawater.
The founder of biogeochemistry, academician Vernadsky, studying the distribution of chemical elements in the Earth's crust, first substantiated the role of living matter in the migration of elements and showed the significance of chemical elements for the life and evolution of human and animal organisms.
Changes in the Earth's crust that occur over millennia affect the chemical composition and flow of biochemical reactions in living systems, which in turn determine the migration of chemical elements in nature.
Chemical element migration refers to their movement in the environment. If such movement occurs involving living matter, the migration is called biogenic.
Thus, under the influence of living systems in nature, there is a constant cycle of chemical elements. Organisms selectively assimilate certain chemical elements from the biosphere. Their concentration depends on the solubility of compounds of this element in the organism's habitat, as well as the charge of the nucleus of this element.
For example, Silicon, Aluminum, and Titanium are quite common elements of the Earth's crust, however, due to the low solubility of their compounds in water, these elements enter living systems in small quantities.
Carbon, Nitrogen, Phosphorus, Iodine are elements less common in the Earth's crust, however, due to the good solubility of their compounds in water, the content of these elements in organisms is significantly higher.
Developing V. Vernadsky's doctrine on the chemical composition of the Earth's crust (lithosphere) and living systems, academician A. Vinogradov established the regularity of the distribution of chemical elements in the lithosphere and biosphere, the essence of which is as follows:
- The chemical composition of living organisms is an expression of the chemical composition of the habitat
- The quantitative content of a chemical element in living matter is inversely proportional to the ordinal number of this element in the periodic table of elements or the charge of its nucleus.
Classification of Bioelements
Thus, based on natural selection, chemical elements that are indispensable components of the existence and functioning of living organisms have been identified. They are part of various biological systems and play a specific physiological role in them.
In 1974, Kovalsky proposed to divide chemical elements, which at that time were discovered in the human and animal body, into three main groups.
- The first group consists of 20 essential elements that are constantly present in the human body, as well as animals, and are part of proteins, enzymes, vitamins, hormones, nucleic acids. Non-metals include – C, H, O, N, P, S, Cl, I, Se, and metals – Na, K, Ca, Mg, Zn, Cu, Fe, Co, Mn, V, Mo.
- The second group includes elements that are also constantly present in living organisms, but their function is insufficiently studied. These are non-metals – F, Br, Si, As and metals – Li, Cs, Be, Sr, Ba, Cd, Hg, Ag, Pb, Bi, etc.
- The third group includes elements found in living organisms, but their quantitative composition and biological functions have not yet been studied (Ti, Te, W, Au).
E. Underwood proposed to classify the chemical elements of an organism into three groups:
- elements indispensable in the nutrition of higher organisms (Fe, Cu, Zn, Mn, Co, Mo, Cr, Sn, I, Se);
- possibly necessary for the functioning of living systems (F, B, As, B, Ni, V, etc.);
- elements whose biological role has not been established (Au, Ag, Ti, Sb).
Content of Biometals in the Body
Over the years since the first classification of elements, the biological role of many elements, which can be classified as essential elements, has been proven. These include non-metals – F, Br, I, B, Si, Se and metals – Al, Cr, Ni, Sn.
Therefore, the classification of elements into groups according to B. Kovalsky and E. Underwood is conditional.
| Biometal | % mass | g/70 kg |
|---|---|---|
| Calcium | 1.5 | 1050 |
| Potassium | 0.35 | 245 |
| Sodium | 0.15 | 105 |
| Magnesium | 0.05 | 35 |
| Iron | 0.01 | 5 |
| Zinc | 2.7x10-3 | 1.9 |
| Copper | 2x10-4 | 0.15 |
| Manganese | 2.8x10-5 | 0.02 |
| Cobalt | 4x10-6 | 0.003 |
| Chromium | 2x10-6 | 0.0015 |
The most important of these are chemical elements constituting 97.5% of the total body mass. These are six chemical elements: O, CH, N, P, S, which are called organogenic elements. Their content in the body and biological role are known, but they are the subject of study in the course of bioinorganic chemistry and biochemistry.
A. Vinogradov proposed to divide bioelements based on the quantitative content in the body into macro-, micro-, and ultramicroelements.
Macronutrients and Micronutrients
In addition to the above-mentioned organogenic elements, the following elements are also classified as macronutrients: K, Na, Ca, Mg, Cl. Their mass fraction in the body is 0.01% (10-2% mass) and above. Micronutrients are present in living organisms in smaller quantities, ranging from 10-3 to 10-6% mass.
The biological role of micronutrients has been studied for several centuries. As early as the beginning of the 17th century, French scientists Lemery and Teoria discovered Iron in human and animal tissues, but more detailed studies began in the second half of the 19th century.
In 1852, it became known to physicians that Iodine activates the function of the thyroid gland. Later, reports emerged about the involvement of Cu2+ ions in blood formation, as well as information about the influence of Lithium ions on metabolism.
Important research of that period was associated with the study of the role of Iron and Copper in blood formation. It was also confirmed that certain micronutrients influence metabolic processes in living organisms.
When animals in some countries frequently suffered from anemia, lost weight significantly, and died, active searches for the causes of this phenomenon led researchers to discover a deficiency of Copper and Cobalt in the feed of these animals.
The condition of sick animals improved when these chemical elements were introduced into their feed. Later, methods of treating such a severe disease as malignant anemia, which had long been considered incurable, were developed.
With a deficiency of Copper and Iron in soils, plants suffer from chlorosis, while an excess of Molybdenum, Selenium, and Fluorine in them also causes various diseases in animals and humans.
There are entire geographical territories distinguished by the qualitative composition and quantitative content of chemical elements in soils; these are called biogeochemical provinces.
In living organisms inhabiting these territories, certain pathological changes may occur, endemic diseases may arise.
Provinces with reduced levels of Iodine (mountainous regions of western Ukraine) or Cobalt, Copper, Molybdenum (some regions in Russia, the Baltic states), as well as provinces with increased levels of Copper (Bashkortostan), Copper and Nickel (Kazakhstan) are known.
It has been proven that diseases such as goiter, gout, and dental caries are closely related to the content of certain chemical elements in the body. Therefore, the animal and plant worlds are in constant and close connection with the biosphere (hydrosphere, lithosphere, and atmosphere).
Despite the fact that some elements are present in living organisms in trace amounts, they play an important role in their vital processes. Currently, more than 20 chemical elements are classified as trace elements, the quantitative content of which in the body is known, and their biological role has been proven.
Trace Elements
If the mass fraction of an element in the body is less than 10-6 mass.%, they are classified as trace elements or trace elements (Au, Hg, Ti).
Studying the content and role of these components in the organism requires complex analytical equipment. However, our knowledge of these elements is gradually expanding as methods of physicochemical analysis are constantly improving.
The systematic classification of biogenic elements by A. Venchikov deserves attention, where the primary significance is the element's role in physiological processes. According to this classification, all chemical elements with a known physiological function, regardless of their quantitative content in the body, are referred to as biotics.
On one hand, biotics are macronutrients and micronutrients, as they are constantly present in various organs and the deficiency of them disrupts the normal functioning of these organs. On the other hand, they are vitamins, enzymes, hormones, and other biologically active substances involved in the metabolic processes of living organisms.
According to this classification, all bioelements can be divided into four groups:
- Elements (C, H, O, N, P, Cl, K, Na, Ca, Mg) that create conditions for physiological processes in body fluids, maintaining acid-base balance, a certain pH value, osmotic pressure, as well as elements that serve as a plastic material for building tissues.
- Elements involved in metabolism, as they are part of a significant number of metalloenzymes (Fe, Zn, Cu, Mo), vitamins (Co), hormones (1).
- Elements that contribute to the formation in the body of substances that suppress the reproduction and development of microorganisms (As, Sb, Ag).
- Elements regulating the course of various oxidation-reduction reactions (Mn, Cu, Cr). There are other types of classification of bioelements, but they all have certain drawbacks, as chemical elements in living systems mostly perform not one, but several functions. Therefore, research in this area is actively ongoing.
In the second half of the 20th century, a new science emerged about the role of metal ions and their compounds with proteins, nucleic acids, lipids in the life of organisms, called bioinorganic chemistry.
The task of bioinorganic chemistry is to model biocomplexes and biological processes, explain the mechanism of biological activity of metals, prevent diseases, and search for new medicinal preparations.
The founders of bioinorganic chemistry are considered to be such scientists as V. Vernadsky, P. Pfeiffer, L. Chugaev, K. Yatsimirsky.
The achievements of bioinorganic chemistry are now being applied in human practical activities. For example, based on scientific generalizations, recommendations have been developed for the rational management of agriculture, the effective use of microfertilizers, and in the field of environmental protection.
