Non-metals as trace elements.
We paid great attention to the role of metals. However, it must be borne in mind that some non-metals are also absolutely necessary for the functioning of the body.
SILICON
Silicon is also an essential trace element. This has been confirmed by a careful study of the nutrition of rats using various diets. Rats noticeably gained weight when sodium metasilicate was added. (Na2(SiO)3 . 9H2O) in their diet (50mg per 100g). chickens and rats need silicon for the growth and development of the skeleton. The lack of silicon leads to a violation of the structure of bones and connective tissue. As it turned out, silicon is present in those areas of the bone where active calcification occurs, for example, in bone-forming cells, osteoblasts. With age, the concentration of silicon in cells decreases.
Little is known about the processes in which silicon is involved in living systems. There it is in the form of silicic acid and, probably, participates in the cross-linking of carbons. In humans, umbilical cord hyaluronic acid turned out to be the richest source of silicon. It contains 1.53mg free and 0.36mg bound silicon per gram.
SELENIUM
The lack of selenium causes the death of muscle cells and leads to muscle failure, in particular heart failure. The biochemical study of these conditions led to the discovery of the enzyme glutathione peroxidase, which destroys peroxides. A lack of selenium leads to a decrease in the concentration of this enzyme, which in turn causes lipid oxidation. The ability of selenium to protect against mercury poisoning is well known. Much less well known is the fact that there is a correlation between high dietary selenium and low cancer mortality. Selenium is included in the human diet in the amount 55 110mg per year, and the concentration of selenium in the blood is 0.09 0.29 µg/cm. When taken orally, selenium is concentrated in the liver and kidneys. Another example of the protective effect of selenium against intoxication with light metals is its ability to protect against poisoning by cadmium compounds. It turned out that, as in the case of mercury, selenium forces these toxic ions to bind to ionic active centers, to those that are not affected by their toxic effect.
ARSENIC
Despite the well-known toxic effects of arsenic and its compounds, there is reliable evidence that a lack of arsenic leads to a decrease in fertility and growth inhibition, and the addition of sodium arsenite to food has led to an increase in the growth rate in humans.
CHLORINE AND BROMINE
Halogen anions differ from all other ones in that they are simple and not oxo anions. Chlorine is extremely widespread, it is able to pass through the membrane and plays an important role in maintaining osmotic balance. Chlorine is present as hydrochloric acid in gastric juice. The concentration of hydrochloric acid in human gastric juice is 0,4-0,5%. There are some doubts about the role of bromine as a trace element, although its sedative effect is reliably known.
FLUORINE
Fluorine is absolutely necessary for normal growth, and its deficiency leads to anemia. Much attention has been paid to the metabolism of fluorine in connection with the problem of dental caries, since fluorine protects teeth from caries. Dental caries has been studied in sufficient detail. It begins with the formation of a stain on the surface of the tooth. Acids produced by bacteria dissolve tooth enamel under the stain, but, oddly enough, not from its surface. Often the top surface remains intact until the areas below it are completely destroyed. It is assumed that at this stage, the fluoride ion can facilitate the formation of appatite. Thus, reminelization of the damage that has begun is performed.
Fluoride is used to prevent damage to tooth enamel. Fluorides can be added to toothpaste or applied directly to teeth. The concentration of fluoride required to prevent caries in drinking water is about 1mg/l, but the level of consumption depends not only on this. Application of high concentrations of fluorides (more than 8mg/l) can adversely affect the delicate equilibrium processes of bone tissue formation. Excessive absorption of fluoride leads to fluorosis. Fluorosis leads to disturbances in the functioning of the thyroid gland, growth inhibition and kidney damage. Prolonged exposure to fluoride on the body leads to mineralization of the body. As a result, the bones are deformed, which can even grow together, and ligaments calcify.
IODINE
The main physiological role of iodine is participation in the metabolism of the thyroid gland and its inherent hormones. The ability of the thyroid gland to accumulate iodine is also inherent in the salivary and mammary glands. As well as some other organs. At present, however, it is believed that iodine plays a leading role only in the life of the thyroid gland.
Lack of iodine leads to characteristic symptoms: weakness, yellowing of the skin, feeling cold and dry. Treatment with thyroid hormones or iodine eliminates these symptoms. A lack of thyroid hormones can lead to an enlarged thyroid gland. In rare cases (burdening in the body of various compounds that interfere with the absorption of iodine, such as thiocyanate or the antithyroid agent goitrin, found in various types of cabbage), a goiter is formed. Lack of iodine has a particularly strong effect on the health of children; they lag behind in physical and mental development. An iodine deficient diet during pregnancy leads to the birth of hypothyroid children (cretins).
Excess thyroid hormone leads to exhaustion, nervousness, tremors, weight loss, and excessive sweating. This is associated with an increase in peroxidase activity and, consequently, with an increase in thyroglobulin iodination. An excess of hormones can be the result of a thyroid tumor. In the treatment, radioactive isotopes of iodine are used, which are easily absorbed by the cells of the thyroid gland.
non-metals- chemical elements that form simple bodies that do not have the properties characteristic of metals. A qualitative characteristic of non-metals is electronegativity.
Electronegativity- this is the ability to polarize a chemical bond, to pull common electron pairs towards itself.
22 elements are classified as non-metals.
1st period
3rd period
4th period
5th period
6th period
As can be seen from the table, non-metallic elements are mainly located in the upper right part of the periodic table.
The structure of atoms of non-metals
A characteristic feature of non-metals is more (compared to metals) electrons at the external energy level of their atoms. This determines their greater ability to add additional electrons and exhibit higher oxidative activity than metals. Particularly strong oxidizing properties, i.e., the ability to attach electrons, are exhibited by non-metals that are in the 2nd and 3rd periods of groups VI-VII. If we compare the arrangement of electrons in orbitals in the atoms of fluorine, chlorine and other halogens, then we can judge their distinctive properties. The fluorine atom has no free orbitals. Therefore, fluorine atoms can only show I and the oxidation state is 1. The strongest oxidizing agent is fluorine. In the atoms of other halogens, for example, in the chlorine atom, there are free d-orbitals at the same energy level. Due to this, the depairing of electrons can occur in three different ways. In the first case, chlorine can show an oxidation state of +3 and form hydrochloric acid HClO2, which corresponds to salts - for example, potassium chlorite KClO2. In the second case, chlorine can form compounds in which chlorine is +5. These compounds include HClO3 and its -, for example, potassium chlorate KClO3 (bertoletova). In the third case, chlorine exhibits an oxidation state of +7, for example, in perchloric acid HClO4 and in its salts, perchlorates (in potassium perchlorate KClO4).
Structures of non-metal molecules. Physical properties of non-metals
In the gaseous state at room temperature are:
hydrogen - H2;
nitrogen - N2;
oxygen - O2;
fluorine - F2;
radon - Rn).
In liquid - bromine - Br.
In solid:
boron - B;
carbon - C;
silicon - Si;
phosphorus - P;
selenium - Se;
Tellurium - Te;
Much richer in non-metals and colors: red - in phosphorus, brown - in bromine, yellow - in sulfur, yellow-green - in chlorine, purple - in iodine vapor, etc.
The most typical non-metals have a molecular structure, while the less typical ones have a non-molecular structure. This explains the difference in their properties.
Composition and properties of simple substances - non-metals
Non-metals form both monatomic and diatomic molecules. TO monatomic non-metals include inert gases that practically do not react even with the most active substances. are located in group VIII of the periodic system, and the chemical formulas of the corresponding simple substances are as follows: He, Ne, Ar, Kr, Xe and Rn.
Some nonmetals form diatomic molecules. These are H2, F2, Cl2, Br2, Cl2 (elements of group VII of the periodic system), as well as oxygen O2 and nitrogen N2. From triatomic molecules consists of ozone (O3) gas. For non-metal substances that are in the solid state, it is quite difficult to make a chemical formula. The carbon atoms in graphite are connected to each other in various ways. It is difficult to isolate an individual molecule in the given structures. When writing the chemical formulas of such substances, as in the case of metals, the assumption is introduced that such substances consist only of atoms. , at the same time, are written without indices: C, Si, S, etc. Such simple substances, like oxygen, having the same qualitative composition (both consist of the same element - oxygen), but differing in the number of atoms in the molecule, have different properties. So, oxygen has no smell, while ozone has a pungent smell that we feel during a thunderstorm. The properties of solid non-metals, graphite and diamond, which also have the same qualitative composition, but different structure, differ sharply (graphite is brittle, hard). Thus, the properties of a substance are determined not only by its qualitative composition, but also by how many atoms are contained in a substance molecule and how they are interconnected. in the form of simple bodies are in a solid gaseous state (excluding bromine - liquid). They do not have the physical properties of metals. Solid non-metals do not have the luster characteristic of metals, they are usually brittle, and conduct heat poorly (with the exception of graphite). Crystalline boron B (like crystalline silicon) has a very high melting point (2075°C) and high hardness. The electrical conductivity of boron increases greatly with increasing temperature, which makes it possible to widely use it in semiconductor technology. The addition of boron to steel and alloys of aluminum, copper, nickel, etc. improves their mechanical properties. Borides (compounds with some metals, for example, with titanium: TiB, TiB2) are necessary in the manufacture of jet engine parts, gas turbine blades. As can be seen from Scheme 1, carbon - C, silicon - Si, - B have a similar structure and have some common properties. As simple substances, they occur in two modifications - crystalline and amorphous. The crystalline modifications of these elements are very hard, with high melting points. Crystalline has semiconductor properties. All these elements form compounds with metals - , and (CaC2, Al4C3, Fe3C, Mg2Si, TiB, TiB2). Some of them have higher hardness, such as Fe3C, TiB. used to produce acetylene.
Chemical properties of non-metals
In accordance with the numerical values of the relative electronegativities, the oxidizing nonmetals increase in the following order: Si, B, H, P, C, S, I, N, Cl, O, F.
Nonmetals as oxidizers
The oxidizing properties of non-metals are manifested when they interact:
with metals: 2Na + Cl2 = 2NaCl;
With hydrogen: H2 + F2 = 2HF;
With non-metals that have a lower electronegativity: 2P + 5S = P2S5;
With some complex substances: 4NH3 + 5O2 = 4NO + 6H2O,
2FeCl2 + Cl2 = 2FeCl3.
Nonmetals as reducing agents
1. All non-metals (except fluorine) exhibit reducing properties when interacting with oxygen:
S + O2 = SO2, 2H2 + O2 = 2H2O.
Oxygen in combination with fluorine can also exhibit a positive oxidation state, i.e., be a reducing agent. All other non-metals exhibit reducing properties. So, for example, chlorine does not combine directly with oxygen, but its oxides (Cl2O, ClO2, Cl2O2) can be obtained indirectly, in which chlorine exhibits a positive oxidation state. Nitrogen at high temperatures directly combines with oxygen and exhibits reducing properties. Sulfur reacts even more easily with oxygen.
2. Many non-metals exhibit reducing properties when interacting with complex substances:
ZnO + C \u003d Zn + CO, S + 6HNO3 conc \u003d H2SO4 + 6NO2 + 2H2O.
3. There are also such reactions in which the same non-metal is both an oxidizing agent and a reducing agent:
Cl2 + H2O = HCl + HClO.
4. Fluorine is the most typical non-metal, which does not have reducing properties, i.e., the ability to donate electrons in chemical reactions.
Compounds of non-metals
Nonmetals can form compounds with different intramolecular bonds.
Types of non-metal compounds
The general formulas of hydrogen compounds according to the groups of the periodic system of chemical elements are given in the table:
|
Volatile hydrogen compounds |
total chalcogens.
In the main subgroup of the sixth group of the Periodic Table of the Elements. I. Mendeleev are the elements: oxygen (O), sulfur (S), selenium (Se), (Te) and (Po). These elements are collectively known as chalcogens, which means "forming ores".
In the subgroup of chalcogens, from top to bottom, with an increase in the charge of the atom, the properties of the elements naturally change: their non-metallic properties decrease and their metallic properties increase. So is a typical non-metal, and polonium is a metal (radioactive).
gray selenium
Production of photocells and electric current rectifiers
in semiconductor technology
The biological role of chalcogens
Sulfur plays an important role in the life of plants, animals and humans. In animal organisms, sulfur is part of almost all proteins, in sulfur-containing ones - and, as well as in the composition of vitamin B1 and the hormone insulin. With a lack of sulfur in sheep, wool growth slows down, and poor feathering is noted in birds.
Of the plants, cabbage, lettuce, and spinach consume the most sulfur. Pods of peas and beans, radishes, turnips, onions, horseradish, pumpkins, cucumbers are also rich in sulfur; poor in sulfur and beets.
In terms of chemical properties, selenium and tellurium are very similar to sulfur, but in terms of physiological properties they are its antagonists. Very small amounts of selenium are needed for the normal functioning of the body. Selenium has a positive effect on the cardiovascular system, red blood, increases the body's immune properties. An increased amount of selenium causes a disease in animals, manifested in emaciation and drowsiness. The lack of selenium in the body leads to disruption of the heart, respiratory organs, the body rises and may even occur. Selenium has a significant effect on animals. For example, in deer, which are distinguished by high visual acuity, the retina contains 100 times more selenium than in other parts of the body. In the plant kingdom, all plants contain a lot of selenium. The plant accumulates especially large amounts of it.
The physiological role of tellurium for plants, animals, and humans has been less studied than that of selenium. It is known that tellurium is less toxic than selenium, and tellurium compounds in the body are quickly reduced to elemental tellurium, which in turn combines with organic substances.
General characteristics of the elements of the nitrogen subgroup
The main subgroup of the fifth group includes nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb) and (Bi).
From top to bottom, in the subgroup from nitrogen to bismuth, non-metallic properties decrease, while metallic properties and atomic radius increase. Nitrogen, phosphorus, arsenic are non-metals, but belong to metals.
Nitrogen subgroup
|
Comparative characteristics |
7 N nitrogen |
15 P phosphorus |
33 As arsenic |
51 Sb antimony |
83 Bi bismuth |
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Electronic structure |
…4f145d106S26p3 |
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Oxidation state |
1, -2, -3, +1, +2, +3, +4, +5 |
3, +1, +3, +4,+5 |
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Electro- negativity |
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Being in nature |
In the free state - in the atmosphere (N2 - ), in the bound state - in the composition of NaNO3 - ; KNO3 - Indian saltpeter |
Ca3(PO4)2 is phosphorite, Ca5(PO4)3(OH) is hydroxylapatite, Ca5(PO4)3F is fluorapatite |
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|
Allotropic forms under normal conditions |
Nitrogen (one form) |
NH3 + H2O ↔ NH4OH ↔ NH4+ + OH - (ammonium hydroxide); PH3 + H2O ↔ PH4OH ↔ PH4+ + OH- (phosphonium hydroxide). The biological role of nitrogen and phosphorus Nitrogen plays an extremely important role in plant life, since it is part of amino acids, proteins and chlorophyll, B vitamins, and activating enzymes. Therefore, the lack of nitrogen in the soil has a negative effect on plants, and primarily on the content of chlorophyll in the leaves, which is why they turn pale. consume from 50 to 250 kg of nitrogen per 1 hectare of soil area. Most nitrogen is found in flowers, young leaves and fruits. Nitrogen is the most important source of nitrogen for plants - it is mainly ammonium nitrate and ammonium sulfate. It should also be noted the special role of nitrogen as an integral part of air - the most important component of living nature. None of the chemical elements takes such an active and diverse part in the life processes of plant and animal organisms as phosphorus. It is an integral part of nucleic acids, is part of some enzymes and vitamins. In animals and humans, up to 90% of phosphorus is concentrated in bones, up to 10% in muscles, and about 1% in the nervous system (in the form of inorganic and organic compounds). It is found in muscles, liver, brain and other organs in the form of phosphatides and phosphoric esters. Phosphorus is involved in muscle contractions and in building muscle and bone tissue. People engaged in mental work need to consume an increased amount of phosphorus in order to prevent the depletion of nerve cells that function with an increased load during mental work. With a lack of phosphorus, efficiency decreases, neurosis develops, divalent germanium, tin and lead GeO, SnO, PbO are disturbed by amphoteric oxides. Higher oxides of carbon and silicon CO2 and SiO2 are acidic oxides, which correspond to hydroxides exhibiting weakly acidic properties - H2CO3 and silicic acid H2SiO3. Amphoteric oxides - GeO2, SnO2, PbO2 - correspond to amphoteric hydroxides, and when passing from germanium hydroxide Ge(OH)4 to lead hydroxide Pb(OH)4, the acidic properties are weakened, and the basic ones are enhanced. The biological role of carbon and silicon Carbon compounds are the basis of plant and animal organisms (45% of carbon is found in plants and 26% in animal organisms). Characteristic biological properties are exhibited by carbon monoxide (II) and carbon monoxide (IV). Carbon monoxide (II) is a very toxic gas, as it binds strongly with blood hemoglobin and deprives hemoglobin of the ability to carry oxygen from the lungs to the capillaries. When inhaled, CO can cause poisoning, possibly even fatal. Carbon monoxide (IV) is especially important for plants. In plant cells (especially in leaves), in the presence of chlorophyll and the action of solar energy, glucose occurs from carbon dioxide and water with the release of oxygen. As a result of photosynthesis, plants annually bind 150 billion tons of carbon and 25 billion tons of hydrogen, and release up to 400 billion tons of oxygen into the atmosphere. Scientists have found that plants receive about 25% of CO2 through the root system from carbonates dissolved in the soil. Plants use silicon to build integumentary tissues. Silicon contained in plants, impregnating the cell walls, makes them more solid and resistant to damage by insects, protects them from the penetration of fungal infection. Silicon is found in almost all tissues of animals and humans, especially in the liver, cartilage. Tuberculosis patients have much less silicon in their bones, teeth, and cartilage than healthy people. In diseases such as Botkin, there is a decrease in the content of silicon in the blood, and with damage to the large intestine, on the contrary, an increase in its content in the blood. |
"Biogenic elements in the human body"
INTRODUCTION
1.1 Biogenic elements - non-metals that are part of the human body
2 Biogenic elements - metals that are part of the human body
THE ROLE OF OXYGEN IN THE HUMAN BODY
ROLE OF CARBON IN THE HUMAN BODY
THE ROLE OF HYDROGEN IN THE HUMAN BODY
THE ROLE OF POTASSIUM IN THE HUMAN BODY
THE ROLE OF SULFUR IN THE HUMAN BODY
THE ROLE OF CALCIUM IN THE HUMAN BODY
CONCLUSION
BIBLIOGRAPHY
INTRODUCTION
The opinion that almost all elements of the periodic system of D.I. Mendeleev, becomes familiar. However, scientists suggest that not only all chemical elements are present in a living organism, but each of them performs some biological function. It is possible that this hypothesis will not be confirmed. As research in this direction develops, the biological role of an increasing number of chemical elements is revealed.
To maintain his health, a person must provide the body with a balanced intake of nutrients from food, water, and inhaled air. Food products with a high content of calcium, iodine and other chemical elements are often advertised, but is this good for our body? What diseases can be caused by an excess or deficiency of one or another chemical element in children and adults?
In our time, when there are less and less healthy people from childhood, this problem is really relevant.
An unimaginable number of different chemical compounds are continuously formed in the human body. Some of the synthesized compounds are used as a building material or energy source and provide the body with growth, development and vital activity; the other part, which can be considered as slag or waste, is excreted from the body.
Both inorganic and organic substances are involved in the metabolism. The chemical elements that form these substances are called biogenic elements. About 30 elements are considered to be reliably biogenic.
Figure 1 shows the main chemical elements that make up the human body.
Figure 1 - Diagram. The elemental composition of the human body.
1.1 Biogenic elements - non-metals that are part of the human body
Among biogenic elements, a special place is occupied by organogenic elements that form the most important substances of the body - water, proteins, carbohydrates, fats, vitamins, hormones, and others. Organogens include 6 chemical elements: carbon, oxygen, hydrogen, nitrogen, phosphorus, sulfur. Their total mass fraction in the human body is approximately 97.3% (see table 1).
All organogenic elements are non-metals. Among non-metals, chlorine (mass fraction 0.15%), fluorine, iodine and bromine are also biogenic. These elements are not included among the organogenic elements, since, unlike the latter, they do not play such a universal role in the construction of the organic structures of the body. There are data on the biogenicity of silicon, boron, arsenic, and selenium.
Table 1. The content of organogen elements in the human body.
|
Elements - organogens |
Mass fraction (in%) |
Weight (in g / 70 kg) |
|
carbon (C) |
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oxygen (O) |
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hydrogen (H) |
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phosphorus (P) |
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|
68117 ≈ 68 kg |
1.2 Biogenic elements - metals that are part of the human body
Nutrient elements include a number of metals, among which 10 so-called "metals of life" perform especially important biological functions. These metals are calcium, potassium, sodium, magnesium, iron, zinc, copper, manganese, molybdenum, cobalt (see table 2).
In addition to the 10 "metals of life", several more metals are included among the biogenic elements, for example, tin, lithium, chromium and some others.
Table 2. The content of "metals of life" in the human body
|
Mass fraction (in%) |
Weight (in g / 70 kg) |
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Calcium (Ca) |
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Sodium (Na) |
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Magnesium (Mg) |
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Iron (Fe) |
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Manganese (Mn) |
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Molybdenum (Mo) |
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Cobalt (Co) |
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Depending on the mass fraction in the body, all biogenic elements are divided into:
a) macronutrients (mass fraction in the body is more than 10 -2%, or more than 7 g);
b) trace elements (mass fraction in the body is less than 10 -2%, or less than 7 g).
Macroelements include all organogens, chlorine and 4 "metals of life": magnesium, potassium, calcium, sodium. They make up 99.5%, with more than 96% accounted for by 4 elements (carbon, oxygen, hydrogen, nitrogen). They are the main components of all organic compounds.
Trace elements are contained in cells in very small quantities. These include zinc, manganese, copper, iodine, fluorine and others. But even those elements that are contained in negligible amounts are necessary for life and cannot be replaced by anything. The biological role and functions that these elements perform in the human body are very diverse, and their deficiency or excess can lead to serious diseases (see Appendices B and D). Suffice it to say that about 200 enzymes are activated by metals. In total, about 70 minerals have been identified in the human body, of which 14 trace elements are considered essential - these are iron, cobalt, copper, chromium, nickel, manganese, molybdenum, zinc, iodine, tin, fluorine, silicon, vanadium, selenium. Many trace elements enter the body almost exclusively through fruit and vegetable nutrition. Wild edible plants are also rich in trace elements, which, when extracted from the deep layers, accumulate in leaves, flowers, and fruits.
2. THE ROLE OF OXYGEN IN THE HUMAN BODY
The main function of molecular oxygen in the body is the oxidation of various compounds. Together with hydrogen, oxygen forms water, the content of which in the body of an adult is on average about 55-65%.
Oxygen is a part of proteins, nucleic acids and other vital components of the body. Oxygen is essential for respiration, oxidation of fats, proteins, carbohydrates, amino acids, and many other biochemical processes.
The usual way oxygen enters the body lies through the lungs, where this bioelement penetrates into the blood, is absorbed by hemoglobin and forms an easily dissociating compound - oxyhemoglobin, and then from the blood enters all organs and tissues. Oxygen enters the body also in a bound state, in the form of water. In tissues, oxygen is consumed mainly for the oxidation of various substances in the process of metabolism. In the future, almost all oxygen is metabolized to carbon dioxide and water, and excreted from the body through the lungs and kidneys.
Decreased oxygen content in the body.
With insufficient supply of body tissues with oxygen or a violation of its utilization, hypoxia (oxygen starvation) develops.
The main causes of oxygen deficiency:
cessation or reduction of oxygen supply to the lungs, reduced partial pressure of oxygen in the inhaled air;
a significant decrease in the number of red blood cells or a sharp decrease in the content of hemoglobin in them;
violation of the ability of hemoglobin to bind, transport or give oxygen to tissues;
violation of the ability of tissues to utilize oxygen;
Inhibition of redox processes in tissues;
stagnation in the vascular bed due to disorders of cardiac activity, blood circulation and respiration;
endocrinopathies, beriberi;
The main manifestations of oxygen deficiency:
In acute cases (with a complete cessation of oxygen supply, acute poisoning): loss of consciousness, dysfunction of the higher parts of the central nervous system;
In chronic cases: increased fatigue, functional disorders of the central nervous system, palpitations and shortness of breath with little physical exertion, decreased reactivity of the immune system.
Toxic dose for humans: toxic in the form of O 3 .
Increased oxygen content in the body.
A prolonged increase in the oxygen content in the tissues of the body (hyperoxia) may be accompanied by oxygen poisoning; hyperoxia is usually accompanied by an increase in the oxygen content in the blood (hyperoxemia).
The toxic effect of ozone and excess oxygen is associated with the formation in tissues of a large number of radicals resulting from the breaking of chemical bonds. In a small amount, radicals are also formed normally, as an intermediate product of cellular metabolism. With an excess of radicals, the process of oxidation of organic substances is initiated, including lipid peroxidation, with their subsequent decay and the formation of oxygen-containing products (ketones, alcohols, acids).
Oxygen is part of the molecules of many substances - from the simplest to complex polymers; the presence in the body and the interaction of these substances ensures the existence of life. Being an integral part of the water molecule, oxygen is involved in almost all biochemical processes occurring in the body.
Oxygen is indispensable, with its lack, only the restoration of a normal supply of oxygen to the body can be an effective remedy. Even a short-term (several minutes) cessation of oxygen supply to the body can cause severe impairment of its functions and subsequent death.
3. THE ROLE OF CARBON IN THE HUMAN BODY
CARBON is the most important biogenic element that forms the basis of life on Earth, the structural unit of a huge number of organic compounds involved in building organisms and ensuring their vital activity (biopolymers, as well as numerous low molecular weight biologically active substances - vitamins, hormones, mediators, etc.). A significant part of the energy needed by organisms is formed in cells due to the oxidation of carbon. The emergence of life on Earth is considered in modern science as a complex process of evolution of carbonaceous compounds.
Carbon enters the human body with food (normally about 300 g per day). The total carbon content reaches about 21% (15 kg per 70 kg of total body weight). Carbon makes up 2/3 of muscle mass and 1/3 of bone mass. It is excreted from the body mainly with exhaled air (carbon dioxide) and urine (urea).
The main function of carbon is the formation of a variety of organic compounds, thereby ensuring biological diversity, participation in all functions and manifestations of living things. In biomolecules, carbon forms polymer chains and is firmly connected to hydrogen, oxygen, nitrogen and other elements. Such a significant physiological role of carbon is determined by the fact that this element is part of all organic compounds and takes part in almost all biochemical processes in the body. Oxidation of carbon compounds under the action of oxygen leads to the formation of water and carbon dioxide; This process serves as a source of energy for the body. Carbon dioxide CO 2 (carbon dioxide) is formed in the process of metabolism, is a stimulator of the respiratory center, plays an important role in the regulation of respiration and blood circulation.
In its free form, carbon is not toxic, but many of its compounds are highly toxic. Such compounds include carbon monoxide CO (carbon monoxide), carbon tetrachloride CCl 4, carbon disulfide CS 2, cyanide salts HCN, benzene C 6 H 6 and others. Carbon dioxide in concentrations above 10% causes acidosis (decrease in blood pH), shortness of breath and paralysis of the respiratory center.
Prolonged inhalation of coal dust can lead to anthracosis, a disease accompanied by the deposition of coal dust in the lung tissue and lymph nodes, sclerotic changes in the lung tissue. The toxic effect of hydrocarbons and other oil compounds in oil industry workers can manifest itself in roughening of the skin, the appearance of cracks and ulcers, and the development of chronic dermatitis.
For humans, carbon can be toxic in the form of carbon monoxide (CO) or cyanides (CN-).
4. ROLE OF HYDROGEN IN THE HUMAN BODY
Water is the most important hydrogen compound in a living organism. The main functions of water are as follows:
Water, which has a high specific heat capacity, maintains a constant body temperature. When the body overheats, water evaporates from its surface. Due to the high heat of vaporization, this process is accompanied by a large expenditure of energy, resulting in a decrease in body temperature. This is how the heat balance of the body is maintained.
Water maintains the acid-base balance of the body. Most tissues and organs are primarily made up of water. Compliance with the overall acid-base balance in the body does not exclude large differences in pH values for different organs and tissues. An important hydrogen compound is hydrogen peroxide H2O2 (traditionally called hydrogen peroxide). H2O2 oxidizes the lipid layer of cell membranes, destroying it.
5. THE ROLE OF POTASSIUM IN THE HUMAN BODY
Potassium is an obligatory participant in many metabolic processes. Potassium is important in maintaining the automatism of contraction of the heart muscle - myocardium; ensures the removal of sodium ions from cells and their replacement with potassium ions, which in turn is accompanied by the removal of excess fluid from the body.
Compared to other potassium products, dried apricots, figs, oranges, tangerines, potatoes (500 g of potatoes provide the daily requirement), dried peaches, turnips, rose hips, black and red currants, lingonberries, strawberries, watermelons, melons, soybeans, cherry plum, fresh cucumbers, Brussels sprouts, walnuts and hazelnuts, parsley, raisins, prunes, rye bread, oatmeal.
The daily requirement of potassium for an adult is 2-3 g per day, and for a child - 16-30 mg per kg of body weight. The required minimum intake of potassium for a person per day is about 1 g. With a normal diet, the daily need for potassium is fully satisfied, but seasonal fluctuations in potassium intake are also noted. So, in spring its consumption is low - about 3 g / day, and in autumn the maximum consumption is 5-6 g / day.
Given the trend of modern people to consume large amounts of salt with food, the need for potassium is also increasing, which can neutralize the adverse effects of excess sodium on the body.
A lack of potassium intake from food can lead to dystrophy even with a normal protein content in the diet. Violation of potassium metabolism is manifested in chronic diseases of the kidneys and the cardiovascular system, in diseases of the gastrointestinal tract (especially those accompanied by diarrhea and vomiting), in diseases of the endocrine glands and other pathologies.
The lack of potassium in the body is manifested primarily by disorders of the neuromuscular and cardiovascular systems (drowsiness, impaired movement, trembling of the limbs, slow heartbeat). Potassium preparations are used for medicinal purposes.
Excess potassium is observed much less frequently, but is an extremely dangerous condition: flaccid paralysis of the limbs, changes in the cardiovascular system. This condition can manifest itself with severe dehydration, hypercortisolism with impaired renal function, and with the introduction of a large amount of potassium to the patient.
Sulfur in the human body is an indispensable component of cells, organ tissues, enzymes, hormones, in particular, insulin, the most important pancreatic enzyme, and sulfur-containing amino acids; provides the spatial organization of protein molecules necessary for their functioning, protects cells, tissues and pathways of biochemical synthesis from oxidation, and the entire body from the toxic effects of foreign substances. Quite a lot of it in the nervous, connective, bone tissues. Sulfur is a component of the structural protein of collagen. Replenishment of the body with sulfur is provided by properly organized nutrition, which includes meat, chicken eggs, oatmeal and buckwheat, flour products, milk, cheeses, legumes and cabbage.
Despite a significant number of studies, the role of sulfur in ensuring the vital activity of the body has not been fully elucidated. So, while there are no clear clinical descriptions of any specific disorders associated with insufficient intake of sulfur in the body. At the same time, acidoaminopathies are known - disorders associated with impaired metabolism of sulfur-containing amino acids (homocystinuria, cystationuria). There is also an extensive literature relating to the clinic of acute and chronic intoxication with sulfur compounds.
The main manifestations of sulfur deficiency:
symptoms of liver disease
· symptoms of diseases of the joints;
symptoms of skin diseases;
Various and numerous manifestations of deficiency in the body and metabolic disorders of biologically active sulfur-containing compounds.
Increased sulfur content in the body.
At high concentrations of hydrogen sulfide in the inhaled air, the clinical picture of intoxication develops very quickly, convulsions, loss of consciousness, and respiratory arrest occur within a few minutes. In the future, the consequences of the poisoning can be manifested by persistent headaches, mental disorders, paralysis, disorders of the functions of the respiratory system and the gastrointestinal tract.
It has been established that parenteral administration of finely ground sulfur in an oil solution in an amount of 1-2 ml is accompanied by hyperthermia with hyperleukocytosis and hypoglycemia. It is believed that when administered parenterally, the toxicity of sulfur ions is 200 times higher than that of chloride ions.
The toxicity of sulfur compounds that have entered the gastrointestinal tract is associated with their conversion by the intestinal microflora into hydrogen sulfide, a highly toxic compound.
In cases of death after sulfur poisoning at autopsy, there are signs of emphysema, inflammation of the brain, acute catarrhal enteritis, liver necrosis, hemorrhage (petechiae) in the myocardium.
With chronic intoxication (carbon disulfide, sulfur dioxide), mental disorders, organic and functional changes in the nervous system, muscle weakness, visual impairment and various disorders of the activity of other body systems are observed.
In recent decades, sulfur-containing compounds (sulfites), which are added to many foods, alcoholic and non-alcoholic beverages as preservatives, have become one of the sources of excess sulfur in the human body. Especially a lot of sulfites in smoked meats, potatoes, fresh vegetables, beer, cider, ready-made salads, vinegar, wine dyes. It is possible that the increased consumption of sulfites is partly to blame for the increase in the incidence of bronchial asthma. It is known, for example, that 10% of patients with bronchial asthma exhibit hypersensitivity to sulfites (i.e., are sensitized to sulfite). To reduce the negative effect of sulfites on the body, it is recommended to increase the content of cheese, eggs, fatty meat, and poultry in the diet.
The main manifestations of excess sulfur:
skin itching, rashes, furunculosis;
redness and swelling of the conjunctiva;
The appearance of small point defects on the cornea;
ache in the eyebrows and eyeballs, a feeling of sand in the eyes;
photophobia, lacrimation;
general weakness, headaches, dizziness, nausea;
catarrh of the upper respiratory tract, bronchitis;
Hearing loss
Digestive disorders, diarrhea, weight loss;
Anemia
convulsions and loss of consciousness (with acute intoxication);
Mental disorders, lowering of intelligence.
The role of sulfur in the human body is extremely important, and sulfur metabolism disorders are accompanied by numerous pathologies. Meanwhile, the clinic of these disturbances is insufficiently developed. More precisely, various "non-specific" manifestations of human health disorders are not yet associated by clinicians with sulfur metabolism disorders.
7. THE ROLE OF CALCIUM IN THE HUMAN BODY
Calcium is directly involved in the most complex processes, such as blood clotting; regulation of intracellular processes; regulation of cell membrane permeability; regulation of the processes of nerve conduction and muscle contractions; maintaining stable cardiac activity; bone formation, mineralization of teeth.
Calcium is an important part of the body; its total content is about 1.4% (1000 g per 70 kg of body weight). In the body, calcium is unevenly distributed: about 99% of its amount is in bone tissue and only 1% is found in other organs and tissues. Calcium is excreted from the body through the intestines and kidneys.
In addition, a prolonged lack of calcium in food undesirably affects the excitability of the heart muscle and the rhythm of its contractions.
Despite the fact that in the diet of most people there is enough calcium-containing foods, many people suffer from calcium deficiency. The reason is that calcium is hard to digest.
First of all, it should be noted that calcium is lost during heat treatment (for example, when cooking vegetables - 25%). Calcium loss will be negligible if the water in which the vegetables were boiled is consumed.
It must also be remembered that the absorption of calcium in the intestines is hampered by phytic acid, which is most in rye bread, and oxalic acid, which is abundant in sorrel, cocoa. The utilization of calcium by food rich in fats is difficult. The "enemies" of calcium are cane sugar, chocolate and cocoa.
The main manifestations of calcium deficiency.
The consequences of calcium deficiency can manifest themselves both at the level of the whole organism and its individual systems:
general weakness, increased fatigue;
Pain, muscle cramps
bone pain, gait disturbances;
violations of growth processes;
hypocalcemia, hypocalcinosis;
Skeletal decalcification, deforming osteoarthritis, osteoporosis, vertebral deformity, bone fractures;
· urolithiasis disease;
Kashin-Beck disease;
Immunity disorders;
Reduced blood clotting, bleeding.
Increased calcium content in the body.
The toxic effect of calcium is manifested only with long-term use and usually in persons with impaired metabolism of this bioelement (eg, with hyperparathyroidism). Poisoning can occur with regular consumption of more than 2.5 g of calcium per day.
The main manifestations of excess calcium:
suppression of excitability of skeletal muscles and nerve fibers;
Decreased tone of smooth muscles;
hypercalcemia, increased calcium in the blood plasma;
Increased acidity of gastric juice, hyperacid gastritis, stomach ulcers;
Calcinosis, calcium deposition in organs and tissues (in the skin and subcutaneous tissue; connective tissue along the fascia, tendons, aponeuroses; muscles; walls of blood vessels; nerves);
bradycardia, angina;
gout, calcification of tuberculous foci, etc.;
An increase in the content of calcium salts in the urine;
nephrocalcinosis, kidney stone disease;
increase in blood clotting;
Increased risk of developing dysfunction of the thyroid and parathyroid glands, autoimmune thyroiditis;
Displacement of phosphorus, magnesium, zinc, iron from the body.
The most easily digestible is the calcium of milk and dairy products (with the exception of butter) in combination with vegetables and fruits. To meet the daily requirement, 0.5 l of milk or 100 g of cheese is enough. By the way, milk is not only an excellent source of calcium, but also promotes the absorption of calcium contained in other products.
Very important for the absorption of calcium is the presence of vitamin D in the diet, which neutralizes the action of various anti-calcifying substances and is a regulator of phosphorus-calcium metabolism.
chemical biological organogen oxygen
CONCLUSION
All living organisms have close contact with the environment. Life requires constant metabolism in the body. The intake of chemical elements in the body is facilitated by food and consumed water. The body consists of 60% water, 34% organic matter and 6% inorganic. The main components of organic substances are C, H, O. They also include N, P, S. The composition of inorganic substances necessarily contains 22 chemical elements (see table No. 1). For example, if a person weighs 70 kg, then it contains (in grams): Ca - 1700, K - 250, Na -70, Mg - 42, Fe - 5, Zn - 3. Metals account for 2.1 kg . The content in the body of elements of IIIA-VIA groups, covalently bound to the organic part of the molecules, decreases with an increase in the charge of the nucleus of atoms of this group of the periodic system of D. I. Mendeleev.
The current state of knowledge about the biological role of elements can be characterized as a superficial touch on this problem. A lot of factual data has been accumulated on the content of elements in various components of the biosphere, the body's responses to their deficiency and excess. Maps of biogeochemical zoning and biogeochemical provinces were compiled. But there is no general theory considering the function, the mechanism of action and the role of microelements in the biosphere
Ordinary trace elements, when their concentration in the body exceeds the biotic concentration, exhibit a toxic effect on the body. Toxic elements at very low concentrations do not have a harmful effect on plants and animals. For example, arsenic at microconcentrations has a biostimulating effect. Therefore, there are no toxic elements, but there are toxic doses. Thus, small doses of an element are medicine, large doses are poison. “Everything is poison, and nothing is devoid of poison, only one dose makes the poison invisible” - Paracelsus. It is appropriate to recall the words of the Tajik poet Rudaki: “What is reputed to be a drug today will become poison tomorrow.”
BIBLIOGRAPHY
1. Avtsyn A.P., Zhavoronkov A.A. and other Trace elements of man. -M.: Medicine, 1991. -496 p.
Ershov Yu.A., Popkov V.A., Berlyand A.S., Knizhnik A.Z., Mikhailichenko N.I. General chemistry. Biophysical chemistry. Chemistry of biogenic elements. -M.: Higher School, 1993. -560 p.
Ershov Yu.A., Pletneva T.V. Mechanisms of toxic action of inorganic compounds. -M.: Medicine, 1989. -272 p.
Zholnin A.V. complex compounds. Chelyabinsk: ChGMA, 2000. -28 p.
Bingham FG, Costa M., Eichenberg E. et al. Some questions of the toxicity of metal ions. -M.: Medicine, 1993. -368 p.
Fremantle M. Chemistry in action. -M.: Mir, 1991. v.2, 620 p.
Hughes M. Inorganic chemistry of biological processes. -M.: Mir, 1983. - 416 p.
Zholnin A.V., Arbuzina R.F., Konstanz E.V., Rylnikova G.I. Methodical manual for laboratory studies in general chemistry. part II. -Chelyabinsk: ChGMA, 1993 -176 p.
Enterosorption. /Under. ed. prof. ON THE. Belyakova. Center for sorption technology. - L., 1991. - 336 p.
We paid great attention to the role of metals. However, it must be borne in mind that some non-metals are also absolutely necessary for the functioning of the body.
Silicon
Silicon is also an essential trace element. This has been confirmed by a careful study of the nutrition of rats using various diets. Rats noticeably gained weight when sodium metasilicate (Na2(SiO)3 . 9H2O) was added to their diet (50mg per 100g). chickens and rats need silicon for the growth and development of the skeleton. The lack of silicon leads to a violation of the structure of bones and connective tissue. As it turned out, silicon is present in those areas of the bone where active calcification occurs, for example, in bone-forming cells, osteoblasts. With age, the concentration of silicon in cells decreases.
Little is known about the processes in which silicon is involved in living systems. There it is in the form of silicic acid and, probably, participates in the cross-linking of carbons. In humans, umbilical cord hyaluronic acid turned out to be the richest source of silicon. It contains 1.53 mg of free and 0.36 mg of bound silicon per gram.
Selenium
The lack of selenium causes the death of muscle cells and leads to muscle failure, in particular heart failure. The biochemical study of these conditions led to the discovery of the enzyme glutathione peroxidase, which destroys peroxides. A lack of selenium leads to a decrease in the concentration of this enzyme, which in turn causes lipid oxidation. The ability of selenium to protect against mercury poisoning is well known. Much less well known is the fact that there is a correlation between high dietary selenium and low cancer mortality. Selenium is included in the human diet in the amount of 55 110 mg per year, and the concentration of selenium in the blood is 0.09 0.29 µg/cm. When taken orally, selenium is concentrated in the liver and kidneys. Another example of the protective effect of selenium against intoxication with light metals is its ability to protect against poisoning by cadmium compounds. It turned out that, as in the case of mercury, selenium forces these toxic ions to bind to ionic active centers, to those that are not affected by their toxic effect.
Arsenic
Despite the well-known toxic effects of arsenic and its compounds, there is reliable evidence that a lack of arsenic leads to a decrease in fertility and growth inhibition, and the addition of sodium arsenite to food has led to an increase in the growth rate in humans.
Chlorine and bromine
Halogen anions differ from all other ones in that they are simple and not oxo anions. Chlorine is extremely widespread, it is able to pass through the membrane and plays an important role in maintaining osmotic balance. Chlorine is present as hydrochloric acid in gastric juice. The concentration of hydrochloric acid in human gastric juice is 0.4-0.5%.
There are some doubts about the role of bromine as a trace element, although its sedative effect is reliably known.
Fluorine
Fluorine is absolutely necessary for normal growth, and its deficiency leads to anemia. Much attention has been paid to the metabolism of fluoride in connection with the problem of dental caries, since fluoride protects teeth from caries.
Dental caries has been studied in sufficient detail. It begins with the formation of a stain on the surface of the tooth. Acids produced by bacteria dissolve tooth enamel under the stain, but, oddly enough, not from its surface. Often the top surface remains intact until the areas below it are completely destroyed. It is assumed that at this stage, the fluoride ion can facilitate the formation of appatite. Thus, reminelization of the damage that has begun is performed.
Fluoride is used to prevent damage to tooth enamel. Fluorides can be added to toothpaste or applied directly to teeth. The concentration of fluoride required to prevent caries in drinking water is about 1 mg/l, but the level of consumption depends not only on this. The use of high concentrations of fluorides (more than 8 mg / l) can adversely affect the delicate equilibrium processes of bone tissue formation. Excessive absorption of fluoride leads to fluorosis. Fluorosis leads to disturbances in the functioning of the thyroid gland, growth inhibition and kidney damage. Prolonged exposure to fluoride on the body leads to mineralization of the body. As a result, the bones are deformed, which can even grow together, and ligaments calcify.
Iodine
The main physiological role of iodine is participation in the metabolism of the thyroid gland and its inherent hormones. The ability of the thyroid gland to accumulate iodine is also inherent in the salivary and mammary glands. As well as some other organs. At present, however, it is believed that iodine plays a leading role only in the life of the thyroid gland.
Lack of iodine leads to characteristic symptoms: weakness, yellowing of the skin, feeling cold and dry. Treatment with thyroid hormones or iodine eliminates these symptoms. A lack of thyroid hormones can lead to an enlarged thyroid gland. In rare cases (burdening in the body of various compounds that interfere with the absorption of iodine, such as thiocyanate or the antithyroid agent goitrin, found in various types of cabbage), a goiter is formed. Lack of iodine has a particularly strong effect on the health of children; they lag behind in physical and mental development. An iodine deficient diet during pregnancy leads to the birth of hypothyroid children (cretins).
Excess thyroid hormone leads to exhaustion, nervousness, tremors, weight loss, and excessive sweating. This is associated with an increase in peroxidase activity and, consequently, with an increase in thyroglobulin iodination. An excess of hormones can be the result of a thyroid tumor. In the treatment, radioactive isotopes of iodine are used, which are easily absorbed by the cells of the thyroid gland.
Non-metals-organogens (O, C, H, N, P, S), as well as halogens, form the main biogeochemical cycles of nature. Simple inorganic compounds of these non-metals (H2 O, CO, CO2, NH3, NO2, SO2, H2 SO4, H3 PO4, etc.) are waste products of humans and animals. Fragments of these cycles are the transformation of some compounds of organogens into others with the participation of various types of bacteria, for example, in the soil, the transitions H2 → H2 O, CO → CO2, N2 → NH3, NH3 → NO2, NO3 - → NO2, NO3 - → NH3, S → S2 O3 2- → SO2 → SO4 2- . Arranging organogenic elements in descending order of their content (in wt.%), we get: O > C > H > N > P > S. According to this series, and not the traditional appeal to the groups of the Periodic System, we will consider the properties of non-metals-organogens.
4.1. Oxygen
Oxygen is the element that sustains life on Earth. The atmosphere contains about 20.8% oxygen. The steel components of air are the predominant nitrogen N2 (78.08%), as well as Ar (0.93%), CO2 (0.02 - 0.04%), Ne (1.92 10-3%), He (5.24 10-4%), Kr (1.14 10-4%), H2 (5.0 10-5%), Xe (8.7 10-6%). It should be noted that the content of
Oxygen in the atmosphere remains surprisingly constant, despite all the oxidative processes of respiration and combustion occurring on Earth. The main factor maintaining the constancy of the oxygen content in the Earth's atmosphere is photosynthesis, and the main contribution is made not by terrestrial green plants, but by plankton and algae of the world's oceans, which account for about 80% of the released oxygen. In general, life on Earth is possible only in a fairly narrow range of oxygen content in the atmosphere: from 13 to 30%. At an oxygen content of less than 13%, aerobic creatures (i.e., using oxygen in their life) die, and at a higher than 30%, the oxidation and combustion processes are so intense that even a wet rag can catch fire, and the first lightning strike burn everything on earth to ashes.
For numerous living organisms, an important part of metabolism (metabolism) is the respiratory cycle, which leads to the rapid formation of many substances. So, in the exhaled air, in addition to CO2, small amounts contain hydrocarbons, alcohols, ammonia, formic acid HCOOH, acetic acid CH3 COOH, formaldehyde HCHO, sometimes acetone (CH3) 2 CO. When a person breathes at a height of 10 km in rarefied air, due to a lack of oxygen in it, the content of ammonia, amines, phenol, acetone sharply increases in the exhaled mixture of gases, and even hydrogen sulfide appears.
Without oxygen, numerous and extremely important life processes, especially respiration, are impossible. Only a few plants and the simplest animals can do without oxygen and therefore are called anaerobic. In living organisms, oxygen is spent on the oxidation of various substances, and the main process is the reaction of oxygen with hydrogen atoms to form water, as a result of which a significant amount of energy is released. Aerobic organisms also obtain energy by oxidizing nutrients in cells and tissues to CO2, H2O,
(NH2)2CO.
During normal respiration, molecular oxygen entering the lungs is reduced to water: O2 + 4H+ + 4e 2H2 O, and H+ ions together with electrons are released when the body's organic substrate loses H atoms: [substrate (4H)] → 4H + substrate → 4H + + 4e + substrate. In pathology, incomplete recovery occurs: O2 + 2H + + 2e H2 O2 or O2 + e O2 -. This radical is called
is superoxide radical (SOP). It can be useful when it destroys cells that grow out of control, but it can also be very toxic when it destroys the cell membranes of healthy cells that the body needs. In addition, the harmful effect of COP is that it inactivates enzymes, depolymerizes polysaccharides, and causes single breaks in the DNA structure. Any substances of the organism with a suitable potential can take part in the intermediate slow one-electron reduction of O2 to COP. In this case, H2 O2 is formed, which in the next stage of one-electron reduction gives a highly reactive hydroxide radical OH, which quickly oxidizes any cell substance. The hydrophobic O2 molecule easily passes into the cell through hydrophobic lipid membranes and begins to oxidize organic substances to O2 - and OH radicals. These polar radicals are "locked" in the cell, as they cannot get back through the cell membranes. To repay their "aggressiveness" are special enzymes superoxide dismutase, catalase and peroxidase. In addition, there are low-molecular substances - antioxidants (for example, vitamins A and E), which non-enzymatically neutralize these dangerous particles. COP, for example, is also actively bound by Fe(3+) ions. Sometimes the isolation of COP is useful, for example, antitumor antibiotics (bleomycin) form a complex with Mn + metal ions, which catalyze the rapid reduction of O2 to COP, which destroys DNA in the tumor.
Allotropic modification of oxygen - ozone O3. In the atmosphere, ozone is formed by the photochemical reaction O2 + O → hν → O3, and atomic active oxygen is also formed due to the reaction NO + O2 → NO2 + O. The useful effect of ozone in the atmosphere lies in the fact that ozone not only absorbs the biologically active and thus dangerous part of the ultraviolet radiation of the Sun, but also takes part in the formation of the thermal regime of the surface of our planet. It traps the heat leaving the Earth in those spectral intervals (“transparency windows”) where CO2 and H2O absorb this heat poorly. Ozone is highly toxic to humans. Its maximum permissible concentration (MAC) in the air is 0.5 mg/m3. Ozone changes the structure of the lungs, inhibiting their functions, thereby reducing resistance to respiratory diseases. Being the strongest oxidizing agent (on the 2nd place after fluorine), ozone intensively oxidizes amino acids and enzymes containing sulfur.
(cysteine HSCH2 CH(NH2 )COOH, methionine CH3 SCH2 CH2 CH(NH2 )COOH, also tryptophan C8 H6 NCH2 CH(NH2 )COOH, histidine C3 H3 N2 CH(NH2 )COOH, tyrosine HOC6 H4 CH2 CH(NH2 )COOH .
Thus, molecular oxygen O2 is not toxic to living organisms, unlike other forms: ozone O3, excited O2 molecule, OH radical, atomic O, HO2 radical, COP O2 - .
4.2. Carbon
Carbon in terms of its content in the body (21%) and importance for living organisms is one of the most important organogens. Since this manual is devoted specifically to bioinorganic chemistry, we will not touch on organic compounds of wildlife, which is the subject of study of bioorganic chemistry. The simplest carbon compounds, such as free carbon in the form of soot and its oxide CO, are toxic to humans. Prolonged contact with soot or coal dust causes skin cancer ("chimney sweep disease", as it was previously called). The smallest dust of coal causes a change in the structure of the lungs, and therefore disrupts their functions. Extremely toxic is CO oxide, the toxic effect of which is caused by the fact that CO binds to blood hemoglobin ~ 10 3 times easier than oxygen, and therefore causes suffocation.
Carbon dioxide CO2 is present in the biosphere as a product of respiration and oxidation products. The annual emission of CO and CO2 into the atmosphere is 2,108 and 9,109 tons
respectively (for comparison, the release of hydrocarbons is 8,107 tons per year). CO2 is slightly soluble in water, so its presence in biofluids is negligible. However, an important enzymatic reaction CO2 + Cl- + H2 O → HCO3 - + H + + Cl- takes place in the stomach, as a result of which proteins are broken down in an acidic environment. Note that without enzymes, this reaction proceeds in the opposite direction.
4.3. Hydrogen
Hydrogen is present in nature in the form of water and numerous organic compounds (Table 1). Water is the main living environment of an organism. It dissolves most of the substances involved in metabolic processes. The water content in the organs and tissues of the body is quite high:
Table 3
tissue, organ, bio |
||
liquid |
||
Brain |
||
Spinal cord |
||
Gastric juice |
||
blood plasma |
||
tear fluid |
The physiological environment for humans is a 0.9% NaCl solution. Water has a high specific heat and, due to slow heat exchange with the environment, maintains a constant body temperature. When overheated, water evaporates from the surface of the body. Due to the high heat of vaporization of water, this process is accompanied by energy costs, and the body temperature drops. In the aquatic environment, due to buffer systems (carbonate, phosphate and hemoglobin), the acid-base balance of the body is maintained.
As can be seen from Table 3, the average pH of the body corresponds to the pH of saline and ranges from 6.8 to 7.4. However, individual organs and tissues may have pH values that are very different from physiological. So, in the stomach, acidity is high, and the pH is 0.9 - 1.1. This is necessary so that under the action of the pepsin enzyme, which is active in an acidic environment, the peptides of the protein component of the food are cleaved. Bile has a slightly alkaline reaction (pH 7.5 - 8.5), which is necessary for alkaline hydrolysis of fats.
4.4. Nitrogen
Nitrogen is present in living organisms in the form of a variety of organic compounds: amino acids, peptides, purine bases, etc., as well as in the form of free N2 coming from the inhaled air. The nitrogen cycle in nature is closely related
calls the geosphere and biosphere, confirming their unity. There are many bacteria that can easily convert one nitrogen compound into another, and with a change in the oxidation state of nitrogen. So, for example, if in technology the synthesis of ammonia is carried out under harsh conditions, then in the biosphere the binding of atmospheric N 2 and its conversion into NH3 proceeds in an easier enzymatic way with the participation of nitrogenase:
N2 + 16ATP + 8e + 8H+ 2NH3 + 16ADP + 16[P in inorganic phosphates] + H2, where ATP and ADP are adenosine triphosphate and adenosine diphosphate, respectively, and it is believed that the original ATP is in the form of a complex with Mg. The microorganisms involved in this reaction are present in the root nodules of some plants, as well as
V blue-green algae. The enzyme nitrogenase, which contains proteins, as well as Mo and Fe, is active only under anaerobic conditions. Studies have shown that when restoring
When N2 is reduced to NH3, NH=NH and NH2 -NH2 are not formed. This suggests that there are probably 2 active centers on the enzyme: on one, the nitrogen molecule is split, and on the other, the H atom is coordinated. Other mutual transformations also occur in nature.
nitrogen compounds: nitrification or oxidation of NH3 to NO2, as well as the reduction of nitrate ion from fertilizers under the action of plant enzymes or anaerobic bacteria
riy to NO2 or even to NH3. Inorganic nitrogen compounds are usually toxic
ny, with the exception of a simple substance N2 and small amounts of N2 O. Every year, ~ 5 107 tons of various nitrogen oxides NOx and ~ 107 tons of other nitrogen compounds are emitted into the atmosphere. The NO molecule, according to modern concepts, despite the seeming
the difficulty of its formation from simple substances is present in the atmosphere in huge quantities. It is believed that up to 7,107 tons of atmospheric N2 per year react with O2 as a result of high-temperature processes such as industrial combustion and transport. It is shown that nitrogen oxides, like ozone, are able to interact with the products of incomplete combustion of fuel with the formation of high-current
sine peroxonitrates RCOOONO2 . Under the action of solar radiation in the upper atmosphere, photochemical reactions occur with the participation of NOx, which are catalyzed by the solid dust particles contained there. NO in the human body
is formed in an amount of ~100 mg per day from arginine according to the reaction: NH \u003d C (NH2) - NH (CH2) 3 CH (NH2) COOH + 3 / 2O2 → NO-synthetase enzyme → H2 NCONH (CH2) 3 CH (NH2) COOH + 2NO + H2 O. It is known that NO molecules are able to penetrate into the cells of the walls of blood vessels and regulate blood flow; in addition, NO controls insulin secretion, renal filtration, reparative processes
V tissues, etc. Thus, NO is a two-faced molecule that exhibits both toxic and undoubtedly beneficial effects. For example, when taking such a common cardiological drug as nitroglycerin, it is hydrolyzed with the formation nitrate ion, which is reduced by hemoglobin iron to NO, and then it is NO that causes relaxation of vascular smooth muscles. Other nitrogen oxides
NO2 , N2 O3 are highly toxic and can cause suffocation and pulmonary edema. The nitrite ion NO2 - is especially toxic, because it oxidizes methemoglobin and disrupts the process of O2 transfer in the body. In addition, nitrite ion forms carcinogenic nitrosamine in the stomach. However, NaNO2 was previously used as a vasodilator for angina pectoris and cerebral vasospasm. Recently, because of its undoubted toxicity, NaNO2 was abandoned, replacing it with nitroglycerin or nitrosorbate.
that do not have these side effects. Inhalation of ammonia NH3 vapors in large quantities is harmful, since ammonia creates a strongly alkaline environment on the surface of the mucous membranes of the larynx and lungs, which causes irritation and swelling.
In addition, small NH3 molecules easily penetrate cell membranes and compete with many ligands in coordination with metal ions.
