A. Biologically important chemical elements. Inorganic compounds

There are 81 stable chemical elements in nature. The composition of living matter includes 15 elements, 8-10 more elements are found only in certain organisms. The diagram shows part Periodic table of elements, which contains all biologically important chemical elements, given their physical and chemical characteristics, as well as their content in living matter and the human body. The regularities of the structure of atoms that underlie the periodic system are discussed in detail in textbooks on chemistry.

Living organisms are almost 99% composed of four chemical elements: hydrogen (H), oxygen (O), carbon (C) and nitrogen (N). Hydrogen and oxygen are the constituent elements of water, which accounts for 60-70% of the cell mass (see). Along with carbon and nitrogen, these two elements are also the main constituents organic compounds participating in most life processes. Many biomolecules also contain sulfur (S) and phosphorus (P) atoms. The listed macronutrients are part of all living organisms.

Chemical elements belonging to the second biologically important group and in total constituting about 0.5% of a person's mass are present, with a few exceptions, in the form ions... This group includes alkali metals sodium (Na) and potassium (K), alkaline earth metals magnesium (Mg) and calcium (Ca). Halogen chlorine (Cl) is also always present in cells in the form of an anion. Other vital (essential) chemical elements are present in such small quantities that they are called trace elements... This group includes the transition metals iron (Fe), zinc (Zn), copper (Cu), cobalt (Co), and manganese (Mn). Some non-metals such as iodine (I) and selenium (Se) are also essential trace minerals.

Articles of the section "Periodic table of elements of D. I. Mendeleev":

A. Biologically important chemical elements

2012-2017. Visual biochemistry. Molecular biology. The structure and metabolism of carbohydrates.

The reference book in a visual form - in the form of color schemes - describes all biochemical processes. Biochemically important chemical compounds, their structure and properties, the main processes with their participation, as well as the mechanisms and biochemistry of the most important processes in living nature are considered. For students and teachers of chemical, biological and medical universities, biochemists, biologists, physicians, as well as anyone interested in life processes.

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The biological role of chemical elements in living organisms

1. Macro and microelements in the environment and the human body

The biological role of chemical elements in the human body is extremely diverse.

The main function of macronutrients is to build tissues, maintain a constant osmotic pressure, ionic and acid-base composition.

Microelements, being a part of enzymes, hormones, vitamins, biologically active substances as complexing agents or activators, are involved in metabolism, reproduction processes, tissue respiration, and neutralization of toxic substances. Microelements actively affect the processes of hematopoiesis, oxidation-reduction, vascular and tissue permeability. Macro and microelements - calcium, phosphorus, fluorine, iodine, aluminum, silicon - determine the formation of bone and dental tissues.

There is evidence that the content of some elements in the human body changes with age. Thus, the content of cadmium in the kidneys and molybdenum in the liver increases with old age. The maximum zinc content is observed during puberty, then it decreases and reaches a minimum in old age. The content of other trace elements, such as vanadium and chromium, also decreases with age.

A lot of diseases associated with a deficiency or excessive accumulation of various microelements have been identified. Fluoride deficiency causes dental caries, iodine deficiency - endemic goiter, excess molybdenum - endemic gout. Regularities of this kind are associated with the fact that the human body maintains a balance of optimal concentrations of biogenic elements - chemical homeostasis. Violation of this balance due to a lack or excess of an element can lead to various diseases.

In addition to the six main macronutrients - organogens - carbon, hydrogen, nitrogen, oxygen, sulfur and phosphorus, of which carbohydrates, fats, proteins and nucleic acids are composed, “inorganic” macronutrients - calcium, chlorine , magnesium, potassium, sodium - and trace elements - copper, fluorine, iodine, iron, molybdenum, zinc, and also, possibly (proven for animals), selenium, arsenic, chromium, nickel, silicon, tin, vanadium.

A deficiency in the diet of elements such as iron, copper, fluorine, zinc, iodine, calcium, phosphorus, magnesium and some others leads to serious consequences for human health.

However, it must be remembered that not only a deficiency, but also an excess of biogenic elements is harmful to the body, since this disrupts chemical homeostasis. For example, when an excess of manganese is supplied with food, the level of copper in the plasma increases (synergism of Mn and Cu), while in the kidneys it decreases (antagonism). An increase in the content of molybdenum in food leads to an increase in the amount of copper in the liver. An excess of zinc in food causes inhibition of the activity of iron-containing enzymes (antagonism of Zn and Fe).

Mineral components, which are vital in negligible amounts, become toxic at higher concentrations.

A number of elements (silver, mercury, lead, cadmium, etc.) are considered toxic, since their ingress into the body already in trace amounts leads to severe pathological phenomena. The chemical mechanism of the toxic effects of some trace elements will be discussed below.

Biogenic elements are widely used in agriculture. Adding small amounts of microelements to the soil - boron, copper, manganese, zinc, cobalt, molybdenum - dramatically increases the yield of many crops. It turns out that trace elements, by increasing the activity of enzymes in plants, promote the synthesis of proteins, vitamins, nucleic acids, sugars and starch. Some of the chemical elements have a positive effect on photosynthesis, accelerate the growth and development of plants, and the maturation of seeds. Trace elements are added to animal feed to increase their productivity.

Various elements and their compounds are widely used as medicines.

Thus, the study of the biological role of chemical elements, the elucidation of the relationship between the exchange of these elements and other biologically active substances - enzymes, hormones, vitamins contributes to the creation of new drugs and the development of optimal dosage regimens for both therapeutic and prophylactic purposes.

The basis for studying the properties of elements and, in particular, their biological role is the periodic law of D.I. Mendeleev. Physicochemical properties, and, consequently, their physiological and pathological role, are determined by the position of these elements in the periodic system of D.I. Mendeleev.

As a rule, with an increase in the charge of the atomic nucleus, the toxicity of the elements of this group increases and their content in the body decreases. The decrease in the content is obviously due to the fact that many elements of long periods are poorly assimilated by living organisms due to large atomic and ionic radii, high nuclear charge, complexity of electronic configurations, and low solubility of compounds. The body contains significant amounts of light elements.

Macronutrients include s-elements of the first (hydrogen), third (sodium, magnesium) and fourth (potassium, calcium) periods, as well as p-elements of the second (carbon, nitrogen, oxygen) and third (phosphorus, sulfur, chlorine) periods. They are all vital. Most of the remaining s- and p-elements of the first three periods (Li, B, Al, F) are physiologically active, s- and p-elements of large periods (n> 4) rarely act as irreplaceable. The exception is s-elements - potassium, calcium, iodine. Physiologically active include some s- and p-elements of the fourth and fifth periods - strontium, arsenic, selenium, bromine.

Among the d-elements, the elements of the fourth period are vitally necessary: manganese, iron, zinc, copper, cobalt. Recently, it has been established that the physiological role of some other d-elements of this period is also undoubted: titanium, chromium, vanadium.

d-Elements of the fifth and sixth periods, with the exception of molybdenum, do not show pronounced positive physiological activity. Molybdenum, on the other hand, is part of a number of redox enzymes (for example, xanthine oxide, aldehyde oxidase) and plays an important role in the course of biochemical processes.

Some f-elements (lanthanides and actinides) are found in trace amounts in the human body; the presence of many of them has not yet been established. As a rule, they are highly toxic, form stable compounds with complexones, polyphosphates, hydroxy acids, and other polydentate ligands. Therefore, their ingestion can change the course of many biochemical reactions. The similarity and difference in biological action is associated with the electronic structure of atoms and ions. Close values of atomic and ionic radii, ionization energies, coordination numbers, the tendency to form bonds with the same elements in bioligand molecules determines the effects of substitution of elements in biological systems. Such a substitution of ions can occur both with an increase (synergism) and with a suppression of the activity (antagonism) of the element being replaced.

2. General aspects of the toxicity of heavy metals for living organisms

A comprehensive study of the problems associated with assessing the state of the natural environment shows that it is very difficult to draw a clear line between natural and anthropogenic factors of changes in ecological systems. The last decades have convinced us of this. that human impact on nature causes it not only direct, easily identifiable damage, but also causes a number of new, often hidden processes that transform or destroy the environment. Natural and anthropogenic processes in the biosphere are in a complex relationship and interdependence. So, the course of chemical transformations leading to the formation of toxic substances is influenced by the climate, the state of the soil cover, water, air, the level of radioactivity, etc. Under the prevailing conditions in the study of processes chemical pollution ecosystems, the problem of finding natural, mainly due to natural factors, levels of the content of certain chemical elements or compounds arises. The solution to this problem is possible only on the basis of long-term systematic observations of the state of the components of the biosphere, the content of various substances in them, that is, on the basis of environmental monitoring.

Environmental pollution with heavy metals is directly related to the ecological and analytical monitoring of supertoxicants, since many of them show high toxicity already in trace amounts and are able to concentrate in living organisms.

The main sources of pollution of the environment with heavy metals can be divided into natural (natural) and artificial (anthropogenic). The natural sources include volcanic eruptions, dust storms, forest and steppe fires, sea salts raised by the wind, vegetation, etc. Natural sources of pollution are either systematic uniform or short-term spontaneous and, as a rule, have little effect on the overall level of pollution. The main and most dangerous sources of pollution of nature with heavy metals are anthropogenic.

In the process of studying the chemistry of metals and their biochemical cycles in the biosphere, a dual role is revealed that they play in physiology: on the one hand, most metals are necessary for the normal course of life; on the other hand, at high concentrations, they show high toxicity, that is, they have a harmful effect on the state and activity of living organisms. The borderline between the required and toxic concentrations of elements is rather vague, which complicates a reliable assessment of their impact on the environment. The amount at which some metals become really dangerous depends not only on the degree of their pollution of ecosystems, but also on the chemical characteristics of their biochemical cycle. Table 1 shows the series of molar toxicity of metals for different types living organisms.

Table 1. Representative sequence of molar toxicity of metals

For each type of organism, the order of the metals in the rows of the table from left to right reflects the increase in the molar amount of metal required for the manifestation of the toxic effect. The smallest molar value refers to the most toxic metal.

V.V. Kowalski, based on their importance for life, subdivided chemical elements into three groups:

Vital (irreplaceable) elements that are constantly contained in the body (are part of enzymes, hormones and vitamins): H, O, Ca, N, K, P, Na, S, Mg, Cl, C, I, Mn, Cu, Co, Fe, Mo, V. Their deficiency leads to disruption of the normal life of humans and animals.

Table 2. Characteristics of some metalloenzymes - bioinorganic complexes

Metalloenzyme	Central atom	Ligand environment	Concentration object	Enzyme action
Carbonic anhydrase		Amino acid residues	Erythrocytes	Catalyzes the reversible hydration of carbon dioxide: CO 2 + H 2 O-H 2 CO 3 -H + + HCO 3
Carboskepeptidase		Amino acid residues	Pancreas, liver, intestines	Catalyzes the digestion of proteins, participates in the hydrolysis of the peptide bond: R 1 CO-NH-R 2 + H 2 O-R 1 -COOH + R 2 NH 2
Catalase		Amino acid residues, histidine, tyrosine		Catalyzes the decomposition reaction of hydrogen peroxide: 2H 2 O 2 = 2H 2 O + O 2
Peroxidase			Cloth, blood	Oxidation of substrates (RH 2) hydrogen peroxide: RH 2 + H 2 O 2 = R + 2H 2 O
Oxy reductase		Amino acid residues	Heart, liver, kidneys	Catalyzes oxidation with molecular oxygen: 2H 2 R + O 2 = 2R + 2H 2 O
Pyruvate carboxylase		Tissue proteins	Liver, thyroid gland	Strengthens the action of hormones. Catalyzes the process of carboxylation with pyruvic acid
Aldehyde oxidase		Tissue proteins		Participates in the oxidation of aldehydes
Ribonucleotide reductase		Tissue proteins		Participates in the biosynthesis of ribonucleic acids

impurity elements constantly contained in the body: Ga, Sb, Sr, Br, F, B, Be, Li, Si, An, Cs, Al, Ba, Ge, As, Rb, Pb, Ra, Bi, Cd, Cr, Ni, Ti, Ag, Th, Hg, U, Se. Their biological role is little understood or unknown.

impurity elements found in the body Sc, Tl, In, La, Pr, Sm, W, Re, Tb, etc. Data on the amount and biological role have not been clarified.

The table shows the characteristics of a number of metalloenzymes, which include such vital metals as Zn, Fe, Cu, Mn, Mo.

Depending on the behavior in living systems, metals can be divided into 5 types:

Necessary elements, in the absence of which functional disorders occur in the body;

Stimulants (both necessary and unnecessary metals for the body can act as stimulants);

inert elements that are harmless at certain concentrations that do not have any effect on the body (for example, inert metals used as surgical implants):

therapeutic agents used in medicine;

toxic elements, at high concentrations leading to irreversible functional disorders, death of the body.

Depending on the concentration and contact time, the metal can act in one of the indicated types.

Figure 1 shows a diagram of the dependence of the state of the body on the concentration of metal ions. The solid curve in the diagram describes the immediate positive response, the optimal level and the transition of a positive effect to a negative one after the concentration of the required element passes the maximum. At high concentrations, the required metal becomes toxic.

The dashed curve shows the biological response to a metal toxic to the body that does not have the effect of a necessary or stimulating element. This curve comes with some delay, which indicates the ability of a living organism to "not react" to small amounts of a toxic substance (threshold concentration).

It follows from the diagram that the required elements become toxic in excess quantities. The body of animals and humans maintains the concentration of elements in the optimal range through a complex of physiological processes called homeostasis. The concentration of all necessary metals, without exception, is under the strict control of homeostasis.

Fig.1 Biological response depending on the concentration of the metal. (The relative position of the two curves relative to the concentration scale is conditional)

metal toxicity ion poisoning

Of particular interest is the content of chemical elements in the human body. Human organs in different ways concentrate in themselves various chemical elements, that is, macro- and microelements are unevenly distributed between different organs and tissues. Most of the microelements (content in the body is in the range of 10 -3 -10 -5%) accumulates in the liver, bone and muscle tissues. These fabrics are the main depot for many metals.

Elements can exhibit specific affinity for certain organs and are contained in them in high concentrations. It is known that zinc is concentrated in the pancreas, iodine in the thyroid gland, vanadium, along with aluminum and arsenic, accumulates in hair and nails, cadmium, mercury, molybdenum - in the kidneys, tin in the intestinal tissues, strontium - in the prostate gland, bone tissue , manganese in the pituitary gland, etc. In the body, trace elements can be both in a bound state and in the form of free ionic forms. It was found that aluminum, copper and titanium in the brain tissues are in the form of complexes with proteins, while manganese is in the ionic form.

In response to the intake of excessive concentrations of elements into the body, the living organism is able to limit or even eliminate the toxic effect arising from this due to the presence of certain detoxification mechanisms. The specific mechanisms of detoxification in relation to metal ions are currently not well understood. Many metals in the body can be converted to less harmful forms in the following ways:

the formation of insoluble complexes in the intestinal tract;

transport of metal with blood to other tissues, where it can be immobilized (as, for example, Pb +2 in bones);

Transformation by the liver and kidneys into a less toxic form.

So, in response to the action of toxic ions of lead, mercury, cadmium, etc., the human liver and kidneys increase the synthesis of metallothionins - proteins of low molecular weight, in which about 1/3 of the amino acid residues is cysteine. The high content and specific arrangement of sulfhydryl SH-groups provide the possibility of strong binding of metal ions.

The mechanisms of metal toxicity are generally well known, but it is very difficult to find them for any particular metal. One of these mechanisms is the concentration between necessary and toxic metals for the possession of binding sites in proteins, since metal ions stabilize and activate many proteins, being part of many enzyme systems. In addition, many protein macromolecules have free sulfhydryl groups capable of interacting with toxic metal ions such as cadmium, lead, and mercury, resulting in toxic effects. However, it has not been precisely established which macromolecules harm a living organism in this case. The manifestation of the toxicity of metal ions in various organs and tissues is not always associated with the level of their accumulation - there is no guarantee that the greatest damage occurs in that part of the body where the concentration of this metal is higher. Thus, lead (II) ions, being immobilized in bones by more than 90% of the total amount in the body, exhibit toxicity due to 10% distributed in other tissues of the body. The immobilization of lead ions in the bones can be considered a detoxification process.

The toxicity of a metal ion is usually not related to its need for the body. However, for toxicity and necessity, there is one thing in common: as a rule, there is a relationship between metal ions from each other, just like between metal and non-metal ions, in the overall contribution to their effectiveness. For example, cadmium toxicity is more pronounced in a system with zinc deficiency, and lead toxicity is aggravated by calcium deficiency. Similarly, the adsorption of iron from vegetable food is suppressed by the complexing ligands present in it, and an excess of zinc ions can inhibit the adsorption of copper, etc.

Determination of the mechanisms of toxicity of metal ions is often complicated by the existence of various ways of their penetration into a living organism. Metals can enter with food, water, be absorbed through the skin, penetrate by inhalation, etc. Dust absorption is the main route of penetration in industrial pollution. As a result of inhalation, most metals are deposited in the lungs and only then spread to other organs. But the most common route for toxic metals to enter the body is through food and water.

Bibliographic list

1. Karapetyants M.Kh., Drakin S.I. General and inorganic chemistry. - M .: Chemistry, 1993 .-- 590 p.

2. Akhmetov N.S. General and inorganic chemistry. Textbook for universities. - M .: Higher. shk., 2001 .-- 679 p.

3. Ugai Ya.A. General and inorganic chemistry. - M .: Higher. shk., 1997 .-- 527 p.

4. Drozdov D.A., Zlomanov V.P., Mazo G.N., Spiridonov F.M. Inorganic chemistry. In 3 volumes. T. Chemistry of intransitive elements. / Ed. Yu.D. Tretyakov - Moscow: Ed. "Academy", 2004, 368s.

5. Tamm IE, Tretyakov Yu.D. Inorganic chemistry: In 3 volumes, Vol. 1. Physical and chemical foundations of inorganic chemistry. Textbook for university students / Ed. Yu.D. Tretyakov. - M .: Ed. "Academy", 2004, 240s.

6. Korzhukov N.G. General and inorganic chemistry. Textbook. Benefit. / Edited by V.I. Delyana-M .: Ed. MISIS: INFRA-M, 2004, 512s.

7. Ershov Yu.A., Popkov V.A., Berlyand A.S., Knizhnik A.Z. General chemistry. Biophysical chemistry. Chemistry of biogenic elements. Textbook for universities. / Ed. Yu.A. Ershova. 3rd ed., - M .: Integral-Pres, 2007 .-- 728 p.

8. Glinka N.L. General chemistry. Tutorial for universities. Ed. 30th revised / Ed. A.I. Ermakova. - M .: Integral-Press, 2007, - 728 p.

9. Chernykh, M.M. Ovcharenko. Heavy metals and radionuclides in biogeocinosis. - M .: Agroconsult, 2004.

10. N.V. Gusakov. Environmental chemistry. - Rostov-on-Don, Phoenix, 2004.

11. Baletskaya L.G. Inorganic chemistry. - Rostov-on-Don, Phoenix, 2005.

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13. Korovin N.V. General chemistry. - M .: Higher. shk., 1998 .-- 558 p.

14. Petrova V.V. and other Review of the properties of chemical elements and their compounds. Textbook for the course "Chemistry in Microelectronics". - Moscow: MIET Publishing House, 1993 .-- 108 p.

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Signs that distinguish living matter from non-living matter:

the ability to reproduce and transfer hereditary information to the next generation;
metabolism and energy;
excitability;
adaptation to specific living conditions;
building material - biopolymers (the most important of them are proteins and nucleic acids);
specialization from molecules to organs and a high degree of their organization;
height;
aging;
death.

Organizational levels of living matter:

molecular,
cellular,
tissue,
organ,
organismic,
population-specific,
biogeocenotic,
biosphere.

Diversity of life

Nuclear-free cells were the first to appear on our planet. Most scientists accept that nuclear organisms appeared as a result of the symbiosis of ancient archaebacteria with blue-green algae and oxidizing bacteria (the theory of symbiogenesis).

Cytology

Cytology- science about cage... Studies the structure and function of cells in unicellular and multicellular organisms. The cell is an elementary unit of the structure, functioning, growth and development of all living things. Therefore, the processes and patterns characteristic of cytology underlie the processes studied by many other sciences (anatomy, genetics, embryology, biochemistry, etc.).

Cell chemical elements

Chemical element- a certain kind of atoms with the same positive nuclear charge. About 80 chemical elements are found in the cells. They can be divided into four groups:
Group 1 - carbon, hydrogen, oxygen, nitrogen (98% of the cell content),
Group 2 - potassium, sodium, calcium, magnesium, sulfur, phosphorus, chlorine, iron (1.9%),
Group 3 - zinc, copper, fluorine, iodine, cobalt, molybdenum, etc. (less than 0.01%),
Group 4 - gold, uranium, radium, etc. (less than 0.00001%).

The elements of the first and second groups in most textbooks are called macronutrients, elements of the third group - microelements, elements of the fourth group - ultramicroelements... For macro- and microelements, the processes and functions in which they participate have been clarified. For the majority of ultramicroelements, no biological role has been identified.

Chemical element	Substances in which the chemical element is contained	Processes in which a chemical element is involved
Carbon, hydrogen, oxygen, nitrogen	Proteins, nucleic acids, lipids, carbohydrates and other organic substances	Synthesis of organic substances and the whole complex of functions carried out by these organic substances
Potassium, sodium	Na + and K +	Ensuring the function of membranes, in particular, maintaining the electrical potential of the cell membrane, the operation of the Na + / Ka + pump, conduction of nerve impulses, anionic, cationic and osmotic balances
Calcium	Ca +2	Participation in the process of blood clotting
	Calcium Phosphate, Calcium Carbonate	Bone tissue, tooth enamel, shells of molluscs
	Calcium pectate	Formation of the median lamina and cell wall in plants
Magnesium	Chlorophyll	Photosynthesis
Sulfur	Protein	Formation of the spatial structure of the protein due to the formation of disulfide bridges
Phosphorus	Nucleic acids, ATP	Nucleic acid synthesis
Chlorine	Cl -	Maintaining the electrical potential of the cell membrane, the work of the Na + / Ka + pump, conduction of nerve impulses, anionic, cationic and osmotic balances
Chlorine	HCl	Activation of digestive enzymes of gastric juice
Iron	Hemoglobin	Oxygen transport
Iron	Cytochromes	Transfer of electrons during photosynthesis and respiration
Manganese	Decarboxylase, dehydrogenase	Oxidation of fatty acids, participation in the processes of respiration and photosynthesis
Copper	Hemocyanin	Oxygen transport in some invertebrates
Copper	Tyrosinase	Melanin formation
Cobalt	Vitamin B 12	Formation of red blood cells
Zinc	Alcohol dehydrogenase	Anaerobic respiration in plants
Zinc	Carbonic anhydrase	CO 2 transport in vertebrates
Fluorine	Calcium fluoride	Bone tissue, tooth enamel
Iodine	Thyroxine	Regulation of basal metabolism
Molybdenum	Nitrogenase	Nitrogen fixation

Atoms of chemical elements in living organisms form inorganic(water, salt) and organic compounds(proteins, nucleic acids, lipids, carbohydrates). At the atomic level, there are no differences between living and inanimate matter; differences will appear at the next, higher, levels of organization of living matter.

Water

Water- the most common inorganic compound. The water content ranges from 10% (tooth enamel) to 90% of the cell mass (developing embryo). Life is impossible without water biological significance water is determined by its chemical and physical properties.

The water molecule has an angular shape: hydrogen atoms in relation to oxygen form an angle equal to 104.5 °. The part of the molecule where hydrogen is located is positively charged, the part where oxygen is located is negatively charged, and therefore the water molecule is a dipole. Hydrogen bonds are formed between water dipoles. Physical properties of water: transparent, maximum density at 4 ° С, high heat capacity, practically does not compress; pure water poorly conducts heat and electricity, freezes at 0 ° C, boils at 100 ° C, etc. Chemical properties of water: good solvent, forms hydrates, enters into hydrolytic decomposition reactions, interacts with many oxides, etc. In relation to the ability to dissolve in water, there are: hydrophilic substances- well soluble, hydrophobic substances- practically insoluble in water.

Biological significance of water:

is the basis of the internal and intracellular environment,
ensures the maintenance of the spatial structure,
provides transport of substances,
hydrates polar molecules,
serves as a solvent and diffusion medium,
participates in the reactions of photosynthesis and hydrolysis,
helps to cool the body,
is a habitat for many organisms,
promotes migration and spread of seeds, fruits, larval stages,
is the environment in which fertilization takes place,
in plants provides transpiration and germination of seeds,
promotes an even distribution of heat in the body and many others. dr.

Other inorganic compounds of the cell

Other inorganic compounds are mainly represented by salts, which can be contained either in dissolved form (dissociated into cations and anions) or solid. Cations K +, Na +, Ca 2+, Mg 2+ (see table above) and anions HPO 4 2—, Cl -, HCO 3 -, which provide the buffer properties of the cell, are of great importance for the vital activity of the cell. Buffering- the ability to maintain pH at a certain level (pH is the decimal logarithm of the value inverse to the concentration of hydrogen ions). A pH value of 7.0 corresponds to a neutral solution, below 7.0 to an acidic solution, above 7.0 to an alkaline solution. A slightly alkaline environment is characteristic of cells and tissues. The phosphate (1) and bicarbonate (2) buffer systems are responsible for maintaining this weakly alkaline reaction.