Chemical elements and their biological role. Biological role of chemical elements in living organisms

Table 4.1

Function of macroelements in the body

Elements	Function	Flaw
Phosphorus	Participates in the construction of all cells of the body, in all metabolic processes, is very important for brain function, and participates in the formation of hormones.	Chronic fatigue, decreased attention. Immunodeficiency states. Decreased resistance to infections. Dystrophic changes in the myocardium. Osteoporosis.
Calcium	Formation of bone tissue, mineralization of teeth. Participation in blood clotting processes. Regulation of cell membrane permeability. Regulation of nerve conduction processes and muscle contractions. Maintaining stable cardiac activity. Activator of enzymes and hormones.	General weakness, increased fatigue. Pain, muscle cramps. Disorders of growth processes. Skeletal decalcification, osteoporosis, skeletal deformity. Immunity disorders. Decreased blood clotting, bleeding.
Magnesium	Participation in metabolic processes, interaction with potassium, sodium, calcium. Activator for many enzymatic reactions. Regulation of neuromuscular conduction, smooth muscle tone	Irritability, headaches, swings blood pressure, heartbeat.
Potassium	Helps produce almost all enzymes. Responsible for cardiac conduction and the state of the cardiovascular system as a whole. Formation electric potential by exchange with sodium ions (“ potassium-sodium pump»)	Cardiac arrhythmias, drowsiness, muscle weakness, nausea, urinary retention, decreased blood pressure.
Sodium	Provides acid-base balance. Helps tissues retain water. Formation of electrical potential by exchange with potassium ions (“potassium-sodium pump”)	Weight loss, weakness, hair loss, intestinal disorders, muscle spasms
Iron	Participates in the production of hemoglobin and respiratory enzymes. Stimulates hematopoiesis.	Iron deficiency anemia and hypoxia. Headaches, memory loss. Slowing down of mental and physical development in children. Cardiopalmus. Immune suppression. Increased risk of developing infectious and tumor diseases.

Table 4. 1 (end)

Function of microelements and ultramicroelements in the human body

Elements	Function	Flaw
Iodine	Playing important role in the formation of the thyroid hormone - thyroxine.	The functions of the thyroid gland are disrupted, and with iodine deficiency, its structure also changes - up to the development of goiter.
Chromium	Controls the processing of sugars and other carbohydrates, insulin metabolism.	Increased blood sugar, impaired glucose absorption, and with prolonged deficiency, diabetes can develop.
Copper	Participates in the synthesis of red blood cells, collagen (responsible for skin elasticity), and renewal of skin cells. Promotes proper absorption of iron.	Anemia, impaired pigmentation of hair and skin, temperature below normal, mental disorders.
Selenium	Slows down the aging process, strengthens the immune system. It is a natural antioxidant - protects cells from cancer.	Decreased immunity, deterioration of heart function
Zinc	Helps pancreatic cells produce insulin. Participates in fat, protein and vitamin metabolism, the synthesis of a number of hormones. Stimulates reproductive function in men, general immunity, resistance to infections.	Delayed psychomotor development in children, baldness, dermatitis, decreased immunity and reproductive function, irritability, depression.
Manganese	Participates in oxidative processes, fatty acid metabolism and controls cholesterol levels.	Cholesterol metabolism disorders, vascular atherosclerosis.
Molybdenum	Stimulates metabolism, helps normal breakdown of fats.	Lipid (fat) and carbohydrate metabolism disorders, digestive problems.
Fluorine	Participates in the formation of hard dental tissues and tooth enamel. The strength of bones largely depends on it.	Fragility of tooth enamel, inflammatory gum diseases (for example, periodontitis).
Cobalt	Activates a number of enzymes, enhances protein production, participates in the production of vitamin B12 and the formation of insulin.	Vitamin B12 deficiency, which leads to metabolic disorders.

Organic matter

Organic compounds make up on average 20–30% of the cell mass of a living organism. These include biological polymers - proteins, nucleic acids and polysaccharides, as well as fats and a number of low molecular weight organic matter– amino acids, simple sugars, nucleotides, etc.

Polymers - complex branched or linear molecules, which decompose to monomers upon hydrolysis. If a polymer consists of one type of monomer, then such a polymer is called a homopolymer; if the polymer molecule contains different monomers, then it is a heteropolymer.

If a group of different monomers in a polymer molecule is repeated, it is a regular heteropolymer; if there is no repetition of a certain group of monomers, it is an irregular heteropolymer.

As part of the cell, they are represented by proteins, carbohydrates, fats, nucleic acids (DNA and RNA) and adenosine triphosphate (ATP).

Squirrels

Of the organic substances of the cell, proteins come first in quantity and importance. Proteins, or proteins (from the Greek protos - first, main) are high-molecular heteropolymers, organic substances that decompose during hydrolysis to amino acids.

Simple proteins (made up of amino acids only) contain carbon, hydrogen, nitrogen, oxygen and sulfur.

Some proteins (complex proteins) form complexes with other molecules containing phosphorus, iron, zinc and copper - these are complex proteins that, in addition to amino acids, also contain a non-protein - prosthetic group. It can be represented by metal ions (metalloproteins - hemoglobin), carbohydrates (glycoproteins), lipids (lipoproteins), nucleic acids (nucleoproteins).

Proteins have a huge molecular weight: One of the proteins, milk globulin, has a molecular weight of 42,000.

Proteins are irregular heteropolymers whose monomers are α-amino acids. Over 170 different amino acids have been found in cells and tissues, but proteins contain only 20 α-amino acids.

Depending on whether amino acids can be synthesized in the body, they are distinguished: nonessential amino acids - ten amino acids synthesized in the body and essential amino acids– amino acids that are not synthesized in the body. Essential amino acids must be supplied to the body through food.

Depending on the amino acid composition, proteins are complete, if they contain the entire set of essential amino acids and defective, if some essential amino acids are missing in their composition.

The general formula of amino acids is shown in the figure. All α -amino acids at α The -carbon atom contains a hydrogen atom, a carboxyl group (-COOH) and an amino group (-NH 2). The rest of the molecule is represented by a radical.

The amino group easily attaches a hydrogen ion, i.e. exhibits basic properties. The carboxyl group easily gives up a hydrogen ion and exhibits the properties of an acid. Amino acids are amphoteric compounds, since in solution they can act as both acids and bases. In aqueous solutions, amino acids exist in different ionic forms Oh. This depends on the pH of the solution and whether the amino acid is neutral, acidic or basic.

Depending on the number of amino groups and carboxyl groups included in the composition of amino acids, neutral amino acids are distinguished, having one carboxyl group and one amino group, basic amino acids, which have one more amino group in the radical, and acidic amino acids, which have one more carboxyl group in the radical.

Peptides– organic substances consisting of a small number of amino acid residues connected by a peptide bond. The formation of peptides occurs as a result of the condensation reaction of amino acids (Fig. 4.6).

When the amino group of one amino acid interacts with the carboxyl group of another, a covalent nitrogen-carbon bond occurs between them, which is called peptide. Depending on the number of amino acid residues included in the peptide, dipeptides, tripeptides, tetrapeptides, etc. are distinguished. The formation of a peptide bond can be repeated many times. This leads to the formation polypeptides. If a polypeptide consists of a large number of amino acid residues, then it is already called a protein. At one end of the molecule there is a free amino group (called the N-terminus), and at the other there is a free carboxyl group (called the C-terminus).

Structure of a protein molecule

The performance of certain specific functions by proteins depends on the spatial configuration of their molecules; in addition, it is energetically unfavorable for the cell to keep proteins in an unfolded form, in the form of a chain, therefore polypeptide chains undergo folding, acquiring a certain three-dimensional structure, or conformation. There are 4 levels spatial organization proteins.

Primary structure protein - the sequence of arrangement of amino acid residues in the polypeptide chain that makes up the protein molecule. The bond between amino acids is a peptide bond.

The primary structure of a protein molecule determines the properties of protein molecules and its spatial configuration. Replacing just one amino acid with another in a polypeptide chain leads to a change in the properties and functions of the protein.

For example, replacing the sixth glutamine amino acid in the b-subunit of hemoglobin with valine leads to the fact that the hemoglobin molecule as a whole cannot perform its main function - oxygen transport (in such cases, a person develops a disease - sickle cell anemia).

The first protein whose amino acid sequence was identified was the hormone insulin. Research was carried out in Cambridge University F. Sanger from 1944 to 1954. It was found that the insulin molecule consists of two polypeptide chains (21 and 30 amino acid residues) held near each other by disulfide bridges. For your painstaking work F. Sanger was awarded the Nobel Prize.

Rice. 4.6. Primary structure of a protein molecule

Secondary structure– ordered folding of the polypeptide chain into α-helix(looks like an extended spring) and β-structure (folded layer). IN α- spirals NH-group of this amino acid residue interacts with CO group the fourth remnant of it. Almost all “SO-” and “NN-groups” take part in education hydrogen bonds. They are weaker than peptide ones, but, repeated many times, impart stability and rigidity to this configuration. At the level secondary structure There are proteins: fibroin (silk, spider web), keratin (hair, nails), collagen (tendons).

Tertiary structure- laying of polypeptide chains in globules, arising as a result of the occurrence of chemical bonds (hydrogen, ionic, disulfide) and the establishment of hydrophobic interactions between the radicals of amino acid residues. The main role in the formation of the tertiary structure is played by hydrophilic-hydrophobic interactions. In aqueous solutions, hydrophobic radicals tend to hide from water, grouping inside the globule, while hydrophilic radicals, as a result of hydration (interaction with water dipoles), tend to appear on the surface of the molecule.

For some proteins, the tertiary structure is stabilized by disulfides. covalent bonds, arising between the sulfur atoms of two cysteine residues. At the tertiary structure level there are enzymes, antibodies, and some hormones. Based on the shape of the molecule, proteins are distinguished between globular and fibrillar. If fibrillar proteins perform mainly supporting functions, then globular proteins are soluble and perform many functions in the cytoplasm of cells or in internal environment body.

Quaternary structure characteristic of complex proteins whose molecules are formed by two or more globules. Subunits are held in the molecule exclusively by non-covalent bonds, primarily hydrogen and hydrophobic.

The most studied protein with a quaternary structure is hemoglobin. It is formed by two a-subunits (141 amino acid residues) and two b-subunits (146 amino acid residues). Each subunit is associated with a heme molecule containing iron. Many proteins with a quaternary structure occupy an intermediate position between molecules and cellular organelles– for example, microtubules of the cytoskeleton consist of protein tubulin, consisting of two subunits. The tube lengthens as a result of the attachment of dimers to the end.

If for some reason the spatial conformation of proteins deviates from normal, the protein cannot perform its functions

Rice. 4.7. Structures of protein molecules

Properties of proteins

Proteins are amphoteric compounds, combine basic and acidic properties determined by amino acid radicals. There are acidic, basic and neutral proteins. The ability to donate and add H + is determined buffer properties proteins, one of the most powerful buffers is hemoglobin in red blood cells, which maintains the pH of the blood at a constant level.
There are squirrels soluble, There is insoluble proteins that perform mechanical functions(fibroin, keratin, collagen).
There are proteins chemically active(enzymes), eat chemically inactive.
Eat sustainable to influence various conditions external environment and extremely unstable. External factors(changes in temperature, salt composition of the environment, pH, radiation) can cause disruption of the structural organization of the protein molecule.
The process of loss of the three-dimensional conformation inherent in a given protein molecule is called denaturation. The cause of denaturation is the breaking of bonds that stabilize a certain protein structure. At the same time, denaturation is not accompanied by destruction of the polypeptide chain. A change in the spatial configuration leads to a change in the properties of the protein and, as a consequence, makes it impossible for the protein to perform its inherent biological functions.
Denaturation can be: reversible, the process of restoring protein structure after denaturation is called renaturation. If restoration of the spatial configuration of the protein is impossible, then denaturation is called irreversible.
Destruction primary structure protein molecule is called degradation.

Rice. 4.8. Protein denaturation and renaturation

Functions of proteins

Proteins perform a variety of functions in the cell.

Proteins with tertiary structural organization, but in most cases only the transition of proteins of tertiary organization to quaternary structure provides a specific function.

Enzymatic function

All biological reactions in a cell occur with the participation of special biological catalysts - enzymes, and any enzyme is a protein; enzymes are localized in all cell organelles and not only direct the course of various reactions, but also accelerate them tens and hundreds of thousands of times. Each enzyme is strictly specific.

Thus, the breakdown of starch and its conversion into sugar (glucose) is caused by the enzyme amylase, cane sugar is broken down only by the enzyme invertase, etc.

Many enzymes have long been used in the medical and food (baking, brewing, etc.) industries.

Enzymes are specific - they can catalyze one type of reaction - a specific substrate molecule enters the active center.

Since almost all enzymes are proteins (there are ribozymes, RNAs that catalyze certain reactions), their activity is highest when physiologically normal conditions: most enzymes work most actively only when certain temperature, pH, rate depends on the concentration of the enzyme and substrate.

When the temperature increases to a certain value (on average up to 50°C), the catalytic activity increases (for every 10°C the reaction rate increases approximately 2 times).

Structural function

Proteins are part of all membranes surrounding and permeating the cell and organelles.

When combined with DNA, protein makes up the body of chromosomes, and when combined with RNA, it makes up the body of ribosomes.

Solutions of low molecular weight proteins are part of the liquid fractions of cells.

Regulatory function

Some proteins are hormones - biologically active substances released into the blood by various glands that take part in the regulation of metabolic processes.

Hormones insulin and glucagon regulates the level of carbohydrates in the blood.

Transport function

It is proteins that are associated with the transfer of oxygen, as well as hormones in the body of animals and humans (it is carried out by the blood protein hemoglobin).

Motor function

All types motor reactions cells are made of special contractile proteins actin and myosin, which determine muscle contraction, the movement of flagella and cilia in protozoa, the movement of chromosomes during cell division, and the movement of plants.

Protective function

Many proteins form a protective covering that protects the body from harmful influences, for example, horny formations - hair, nails, hooves, horns. This is mechanical protection. In response to the introduction of foreign proteins (antigens) into the body, blood cells produce protein substances (antibodies) that neutralize them, protecting the body from damaging effects. This is an immunological defense.

Energy function

Proteins can serve as a source of energy. Breaking down into the final breakdown products - carbon dioxide, water and nitrogen-containing substances, they release the energy necessary for many life processes in the cell 17.6 KJ.

Receptor function

Receptor proteins are protein molecules built into the membrane that can change their structure in response to the addition of a certain chemical substance.

Storage function

This function is performed by so-called reserve proteins, which are sources of nutrition for the fetus, for example egg proteins (ovalbumin). The main protein in milk (casein) also has a primarily nutritional function.

A number of other proteins are used in the body as a source of amino acids, which in turn are precursors of biologically active substances that regulate metabolic processes.

Toxic function

Toxins, toxic substances of natural origin. Typically, toxins include high-molecular compounds (proteins, polypeptides, etc.), when they enter the body, antibodies are produced.

According to the target of action, toxins are divided into the following groups:

Hematic poisons are poisons that affect the blood.

Neurotoxins are poisons that affect nervous system and brain.

Myoxic poisons are poisons that damage muscles.

Hemotoxins are toxins that damage blood vessels and cause bleeding.

Hemolytic toxins are toxins that damage red blood cells.

Nephrotoxins are toxins that damage the kidneys.

Cardiotoxins are toxins that damage the heart.

Necrotoxins are toxins that destroy tissues, causing them to die (necrosis).

Toxic substances phallotoxins and amatoxins are found in various species: toadstool, stinking fly agaric, spring fly.

Carbohydrates

Carbohydrates, or saccharides, - organic substances, which include carbon, oxygen, hydrogen. Carbohydrates make up about 1% of the dry matter mass in animal cells, and up to 5% in liver and muscle cells. Plant cells are the richest in carbohydrates (up to 90% of dry mass).

The chemical composition of carbohydrates is characterized by their general formula C m (H 2 O) n, where m≥n. The number of hydrogen atoms in carbohydrate molecules is usually twice the number of oxygen atoms (that is, the same as in a water molecule). Hence the name - carbohydrates.

IN plant cells there are much more of them than in animals. Carbohydrates contain only carbon, hydrogen and oxygen.

The simplest carbohydrates include simple sugars (monosaccharides). They contain five (pentoses) or six (hexoses) carbon atoms and the same number of water molecules.

Examples of monosaccharides are glucose and fructose, found in many plant fruits. In addition to plants, glucose is also found in the blood.

Complex carbohydrates are made up of several molecules of simple carbohydrates. A disaccharide is formed from two monosaccharides.

Table sugar (sucrose), for example, consists of a glucose molecule and a fructose molecule.

Much larger number molecules of simple carbohydrates are included in such complex carbohydrates, such as starch, glycogen, fiber (cellulose).

In a fiber molecule, for example, there are from 300 to 3000 glucose molecules.

Functions of carbohydrates

Energy function

one of the main functions of carbohydrates. Carbohydrates (glucose) are the main sources of energy in the animal body. Provide up to 67% of daily energy consumption (at least 50%). When 1 g of carbohydrate is broken down, 17.6 kJ, water and carbon dioxide are released.

Saving function

is expressed in the accumulation of starch in plant cells and glycogen in animal cells, which play the role of sources of glucose, easily releasing it as needed.

Support and construction function

Carbohydrates are part of cell membranes and cell walls (cellulose is part of the cell wall of plants, the shell of arthropods is formed from chitin, murein forms the cell wall of bacteria). Combining with lipids and proteins, they form glycolipids and glycoproteins. Ribose and deoxyribose are part of the monomers of nucleotides.

Receptor function

Oligosaccharide fragments of glycoproteins and glycolipids of cell walls perform a receptor function, perceiving signals coming from the external environment.

Protective function

The mucus secreted by various glands is rich in carbohydrates and their derivatives (for example, glycoproteins). They protect the esophagus, intestines, stomach, bronchi from mechanical damage, and prevent bacteria and viruses from entering the body.

Lipids

Lipids - a group organic compounds, who do not have a single chemical characteristics. What they have in common is that they are all insoluble in water, but highly soluble in organic solvents (ether, chloroform, gasoline).

There are simple and complex lipids.

Simple lipids are two-component substances that are esters of higher fatty acids and some alcohol, most often glycerol.

Complex lipids consist of multicomponent molecules.

From simple lipids consider fats and waxes.

Fats widely distributed in nature. Fats are esters of higher fatty acids and trihydric alcohol - glycerol. In chemistry, this group of organic compounds is usually called triglycerides, since all three hydroxyl groups of glycerol are associated with fatty acids.

More than 500 fatty acids have been found in triglycerides, the molecules of which have a similar structure.

Like amino acids, fatty acids have the same grouping for all acids - a hydrophilic carboxyl group (–COOH) and a hydrophobic radical, which distinguishes them from each other. Therefore, the general formula of fatty acids is R-COOH. The radical is a hydrocarbon tail that differs in different fatty acids in the number of –CH 2 groups.

Most of contains fatty acids in the "tail" even number carbon atoms, from 14 to 22 (most often 16 or 18). In addition, the hydrocarbon tail may contain varying numbers of double bonds. Based on the presence or absence of double bonds in the hydrocarbon tail, they distinguish saturated fatty acids, which do not contain double bonds in the hydrocarbon tail and unsaturated fatty acids that have double bonds between carbon atoms (-CH=CH-). If saturated fatty acids predominate in triglycerides, then they are solid when room temperature(fats), if unsaturated – liquid (oils). The density of fats is lower than that of water, so in water they float and are on the surface.

Wax– a group of simple lipids, which are esters of higher fatty acids and higher high molecular weight alcohols. They are found in both the animal and plant kingdoms, where they perform mainly protective functions.

In plants, for example, they cover leaves, stems and fruits with a thin layer, protecting them from wetting with water and the penetration of microorganisms. The shelf life of fruit depends on the quality of the wax coating. Honey is stored under the cover of beeswax and the larvae develop.

To complex lipids include phospholipids, glycolipids, lipoproteins, steroids, steroid hormones, vitamins A, D, E, K.

Phospholipids– esters of polyhydric alcohols with higher fatty acids containing a phosphoric acid residue. Sometimes additional groups (nitrogenous bases, amino acids) may be associated with it.

As a rule, a phospholipid molecule contains two higher fatty acid residues and one phosphoric acid residue. Phospholipids are present in all cells of living beings, participating mainly in the formation of the phospholipid bilayer of cell membranes - phosphoric acid residues are hydrophilic and always directed towards the outer and inner surfaces of the membrane, and hydrophobic tails are directed towards each other inside the membrane.

Glycolipids- These are carbohydrate derivatives of lipids. The composition of their molecules, along with polyhydric alcohol and higher fatty acids also include carbohydrates. They are localized primarily on the outer surface of the plasma membrane, where their carbohydrate components are included among other cell surface carbohydrates.

Lipoproteins– lipid molecules associated with proteins. There are a lot of them in membranes, proteins can penetrate the membrane right through, are located under or above the membrane, and can be immersed in the lipid bilayer to different depths.

Lipoids- fat-like substances. These include steroids(widely distributed in animal tissues, cholesterol and its derivatives - hormones of the adrenal cortex - mineralocorticoids, glucocorticoids, estradiol and testosterone - female and male sex hormones, respectively). Lipoids include terpenes (essential oils on which the smell of plants depends), gibberellins (plant growth substances), some pigments (chlorophyll, bilirubin), fat-soluble vitamins (A, D, E, K).

The functions of lipids are shown in Table 4.1.

Table 4.2.

Functions of fats

Energy	The main function of triglycerides. When 1 g of lipids is broken down, 38.9 kJ is released
Structural	Phospholipids, glycolipids and lipoproteins take part in the formation of cell membranes.
Storage	Fats and oils are reserve nutrients in animals and plants. Important for animals that hibernate during the cold season or make long treks through areas where there are no food sources. Plant seed oils are necessary to provide energy to the seedling.
Protective	Layers of fat and fat capsules provide cushioning for internal organs. Layers of wax are used as a water-repellent coating on plants and animals.
Thermal insulation	Subcutaneous fatty tissue prevents the outflow of heat into the surrounding space. Important for aquatic mammals or mammals living in cold climates.
Regulatory	Gibberellins regulate plant growth. The sex hormone testosterone is responsible for the development of male secondary sexual characteristics. The sex hormone estrogen is responsible for the development of female secondary sexual characteristics and regulates the menstrual cycle. Mineralocorticoids (aldosterone, etc.) control water-salt metabolism. Glucocorticoids (cortisol, etc.) take part in the regulation of carbohydrate and protein metabolism.
Metabolic water source	When 1 kg of fat is oxidized, 1.1 kg of water is released. Important for desert inhabitants.
Catalytic	Fat-soluble vitamins A, D, E, K are cofactors of enzymes, i.e., these vitamins themselves do not have catalytic activity, but without them enzymes cannot perform their functions.

Rice. 9. Chemical structure of lipids and carbohydrates

Adenosine triphosphate (ATP)

It is part of any cell, where it performs one of the most important functions - energy storage. ATP molecules consist of the nitrogenous base adenine, the carbohydrate ribose, and three molecules of phosphoric acid.

Unstable chemical bonds, which connect phosphoric acid molecules in ATP, are very rich in energy (macroergic bonds): when these bonds are broken, energy is released and used in a living cell to support vital processes and the synthesis of organic substances.

Rice. 4.10. The structure of the ATP molecule

4.4. Practical task

Biological role 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 macroelements is to build tissues, maintain constant osmotic pressure, ionic and acid-base composition.

Microelements, being part of enzymes, hormones, vitamins, biologically active substances as complexing agents or activators, are involved in metabolism, reproduction processes, tissue respiration, neutralization toxic substances. Microelements actively influence the processes of hematopoiesis, oxidation - reduction, permeability of blood vessels and tissues. 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.

Many diseases associated with a deficiency or excess accumulation of various microelements have been identified. Fluoride deficiency causes dental caries, iodine deficiency causes endemic goiter, and excess molybdenum causes endemic gout. These kinds of patterns are associated with the fact that the human body maintains a balance of optimal concentrations nutrients- chemical homeostasis. Disturbance of this balance due to deficiency or excess of the element can lead to various diseases.

In addition to the six main macroelements - organogens - carbon, hydrogen, nitrogen, oxygen, sulfur and phosphorus, which make up carbohydrates, fats, proteins and nucleic acids, "inorganic" macroelements - 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 lack of elements such as iron, copper, fluorine, zinc, iodine, calcium, phosphorus, magnesium and some others in the diet leads to serious consequences for human health.

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

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

A number of elements (silver, mercury, lead, cadmium, etc.) are considered toxic, since their entry into the body even in microquantities leads to severe pathological phenomena. Chemical mechanism 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 microelements, 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 seed ripening. Microelements are added to animal feed to increase their productivity.

Various elements and their compounds are widely used as medicines.

Thus, studying the biological role of chemical elements, elucidating 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 periodic law DI. Mendeleev. Physicochemical properties, and, consequently, their physiological and pathological role, are determined by the position of these elements in periodic table DI. Mendeleev.

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

Macroelements 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. All of them are 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 larger periods (n>4) rarely act as essential. The exception is the s-elements - potassium, calcium, iodine. Some s- and p-elements of the fourth and fifth periods - strontium, arsenic, selenium, bromine - are classified as physiologically active.

Among the d-elements, mainly elements of the fourth period are vital: manganese, iron, zinc, copper, cobalt. IN Lately It has been established that the physiological role of some other d-elements of this period is undoubted: titanium, chromium, vanadium.

d-Elements of the fifth and sixth periods, with the exception of molybdenum, do not exhibit pronounced positive physiological activity. Molybdenum 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.

2. General aspects toxicity of heavy metals to living organisms

A comprehensive study of the problems associated with condition assessment natural environment shows that it is very difficult to draw a clear boundary between natural and anthropogenic factors changes in ecological systems. The last decades have convinced us of this. that human impact on nature not only causes direct, easily identifiable damage to it, 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. Thus, the course of chemical transformations leading to the formation of toxic substances is influenced by climate, soil condition, water, air, level of radioactivity, etc. Under current conditions, when studying processes chemical pollution ecosystems, the problem arises of finding natural, mainly determined natural factors, levels of content of certain chemical elements or compounds. The solution to this problem is possible only through long-term systematic observations on the state of the components of the biosphere, on the content in them various substances, that is, on the basis of environmental monitoring.

Pollution environment heavy metals is directly related to the environmental-analytical monitoring of supertoxicants, since many of them exhibit high toxicity even in trace amounts and are capable of concentrating in living organisms.

The main sources of pollution of the natural environment with heavy metals can be divided into natural (natural) and artificial (anthropogenic). 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 in nature and, as a rule, have little effect on the overall level of pollution. The main and most dangerous sources Pollution of nature with heavy metals is anthropogenic.

In the process of studying the chemistry of metals and their biochemical cycles in the biosphere, the dual role they play in physiology is revealed: on the one hand, most metals are necessary for the normal course of life; on the other hand, at elevated concentrations they exhibit high toxicity, that is, they have bad influence on the state and activity of living organisms. The boundary between necessary and toxic concentrations of elements is very vague, which makes it difficult to reliably assess their impact on the environment. The amount at which some metals become truly hazardous depends not only on the degree to which they pollute ecosystems, but also on chemical features their biochemical cycle. In table 1 shows the series of molar toxicity of metals for different types living organisms.

Table 1. Representative sequence of molar toxicity of metals

Organisms Toxicity series AlgaeНg>Сu>Сd>Fe>Сr>Zn>Со>Мn FungiАg>Нg>Сu>Сd>Сr>Ni>Рb>Со>Zn>FeFlowering plantsHg>Рb>Сu>Сd>Сr>Ni>ZnAnnelidsHg>Сu >Zn > Pb> CdFishAg>Hg>Cu>Pb>Cd>Al>Zn>Ni>Cr>Co >Mn>>SrMammalsAg, Hg, Cd> Cu, Pb, Sn, Be>> Mn, Zn, Ni, Fe , Сr >> Sr >Сs, Li, Al

For each type of organism, the order of metals in the rows of the table from left to right reflects the increase in the molar amount of metal required to produce the toxic effect. The minimum molar value refers to the metal with the greatest toxicity.

V.V. Kowalski, based on their significance for life, divided chemical elements into three groups:

Vital (irreplaceable) elements constantly contained in the body (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 functioning of humans and animals.

Table 2. Characteristics of some metalloenzymes - bioinorganic complexes

Metal enzyme Central atom Ligand environment Object of concentration Enzyme action Carbonic anhydrase Zn (II) Amino acid residues Red blood cells Catalyzes reversible hydration carbon dioxide: CO 2+H 2O↔H 2CO 3↔H ++VAT 3Carbosky peptidase Zn (II) Amino acid residues Pancreas, liver, intestines Catalyzes the digestion of proteins, participates in the hydrolysis of the peptide bond: R 1CO-NH-R 2+H 2O↔R 1-COOH+R 2N.H. 2CatalaseFe (III)Amino acid residues, histidine, tyrosineBloodCatalyzes the decomposition reaction of hydrogen peroxide: 2H 2ABOUT 2= 2H 2O + O 2PeroxidaseFe(III)ProteinsTissue, bloodOxidation of substrates (RH 2) hydrogen peroxide: RH 2+H 2O 2= R + 2H 2OxyreductaseCu(II)Amino acid residuesHeart, liver, kidneysCatalyzes oxidation using molecular oxygen: 2H 2R+O 2= 2R + 2H 2O Pyruvate carboxylase Mn (II) Tissue proteins Liver, thyroid gland Enhances the effects of hormones. Catalyzes the process of carboxylation with pyruvic acid Aldehyde oxidase Mo (VI) Tissue proteins Liver Participates in the oxidation of aldehydes Ribonucleotide reductase Co (II) Tissue proteins Liver 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 poorly understood or unknown.
impurity elements found in the body Sc, Tl, In, La, Pr, Sm, W, Re, Tb, etc. Data on the quantity 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 their behavior in living systems, metals can be divided into 5 types:
- necessary elements, the lack of which causes functional disorders in the body;
- stimulants (both necessary and unnecessary metals for the body can act as stimulants);
inert elements that, at certain concentrations, are harmless and 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 and death of the body.
Depending on the concentration and time of contact, 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 positive effect to negative after the concentration values of the required element pass through the maximum. At high concentrations, the necessary metal becomes toxic.
The dotted curve demonstrates the biological response to a metal that is toxic to the body and 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 toxic substance(threshold concentration).
The diagram shows that essential elements become toxic in excess quantities. The animal and human body maintains the concentration of elements in the optimal range through a set of physiological processes called homeostasis. The concentration of all essential metals without exception is under strict control of homeostasis.

Fig. 1 Biological response depending on metal concentration. ( Mutual arrangement two curves relative to the concentration scale conditionally)
metal toxicity ion poisoning
Of particular interest is the content of chemical elements in the human body. Human organs concentrate various chemical elements in different ways, that is, macro- and microelements are unevenly distributed between different organs and tissues. Most microelements (content in the body is within 10 -3-10-5%) accumulates in the liver, bone and muscle tissues. These fabrics are the main depot for many metals.
Elements may exhibit a specific affinity for certain organs and be 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 intestinal tissues, strontium - in the prostate gland, bone tissue, manganese in the pituitary gland, etc. In the body, microelements can be found both in a bound state and in the form of free ionic forms. It has been established that aluminum, copper and titanium in brain tissue are in the form of complexes with proteins, while manganese is in ionic form.
In response to the intake of excess concentrations of elements into the body, the living organism is able to limit or even eliminate the resulting toxic effect due to the presence of certain detoxification mechanisms. Specific mechanisms of detoxification in relation to metal ions are currently not well understood. Many metals in the body can be converted into less harmful forms in the following ways:
formation of insoluble complexes in the intestinal tract;
transport of the metal with the blood to other tissues, where it can be immobilized (such as Pb+2 in the bones);

- conversion by the liver and kidneys into a less toxic form.

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

The mechanisms of toxicity of metals are generally well known, but it is very difficult to find them for any specific metal. One of these mechanisms is the concentration between essential and toxic metals due to the presence 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 that can interact with toxic metal ions such as cadmium, lead and mercury, resulting in toxic effects. However, it has not been established exactly which macromolecules cause harm to a living organism. Manifestation of toxicity of metal ions in different organs and tissues is not always related to 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 higher. Thus, lead (II) ions, being more than 90% of the total amount in the body immobilized in the bones, exhibit toxicity due to the 10% distributed in other tissues of the body. The immobilization of lead ions in 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 common feature: as a rule, there is a relationship between metal ions from each other, just like between metal and non-metal ions, in overall contribution in the effectiveness of their action. For example, the toxicity of cadmium is more pronounced in a system with zinc deficiency, and the toxicity of lead is aggravated by calcium deficiency. Similarly, the adsorption of iron from vegetable foods is inhibited by the complexing ligands present in it, and excess zinc ions can inhibit the adsorption of copper, etc.

Determining the mechanisms of metal ion toxicity is often complicated by the existence different ways their penetration into a living organism. Metals can enter with food, water, be absorbed through the skin, penetrate through inhalation, etc. Absorption with dust is Main way penetration at industrial pollution. As a result of inhalation, most metals settle in the lungs and only then spread to other organs. But the most common way toxic metals enter the body is through food and water.

Bibliography

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

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Cell

From the point of view of the concept of living systems according to A. Lehninger.

A living cell is an isothermal system capable of self-regulation and self-reproduction organic molecules, extracting energy and resources from the environment.

There is a leak in the cell a large number of successive reactions, the speed of which is regulated by the cell itself.

The cell maintains itself in a stationary dynamic state, far from equilibrium with the environment.

Cells function on the principle of minimal consumption of components and processes.

That. A cell is an elementary living open system capable of independent existence, reproduction and development. It is the elementary structural and functional unit of all living organisms.

Chemical composition of cells.

Of the 110 elements of Mendeleev’s periodic table, 86 were found to be constantly present in the human body. 25 of them are necessary for normal life, 18 of them are absolutely necessary, and 7 are useful. In accordance with the percentage content in the cell, chemical elements are divided into three groups:

Macroelements The main elements (organogens) are hydrogen, carbon, oxygen, nitrogen. Their concentration: 98 – 99.9%. They are universal components of organic cell compounds.

Microelements - sodium, magnesium, phosphorus, sulfur, chlorine, potassium, calcium, iron. Their concentration is 0.1%.

Ultramicroelements - boron, silicon, vanadium, manganese, cobalt, copper, zinc, molybdenum, selenium, iodine, bromine, fluorine. They affect metabolism. Their absence is the cause of diseases (zinc - diabetes mellitus, iodine - endemic goiter, iron - pernicious anemia, etc.).

Modern medicine knows facts about negative interactions between vitamins and minerals:

Zinc reduces copper absorption and competes with iron and calcium for absorption; (and zinc deficiency causes weakening immune system, a number of pathological conditions of the endocrine glands).

Calcium and iron reduce the absorption of manganese;

Vitamin E does not combine well with iron, and vitamin C does not combine well with B vitamins.

Positive interaction:

Vitamin E and selenium, as well as calcium and vitamin K, act synergistically;

Vitamin D is necessary for the absorption of calcium;

Copper promotes the absorption and increases the efficiency of iron use in the body.

Inorganic components of the cell.

Water– the most important component cells, the universal dispersion medium of living matter. Active cells terrestrial organisms consist of 60–95% water. In resting cells and tissues (seeds, spores) there is 10 - 20% water. Water in the cell is in two forms - free and bound to cellular colloids. Free water is a solvent and dispersion medium colloidal system protoplasm. Its 95%. Bound water(4 – 5%) of all cell water forms weak hydrogen and hydroxyl bonds with proteins.

Properties of water:

Water is a natural solvent for mineral ions and other substances.

Water – dispersive phase colloidal system of protoplasm.

Water is the medium for cell metabolic reactions, because physiological processes occur in an exclusively aquatic environment. Provides reactions of hydrolysis, hydration, swelling.

Participates in many enzymatic reactions cells and is formed during metabolism.

Water is a source of hydrogen ions during photosynthesis in plants.

Biological significance of water:

Most biochemical reactions occur only in aqueous solution, many substances enter and exit cells in dissolved form. This characterizes the transport function of water.

Water provides hydrolysis reactions - the breakdown of proteins, fats, carbohydrates under the influence of water.

Due to the high heat of evaporation, the body is cooled. For example, sweating in humans or transpiration in plants.

The high heat capacity and thermal conductivity of water contributes to uniform distribution warmth in the cage.

Due to the forces of adhesion (water - soil) and cohesion (water - water), water has the property of capillarity.

The incompressibility of water determines the stressed state of cell walls (turgor) and the hydrostatic skeleton in roundworms.

Today, many chemical elements of the periodic table have been discovered and isolated in their pure form, and a fifth of them are found in every living organism. They, like bricks, are the main components of organic and inorganic substances.

What chemical elements are included in the composition of the cell, by the biology of what substances one can judge their presence in the body - we will consider all this later in the article.

What is the constancy of chemical composition?

To maintain stability in the body, each cell must maintain the concentration of each of its components at a constant level. This level is determined by species, habitat, and environmental factors.

To answer the question of what chemical elements are included in the composition of a cell, it is necessary to clearly understand that any substance contains any of the components of the periodic table.

Sometimes we are talking about hundredths and thousandths of a percent of the content of a certain element in a cell, but a change in the said number by even a thousandth can already have serious consequences for the body.

Of the 118 chemical elements in a human cell, there must be at least 24. There are no components that would be found in a living organism, but were not part of inanimate objects of nature. This fact confirms the close connection between living and nonliving things in an ecosystem.

The role of various elements that make up the cell

So what chemical elements make up a cell? Their role in the life of the body, it should be noted, directly depends on the frequency of occurrence and their concentration in the cytoplasm. However, despite different content elements in a cell, the significance of each of them in equally high. A deficiency of any of them can lead to detrimental effects on the body, disabling the most important biochemical reactions from metabolism.

When listing what chemical elements make up the human cell, we need to mention three main types, which we will consider further:

Basic biogenic elements of the cell

It is not surprising that the elements O, C, H, N are classified as biogenic, because they form all organic and many inorganic substances. It is impossible to imagine proteins, fats, carbohydrates or nucleic acids without these essential components for the body.

The function of these elements determined their high content in the body. Together they account for 98% of the total dry body mass. What else can the activity of these enzymes be manifested in?

Oxygen. Its content in the cell is about 62% of the total dry mass. Functions: construction of organic and inorganic substances, participation in the respiratory chain;
Carbon. Its content reaches 20%. Main function: included in all ;
Hydrogen. Its concentration takes a value of 10%. In addition to the fact that this element is a component of organic matter and water, it also participates in energy transformations;
Nitrogen. The amount does not exceed 3-5%. Its main role is the formation of amino acids, nucleic acids, ATP, many vitamins, hemoglobin, hemocyanin, chlorophyll.

These are the chemical elements that make up the cell and form most of the substances necessary for normal life.

Importance of Macronutrients

Macronutrients will also help tell you what chemical elements are included in the cell. From the biology course it becomes clear that, in addition to the main ones, 2% of the dry mass consists of other components periodic table. And macroelements include those whose content is not lower than 0.01%. Their main functions are presented in table form.


Calcium (Ca)		Responsible for the contraction of muscle fibers, is part of pectin, bones and teeth. Enhances blood clotting.
Phosphorus (P)		It is part of the most important energy source - ATP.
		Participates in the formation of disulfide bridges during protein folding into a tertiary structure. Part of cysteine and methionine, some vitamins.
		Potassium ions are involved in cells and also influence the membrane potential.
		Main anion of the body
Sodium (Na)		An analogue of potassium, participating in the same processes.
Magnesium (Mg)		Magnesium ions are regulators of the process. In the center of the chlorophyll molecule there is also a magnesium atom.
		Participates in the transport of electrons through the ETC of respiration and photosynthesis, is a structural link in myoglobin, hemoglobin and many enzymes.

We hope that from the above it is not difficult to determine which chemical elements are part of the cell and belong to the macroelements.

Microelements

There are also components of the cell without which the body cannot function normally, but their content is always less than 0.01%. Let's determine which chemical elements are part of the cell and belong to the group of microelements.


		It is part of the enzymes DNA and RNA polymerases, as well as many hormones (for example, insulin).
		Participates in the processes of photosynthesis, hemocyanin synthesis and some enzymes.
		Is a structural component of the hormones T3 and T4 of the thyroid gland
Manganese (Mn)	less than 0.001	Included in enzymes and bones. Participates in nitrogen fixation in bacteria
	less than 0.001	Affects the process of plant growth.
		Part of bones and tooth enamel.

Organic and inorganic substances

In addition to those listed, what other chemical elements are included in the composition of the cell? The answers can be found by simply studying the structure of most substances in the body. Among them, molecules of organic and inorganic origin are distinguished, and each of these groups contains a fixed set of elements.

The main classes of organic substances are proteins, nucleic acids, fats and carbohydrates. They are built entirely from basic biogenic elements: the skeleton of the molecule is always formed by carbon, and hydrogen, oxygen and nitrogen are part of the radicals. In animals, the dominant class is proteins, and in plants, polysaccharides.

Inorganic substances are all mineral salts and, of course, water. Among all the inorganics in the cell, the most is H 2 O, in which the remaining substances are dissolved.

All of the above will help you determine what chemical elements are part of the cell, and their functions in the body will no longer be a mystery to you.

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

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

Microelements, being 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 influence the processes of hematopoiesis, oxidation - reduction, permeability of blood vessels and tissues. Macro- and microelements - calcium, phosphorus, fluorine, iodine, aluminum, silicon - determine the formation of bone and dental tissues.

Many diseases associated with a deficiency or excess accumulation of various microelements have been identified. Fluoride deficiency causes dental caries, iodine deficiency causes endemic goiter, and excess molybdenum causes endemic gout. These kinds of patterns are associated with the fact that the human body maintains a balance of optimal concentrations of biogenic elements - chemical homeostasis. Violation of this balance is followed by

A deficiency or excess of an element can lead to various diseases

In addition to the six main macroelements - organogens - carbon, hydrogen, nitrogen, oxygen, sulfur and phosphorus, which make up carbohydrates, fats, proteins and nucleic acids, “inorganic” macroelements are necessary for normal nutrition of humans and animals - 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 lack of elements such as iron, copper, fluorine, zinc, iodine, calcium, phosphorus, magnesium and some others in the diet leads to serious consequences for human health.

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

The vital necessity, deficiency, toxicity of a chemical element are presented in the form of a dependence curve “Concentration of the element in food products- body reaction” (Fig. 5.5). The approximately horizontal section of the curve (plateau) describes the area of concentrations corresponding to optimal growth, health, and reproduction. The large extent of the plateau indicates not only the low toxicity of the element, but also the greater ability of the body to adapt to significant changes in the content of this element. On the contrary, a narrow plateau indicates significant toxicity of the element and a sharp transition from quantities necessary for the body to life-threatening ones. When you go beyond a plateau (increasing microelement concentration), all elements become toxic. Ultimately, a significant increase in the concentration of trace elements can lead to death.

A number of elements (silver, mercury, lead, cadmium, etc.) are counted

They are toxic, since their entry into the body even in microquantities leads to severe pathological phenomena. The chemical mechanism of the toxic effects of some trace elements will be discussed below.

Various elements and their compounds are widely used as medicines.

Thus, studying the biological role of chemical elements, elucidating the relationship between the metabolism 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.