The biological role of chemical elements in living organisms. Functions of chemical elements in the human body
Elemental composition of the body
By chemical composition The cells of different organisms may differ markedly, but they consist of the same elements. About 70 elements of the periodic table of D.I. Mendeleev, but only 24 of them have importance and are constantly found in living organisms.
Macronutrients - oxygen, hydrocarbon, hydrogen, nitrogen - are part of the molecules of organic substances. Macroelements recently include potassium, sodium, calcium, sulfur, phosphorus, magnesium, iron, chlorine. Their content in the cell is tenths and hundredths of a percent.
Magnesium is part of chlorophyll; iron - hemoglobin; phosphorus - bone tissue, nucleic acids; calcium - bones, shellfish turtles, sulfur - in the composition of proteins; potassium, sodium and chloride ions take part in changing the potential of the cell membrane.
trace elements are presented in a cell with hundredths and thousandths of a percent. These are zinc, copper, iodine, fluorine, molybdenum, boron, etc.
Trace elements are part of enzymes, hormones, pigments.
Ultramicroelements - elements, the content of which in the cell does not exceed 0.000001%. These are uranium, gold, mercury, cesium, etc.
Water and its biological significance
Water quantitatively ranks among chemical compounds first place in all cells. Depending on the type of cells, their functional state, the type of organism and the conditions of its presence, its content in cells varies significantly.
Bone tissue cells contain no more than 20% water, adipose tissue - about 40%, muscle cells - 76%, and embryonic cells - more than 90%.
Remark 1
In the cells of any organism, the amount of water decreases markedly with age.
Hence the conclusion that the higher the functional activity of the organism as a whole and of each cell separately, the greater their water content, and vice versa.
Remark 2
A prerequisite for the vital activity of cells is the presence of water. It is the main part of the cytoplasm, supports its structure and the stability of the colloids that make up the cytoplasm.
The role of water in a cell is determined by its chemical and structural properties. First of all, this is due to the small size of the molecules, their polarity and the ability to combine using hydrogen bonds.
Hydrogen bonds are formed with the participation of hydrogen atoms connected to an electronegative atom (usually oxygen or nitrogen). In this case, the Hydrogen atom acquires such a large positive charge that it can form a new bond with another electronegative atom (oxygen or nitrogen). Water molecules also bind to each other, in which one end has a positive charge, and the other is negative. Such a molecule is called dipole. The more electronegative oxygen atom of one water molecule is attracted to the positively charged hydrogen atom of another molecule to form a hydrogen bond.
Due to the fact that water molecules are polar and capable of forming hydrogen bonds, water is a perfect solvent for polar substances, which are called hydrophilic. These are compounds of an ionic nature, in which charged particles (ions) dissociate (separate) in water when a substance (salt) is dissolved. Some non-ionic compounds have the same ability, in the molecule of which there are charged (polar) groups (in sugars, amino acids, simple alcohols, these are OH groups). Substances consisting of non-polar molecules (lipids) are practically insoluble in water, that is, they hydrophobes.
When a substance passes into a solution, its structural particles (molecules or ions) acquire the ability to move more freely, and, accordingly, the reactivity of the substance increases. Due to this, water is the main medium where most of the chemical reactions. In addition, all redox reactions and hydrolysis reactions take place with the direct participation of water.
Water has the highest specific heat capacity of all known substances. This means that with a significant increase in thermal energy, the water temperature rises relatively slightly. This is due to the use of a significant amount of this energy to break hydrogen bonds, which limit the mobility of water molecules.
Due to its high heat capacity, water serves as a protection for plant and animal tissues from a strong and rapid increase in temperature, and the high heat of vaporization is the basis for reliable stabilization of body temperature. The need for a significant amount of energy to evaporate water is due to the fact that hydrogen bonds exist between its molecules. This energy comes from environment Therefore, evaporation is accompanied by cooling. This process can be observed during sweating, in the case of heat panting in dogs, it is also important in the process of cooling the transpiring organs of plants, especially in desert conditions and in conditions of dry steppes and periods of drought in other regions.
Water also has a high thermal conductivity, which ensures uniform distribution of heat throughout the body. Thus, there is no risk of local “hot spots” that can cause damage to cell elements. So high specific heat and high thermal conductivity for a liquid make water an ideal medium for maintaining the optimal thermal regime of the body.
Water has a high surface tension. This property is very important for adsorption processes, movement of solutions through tissues (blood circulation, upward and downward movement through the plant, etc.).
Water is used as a source of oxygen and hydrogen, which are released during the light phase of photosynthesis.
Important physiological properties of water include its ability to dissolve gases ($O_2$, $CO_2$, etc.). In addition, water as a solvent is involved in the process of osmosis, which plays an important role in the life of cells and the body.
Hydrocarbon properties and its biological role
If we do not take into account water, we can say that most of the cell molecules belong to hydrocarbon, so-called organic compounds.
Remark 3
Hydrocarbon, having unique chemical abilities fundamental to life, is its chemical basis.
Due to their small size and the presence of outer shell four electrons, a hydrocarbon atom can form four strong covalent bonds with other atoms.
Most important is the ability of hydrocarbon atoms to connect with each other, forming chains, rings and, ultimately, the skeleton of large and complex organic molecules.
In addition, the hydrocarbon easily forms covalent bonds with other biogenic elements (usually with $H, Mg, P, O, S$). This explains the existence of an astronomical amount of various organic compounds that ensure the existence of living organisms in all its manifestations. Their diversity is manifested in the structure and size of molecules, their chemical properties, degree of saturation of the carbon skeleton and different form molecules, which is determined by the angles of intramolecular bonds.
Biopolymers
These are high molecular weight (molecular weight 103 - 109) organic compounds, whose macromolecules are composed of a large number links that repeat - monomers.
Biopolymers are proteins, nucleic acids, polysaccharides and their derivatives (starch, glycogen, cellulose, hemicellulose, pectin, chitin, etc.). The monomers for them are, respectively, amino acids, nucleotides and monosaccharides.
Remark 4
About 90% of the dry mass of a cell is made up of biopolymers: polysaccharides predominate in plants, while proteins predominate in animals.
Example 1
In a bacterial cell there are about 3 thousand types of proteins and 1 thousand nucleic acids, and in humans the number of proteins is estimated at 5 million.
Biopolymers not only form the structural basis of living organisms, but also play a conducting role in life processes.
The structural basis of biopolymers are linear (proteins, nucleic acids, cellulose) or branched (glycogen) chains.
And nucleic acids, immune reactions, metabolic reactions - and are carried out due to the formation of biopolymer complexes and other properties of biopolymers.
Today, a lot has been discovered and isolated in its pure form chemical elements periodic tables, 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 part of the cell, the biology of which substances can be used to judge their presence in the body - we will consider all this later in the article.
What is the constancy of the 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, environmental factors.
To answer the question of what chemical elements are part of the cell, it is necessary to clearly understand that any substance contains any of the components of the periodic table.
Sometimes in question about hundredths and thousandths of a percent of the content of a certain element in a cell, but at the same time, a change in the named number by at least a thousandth part can already have serious consequences for the body.
Of the 118 chemical elements in a human cell, there should be at least 24. There are no such components that would be found in a living organism, but were not part of inanimate objects of nature. This fact confirms the close relationship between living and non-living in the ecosystem.
The role of various elements that make up the cell
So what are the chemical elements that make up a cell? Their role in the life of the organism, it should be noted, directly depends on the frequency of occurrence and their concentration in the cytoplasm. However, despite different content elements in the cell, the significance of each of them is equally high. A deficiency of any of them can lead to a detrimental effect on the body, turning off the most important biochemical reactions from metabolism.
Listing what chemical elements are part of the human cell, we need to mention three main types, which we will consider below:
The main biogenic elements of the cell
It is not surprising that the elements O, C, H, N are 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 weight. How else can the activity of these enzymes be manifested?
- 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 being a component of organic matter and water, this element 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 to suggest which chemical elements are part of the cell. From the biology course, it becomes clear that, in addition to the main ones, 2% of the dry mass is made up of other components of the periodic table. And macronutrients include those whose content is not lower than 0.01%. Their main functions are presented in the form of a table.
Calcium (Ca) | Responsible for the contraction of muscle fibers, is part of pectin, bones and teeth. Enhances blood clotting. |
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Phosphorus (P) | It is part of the most important source of energy - ATP. |
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Participates in the formation of disulfide bridges during protein folding into a tertiary structure. Included in the composition of cysteine and methionine, some vitamins. |
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Potassium ions are involved in cells and also affect the membrane potential. |
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Major anion in the body |
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Sodium (Na) | Analogue of potassium involved in the same processes. |
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Magnesium (Mg) | Magnesium ions are the regulators of the process In the center of the chlorophyll molecule, there is also a magnesium atom. |
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Participates in the transport of electrons through the ETC of respiration and photosynthesis, is a structural link of myoglobin, hemoglobin and many enzymes. |
We hope that from the above it is easy to determine which chemical elements are part of the cell and are macroelements.
trace elements
There are also such 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 of DNA and RNA polymerases, as well as many hormones (for example, insulin). |
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Participates in the processes of photosynthesis, synthesis of hemocyanin and some enzymes. |
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It is a structural component of the hormones T3 and T4 of the thyroid gland |
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Manganese (Mn) | less than 0.001 | Included in enzymes, bones. Participates in nitrogen fixation in bacteria |
less than 0.001 | Influences the process of plant growth. |
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It is part of the bones and tooth enamel. |
Organic and inorganic substances
In addition to these, what other chemical elements are included in the composition of the cell? The answers can be found simply by studying the structure of most substances in the body. Among them, molecules of organic and inorganic origin are distinguished, and each of these groups has a fixed set of elements in its composition.
The main classes of organic substances are proteins, nucleic acids, fats and carbohydrates. They are built entirely from the main biogenic elements: the skeleton of the molecule is always formed by carbon, and hydrogen, oxygen and nitrogen are part of the radicals. In animals, proteins are the dominant class, 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 rest of the substances are dissolved.
All of the above will help you determine which chemical elements are part of the cell, and their functions in the body will no longer be a mystery to you.
AT modern conditions one of the most urgent problems of teaching chemistry is to ensure the practical orientation of subject knowledge. This means the need to clarify the close relationship between the studied theoretical positions and the practice of life, to demonstrate the applied nature of chemical knowledge. Students are excited to learn chemistry. In order to maintain the cognitive interest of students, it is necessary to convince them of the effectiveness of chemical knowledge, to form a personal need for mastering educational material.
Purpose of this lesson: broaden the horizons of students and increase cognitive interest in the study of the subject, form worldview concepts about the cognizability of nature. This lesson is proposed to be held in the 8th grade after studying the chemical elements of the Periodic Table, when the children already have an idea of their diversity.
DURING THE CLASSES
Teacher:
There is nothing else in nature
Neither here nor there, in the depths of space:
Everything - from small grains of sand to planets -
It consists of single elements.
Like a formula, like a labor schedule,
The structure of the Mendeleev system is strict.
The world around you is alive
Enter it, breathe in, touch it with your hands.
The lesson begins with a theatrical scene “Who is the most important in the table?” (cm. Appendix 1).
Teacher: The human body contains 81 chemical elements out of 92 found in nature. The human body is a complex chemical laboratory. It is hard to imagine that our daily well-being, mood and even appetite can depend on minerals. Without them, vitamins are useless, the synthesis and breakdown of proteins, fats and carbohydrates are impossible.
On the tables of the students there are tables “The biological role of chemical elements” (see. Annex 2). Take time to get to know her. The teacher, together with the students, analyzes the table by asking questions.
Teacher: The basis of life is the six elements of the first three periods (H, C, N, O, P, S), which account for 98% of the mass of living matter (the remaining elements of the periodic system are no more than 2%).
Three main attributes of biogenic elements (H, C, N, O, P, S):
- small size of atoms
- small relative atomic mass,
- the ability to form strong covalent bonds.
Students are given texts (see. Annex 3). Task: read the text carefully; highlight the elements necessary for life and the elements dangerous to living organisms; find them in the Periodic system and explain their role.
After completing the task, several students analyze different texts.
Teacher: Elements-analogues in the natural environment enter into competition and can be interchanged in living organisms, negatively affecting them.
Replacing sodium and potassium in the organisms of animals and humans with lithium causes disorders of the nervous system, since in this case the cells do not conduct a nerve impulse. Such disorders lead to schizophrenia.
Thallium, a biological competitor of potassium, replaces it in cell walls, affects the central and peripheral nervous system, gastrointestinal tract and kidneys.
Selenium can replace sulfur in proteins. This is the only element that, when found in high concentrations in plants, can cause sudden death in animals and humans who eat them.
Calcium, when it is deficient in the soil, is replaced in the body by strontium, which gradually disrupts the normal structure of the skeleton. Especially dangerous is the replacement of calcium with strontium-90, which accumulates in huge quantities in places of nuclear explosions (when testing nuclear weapons) or during accidents at nuclear power plants. This radionuclide destroys the bone marrow.
Cadmium competes with zinc. This element reduces the activity of digestive enzymes, disrupts the formation of glycogen in the liver, causes skeletal deformity, inhibits bone growth, and also causes severe pain in the lower back and leg muscles, bone fragility (for example, broken ribs when coughing). Other negative consequences are lung and rectal cancer, pancreatic dysfunction. Kidney damage, decreased blood levels of iron, calcium, phosphorus. This element inhibits self-purification processes in aquatic and terrestrial plants (for example, a 20-30-fold increase in cadmium in tobacco leaves is noted).
Halogens can be very easily interchanged in the body. An excess of fluorine in the environment (fluorinated water, soil contamination with fluorine compounds around an aluminum production plant, and other reasons) prevents iodine from entering the human body. As a result, thyroid disease endocrine system generally.
Student messages prepared in advance.
1st student:
Medieval alchemists considered gold to be perfection, and other metals - a mistake in the act of creation and, as you know, made great efforts to eliminate this error. The idea of introducing gold into medical practice is attributed to Paracelsus, who proclaimed that the goal of chemistry should not be the transformation of all metals into gold, but the preparation of medicines. Medicines made from gold and its compounds have been tried to treat many diseases. They were treated for leprosy, lupus, and tuberculosis. In people sensitive to gold, it could cause a violation of the composition of the blood, a reaction from the kidneys, liver, affect mood, growth of teeth, hair. Gold ensures the functioning of the nervous system. It is found in corn. And the strength of blood vessels depends on germanium. The only food product containing germanium is garlic.
2nd student:
AT human body the largest amount of copper is found in the brain and liver, and this circumstance alone indicates its importance in life. It was found that with pain, the concentration of copper in the blood and cerebrospinal fluid increases. In Syria and Egypt, newborns wear copper bracelets to prevent rickets and epilepsy.
3rd student:
ALUMINUM
Aluminum utensils are called the utensils of the poor, as this metal contributes to the development of senile atherosclerosis. When cooking in such dishes, aluminum partially passes into the body, where it accumulates.
4th student:
- What element is found in apples? (Iron.)
- What is its biological role? (The body contains 3 g of iron, of which 2 g is in the blood. Iron is part of hemoglobin. Insufficient iron leads to headache, rapid fatigue.)
Then students conduct a laboratory experiment, the purpose of which is to experimentally prove the effect of salts of certain metals on protein. They mix the protein with solutions of alkali and copper sulphate and observe the precipitation of a purple precipitate. Make a conclusion about the destruction of the protein.
5th student:
Man is also nature.
He is also a sunset and a sunrise.
And it has four seasons.
And a special move in music.
And a special sacrament of color,
Now with cruel, now with good fire.
Man is winter. Or summer.
Or autumn. With thunder and rain.All contained in itself - miles and time.
And from atomic storms he was blind.
Man is both soil and seed.
And weeds in the middle of the field. And bread.And what is the weather like in it?
How much loneliness is there? Meetings?
Man is nature too...
So let's take care of nature!
(S. Ostrovoy)
To consolidate the knowledge gained in the lesson, the “Smile” test is carried out (see. Appendix 4).
Next, it is proposed to fill in the crossword “Chemical Kaleidoscope” (see. Annex 5).
The teacher sums up the lesson, noting the most active students.
6th student:
Change, change!
The call is pouring.
Finally it's finished
Boring lesson!Pulling sulfur by the pigtail,
Magnesium ran past.
Iodine evaporated from the classroom
It's like it never happened at all.Fluorine accidentally set fire to water,
Chlorine ate someone else's book.
Carbon suddenly with hydrogen
I managed to become invisible.Potassium, bromine are fighting in the corner:
They don't share an electron.
Oxygen - naughty on boron
Past galloped on horseback.
Used Books:
- O.V. Baidalina On the applied aspect of chemical knowledge. “Chemistry at school” No. 5, 2005
- Chemistry and ecology in the school course. “First of September” No. 14, 2005
- I. N. Pimenova, A. V. Pimenov“Lectures on general biology”, textbook, Saratov, JSC Publishing House “Lyceum”, 2003
- About chemistry in verse, Who is the most important in the table? “First of September”, No. 15, 2005
- Metals in the human body. “Chemistry at school”, No. 6, 2005
- Crossword "Chemical kaleidoscope". “First of September”, No. 1 4, 2005
- "I'm going to chemistry class." The book for the teacher. M. “First of September”, 2002, p. 12.
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.
Trace elements, 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. Trace elements actively influence the processes of hematopoiesis, oxidation - recovery, 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. So, the content of cadmium in the kidneys and molybdenum in the liver increases with old age. The maximum content of zinc is observed during puberty, then it decreases and in old age reaches a minimum. The content of other trace elements, such as vanadium and chromium, also decreases with age.
Many diseases associated with a deficiency or excessive accumulation of various trace elements have been identified. Fluorine deficiency causes dental caries, iodine deficiency - endemic goiter, excess molybdenum - endemic gout. Such patterns are connected with the fact that the balance of optimal concentrations of biogenic elements is maintained in the human body - chemical homeostasis. Violation of this balance due to a lack 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 are necessary for normal human and animal nutrition - 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.
The 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 biogenic elements is harmful to the body, since this disrupts chemical homeostasis. For example, with the intake of excess manganese with food, the level of copper in the plasma increases (synergism of Mn and Cu), and in the kidneys it decreases (antagonism). Increasing 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 entry into the body already in trace amounts leads to severe pathological phenomena. chemical mechanism The toxic effects of certain trace elements will be discussed below.
Biogenic elements are widely used in agriculture. The addition of small amounts of microelements - boron, copper, manganese, zinc, cobalt, molybdenum - to the soil dramatically increases the yield of many crops. It turns out that microelements, by increasing the activity of enzymes in plants, contribute to 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, seed maturation. 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 modes their dosing 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 characteristics, and, consequently, their physiological and pathological role, are determined by the position of these elements in periodic system DI. Mendeleev.
As a rule, with an increase in the charge of the nucleus of atoms, the toxicity of the elements of this group increases and their content in the body decreases. The decrease in content is obviously due to the fact that many elements of long periods are poorly absorbed 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.
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 large periods (n> 4) rarely act as indispensable. 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, it is mainly the elements of the fourth period that are vital: 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.
2. General aspects of the toxicity of heavy metals to 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 in changing ecological systems. The last decades have convinced us of this. that human impact on nature causes 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 climate, the state of the soil cover, water, air, the level of radioactivity, etc. Under the current conditions, when studying the processes of chemical pollution of ecosystems, the problem arises of finding natural, mainly due to natural factors, levels of content of certain chemical elements or compounds. 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 exhibit high toxicity already in trace amounts and are able to concentrate in living organisms.
The main sources of environmental pollution with heavy metals can be divided into natural (natural) and artificial (anthropogenic). Natural include volcanic eruption, dust storms, forest and steppe fires, sea salts blown up 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 general level 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, the dual role that 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 the necessary and toxic concentrations of elements is very vague, which complicates the reliable assessment of their impact on the environment. The amount at which some metals become truly dangerous depends not only on the degree of pollution of ecosystems by them, but also on the chemical characteristics of 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 Algae Hg>Cu>Cd>Fe>Cr>Zn>Co>MnFungiAg>Hg>Cu>Cd>Cr>Ni>Pb>Co>Zn>Fe >Zn > Pb> CdFishAg>Hg>Cu> Pb>Cd>Al> Zn> Ni> Cr>Co>Mn>>SrMammalsAg, Hg, Cd> Cu, Pb, Sn, Be>> Mn, Zn, Ni, Fe , Cr >> Sr >Сs, Li, Al
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 the metal required for the manifestation of the toxicity effect. The minimum molar value refers to the metal with the highest toxicity.
V.V. Kovalsky, based on their importance for life, divided the 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
Metal-enzyme Central atom Ligand environment Object of concentration Enzyme action Carboanhydrase Zn (II) Amino acid residues Erythrocytes Catalyzes reversible hydration of carbon dioxide: CO 2+H 2O↔N 2SO 3↔N ++NSO 3Zn (II) carboxypeptidase Amino acid residues Pancreas, liver, intestines Catalyzes protein digestion, participates in peptide bond hydrolysis: R 1CO-NH-R 2+H 2O↔R 1-COOH+R 2NH 2Catalase Fe (III) Amino acid residues, histidine, tyrosine Blood Catalyzes the decomposition reaction of hydrogen peroxide: 2H 2O 2= 2N 2O + O 2Fe(III) peroxidaseProteinsTissue, bloodOxidation of substrates (RH 2) hydrogen peroxide: RH 2+ H 2O 2=R+2H 2Oxireductase Cu (II) Amino acid residues Heart, liver, kidneys Catalyzes oxidation with the help of molecular oxygen: 2H 2R+O 2= 2R + 2H 2O Pyruvate carboxylase Mn (II) Tissue proteins Liver, thyroid gland Enhances the action 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 So, in response to the action of toxic ions of lead, mercury, cadmium, etc., the human liver and kidneys increase the synthesis of metallothiones - proteins of low molecular weight, in which approximately 1/3 of the amino acid residues is cysteine. high content and certain location 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 essential and toxic metals for possessing 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 is not exactly established which macromolecules harm a living organism in this case. The manifestation of toxicity of metal ions in different bodies 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 is higher. So lead (II) ions, being more than 90% of the total amount in the body immobilized in the bones, exhibit toxicity due to 10% distributed in other tissues of the body. The immobilization of lead ions in the bones can be considered as a detoxification process. The toxicity of a metal ion is usually not associated with its need for the body. However, for toxicity and necessity, there is one common feature: as a rule, there is an interrelation of metal ions from each other, exactly, as well as between metal and non-metal ions, in the overall contribution to the effectiveness of their action. For example, cadmium toxicity is more pronounced in a system with zinc deficiency, while lead toxicity is exacerbated by calcium deficiency. Similarly, the adsorption of iron from vegetable food is inhibited 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 be ingested with food, water, absorbed through the skin, penetrated by 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 route for toxic metals to enter the body is ingestion through food and water. Bibliographic list 1. Karapetyants M.Kh., Drakin S.I. General and inorganic chemistry. - M.: Chemistry, 1993. - 590 p. Akhmetov N.S. General and inorganic chemistry. Textbook for high schools. - M.: Higher. school, 2001. - 679 p. 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. Tretyakova - M.: Ed. "Academy", 2004, 368s. 5. Tamm I.E., Tretyakov Yu.D. Inorganic chemistry: In 3 volumes, V.1. Physical and chemical bases inorganic chemistry. Textbook for university students / Ed. Yu.D. Tretyakov. - M.: Ed. "Academy", 2004, 240s. Korzhukov N.G. General and inorganic chemistry. Proc. Benefit. / Under the editorship of V.I. Delyan-M.: Ed. MISIS: INFRA-M, 2004, 512s. 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. Ershov. 3rd ed., - M.: Integral-Pres, 2007. - 728 p. Glinka N.L. General chemistry. Tutorial for universities. Ed. 30th revised./ Ed. A.I. Ermakov. - M.: Integral-Press, 2007, - 728 p. Chernykh, M.M. Ovcharenko. Heavy metals and radionuclides in biogeocinoses. - M.: Agroconsult, 2004. N.V. Gusakov. Chemistry of the environment. - Rostov-on-Don, Phoenix, 2004. Baletskaya L.G. Inorganic chemistry. - Rostov-on-Don, Phoenix, 2005. M. Henze, P. Armoes, J. Lakuriansen, E. Arvan. cleaning Wastewater. - M.: Mir, 2006. Korovin N.V. General chemistry. - M.: Higher. school, 1998. - 558 p. Petrova V.V. and other Review of the properties of chemical elements and their compounds. Textbook for the course Chemistry in microelectronics. - M.: Publishing House of MIET, 1993. - 108 p. Kharin A.N., Kataeva N.A., Kharina L.T. Chemistry course. - M.: Higher. school, 1983. - 511 p.
- transformation by the liver and kidneys into a less toxic form.
>> Chemistry: Chemical elements in the cells of living organisms
More than 70 elements have been found in the composition of substances that form the cells of all living organisms (humans, animals, plants). These elements are usually divided into two groups: macroelements and microelements.
Macronutrients are found in cells in large quantities. First of all, these are carbon, oxygen, nitrogen and hydrogen. In total, they make up almost 98% of the total contents of the cell. In addition to these elements, macronutrients also include magnesium, potassium, calcium, sodium, phosphorus, sulfur and chlorine. Their total content is 1.9%. Thus, the share of other chemical elements accounts for about 0.1%. These are micronutrients. These include iron, zinc, manganese, boron, copper, iodine, cobalt, bromine, fluorine, aluminum, etc.
23 trace elements were found in the milk of mammals: lithium, rubidium, copper, silver, barium, strontium, titanium, arsenic, vanadium, chromium, molybdenum, iodine, fluorine, manganese, iron, cobalt, nickel, etc.
The composition of the blood of mammals includes 24 microelements, and the composition of the human brain - 18 microelements.
As you can see, there are no special elements in the cell that are characteristic only for living nature, i.e. on atomic level there is no difference between living and non-living nature. These differences are found only at the level complex substances- on the molecular level. So, along with inorganic substances(water and mineral salts) the cells of living organisms contain substances that are characteristic only for them - organic substances (proteins, fats, carbohydrates, nucleic acids, vitamins, hormones, etc.). These substances are built mainly from carbon, hydrogen, oxygen and nitrogen, i.e. from macroelements. Trace elements are contained in these substances in small quantities, however, their role in the normal life of organisms is enormous. For example, compounds of boron, manganese, zinc, cobalt dramatically increase the yield of individual agricultural plants and increase their resistance to various diseases.
Man and animals receive the trace elements they need for normal life through the plants they feed on. If there is not enough manganese in the food, then growth retardation, a slowdown in the onset of puberty, and metabolic disorders during the formation of the skeleton are possible. The addition of fractions of a milligram of manganese salts to daily ration animals eliminates these diseases.
Cobalt is part of vitamin B12, which is responsible for the work of hematopoietic organs. The lack of cobalt in food often causes a serious illness that leads to depletion of the body and even death.
The importance of trace elements for humans was first revealed in the study of such a disease as endemic goiter, which was caused by a lack of iodine in food and water. The intake of salt containing iodine leads to recovery, and its addition to food in small quantities prevents the disease. For this purpose, iodized table salt is carried out, to which 0.001-0.01% potassium iodide is added.
The composition of most biological enzyme catalysts includes zinc, molybdenum and some other metals. These elements, contained in the cells of living organisms in very small quantities, ensure the normal operation of the finest biochemical mechanisms, and are true regulators of vital processes.
Many trace elements are contained in vitamins - organic substances of various chemical nature, which enter the body with food in small doses and have a great influence on the metabolism and overall vital activity of the body. In their biological action, they are close to enzymes, but enzymes are formed by the cells of the body, and vitamins usually come from food. Plants serve as sources of vitamins: citrus fruits, rose hips, parsley, onions, garlic and many others. Some vitamins - A, B1, B2, K - are obtained synthetically. Vitamins got their name from two words: vita - life and amine - containing nitrogen.
Trace elements are also part of hormones - biologically active substances that regulate the functioning of organs and systems of human and animal organs. They take their name from Greek word harmao - I win. Hormones are produced by the endocrine glands and enter the blood, which carries them throughout the body. Some hormones are obtained synthetically.
1. Macroelements and microelements.
2. The role of trace elements in the life of plants, animals and humans.
3. Organic substances: proteins, fats, carbohydrates.
4. Enzymes.
5. Vitamins.
6. Hormones.
At what level of forms of existence of a chemical element does the difference between animate and inanimate nature begin?
Why are individual macronutrients also called biogenic? List them.
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