Chemical composition of the cell

Mineral salts

water.
good solvent

Hydrophilic(from Greek hydro- water and filleo

Hydrophobic(from Greek hydro- water and Phobos

elasticity

Water. Water- universal solvent hydrophilic. 2- hydrophobic. .3- heat capacity. 4- Water is characterized 5- 6- Water provides movement of substances 7- In plants, water determines turgor support functions, 8- Water is an integral part lubricating fluids slime

Mineral salts. action potential ,

Physico-chemical properties of water as the main medium in the human body.

Of the inorganic substances that make up the cell, the most important is water. Its amount ranges from 60 to 95% of the total cell mass. Water plays a vital role in the life of cells and living organisms in general. In addition to the fact that it is part of their composition, for many organisms it is also a habitat. The role of water in the cell is determined by its unique chemical and physical properties, associated mainly with the small size of its molecules, the polarity of its molecules and their ability to form hydrogen bonds with each other.

Lipids. Functions of lipids in the human body.

Lipids are a large group of substances of biological origin, highly soluble in organic solvents such as methanol, acetone, chloroform and benzene. At the same time, these substances are insoluble or slightly soluble in water. Poor solubility is associated with the insufficient content of atoms with a polarizable electron shell, such as O, N, S or P, in lipid molecules.

The system of humoral regulation of physiological functions. Principles of hum..

Humoral physiological regulation uses body fluids (blood, lymph, cerebrospinal fluid, etc.) to transmit information. Signals are transmitted through chemicals: hormones, mediators, biologically active substances (BAS), electrolytes, etc.

Features of humoral regulation: does not have an exact addressee - with the flow of biological fluids, substances can be delivered to any cells of the body; the speed of information delivery is low - determined by the speed of flow of biological fluids - 0.5-5 m/s; duration of action.

The transmission of humoral regulation is carried out by the blood flow, lymph, by diffusion, nervous regulation is carried out by nerve fibers. The humoral signal travels more slowly (with the blood flow through the capillary at a speed of 0.05 mm/s) than the nervous signal (nerve transmission speed is 130 m/s). A humoral signal does not have such a precise addressee (it works on the principle of “everyone, everyone, everyone”) as a nervous one (for example, a nerve impulse is transmitted by the contracting muscles of a finger). But this difference is not significant, since cells have different sensitivity to chemicals. Therefore, chemicals act on strictly defined cells, that is, on those that are able to perceive this information. Cells that have such a high sensitivity to any humoral factor are called target cells.
Among humoral factors, substances with a narrow
spectrum of action, that is, directed action on a limited number of target cells (for example, oxytocin), and wider (for example, adrenaline), for which there is a significant number of target cells.
Humoral regulation is used to ensure reactions that do not require high speed and accuracy of execution.
Humoral regulation, like nervous regulation, is always carried out
a closed regulatory loop in which all elements are interconnected by channels.
As for the monitoring element of the device circuit (SP), it is absent as an independent structure in the humoral regulation circuit. The function of this link is usually performed by the endocrine system.
cell.
Humoral substances that enter the blood or lymph diffuse into the intercellular fluid and are quickly destroyed. In this regard, their effect can only extend to nearby organ cells, that is, their influence is local in nature. In contrast to local effects, distant effects of humoral substances extend to target cells at a distance.

HYPOTHALAMUS HORMONES

hormone effect

Corticoliberin - Stimulates the formation of corticotropin and lipotropin

Gonadotropin-releasing hormone - Stimulates the formation of lutropin and follitropin

Prolactoliberin - Promotes the release of prolactin

Prolactostatin - Inhibits the release of prolactin

Somatoliberin Stimulates the secretion of growth hormone

Somatostatin - Inhibits the secretion of growth hormone and thyrotropin

Thyroliberin - Stimulates the secretion of thyrotropin and prolactin

Melanoliberin - Stimulates the secretion of melanocyte-stimulating hormone

Melanostatin - Inhibits the secretion of melanocyte-stimulating hormone

ADENOGYPOPHYSIC HORMONES

STH (somatotropin, growth hormone) - Stimulates body growth, protein synthesis in cells, glucose formation and lipid breakdown

Prolactin - Regulates lactation in mammals, the instinct to nurse offspring, differentiation of various tissues

TSH (thyrotropin) - Regulates the biosynthesis and secretion of thyroid hormones

Corticotropin - Regulates the secretion of hormones from the adrenal cortex

FSH (follitropin) and LH (luteinizing hormone) - LH regulates the synthesis of female and male sex hormones, stimulates the growth and maturation of follicles, ovulation, the formation and functioning of the corpus luteum in the ovaries FSH has a sensitizing effect on follicles and Leydig cells to the action of LH, stimulates spermatogenesis

THYROID HORMONES The release of thyroid hormones is controlled by two “superior” endocrine glands. The area of ​​the brain that connects the nervous and endocrine systems is called the hypothalamus. The hypothalamus receives information about the level of thyroid hormones and secretes substances that affect the pituitary gland. Pituitary also located in the brain in the area of ​​a special depression - the sella turcica. It secretes several dozen hormones that are complex in structure and action, but only one of them acts on the thyroid gland - thyroid-stimulating hormone or TSH. The level of thyroid hormones in the blood and signals from the hypothalamus stimulate or inhibit the release of TSH. For example, if the amount of thyroxine in the blood is small, then both the pituitary gland and hypothalamus will know about it. The pituitary gland will immediately release TSH, which activates the release of hormones from the thyroid gland.

Humoral regulation is the coordination of the physiological functions of the human body through blood, lymph, and tissue fluid. Humoral regulation is carried out by biologically active substances - hormones that regulate body functions at the subcellular, cellular, tissue, organ and system levels and mediators that transmit nerve impulses. Hormones are produced by the endocrine glands (endocrine), as well as by the external secretion glands (tissue - the walls of the stomach, intestines, and others). Hormones affect the metabolism and activity of various organs, entering them through the blood. Hormones have the following properties: High biological activity; Specificity – effects on certain organs, tissues, cells; They are quickly destroyed in tissues; The molecules are small in size and penetrate easily through the walls of capillaries into tissues.

Adrenal glands - paired endocrine glands of vertebrates animals and person. The zona glomerulosa produces hormones called mineralcorticoids. These include :Aldosterone (basic mineralocorticosteroid hormone adrenal cortex) Corticosterone (insignificant and relatively inactive glucocorticoid hormone). Mineralcorticoids increase reabsorption Na + and K + excretion in the kidneys. In the beam zone there are formed glucocorticoids, which include: Cortisol. Glucocorticoids have an important effect on almost all metabolic processes. They stimulate education glucose from fat And amino acids(gluconeogenesis), oppress inflammatory, immune And allergic reactions, reduce proliferation connective tissue and also increase sensitivity sense organs And excitability of the nervous system. Produced in the mesh zone sex hormones (androgens, which are precursor substances estrogen). These sex hormones play a slightly different role than the hormones secreted gonads. Adrenal medulla cells produce catecholamines - adrenalin And norepinephrine . These hormones increase blood pressure, increase heart function, dilate the lumen of the bronchi, and increase blood sugar levels. When at rest, they constantly release small amounts of catecholamines. Under the influence of a stressful situation, the secretion of adrenaline and norepinephrine by the cells of the adrenal medulla increases sharply.

The resting membrane potential is a deficiency of positive electrical charges inside the cell, resulting from the leakage of positive potassium ions from it and the electrogenic action of the sodium-potassium pump.

Action potential (AP). All stimuli acting on the cell primarily cause a decrease in PP; when it reaches a critical value (threshold), an active propagating response—PD—occurs. AP amplitude approximately = 110-120 mv. A characteristic feature of AP, which distinguishes it from other forms of cell response to stimulation, is that it obeys the “all or nothing” rule, i.e., it occurs only when the stimulus reaches a certain threshold value, and a further increase in the intensity of the stimulus no longer affects amplitude, nor on AP duration. The action potential is one of the most important components of the excitation process. In nerve fibers it ensures the conduction of excitation from sensory endings ( receptors) to the body of the nerve cell and from it to the synaptic endings located on various nerve, muscle or glandular cells. The conduction of PD along nerve and muscle fibers is carried out by the so-called. local currents, or currents of action that arise between the excited (depolarized) and the resting sections of the membrane adjacent to it.

Postsynaptic potentials (PSPs) arise in areas of the membrane of nerve or muscle cells directly adjacent to synaptic terminals. They have an amplitude of the order of several mv and duration 10-15 msec. PSPs are divided into excitatory (EPSP) and inhibitory (IPSP).

Generator potentials arise in the membrane of sensitive nerve endings - receptors. Their amplitude is on the order of several mv and depends on the strength of stimulation applied to the receptor. The ionic mechanism of generator potentials has not yet been sufficiently studied.

Action potential

An action potential is a rapid change in membrane potential that occurs when nerve, muscle, and some glandular cells are excited. Its occurrence is based on changes in the ionic permeability of the membrane. In the development of an action potential, four successive periods are distinguished: local response, depolarization, repolarization and trace potentials.

Irritability is the ability of a living organism to respond to external influences by changing its physicochemical and physiological properties. Irritability manifests itself in changes in the current values ​​of physiological parameters that exceed their shifts at rest. Irritability is a universal manifestation of the vital activity of all biosystems. These environmental changes that cause an organism's response can include a wide repertoire of reactions, ranging from diffuse protoplasmic reactions in protozoa to complex, highly specialized reactions in humans. In the human body, irritability is often associated with the property of nervous, muscle and glandular tissues to respond in the form of producing a nerve impulse, muscle contraction or secretion of substances (saliva, hormones, etc.). In living organisms lacking a nervous system, irritability can manifest itself in movements. Thus, amoebas and other protozoa leave unfavorable solutions with high salt concentrations. And plants change the position of the shoots to maximize light absorption (stretch towards the light). Irritability is a fundamental property of living systems: its presence is a classic criterion by which living things are distinguished from nonliving things. The minimum magnitude of the stimulus sufficient for the manifestation of irritability is called the perception threshold. The phenomena of irritability in plants and animals have much in common, although their manifestations in plants differ sharply from the usual forms of motor and nervous activity of animals

Laws of irritation of excitable tissues: 1) law of force– excitability is inversely proportional to the threshold force: the greater the threshold force, the less excitability. However, for excitation to occur, the force of stimulation alone is not enough. It is necessary that this irritation last for some time; 2) law of time action of the stimulus. When the same force is applied to different tissues, different durations of irritation will be required, which depends on the ability of a given tissue to manifest its specific activity, that is, excitability: the least time will be required for tissue with high excitability and the longest time for tissue with low excitability. Thus, excitability is inversely proportional to the duration of the stimulus: the shorter the duration of the stimulus, the greater the excitability. The excitability of tissue is determined not only by the strength and duration of irritation, but also by the rate (speed) of increase in the strength of irritation, which is determined by the third law - law of the rate of increase in the strength of irritation(the ratio of the strength of the stimulus to the time of its action): the greater the rate of increase in the strength of stimulation, the less excitability. Each tissue has its own threshold rate of increase in the strength of irritation.

The ability of a tissue to change its specific activity in response to stimulation (excitability) is inversely dependent on the magnitude of the threshold force, the duration of the stimulus and the speed (speed) of increase in the force of stimulation.

The critical level of depolarization is the value of the membrane potential, upon reaching which an action potential occurs. The critical level of depolarization (CLD) is the level of electrical potential of the membrane of an excitable cell from which the local potential turns into an action potential.

A local response occurs to subthreshold stimuli; spreads over 1-2 mm with attenuation; increases with increasing stimulus strength, i.e. obeys the law of “force”; sums up - increases with repeated frequent subthreshold stimulation 10 - 40 mV increases.

The chemical mechanism of synaptic transmission, compared to the electrical one, more effectively provides the basic functions of the synapse: 1) one-way signal transmission; 2) signal amplification; 3) convergence of many signals on one postsynaptic cell, plasticity of signal transmission.

Chemical synapses transmit two types of signals - excitatory and inhibitory. In excitatory synapses, the neurotransmitter released from the presynaptic nerve endings causes an excitatory post-synaptic potential in the postsynaptic membrane - local depolarization, and in inhibitory synapses - an inhibitory postsynaptic potential, as a rule, hyperpolarization. The decrease in membrane resistance that occurs during an inhibitory postsynaptic potential short-circuits the excitatory postsynaptic current, thereby weakening or blocking the transmission of excitation.

Chemical composition of the cell

Organisms are made up of cells. Cells of different organisms have similar chemical compositions. About 90 elements are found in the cells of living organisms, and about 25 of them are found in almost all cells. Based on their content in the cell, chemical elements are divided into three large groups: macroelements (99%), microelements (1%), ultramicroelements (less than 0.001%).

Macroelements include oxygen, carbon, hydrogen, phosphorus, potassium, sulfur, chlorine, calcium, magnesium, sodium, iron. Microelements include manganese, copper, zinc, iodine, fluorine. Ultramicroelements include silver, gold, bromine, selenium.

A deficiency of any element can lead to illness and even death of the body, since each element plays a specific role. Macroelements of the first group form the basis of biopolymers - proteins, carbohydrates, nucleic acids, as well as lipids, without which life is impossible. Sulfur is part of some proteins, phosphorus is part of nucleic acids, iron is part of hemoglobin, and magnesium is part of chlorophyll. Calcium plays an important role in metabolism. Some of the chemical elements contained in the cell are part of inorganic substances - mineral salts and water.

Mineral salts are found in the cell, as a rule, in the form of cations (K +, Na +, Ca 2+, Mg 2+) and anions (HPO 2-/4, H 2 PO -/4, CI -, HCO 3), the ratio of which determines the acidity of the environment, which is important for the life of cells.

Of the inorganic substances in living nature, plays a huge role water.
It makes up a significant mass of most cells. A lot of water is contained in the cells of the brain and human embryos: more than 80% water; in adipose tissue cells - only 40.% By old age, the water content in cells decreases. A person who has lost 20% of water dies. The unique properties of water determine its role in the body. It is involved in thermoregulation, which is caused by the high heat capacity of water - the consumption of a large amount of energy when heating. Water - good solvent. Due to their polarity, its molecules interact with positively and negatively charged ions, thereby promoting the dissolution of the substance. In relation to water, all cell substances are divided into hydrophilic and hydrophobic.

Hydrophilic(from Greek hydro- water and filleo- love) are called substances that dissolve in water. These include ionic compounds (for example, salts) and some non-ionic compounds (for example, sugars).

Hydrophobic(from Greek hydro- water and Phobos- fear) are substances that are insoluble in water. These include, for example, lipids.

Water plays an important role in the chemical reactions that occur in the cell in aqueous solutions. It dissolves metabolic products that the body does not need and thereby promotes their removal from the body. The high water content in the cell gives it elasticity. Water facilitates the movement of various substances within a cell or from cell to cell.

Inorganic compounds in the human body.

Water. Of the inorganic substances that make up the cell, the most important is water. Its amount ranges from 60 to 95% of the total cell mass. Water plays a vital role in the life of cells and living organisms in general. In addition to the fact that it is part of their composition, for many organisms it is also a habitat. The role of water in the cell is determined by its unique chemical and physical properties, associated mainly with the small size of its molecules, the polarity of its molecules and their ability to form hydrogen bonds with each other. Water as a component of biological systems performs the following essential functions: 1- Water- universal solvent for polar substances, such as salts, sugars, alcohols, acids, etc. Substances that are highly soluble in water are called hydrophilic. 2- Water does not dissolve non-polar substances and does not mix with them, since it cannot form hydrogen bonds with them. Substances that are insoluble in water are called hydrophobic. Hydrophobic molecules or parts of them are repelled by water, and in its presence they are attracted to each other. Such interactions play an important role in ensuring the stability of membranes, as well as many protein molecules, nucleic acids and a number of subcellular structures. .3- Water has a high specific heat capacity. 4- Water is characterized high heat of vaporization, i.e. e. the ability of molecules to carry away a significant amount of heat while simultaneously cooling the body. 5- It is exclusively characteristic of water high surface tension. 6- Water provides movement of substances in the cell and body, absorption of substances and excretion of metabolic products. 7- In plants, water determines turgor cells, and in some animals performs support functions, being a hydrostatic skeleton (round and annelids, echinoderms). 8- Water is an integral part lubricating fluids(synovial - in the joints of vertebrates, pleural - in the pleural cavity, pericardial - in the pericardial sac) and slime(facilitate the movement of substances through the intestines, create a moist environment on the mucous membranes of the respiratory tract). It is part of saliva, bile, tears, sperm, etc.

Mineral salts. Modern methods of chemical analysis have revealed 80 elements of the periodic table in the composition of living organisms. Based on their quantitative composition, they are divided into three main groups. Macroelements make up the bulk of organic and inorganic compounds, their concentration ranges from 60% to 0.001% of body weight (oxygen, hydrogen, carbon, nitrogen, sulfur, magnesium, potassium, sodium, iron, etc.). Microelements are mainly ions of heavy metals. Contained in organisms in the amount of 0.001% - 0.000001% (manganese, boron, copper, molybdenum, zinc, iodine, bromine). The concentration of ultramicroelements does not exceed 0.000001%. Their physiological role in organisms has not yet been fully elucidated. This group includes uranium, radium, gold, mercury, cesium, selenium and many other rare elements. Not only the content, but also the ratio of ions in the cell is significant. The difference between the amounts of cations and anions on the surface and inside the cell ensures the occurrence action potential , what underlies the occurrence of nervous and muscle excitation.

The bulk of the tissues of living organisms inhabiting the Earth are made up of organogenic elements: oxygen, carbon, hydrogen and nitrogen, from which organic compounds are mainly built - proteins, fats, carbohydrates.

Introduction

I chose a rather complex topic, since it combines many sciences, the study of which is very important in the world: biology, ecology, chemistry, etc. My topic is significant in school chemistry and biology courses. Man is a very complex living organism, but studying him seemed quite interesting to me. I believe that every person should know what they consist of.

Target: study in more detail the chemical elements that make up humans and their interaction in the body.

To achieve this goal, the following were set: tasks:

• 1) Study the elemental composition of living organisms;
• 2) Identify the main groups of chemical elements: micro- and macroelements;
• 3) Determine which chemical elements are responsible for growth, muscle function, nervous system, etc.;
• 4) Conduct laboratory experiments confirming the presence of carbon, nitrogen and iron in the human body.

Methods and techniques: analysis of scientific literature, comparative analysis, synthesis, classification and generalization of selected material; observation method, experiment (physical and chemical).

Chemical elements in the human body

All living organisms on Earth, including humans, are in close contact with the environment. Food and drinking water contribute to the entry of almost all chemical elements into the body. They are introduced into and removed from the body every day. Analyzes have shown that the number of individual chemical elements and their ratio in the healthy body of different people is approximately the same.

Many scientists believe that not only are all chemical elements present in a living organism, but each of them performs a specific biological function. The role of about 30 chemical elements has been reliably established, without which the human body cannot exist normally. These elements are called vital. The human body consists of 60% water, 34% organic and 6% inorganic substances.

The body of a person weighing 70 kg consists of:

Carbon - 12.6 kg Chlorine - 200 grams

Oxygen-45.5 kg Phosphorus-0.7 kg

Hydrogen-7 kg Sulfur-175 grams

Nitrogen-2.1 kg Iron-5 grams

Calcium-1.4 kg Fluorine-100 grams

Sodium-150 grams Silicon-3 grams

Potassium-100 grams Iodine-0.1 grams

Magnesium-200 grams Arsenic-0.0005 grams

4 pillars of life

Carbon, oxygen, nitrogen and hydrogen are the four chemical elements that chemists call the “whales of chemistry”, and which at the same time are the basic elements of life. Not only living proteins, but all of nature around us and in us are built from the molecules of these four elements.

In isolation, carbon is a dead stone. Nitrogen, like oxygen, is a free gas. Nitrogen is not bound by anything. Hydrogen combined with oxygen forms water, and together they create the Universe.

In their simple compounds they are water on Earth, clouds in the atmosphere and air. In more complex compounds these are carbohydrates, salts, acids, alkalis, alcohols, sugars, fats and proteins. Becoming even more complex, they reach the highest stage of development - they create life.

Carbon - the basis of life.

All organic substances from which living organisms are built differ from inorganic ones in that they are based on the chemical element carbon. Organic substances also contain other elements: hydrogen, oxygen, nitrogen, sulfur and phosphorus. But they all cluster around carbon, which is the main central element.

Academician Fersman called it the basis of life, because without carbon life is impossible. There is no other chemical element with such unique properties as carbon.

However, this does not mean that carbon makes up the bulk of living matter. In any organism there is only 10% carbon, 80% water, and the remaining ten percent comes from other chemical elements that make up the body.

A characteristic feature of carbon in organic compounds is its unlimited ability to bind different elements into atomic groups in a variety of combinations.

A little chemistry

Of the 92 chemical elements currently known to science, 81 elements are found in the human body. Among them are 4 main ones: C (carbon), H (hydrogen), O (oxygen), N (nitrogen), as well as 8 macro- and 69 microelements.

Macronutrients

Macronutrients- these are substances whose content exceeds 0.005% of body weight. This Ca (calcium), Cl (chlorine), F (fluorine). K (potassium), Mg (magnesium), Na (sodium), P (phosphorus) and S (sulfur). They are part of the main tissues - bones, blood, muscles. Together, major and macroelements make up 99% of a person’s body weight.

Microelements

Microelements- these are substances whose content does not exceed 0.005% for each individual element, and their concentration in tissues does not exceed 0.000001%. Microelements are also very important for normal life.

A special subgroup of microelements are ultramicroelements, contained in the body in extremely small quantities, are gold, uranium, mercury, etc.

70-80% of the human body consists of water, the rest is made up of organic and mineral substances.

Organic matter

Organic matter can be formed (or synthesized artificially) from minerals. The main component of all organic substances is carbon(the study of the structure, chemical properties, methods of production and practical use of various carbon compounds is the subject of organic chemistry). Carbon is the only chemical element capable of forming a huge number of different compounds (the number of these compounds exceeds 10 million!). It is present in proteins, fats and carbohydrates, which determine the nutritional value of our food; is part of all animal organisms and plants.

In addition to carbon, organic compounds often contain oxygen, nitrogen, Sometimes - phosphorus, sulfur and other elements, but many of these compounds have inorganic properties. There is no sharp line between organic and inorganic substances. Main signs of organic compounds hydrocarbons have different carbon-hydrogen compounds and their derivatives. Molecules of any organic substances contain hydrocarbon fragments.

A special science deals with the study of various types of organic compounds found in living organisms, their structure and properties - biochemistry.

Depending on their structure, organic compounds are divided into simple ones - amino acids, sugars and fatty acids, more complex ones - pigments, as well as vitamins and coenzymes (non-protein components of enzymes), and the most complex ones - squirrels And nucleic acids.

The properties of organic substances are determined not only by the structure of their molecules, but also by the number and nature of their interactions with neighboring molecules, as well as their mutual spatial arrangement. These factors are most clearly manifested in the differences in the properties of substances located in different states of aggregation.

The process of transformation of substances, accompanied by a change in their composition and (or) structure, is called chemical reaction. The essence of this process is the breaking of chemical bonds in the starting substances and the formation of new bonds in the reaction products. The reaction is considered complete if the material composition of the reaction mixture no longer changes.

Reactions of organic compounds (organic reactions) obey the general laws of chemical reactions. However, their course is often more complex than in the case of the interaction of inorganic compounds. Therefore, in organic chemistry, much attention is paid to the study of reaction mechanisms.

Minerals

Minerals in the human body less than organic ones, but they are also vital. Such substances include iron, iodine, copper, zinc, cobalt, chromium, molybdenum, nickel, vanadium, selenium, silicon, lithium etc. Despite the small need in quantitative terms, they qualitatively influence the activity and speed of all biochemical processes. Without them, normal digestion of food and synthesis of hormones are impossible. With a deficiency of these substances in the human body, specific disorders arise, leading to characteristic diseases. Microelements are especially important for children during the period of intensive growth of bones, muscles and internal organs. With age, a person's need for minerals decreases somewhat.

As you know, all substances can be divided into two large categories - mineral and organic. You can give a large number of examples of inorganic, or mineral, substances: salt, soda, potassium. But what types of connections fall into the second category? Organic substances are present in any living organism.

Squirrels

The most important example of organic substances are proteins. They contain nitrogen, hydrogen and oxygen. In addition to these, sometimes sulfur atoms can also be found in some proteins.

Proteins are among the most important organic compounds and are the most commonly found in nature. Unlike other compounds, proteins have certain characteristic features. Their main property is their huge molecular weight. For example, the molecular weight of an alcohol atom is 46, benzene is 78, and hemoglobin is 152,000. Compared to the molecules of other substances, proteins are real giants, containing thousands of atoms. Sometimes biologists call them macromolecules.

Proteins are the most complex of all organic structures. They belong to the class of polymers. If you examine a polymer molecule under a microscope, you can see that it is a chain consisting of simpler structures. They are called monomers and are repeated many times in polymers.

In addition to proteins, there are a large number of polymers - rubber, cellulose, as well as ordinary starch. Also, many polymers were created by human hands - nylon, lavsan, polyethylene.

Protein formation

How are proteins formed? They are an example of organic substances, the composition of which in living organisms is determined by the genetic code. In their synthesis, in the vast majority of cases, various combinations are used

Also, new amino acids can be formed already when the protein begins to function in the cell. However, it contains only alpha amino acids. The primary structure of the substance being described is determined by the sequence of amino acid residues. And in most cases, when a protein is formed, the polypeptide chain is twisted into a spiral, the turns of which are located close to each other. As a result of the formation of hydrogen compounds, it has a fairly strong structure.

Fats

Another example of organic substances is fats. Man knows many types of fats: butter, beef and fish oil, vegetable oils. Fats are formed in large quantities in plant seeds. If you place a peeled sunflower seed on a sheet of paper and press it down, an oily stain will remain on the sheet.

Carbohydrates

Carbohydrates are no less important in living nature. They are found in all plant organs. The carbohydrate class includes sugar, starch, and fiber. Potato tubers and banana fruits are rich in them. It is very easy to detect starch in potatoes. When reacting with iodine, this carbohydrate turns blue. You can verify this by dropping a little iodine onto a cut potato.

Sugars are also easy to detect - they all taste sweet. Many carbohydrates of this class are found in the fruits of grapes, watermelons, melons, and apple trees. They are examples of organic substances that are also produced in artificial conditions. For example, sugar is extracted from sugar cane.

How are carbohydrates formed in nature? The simplest example is the process of photosynthesis. Carbohydrates are organic substances that contain a chain of several carbon atoms. They also contain several hydroxyl groups. During photosynthesis, inorganic sugar is formed from carbon monoxide and sulfur.

Cellulose

Another example of organic matter is fiber. Most of it is found in cotton seeds, as well as plant stems and leaves. Fiber consists of linear polymers, its molecular weight ranges from 500 thousand to 2 million.

In its pure form, it is a substance that has no smell, taste or color. It is used in the manufacture of photographic film, cellophane, and explosives. Fiber is not absorbed by the human body, but is a necessary part of the diet, as it stimulates the functioning of the stomach and intestines.

Organic and inorganic substances

We can give many examples of the formation of organic and second always originating from minerals - non-living ones that are formed in the depths of the earth. They are also found in various rocks.

Under natural conditions, inorganic substances are formed during the destruction of minerals or organic substances. On the other hand, organic substances are constantly formed from minerals. For example, plants absorb water with compounds dissolved in it, which subsequently move from one category to another. Living organisms use mainly organic substances for nutrition.

Reasons for diversity

Often, schoolchildren or students need to answer the question of what are the reasons for the diversity of organic substances. The main factor is that carbon atoms are connected to each other using two types of bonds - simple and multiple. They can also form chains. Another reason is the variety of different chemical elements that are included in organic matter. In addition, diversity is also due to allotropy - the phenomenon of the existence of the same element in different compounds.

How are inorganic substances formed? Natural and synthetic organic substances and their examples are studied both in high school and in specialized higher educational institutions. The formation of inorganic substances is not such a complex process as the formation of proteins or carbohydrates. For example, people have been extracting soda from soda lakes since time immemorial. In 1791, chemist Nicolas Leblanc proposed synthesizing it in the laboratory using chalk, salt, and sulfuric acid. Once upon a time, soda, which is familiar to everyone today, was a rather expensive product. To conduct the experiment, it was necessary to calcinate table salt together with acid, and then calcinate the resulting sulfate along with limestone and charcoal.

Another is potassium permanganate, or potassium permanganate. This substance is obtained industrially. The formation process consists of electrolysis of a solution of potassium hydroxide and a manganese anode. In this case, the anode gradually dissolves to form a purple solution - this is the well-known potassium permanganate.

CHEMICAL ELEMENTS IN THE HUMAN BODY (KUKUSHKIN Y. N., 1998), CHEMISTRY

For the human body, the role of about 30 chemical elements has been definitely established, without which it cannot exist normally. These elements are called vital. In addition to them, there are elements that in small quantities do not affect the functioning of the body, but at certain levels are poisons.

CHEMICAL ELEMENTS IN THE HUMAN BODY

Yu. N. KUKUSHKIN

St. Petersburg State Technological Institute

INTRODUCTION

Many chemists know the famous words spoken in the 40s of this century by the German scientists Walter and Ida Noddack, that every cobblestone on the pavement contains all the elements of the Periodic Table. At first, these words were not met with unanimous approval. However, as more and more accurate methods for the analytical determination of chemical elements were developed, scientists became increasingly convinced of the truth of these words.

If we agree that every cobblestone contains all the elements, then this should also be true for a living organism. All living organisms on Earth, including humans, are in close contact with the environment. Life requires constant metabolism in the body. The entry of chemical elements into the body is facilitated by nutrition and consumed water. In accordance with the recommendation of the Dietetic Commission of the US National Academy, the daily intake of chemical elements from food should be at a certain level (Table 1). The same number of chemical elements must be excreted from the body every day, since their contents are relatively constant.

The assumptions of some scientists go further. They believe that not only are all chemical elements present in a living organism, but each of them performs a specific biological function. It is quite possible that this hypothesis will not be confirmed. However, as research in this direction develops, the biological role of an increasing number of chemical elements is revealed.

The human body consists of 60% water, 34% organic matter and 6% inorganic matter. The main components of organic substances are carbon, hydrogen, oxygen, they also include nitrogen, phosphorus and sulfur. Inorganic substances of the human body necessarily contain 22 chemical elements: Ca, P, O, Na, Mg, S, B, Cl, K, V, Mn, Fe, Co, Ni, Cu, Zn, Mo, Cr, Si, I ,F,Se. For example, if a person weighs 70 kg, then it contains (in grams): calcium - 1700, potassium - 250, sodium - 70, magnesium - 42, iron - 5, zinc - 3.

Scientists have agreed that if the mass fraction of an element in the body exceeds 10 -2%, then it should be considered a macroelement. The proportion of microelements in the body is 10 -3 -10 -5%. If the content of an element is below 10 -5%, it is considered ultramicroelement. Of course, such a gradation is arbitrary. Through it, magnesium enters the intermediate region between macro- and microelements.

Table 1. Daily intake of chemical elements into the human body

Chemical element	Daily intake, mg
	adults
	About 0.2 (vitamin B 12)

VITAL ELEMENTS

Undoubtedly, time will make adjustments to modern ideas about the number and biological role of certain chemical elements in the human body. In this article we will proceed from what is already reliably known. The role of macroelements that make up inorganic substances is obvious. For example, the main amount of calcium and phosphorus enters the bones (calcium hydroxyphosphate Ca 10 (PO 4) 6 (OH) 2), and chlorine in the form of hydrochloric acid is found in gastric juice.

Microelements are included in the above-mentioned series of 22 elements that are necessarily present in the human body. Note that most of them are metals, and of the metals more than half are d-elements. The latter form coordination compounds in the body with complex organic molecules. Thus, it has been established that many biological catalysts - enzymes contain transition metal ions ( d-elements). For example, it is known that manganese is part of 12 different enzymes, iron - in 70, copper - in 30, and zinc - in more than 100. Microelements are called vital if their absence or deficiency disrupts the normal functioning of the body. A characteristic feature of the required element is the bell-shaped appearance of the dose curve ( n) - responsiveness ( R, effect) (Fig. 1).

Rice. 1. Response dependence ( R) from dose ( n) for vital elements

With a small intake of this element, significant damage is caused to the body. He functions on the edge of survival. This is mainly due to a decrease in the activity of enzymes that contain this element. As the dose of the element increases, the response increases and reaches the norm (plateau). With a further increase in the dose, the toxic effect of an excess of this element appears, as a result of which death cannot be ruled out. The curve in Fig. 1 can be interpreted as follows: everything should be in moderation and very little and very much are harmful. For example, a lack of iron in the body leads to anemia, since it is part of the hemoglobin in the blood, or more precisely, its component - heme. An adult's blood contains about 2.6 g of iron. In the process of life, the body constantly breaks down and synthesizes hemoglobin. To replenish the iron lost with the breakdown of hemoglobin, a person needs an average daily intake of about 12 mg of this element from food. The connection between anemia and iron deficiency has been known to doctors for a long time, since back in the 17th century in some European countries an infusion of iron filings in red wine was prescribed for anemia. However, excess iron in the body is also harmful. It is associated with siderosis of the eyes and lungs - diseases caused by the deposition of iron compounds in the tissues of these organs. The main regulator of iron content in the blood is the liver.

A lack of copper in the body leads to the destruction of blood vessels, pathological bone growth, and defects in connective tissues. In addition, copper deficiency is believed to be one of the causes of cancer. In some cases, doctors associate lung cancer in older people with an age-related decrease in copper content in the body. However, excess copper in the body leads to mental disorders and paralysis of some organs (Wilson's disease). Only relatively large amounts of copper compounds are harmful to humans. In small doses they are used in medicine as an astringent and bacteriostasis (inhibiting the growth and reproduction of bacteria) agent. For example, copper (II) sulfate is used in the treatment of conjunctivitis in the form of eye drops (25% solution), as well as for cauterization for trachoma in the form of eye pencils (an alloy of copper (II) sulfate, potassium nitrate, alum and camphor) . In case of skin burns with phosphorus, the skin is thoroughly moistened with a 5% solution of copper (II) sulfate.

Table 2. Characteristic symptoms of deficiency of chemical elements in the human body

Element deficiency	Typical symptom
	Slower skeletal growth
	Muscle cramps
	Anemia, immune system disorder
	Skin damage, slowed growth, delayed puberty
	Arterial weakness, liver dysfunction, secondary anemia
	Infertility, deterioration of skeletal growth
	Slow cell growth, susceptibility to caries
	Pernicious anemia
	Increased incidence of depression, dermatitis
	Diabetes symptoms
	Skeletal growth disorder
	Dental caries
	Thyroid dysfunction, slow metabolism
	Muscular (particularly cardiac) weakness

The biological function of other alkali metals in a healthy body is still unclear. However, there are indications that by introducing lithium ions into the body it is possible to treat one of the forms of manic-depressive psychosis. Let's give a table. 2, from which the important role of other vital elements is visible.

IMPURITY ELEMENTS

There are a large number of chemical elements, especially heavy ones, which are poisons for living organisms - they have adverse biological effects. In table 3 shows these elements in accordance with the Periodic Table of D.I. Mendeleev.

Table 3.

Period	Group

With the exception of beryllium and barium, these elements form strong sulfide compounds. There is an opinion that the reason for the action of poisons is associated with the blocking of certain functional groups (in particular, sulfhydryl groups) of the protein or with the displacement of metal ions, such as copper and zinc, from certain enzymes. The elements presented in table. 3 are called impurities. Their dose-response diagram has a different shape compared to life-saving (Figure 2).

Rice. 2. Response dependence ( R) from dose ( n) for impurity chemical elements Up to a certain content of these elements, the body does not experience any harmful effects, but with a significant increase in concentration they become toxic.

There are elements that are poisonous in relatively large quantities, but have a beneficial effect in low concentrations. For example, arsenic, a strong poison that disrupts the cardiovascular system and affects the kidneys and liver, is beneficial in small doses, and doctors prescribe it to improve appetite. Oxygen, which a person needs for breathing, in high concentrations (especially under pressure) has a toxic effect.

From these examples it is clear that the concentration of the element in the body plays a very significant, and sometimes catastrophic, role. Among the impurity elements there are also those that in small doses have effective healing properties. Thus, the bactericidal (causing the death of various bacteria) property of silver and its salts was noticed long ago. For example, in medicine, a solution of colloidal silver (collargol) is used to wash purulent wounds, the bladder, for chronic cystitis and urethitis, as well as in the form of eye drops for purulent conjunctivitis and blennorrhea. Silver nitrate pencils are used to cauterize warts and granulations. In diluted solutions (0.1-0.25%), silver nitrate is used as an astringent and antimicrobial agent for lotions, and also as eye drops. Scientists believe that the cauterizing effect of silver nitrate is associated with its interaction with tissue proteins, which leads to the formation of protein salts of silver - albuminates. Silver is not yet classified as a vital element, but its increased content in the human brain, endocrine glands, and liver has already been experimentally established. Silver enters the body through plant foods, such as cucumbers and cabbage.

The article presents the Periodic Table, in which the bioactivity of individual elements is characterized. The assessment is based on the manifestation of symptoms of deficiency or excess of a particular element. It takes into account the following symptoms (in order of increasing effect): 1 - loss of appetite; 2 - need to change diet; 3 - significant changes in tissue composition; 4 - increased damage to one or more biochemical systems, manifested under special conditions; 5 - incapacity of these systems in special conditions; 6 - subclinical signs of incapacity; 7 - clinical symptoms of incapacity and increased damage; 8 - inhibited growth; 9 - lack of reproductive function. The extreme form of manifestation of deficiency or excess of an element in the body is death. The bioactivity of the element was assessed on a nine-point scale depending on the nature of the symptom for which specificity was identified.

With this assessment, vital elements are characterized by the highest score. For example, the elements hydrogen, carbon, nitrogen, oxygen, sodium, magnesium, phosphorus, sulfur, chlorine, potassium, calcium, manganese, iron, etc. are characterized by a score of 9.

CONCLUSION

Identifying the biological role of individual chemical elements in the functioning of living organisms (humans, animals, plants) is an important and exciting task. Minerals, like vitamins, often act as coenzymes to catalyze chemical reactions that occur all the time in the body.

The efforts of specialists are aimed at revealing the mechanisms of manifestation of the bioactivity of individual elements at the molecular level (see articles by N.A. Ulakhnovich “Metal complexes in living organisms”: Soros Educational Journal. 1997. No. 8. P. 27-32; D.A. Lemenovsky “Compounds of metals in living nature”: Ibid. No. 9. P. 48-53). There is no doubt that in living organisms, metal ions are found mainly in the form of coordination compounds with “biological” molecules that act as ligands. Due to space limitations, the article contains material related mainly to the human body. Clarifying the role of metals in the life of plants will undoubtedly be useful for agriculture. Work in this direction is widely carried out in laboratories in various countries.

A very interesting question is about the principles of nature’s selection of chemical elements for the functioning of living organisms. There is no doubt that their prevalence is not a decisive factor. A healthy body itself is able to regulate the content of individual elements. Given a choice (food and water), animals can instinctively contribute to this regulation. The capabilities of plants in this process are limited. Conscious regulation by humans of the content of microelements in the soil of agricultural land is also one of the important tasks facing researchers. The knowledge acquired by scientists in this direction has already formed into a new branch of chemical science - bioinorganic chemistry. Therefore, it is appropriate to recall the words of the outstanding scientist of the 19th century A. Ampere: “Happy are those who develop science in the years when it is not completed, but when a decisive turn is already ripe in it.” These words can be especially useful to those who are faced with choosing a profession.

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Yuri Nikolaevich Kukushkin, Doctor of Chemical Sciences, Professor, Head. Department of Inorganic Chemistry of the St. Petersburg State Technological Institute, Honored Scientist of the Russian Federation, laureate of the Prize named after. L.A. Chugaev of the USSR Academy of Sciences, academician of the Russian Academy of Natural Sciences. Area of ​​scientific interests: coordination chemistry and chemistry of platinum metals. Author and co-author of more than 600 scientific articles, 14 monographs, textbooks and popular science books, 49 inventions.