Chemical elements in the human body. Organic and inorganic substances

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 apples. 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 their 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.

1 Organic and inorganic substances

I. Inorganic compounds.

1.Water, its properties and importance for biological processes.

Water is a universal solvent. It has a high heat capacity and at the same time high thermal conductivity for liquids. These properties make water an ideal liquid for maintaining the body's thermal balance.

Due to the polarity of its molecules, water acts as a structure stabilizer.

Water is a source of oxygen and hydrogen, it is the main medium where biochemical and chemical reactions take place, the most important reagent and product of biochemical reactions.

Water is characterized by complete transparency in the visible part of the spectrum, which is important for the process of photosynthesis and transpiration.

Water practically does not compress, which is very important for giving shape to organs, creating turgor and ensuring a certain position of organs and parts of the body in space.

Thanks to water, osmotic reactions in living cells are possible.

Water is the main means of transport of substances in the body (blood circulation, ascending and descending currents of solutions throughout the plant’s body, etc.).

2. Minerals.

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.

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.

II. The role and function of individual elements.

Nitrogen in autotrophic plants is the initial product of nitrogen and protein metabolism. Nitrogen atoms are part of many other non-protein, but important compounds: pigments (chlorophyll, hemoglobin), nucleic acids, vitamins.

Phosphorus is part of many vital compounds. Phosphorus is part of AMP, ADP, ATP, nucleotides, phosphorylated saccharides, and some enzymes. Many organisms contain phosphorus in mineral form (soluble cell sap phosphates, bone tissue phosphates).

After the organisms die, phosphorus compounds are mineralized. Thanks to root secretions and the activity of soil bacteria, phosphates are dissolved, which makes it possible for phosphorus to be absorbed by plant and then animal organisms.

Sulfur is involved in the construction of sulfur-containing amino acids (cystine, cysteine), and is part of vitamin B1 and some enzymes. Sulfur and its compounds are especially important for chemosynthetic bacteria. Sulfur compounds are formed in the liver as products of the disinfection of toxic substances.

Potassium is found in cells only in the form of ions. Thanks to potassium, the cytoplasm has certain colloidal properties; Potassium activates protein synthesis enzymes, determines the normal rhythm of cardiac activity, and participates in the generation of bioelectric potentials and in the processes of photosynthesis.

Sodium (contained in ionic form) makes up a significant part of the minerals in the blood and therefore plays an important role in regulating the body’s water metabolism. Sodium ions contribute to the polarization of the cell membrane; the normal rhythm of cardiac activity depends on the presence in the nutrient medium of the required amount of sodium, potassium, and calcium salts.

Calcium in its ionic state is an antagonist of potassium. It is part of membrane structures and, in the form of salts of pectin substances, glues plant cells together. In plant cells it is often found in the form of simple, needle-shaped or fused crystals of calcium oxalate.

Magnesium is contained in cells in a certain ratio with calcium. It is part of the chlorophyll molecule, activates energy metabolism and DNA synthesis.

Iron is an integral part of the hemoglobin molecule. It is involved in the biosynthesis of chlorophyll, so when there is a lack of iron in the soil, plants develop chlorosis. The main role of iron is participation in the processes of respiration and photosynthesis by transferring electrons as part of oxidative enzymes - catalase, ferredoxin. A certain supply of iron in the body of animals and humans is stored in the iron-containing protein ferritin, contained in the liver and spleen.

Copper is found in animals and plants, where it plays an important role. Copper is part of some enzymes (oxidases). The importance of copper for the processes of hematopoiesis, the synthesis of hemoglobin and cytochromes has been established.

Every day, 2 mg of copper enters the human body with food. In plants, copper is part of many enzymes that participate in the dark reactions of photosynthesis and other biosyntheses. Animals with copper deficiency experience anemia, loss of appetite, and heart disease.

Manganese is a microelement, insufficient quantities of which cause chlorosis in plants. Manganese also plays a large role in the processes of nitrate reduction in plants.

Zinc is part of some enzymes that activate the breakdown of carbonic acid.

Boron affects growth processes, especially of plant organisms. In the absence of this microelement in the soil, conducting tissues, flowers and ovaries die off in plants.

Recently, microelements have been widely used in crop production (pre-sowing seed treatment) and in animal husbandry (microelement feed additives).

Other inorganic components of the cell are most often found in the form of salts, dissociated in solution into ions, or in an undissolved state (phosphorus salts of bone tissue, calcareous or silicon shells of sponges, corals, diatoms, etc.).

III. Organic compounds.

Carbohydrates (saccharides). The molecules of these substances are built from only three elements - carbon, oxygen and hydrogen. Carbons are the main source of energy for living organisms. In addition, they provide organisms with compounds that are later used for the synthesis of other compounds.

The most famous and widespread carbohydrates are mono- and disaccharides dissolved in water. They crystallize and taste sweet.

Monosaccharides (monoses) are compounds that cannot be hydrolyzed. Saccharides can polymerize to form higher molecular weight compounds - di-, tri-, and polysaccharides.

Oligosaccharides. The molecules of these compounds are built from 2 to 4 molecules of monosaccharides. These compounds can also crystallize, are easily soluble in water, taste sweet, and have a constant molecular weight. Examples of oligosaccharides include the disaccharides sucrose, maltose, lactose, stachyose tetrasaccharide, etc.

Polysaccharides (polyoses) are water-insoluble compounds (form a colloidal solution) that do not have a sweet taste. Like the previous group of carbohydrates, they can be hydrolyzed (arabans, xylans, starch, glycogen). The main function of these compounds is binding, gluing together connective tissue cells, protecting cells from unfavorable factors.

Lipids are a group of compounds that are found in all living cells; they are insoluble in water. The structural units of lipid molecules can be either simple hydrocarbon chains or residues of complex cyclic molecules.

Depending on their chemical nature, lipids are divided into fats and lipoids.

Fats (triglycerides, neutral fats) are the main group of lipids. They are esters of the trihydric alcohol glycerol and fatty acids or a mixture of free fatty acids and triglycerides.

Free fatty acids are also found in living cells: palmitic, stearic, ricinic.

Lipoids are fat-like substances. They are of great importance because, due to their structure, they form clearly oriented molecular layers, and the ordered arrangement of hydrophilic and hydrophobic ends of molecules is of primary importance for the formation of membrane structures with selective permeability.

Enzymes. These are biological catalysts of a protein nature that can accelerate biochemical reactions. Enzymes are not destroyed during biochemical transformations, so relatively small amounts of them catalyze reactions of large amounts of substance. A characteristic difference between enzymes and chemical catalysts is their ability to accelerate reactions under normal conditions.

According to their chemical nature, enzymes are divided into two groups - one-component (consisting only of protein, their activity is determined by the active center - a specific group of amino acids in a protein molecule (pepsin, trypsin)) and two-component (consisting of protein (apoenzyme - protein carrier) and a protein component ( coenzyme), and the chemical nature of coenzymes can be different, since they can consist of organic (many vitamins, NAD, NADP) or inorganic (metal atoms: iron, magnesium, zinc)).

The function of enzymes is to reduce the activation energy, i.e. in reducing the level of energy required to make a molecule reactivity.

Modern classification of enzymes is based on the types of chemical reactions they catalyze. Hydrolase enzymes accelerate the reaction of breaking down complex compounds into monomers (amylase (hydrolyzes starch), cellulase (decomposes cellulose to monosaccharides), protease (hydrolyzes proteins to amino acids)).

Oxidoreductase enzymes catalyze redox reactions.

Transferases transfer aldehyde, ketone and nitrogen groups from one molecule to another.

Lyases cleave individual radicals to form double bonds or catalyze the addition of groups to double bonds.

Isomerases carry out isomerization.

Ligases catalyze reactions between two molecules using the energy of ATP or other triophosphate.

Pigments are high molecular weight natural colored compounds. Of the several hundred compounds of this type, the most important are metalloporphyrin and flavin pigments.

Metalloporphyrin, which contains a magnesium atom, forms the base of the molecule of green plant pigments - chlorophylls. If there is an iron atom in place of magnesium, then such a metalloporphyrin is called heme.

The hemoglobin of red blood cells in humans, all other vertebrates and some invertebrates contains iron oxide, which gives the blood its red color. Hemerythrin gives the blood a pink color (some polychaete worms). Chlorocruorin colors blood and tissue fluid green.

The most common respiratory pigments in the blood are hemoglobin and hemocyan (the respiratory pigment of higher crustaceans, arachnids, and some octopus mollusks).

Chromoproteins also include cytochromes, catalase, peroxidase, myoglobin (found in muscles and creates a supply of oxygen, which allows marine mammals to stay under water for a long time).

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 a 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 nervous system excitability. 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 bronchial tubes, 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 that lack 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 irritation (excitability) is inversely dependent on the magnitude of the threshold force, the duration of the stimulus and the speed (speed) of increase in the strength of irritation.

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 due to 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 a 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.

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.

Our entire world: plants, fauna, everything that surrounds us, consists of the same microelements, which are present in different concentrations in everything and, of course, in our food.

Every element affects our health. The content of elements in food products is very variable. A more stable and constant value is the content of elements in the body of a healthy person, although it may also have variability (variability).

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.

Macronutrients- content in the body of more than one gram: phosphorus, potassium, sulfur, sodium, chlorine, magnesium, iron, fluorine, zinc, silicon, zirconium - 11 elements.

Microelements- content in the body of more than one milligram: rubidium, strontium, bromine, lead, niobium, copper, aluminum, cadmium, barium, boron (top ten microelements), tellurium, vanadium, arsenic, tin, selenium, titanium, mercury, manganese, iodine , nickel, gold, molybdenum, antimony, chromium, yttrium, cobalt, cesium, germanium - 28 elements. Every element affects our health. The content of elements in food products is very variable. A more stable and constant value is the content of elements in the body of a healthy person, although it may also have variability (variability).

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%.

There are a large number of chemical elements, especially heavy ones, which are poisons for living organisms - they have adverse biological effects. These elements include: Ba, Ni, Pd, Pt, Au, Ag, Hg, Cd, Tl, Pb, As, Sb, Se.

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. 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 urethritis, 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.

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.

Organic substances of the cell. The main vital compounds are proteins, fats and carbohydrates. Biopolymers.

Organic compounds make up on average 20-30% of the cell mass of a living organism. These include biological polymers, proteins, carbohydrates, lipids, hormones, nucleic acids, and vitamins.

Biological polymers– organic compounds that make up the cells of living organisms. A polymer is a multi-link chain of simple substances - monomers (n ÷ 10 thousand - 100 thousand monomers.

The properties of biopolymers depend on the structure of their molecules, on the number and variety of monomer units. If the monomers are different, then their repeated alternations in the chain create a regular polymer.

…A – A – B – A – A – B... regular

…A – A – B – B – A – B – A... irregular

Carbohydrates

General formula Сn(H 2 O)m

Carbohydrates play the role of energy substances in the human body. The most important of them are sucrose, glucose, fructose, and starch. They are quickly absorbed ("burned") in the body. The exception is fiber (cellulose), which is especially abundant in plant foods. It is practically not absorbed by the body, but is of great importance: it acts as ballast and helps digestion, mechanically cleansing the mucous membranes of the stomach and intestines. There are a lot of carbohydrates in potatoes and vegetables, cereals, pasta, fruits and bread.

Example: glucose, ribose, fructose, deoxyribose – monosaccharides. Sucrose – disaccharides. Starch, glycogen, cellulose - polysaccharides

Being in nature: in plants, fruits, pollen, vegetables (garlic, beets), potatoes, rice, corn, wheat grain, wood...

Their functions:

1) energy: during oxidation to CO2 and H2O, energy is released; excess energy is stored in liver and muscle cells in the form of glycogen;

2) construction: in a plant cell - a strong base of cell walls (cellulose);

3) structural: they are part of the intercellular substance of the skin and cartilage tendons;

4) recognition by other cells: as part of cell membranes, if separated liver cells are mixed with kidney cells, they will independently separate into two groups due to the interaction of cells of the same type.

Lipids (lipoids, fats)

Lipids include various fats, fat-like substances, phospholipids... All of them are insoluble in water, but soluble in chloroform, ether...

Being in nature: in animal and human cells in the cell membrane; between the cells is the subcutaneous layer of fat.

Functions:

1) thermal insulation (in whales, pinnipeds...);

2) reserve nutrient;

3) energy: energy is released during the hydrolysis of fats;

4) structural: some lipids serve as an integral part of cell membranes.

Fats also serve as a source of energy for the human body. The body stores them “in reserve” and they serve as a long-term energy source. In addition, fats have low thermal conductivity and protect the body from hypothermia. It is not surprising that the traditional diet of northern peoples contains so much animal fat. For people engaged in heavy physical labor, it is also easiest (although not always healthier) to compensate for the energy expended with fatty foods. Fats are part of cell walls, intracellular formations, and nervous tissue. Another function of fats is to supply fat-soluble vitamins and other biologically active substances to the body tissues.

Squirrels

Drawing - Protein molecule

Squirrels– biopolymers whose monomers are amino acids.

The formation of linear protein molecules occurs as a result of reactions of amino acids with each other.

Sources of proteins can be not only animal products (meat, fish, eggs, cottage cheese), but also plant products, for example, legumes (beans, peas, soybeans, peanuts, which contain up to 22–23% proteins by weight), nuts and mushrooms . However, the most protein is in cheese (up to 25%), meat products (pork 8–15%, lamb 16–17%, beef 16–20%), poultry (21%), fish (13–21%), eggs (13%), cottage cheese (14%). Milk contains 3% proteins, and bread 7–8%. Among cereals, the champion in proteins is buckwheat (13% of proteins in dry cereals), which is why it is recommended for dietary nutrition. To avoid “excesses” and at the same time ensure the normal functioning of the body, it is necessary, first of all, to give a person a complete set of proteins with food. If there is not enough protein in the diet, an adult feels a loss of strength, his performance decreases, and his body is less resistant to infections and colds. As for children, if they have inadequate protein nutrition, they are greatly behind in development: children grow, and proteins are the main “building material” of nature. Every cell of a living organism contains proteins. Human muscles, skin, hair, and nails consist mainly of proteins. Moreover, proteins are the basis of life; they participate in metabolism and ensure the reproduction of living organisms.

Structure:

primary structure– linear, with alternating amino acids;

secondary– in the form of a spiral with weak bonds between the turns (hydrogen);

tertiary– a spiral rolled into a ball;

quaternary– when combining several chains that differ in their primary structure.

Functions:

1) construction: proteins are an essential component of all cellular structures;

2) structural: proteins in combination with DNA make up the body of chromosomes, and with RNA – the body of ribosomes;

3) enzymatic: chemical catalyst. reactions are performed by any enzyme - a protein, but a very specific one;

4) transport: transfer of O 2 and hormones in the body of animals and humans;

5) regulatory: proteins can perform a regulatory function if they are hormones. For example, insulin (a hormone that supports the functioning of the pancreas) activates the uptake of glucose molecules by cells and their breakdown or storage inside the cell. With a lack of insulin, glucose accumulates in the blood, developing diabetes;

6) protective: when foreign bodies enter the body, protective proteins are produced - antibodies, which bind to foreign bodies, combine and suppress their vital activity. This mechanism of resistance of the body is called immunity;

7) energy: with a lack of carbohydrates and fats, amino acid molecules can be oxidized.

The concept of "life". The main signs of living things: nutrition, respiration, excretion, irritability, mobility, reproduction, growth and development.

Biology– the science of the origin and development of living things, their structure, forms of organization and methods of activity. Currently, there are more than 50 sciences within the complex of biological knowledge, among them: botany, zoology, anatomy, morphology, biophysics, biochemistry, ecology, etc. This diversity of scientific disciplines is explained by the complexity of the object of study - living matter.

From this point of view, it is especially important to understand what criteria underlie the division of matter into living and nonliving.

In classical biology, two opposing positions competed, explaining the essence of living things in fundamentally different ways - reductionism and vitalism.

Supporters reductionism believed that all life processes of organisms can be reduced to a set of certain chemical reactions. Term "reductionism" comes from the Latin word redaction - to move back, to return. Ideas of biological reductionism relied on the ideas of vulgar mechanistic materialism, which became most widespread in the philosophy of the 17th and 18th centuries. Mechanistic materialism explained all processes occurring in nature from the point of view of the laws of classical mechanics. Adaptation of the mechanistic materialist position to biological cognition led to the formation of biological reductionism. From the point of view of modern natural science, a reductionistic explanation cannot be considered satisfactory, since it emasculates the very essence of living things. Most widely distributed reductionism received in the 18th century.

The opposite of reductionism is vitalism, whose supporters explain the specificity of living organisms by the presence of a special vital force in them. Term "vitalism" comes from the Latin word vita - life. The philosophical basis of vitalism is idealism. Vitalism did not explain the specifics and mechanisms of the functioning of living things, reducing all the differences between the organic and the inorganic to the action of a mysterious and unknown “vital force”.

Modern biology considers the main properties of living things to be:

1) independent metabolism,

2) irritability,

4) ability to reproduce,

5) mobility,

6) adaptability to the environment

Based on the totality of these properties, living things differ from non-living things. Biological systems- These are holistic open systems that constantly exchange matter, energy, information with the environment and are capable of self-organization. Living systems actively respond to environmental changes and adapt to new conditions. Certain qualities of living things may also be inherent in inorganic systems, but none of the inorganic systems possesses the totality of the listed properties.

There are transitional forms that combine the properties of living and nonliving, for example viruses. Word "virus" derived from the Latin virus - poison. Viruses were discovered in 1892 by the Russian scientist D. Ivanovsky. On the one hand, they consist of proteins and nucleic acids and are capable of self-reproduction, i.e. have signs of living organisms, but on the other hand, outside a foreign organism or cell they do not show signs of living things - they do not have their own metabolism, do not react to stimuli, and are not capable of growth and reproduction.

All living beings on Earth have the same biochemical composition: 20 amino acids, 5 nitrogenous bases, glucose, fats. Modern organic chemistry knows more than 100 amino acids. Apparently, such a small number of compounds that form all living things is the result of selection that occurred at the stage of prebiological evolution. Proteins that make up living systems are high-molecular organic compounds. In any given protein, the order of amino acids is always the same. Most proteins act as enzymes - catalysts for chemical reactions occurring in living systems.

A significant achievement of classical biology was the creation of the theory of the cellular structure of living organisms. In the complex of modern biological knowledge, there is a separate discipline that deals with the study of cells - cytology.

The concept of “cell” was introduced into scientific use by the English botanist R. Hooke in 1665. Examining the media of dried cork, he discovered many cells, or chambers, which he called cells. However, two centuries passed from the moment of this discovery to the creation of the cell theory.

In 1837, the German botanist M. Schleiden proposed a theory of the formation of plant cells. According to Schleiden, the cell nucleus plays an important role in the reproduction and development of cells, the existence of which was established in 1831 by R. Brown.

In 1839, M. Schleiden’s compatriot, anatomist T. Schwann, based on experimental data and theoretical conclusions, created a cellular theory of the structure of living organisms. The creation of cell theory in the mid-19th century was a significant step in the establishment of biology as an independent scientific discipline.

Basic principles of cell theory

1. A cell is an elementary biological unit, the structural and functional basis of all living things.

2. The cell carries out independent metabolism, is capable of division and self-regulation.

3. The formation of new cells from non-cellular material is impossible; cell reproduction occurs only through cell division.

The cellular theory of the structure of living organisms has become a convincing argument in favor of the idea of the unity of the origin of life on Earth and has had a significant influence on the formation of the modern scientific picture of the world.