inorganic substances. Inorganic compounds in the human body

some chemistry

Of the 92 chemical elements currently known to science, 81 elements have been 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 are substances whose content exceeds 0.005% of body weight. This is 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. In total, the main and macronutrients make up 99% of the human body weight.

trace elements

trace elements- these are substances, the content of which does not exceed 0.005% for each individual element, and their concentration in tissues does not exceed 0.000001%. Trace elements are also very important for normal life.

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

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

organic matter

organic matter can be formed (or synthesized artificially) from mineral. The main component of all organic substances is carbon(the study of the structure, chemical properties, methods of obtaining 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 the composition of proteins, fats and carbohydrates, which determine the nutritional value of our food; found in 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 possess hydrocarbons - various compounds of carbon and hydrogen and their derivatives. Molecules of any organic substances contain hydrocarbon fragments.

A special science is engaged in 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 by their mutual spatial arrangement. These factors are most clearly manifested in the difference in the properties of substances 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 the course 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 is less than organic, but they are also vital. Such substances include iron, iodine, copper, zinc, cobalt, chromium, molybdenum, nickel, vanadium, selenium, silicon, lithium and others. Despite the small need in quantitative terms, they qualitatively affect the activity and speed of all biochemical processes. Without them, normal digestion of food and the synthesis of hormones are impossible. With a deficiency of these substances in the human body, specific disorders occur, 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.

Every day a person interacts with a large number of objects. They are made of different materials, have their own structure and composition. Everything that surrounds a person can be divided into organic and inorganic. In the article, we will consider what such substances are, we will give examples. We will also determine what inorganic substances are found in biology.

Description

Inorganic substances are substances that do not contain carbon. They are the opposite of organic. This group also includes several carbon-containing compounds, for example:

  • cyanides;
  • oxides of carbon;
  • carbonates;
  • carbides and others.
  • water;
  • various acids (hydrochloric, nitric, sulfuric);
  • salt;
  • ammonia;
  • carbon dioxide;
  • metals and non-metals.

The inorganic group is distinguished by the absence of a carbon skeleton, which is characteristic of organic substances. According to the composition, it is customary to divide into simple and complex. Simple substances make up a small group. There are approximately 400 of them in total.

Simple inorganic compounds: metals

Metals - simple atoms which is based on a metallic bond. These elements have characteristic metallic properties: thermal conductivity, electrical conductivity, ductility, brilliance, and others. In total, 96 elements are distinguished in this group. These include:

  • alkali metals: lithium, sodium, potassium;
  • alkaline earth metals: magnesium, strontium, calcium;
  • copper, silver, gold;
  • light metals: aluminum, tin, lead;
  • semimetals: polonium, moscovium, nihonium;
  • lanthanides and lanthanum: scandium, yttrium;
  • actinides and actinium: uranium, neptunium, plutonium.

Metals are found mainly in nature in the form of ore and compounds. To obtain pure metal without impurities, it is purified. If necessary, doping or other processing is possible. This is a special science - metallurgy. It is divided into black and color.

Simple inorganic compounds: non-metals

Non-metals are chemical elements that do not have metallic properties. Examples of inorganic substances:

  • water;
  • nitrogen;
  • sulfur;
  • oxygen and others.

Nonmetals are distinguished by a large number of electrons per atom. This causes some properties: the ability to attach additional electrons increases, a higher oxidative activity appears.

In nature, you can find non-metals in a free state: oxygen, chlorine, as well as solid forms: iodine, phosphorus, silicon, selenium.

Some non-metals have a distinctive property - allotropy. That is, they can exist in various modifications and forms. For example:

  • gaseous oxygen has modifications: oxygen and ozone;
  • solid carbon can exist in such forms: diamond, graphite, glassy carbon and others.

Complex inorganic compounds

This group of substances is more numerous. Complex compounds are distinguished by the presence of several chemical elements in the composition of the substance.

Let us consider complex inorganic substances in more detail. Examples and their classification are presented below in the article.

1. Oxides - compounds, one of the elements of which is oxygen. The group includes:

  • non-salt-forming (for example, nitrogen);
  • salt-forming oxides (eg sodium oxide, zinc oxide).

2. Acids - substances that include hydrogen ions and acid residues. For example, nitric hydrogen sulfide.

3. Hydroxides - compounds in which the -OH group is present. Classification:

  • bases - soluble and insoluble alkalis - copper hydroxide, sodium hydroxide;
  • oxygen-containing acids - dihydrogen trioxocarbonate, hydrogen trioxonitrate;
  • amphoteric - chromium hydroxide, copper hydroxide.

4. Salts - substances that contain metal ions and acid residues. Classification:

  • medium: sodium chloride, iron sulfide;
  • acidic: sodium bicarbonate, hydrosulfates;
  • basic: dihydroxochrome nitrate, hydroxochrome nitrate;
  • complex: sodium tetrahydroxozincate, potassium tetrachloroplatinate;
  • double: potassium alum;
  • mixed: potassium aluminum sulfate, potassium copper chloride.

5. Binary compounds - substances consisting of two chemical elements:

  • anoxic acids;
  • anoxic salts and others.

Inorganic compounds containing carbon

Such substances traditionally belong to the group of inorganic. Substance examples:

  • Carbonates - esters and salts of carbonic acid - calcite, dolomite.
  • Carbides - compounds of non-metals and metals with carbon - beryllium carbide, calcium carbide.
  • Cyanides - salts of hydrocyanic acid - sodium cyanide.
  • Carbon oxides - a binary compound of carbon and oxygen - carbon monoxide and carbon dioxide.
  • Cyanates - are derivatives of cyanic acid - fulmic acid, isocyanic acid.
  • Carbonyl metals - a complex of a metal and carbon monoxide - nickel carbonyl.

All considered substances differ in individual chemical and physical properties. In general terms, the distinctive features of each class of inorganic substances can be distinguished:

1. Common metals:

  • high thermal and electrical conductivity;
  • metallic luster;
  • lack of transparency;
  • strength and plasticity;
  • at room temperature, they retain their hardness and shape (except for mercury).

2. Simple non-metals:

  • simple non-metals can be in a gaseous state: hydrogen, oxygen, chlorine;
  • bromine is found in the liquid state;
  • solid non-metals have a non-molecular state and can form crystals: diamond, silicon, graphite.

3. Complex substances:

  • oxides: react with water, acids and acid oxides;
  • acids: react with water, and alkalis;
  • amphoteric oxides: can react with acidic oxides and bases;
  • hydroxides: soluble in water, have a wide range of melting points, can change color when interacting with alkalis.

The cell of any living organism consists of many components. Some of them are inorganic compounds:

  • Water. For example, the amount of water in a cell is between 65 and 95%. It is necessary for the implementation of chemical reactions, the movement of components, the process of thermoregulation. Also, it is water that determines the volume of the cell and the degree of its elasticity.
  • mineral salts. They can be present in the body both in dissolved form and in undissolved form. An important role in cell processes is played by cations: potassium, sodium, calcium, magnesium - and anions: chlorine, bicarbonates, superphosphate. Minerals are necessary to maintain osmotic balance, regulate biochemical and physical processes, generate nerve impulses, maintain blood clotting levels, and many other reactions.

Not only the inorganic substances of the cell are important for maintaining vital activity. Organic components occupy 20-30% of its volume.

Classification:

  • simple organic substances: glucose, amino acids, fatty acids;
  • complex organic substances: proteins, nucleic acids, lipids, polysaccharides.

Organic components are necessary to perform the protective, energy function of the cell, they serve as a source of energy for cellular activity and store nutrients, carry out protein synthesis, and transmit hereditary information.

The article considered the essence and examples of inorganic substances, their role in the composition of the cell. We can say that the existence of living organisms would be impossible without groups of organic and inorganic compounds. They are important in every area of ​​human life, as well as in the existence of every organism.

At the end of the ninth century AD, the Arab scientist Abu Bakr ar-Razi divided all substances known at that time into 3 groups depending on their origin: mineral, animal and vegetable. The classification lasted almost 1000 years. Only in the 19th century did 3 groups turn into 2: organic and inorganic substances.

inorganic substances

Inorganic substances are simple and complex. Simple substances are those substances that contain atoms of only one chemical element. They are divided into metals and non-metals.

Metals are ductile substances that conduct heat and electricity well. Almost all of them are silvery-white and have a characteristic metallic sheen. Such properties are a consequence of a special structure. In a metallic crystal lattice, metal particles (they are called ion-atoms) are connected by mobile common electrons.

Even those who are far from chemistry can name examples of metals. These are iron, copper, zinc, chromium and other simple substances formed by atoms of chemical elements, the symbols of which are located in the PSHE D.I. Mendeleev under the diagonal B - At and above it in the main subgroups.

Non-metals, as their name implies, do not have the properties of metals. They are fragile, electric current, with rare exceptions, do not conduct, do not shine (except for iodine and graphite). Their properties are more diverse than those of metals.

The reason for such differences also lies in the structure of substances. There are no freely moving electrons in crystal lattices of atomic and molecular types. Here they combine in pairs to form covalent bonds. All known non-metals - oxygen, nitrogen, sulfur, phosphorus and others. Elements - non-metals in PSCE are located above the diagonal B-At

Complex inorganic substances are:

  • acids consisting of hydrogen atoms and acid residues (HNO3, H2SO4);
  • bases formed by metal atoms and hydroxo groups (NaOH, Ba(OH)2);
  • salts whose formulas begin with metal symbols and end with acidic residues (BaSO4, NaNO3);
  • oxides formed by two elements, one of which is O in the oxidation state -2 (BaO, Na2O);
  • other binary compounds (hydrides, nitrides, peroxides, etc.)

In total, several hundred thousand are known inorganic substances.

organic matter

Organic compounds differ from inorganic compounds primarily in their composition. If inorganic substances can be formed by any elements of the Periodic system, then C and H atoms must certainly be included in the composition of organic substances. Such compounds are called hydrocarbons (CH4 - methane, C6H6 - benzene). Hydrocarbon raw materials (oil and gas) are of great benefit to humanity. However, the strife causes serious.

Hydrocarbon derivatives also contain O and N atoms. Representatives of oxygen-containing organic compounds are alcohols and isomeric ethers (C2H5OH and CH3-O-CH3), aldehydes and their isomers - ketones (CH3CH2CHO and CH3COCH3), carboxylic acids and complex ethers (CH3-COOH and HCOOCH3). The latter also include fats and waxes. Carbohydrates are also oxygen-containing compounds.

Why did scientists combine plant and animal substances into one group - organic compounds, and how do they differ from inorganic ones? There is no single clear criterion for separating organic and inorganic substances. Consider a number of features that combine organic compounds.

  1. Composition (constructed from atoms C, H, O, N, less often P and S).
  2. Structure (C-H and C-C bonds are mandatory, they form chains and cycles of different lengths);
  3. Properties (all organic compounds are combustible, form CO2 and H2O during combustion).

Among organic substances, there are many polymers of natural (proteins, polysaccharides, natural rubber, etc.), artificial (viscose) and synthetic (plastics, synthetic rubbers, polyester, and others) origin. They have a large molecular weight and a more complex structure compared to inorganic substances.

Finally, there are more than 25 million organic substances.

This is just a superficial look at organic and inorganic substances. More than a dozen scientific papers, articles and textbooks have been written about each of these groups.

Inorganic compounds - video

The chemical composition of the cell

mineral salts

water.
good solvent

hydrophilic(from Greek. hydro- water and fileo

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 ,

Physical and chemical properties of water as the main medium in the human body.

Of the inorganic substances that make up the cell, water is the most important. Its amount is from 60 to 95% of the total cell mass. Water plays an essential role in the life of cells and living organisms in general. In addition to being 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, with the polarity of its molecules and with 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. Weak solubility is associated with an 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 gum..

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 current of biological fluids, substances can be delivered to any cells of the body; the speed of information delivery is low - it is determined by the flow rate of biological fluids - 0.5-5 m / s; duration of action.

The transmission of humoral regulation is carried out by the flow of blood, lymph, by diffusion, nervous - comes from nerve fibers. The humoral signal propagates more slowly (with the capillary blood flow at a speed of 0.05 mm/s) than the nerve signal (the nerve transmission speed is 130 m/s). The humoral signal does not have such an exact addressee (it works on the principle of “everyone, everyone, everyone”) as the nerve signal (for example, a nerve impulse is transmitted to the contracting muscles of the 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 this high sensitivity to any humoral factor are called target cells.
Among the humoral factors, substances with a narrow
spectrum of action, that is directed by 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 provide reactions that do not require high speed and accuracy of execution.
Humoral regulation, like nervous regulation, is always carried out
a closed loop of regulation, in which all elements are interconnected by channels.
As for the element of the circuit of the device that monitors (SP), it is absent in the circuit of humoral regulation as an independent structure. The function of this link is performed, as a rule, by the endocrine
cell.
Humoral substances that enter the blood or lymph diffuse into the intercellular fluid and are quickly destroyed. In this regard, their action can only extend to closely located organ cells, that is, their influence is local in nature. In contrast to local action, the distant effect of humoral substances extends to target cells at a distance.

HORMONES OF THE HYPOTHALAMUS

hormone effect

Corticoliberin - Stimulates the formation of corticotropin and lipotropin
Gonadoliberin - 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

HORMONES OF ADENOHYPOPHYSIS

STH (somatotropin, growth hormone) - Stimulates body growth, protein synthesis in cells, glucose formation and lipid breakdown
Prolactin - Regulates lactation in mammals, instinct for nursing offspring, differentiation of various tissues
TSH (thyrotropin) - Regulates the biosynthesis and secretion of thyroid hormones
Corticotropin - regulates the secretion of adrenal hormones
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 secretion of thyroid hormones is controlled by two "superior" endocrine glands. The region of the brain that connects the nervous and endocrine systems together 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 recess - the Turkish saddle. It secretes several dozens of hormones that are complex in structure and action, but only one of them acts on the thyroid gland - thyroid-stimulating hormone or TTG. 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 the hypothalamus will know about it. The pituitary gland will immediately release TSH, which will activate 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 endocrine glands (endocrine), as well as 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 - impact on certain organs, tissues, cells; Rapidly destroyed in tissues; The size of the molecules is small, penetration through the walls of capillaries into tissues is easy.

Adrenals - paired endocrine glands of vertebrates animals and human. The zona glomeruli produce hormones called mineralcorticoids. These include :Aldosterone (basic minecortex) Corticosterone (insignificant and relatively inactive glucocorticoid hormone). Mineralcorticoids increase reabsorption Na + and excretion of K + in the kidneys. In the beam zone, 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 growth connective tissue and increase the sensitivity sense organs And excitability of the nervous system. In the mesh zone are produced sex hormones (androgens, which are precursors estrogen). These sex hormones play a slightly different role than the hormones secreted by gonads. The cells of the adrenal medulla produce catecholamines - adrenalin And norepinephrine . These hormones increase blood pressure, strengthen the work of the heart, expand the lumen of the bronchi, increase the level of sugar in the blood. At rest, they constantly release small amounts of catecholamines. Under the influence of a stressful situation, the secretion of adrenaline and noradrenaline by the cells of the adrenal medulla increases sharply.

The resting membrane potential is a deficit of positive electric charges inside the cell, which occurs due to 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 cause, first of all, a decrease in PP; when it reaches a critical value (threshold), an active propagating response occurs - AP. 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 the duration of the AP. The action potential is one of the most important components of the excitation process. In nerve fibers, it provides conduction of excitation from sensitive endings ( receptors) to the body of the nerve cell and from it - to the synaptic endings located on various nerve, muscle or glandular cells. Carrying out PD along the nerve and muscle fibers is carried out by the so-called. local currents, or currents of action, arising between the excited (depolarized) and neighboring resting sections of the membrane.

Post-synaptic potentials (PSPs) occur in areas of the membrane of nerve or muscle cells directly adjacent to synaptic endings. They have an amplitude of the order of several mv and duration 10-15 msec. PSPs are subdivided into excitatory (EPSP) and inhibitory (TPSP).

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 the 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 the 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. There are four successive periods in the development of an action potential: 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 is manifested 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 trigger an organism's response may include a wide repertoire of responses, from diffuse protoplasmic responses in protozoa to complex, highly specialized responses in humans. In the human body, irritability is often associated with the property of nervous, muscular and glandular tissues to carry out a response in the form of generating a nerve impulse, muscle contraction or secretion of substances (saliva, hormones, etc.). In living organisms devoid of a nervous system, irritability can manifest itself in movements. So, amoebas and other protozoa leave unfavorable solutions with a high salt concentration. And plants change the position of the shoots for maximum absorption of light (stretch to the light). Irritability is a fundamental property of living systems: its presence is a classic criterion by which living things are distinguished from non-living things. The minimum value of the stimulus sufficient for the manifestation of irritability is called the threshold of perception. 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 the occurrence of excitation, only the action of the force of irritation is not enough. It is necessary that this irritation last for some time; 2) law of time stimulus action. Under the action of the same force on 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 shortest time will be required for a tissue with high excitability and the longest time - with low excitability. Thus, excitability is inversely proportional to the time of action of the stimulus: the shorter the time of action of the stimulus, the greater the excitability. The excitability of the tissue is determined not only by the strength and duration of irritation, but also by the speed (speed) of the increase in the strength of irritation, which is determined by the third law - the law of the rate of increase in the strength of stimulation(the ratio of the strength of the stimulus to the time of its action): the greater the rate of increase in the strength of irritation, the less excitability. Each tissue has its own threshold rate of increase in the strength of stimulation.

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

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

A local response occurs to subthreshold stimuli; extends to 1-2 mm with attenuation; increases with increasing stimulus strength, i.e. obeys the law of "force"; summed up - increases with repeated frequent pre-threshold irritations 10 - 40 mV increases.

The chemical mechanism of synaptic transmission, in comparison with the electrical one, more effectively provides the main functions of the synapse: 1) one-way signal conduction; 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, a neurotransmitter released from presynaptic nerve endings causes an excitatory postsynaptic 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 leads to a short circuit of the excitatory postsynaptic current, thereby weakening or blocking the transmission of excitation.

The chemical composition of the cell

Organisms are made up of cells. Cells of different organisms have similar chemical composition. About 90 elements are found in the cells of living organisms, and approximately 25 of them are found in almost all cells. According to the 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.

The lack of any element can lead to illness, and even death of the body, since each element plays a specific role. Macronutrients of the first group form the basis of biopolymers - proteins, carbohydrates, nucleic acids, and 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. Part of the chemical elements contained in the cell is part of inorganic substances - mineral salts and water.

mineral salts are 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 medium, which is important for the life of cells.

Of the inorganic substances in wildlife, a huge role is played by 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% of water; in adipose tissue cells - only 40%. By old age, the water content in the 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 heated. Water - good solvent. Due to the polarity, its molecules interact with positively and negatively charged ions, thereby contributing to the dissolution of the substance. In relation to water, all substances of the cell are divided into hydrophilic and hydrophobic.

hydrophilic(from Greek. hydro- water and fileo- love) are called substances that dissolve in water. These include ionic compounds (eg salts) and some non-ionic compounds (eg sugars).

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

Water plays an important role in the chemical reactions that take place in the cell in aqueous solutions. It dissolves metabolic products that are unnecessary to the body and thereby contributes to their removal from the body. The high water content in the cell gives it elasticity. Water facilitates the movement of various substances within the cell or from cell to cell.

Inorganic compounds in the human body.

Water. Of the inorganic substances that make up the cell, water is the most important. Its amount is from 60 to 95% of the total cell mass. Water plays an essential role in the life of cells and living organisms in general. In addition to being 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, with the polarity of its molecules and with 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 or mix with non-polar substances, since it cannot form hydrogen bonds with them. Substances that are insoluble in water are called hydrophobic. Hydrophobic molecules or their parts are repelled by water, and in its presence 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, That is, the ability of molecules to carry away with them a significant amount of heat while cooling the body. 5- Water is exclusively high surface tension. 6- Water provides movement of substances in the cell and the body, the absorption of substances and the 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 humid environment on the mucous membranes of the respiratory tract). It is part of saliva, bile, tears, sperm, etc.

mineral salts. In the composition of living organisms, modern methods of chemical analysis have revealed 80 elements of the periodic system. According to their quantitative composition, they are divided into three main groups. Macronutrients 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.). Trace elements are predominantly heavy metal ions. Contained in organisms in an 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. Essential is not only the content, but also the ratio of ions in the cell. The difference between the number of cations and anions on the surface and inside the cell provides the occurrence action potential , what underlies the emergence of nervous and muscular excitation.

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


Inorganic substances and their role in the cell

Water. Of the inorganic substances that make up the cell, water is the most important. Its amount is from 60 to 95% of the total cell mass. Water plays an essential role in the life of cells and living organisms in general. In addition to being 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, with the polarity of its molecules and with their ability to form hydrogen bonds with each other.

Water as a component of biological systems performs the following important functions:

Water is a universal solvent for polar substances, such as salts, sugars, alcohols, acids, etc. Substances that are readily soluble in water are called hydrophilic. When a substance goes into solution, its molecules or ions are allowed to move more freely; the reactivity of the substance increases accordingly. It is for this reason that most of the chemical reactions in the cell proceed in aqueous solutions. Its molecules are involved in many chemical reactions, for example, in the formation or hydrolysis of polymers. In the process of photosynthesis, water is an electron donor, a source of hydrogen ions and free oxygen.

Water does not dissolve or mix with non-polar substances, since it cannot form hydrogen bonds with them. Substances that are insoluble in water are called hydrophobic. Hydrophobic molecules or their parts are repelled by water, and in its presence 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.

Water has a high specific heat capacity. It takes a lot of energy to break the hydrogen bonds that hold water molecules together. This property ensures the maintenance of the thermal balance of the body with significant temperature fluctuations in the environment. In addition, water has a high thermal conductivity, which allows the body to maintain the same temperature throughout its volume.

Water is characterized by a high heat of vaporization, i.e., the ability of molecules to carry away a significant amount of heat with them while cooling the body. Due to this property of water, which is manifested during sweating in mammals, thermal shortness of breath in crocodiles and other animals, transpiration in plants, their overheating is prevented.

Water has an exceptionally high surface tension. This property is very important for adsorption processes, for the movement of solutions through tissues (blood circulation, ascending and descending currents in plants). For many small organisms, surface tension allows them to float or glide across the surface of the water.

Water ensures the movement of substances in the cell and body, the absorption of substances and the excretion of metabolic products.

In plants, water determines the turgor of cells, and in some animals it performs supporting functions, being a hydrostatic skeleton (round and annelids, echinoderms).

Water is an integral part of lubricating fluids (synovial - in the joints of vertebrates, pleural - in the pleural cavity, pericardial - in the pericardial sac) and mucus (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. Inorganic substances in the cell, except for water, contain mineral salts. Molecules of salts in an aqueous solution decompose into cations and anions. Cations (K+, Na+, Ca2+, Mg:+, NH4+) and anions (C1, H2P04 -, HP042-, HC03 -, NO32--, SO4 2-) are of the greatest importance. Not only the content, but also the ratio of ions is essential in a cage.

The difference between the number of cations and anions on the surface and inside the cell provides the emergence of an action potential, which underlies the occurrence of nerve and muscle excitation. The difference in the concentration of ions on different sides of the membrane is due to the active transfer of substances through the membrane, as well as the conversion of energy.

Phosphoric acid anions create a phosphate buffer system that maintains the pH of the intracellular environment of the body at a level of 6.9.

Carbonic acid and its anions form a bicarbonate buffer system that maintains the pH of the extracellular medium (blood plasma) at 7.4.

Some ions are involved in the activation of enzymes, the creation of osmotic pressure in the cell, in the processes of muscle contraction, blood coagulation, etc.

A number of cations and anions are necessary for the synthesis of important organic substances (for example, phospholipids, ATP, nucleotides, hemoglobin, hemocyanin, chlorophyll, etc.), as well as amino acids, being sources of nitrogen and sulfur atoms.

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