For the first time, chemical substances were classified at the end of the 9th century by the Arab scientist Abu Bakr al-Razi. He, based on the origin of the substances, divided them into three groups. In the first group he allotted a place for mineral substances, in the second for plant substances and in the third for animal substances.

This classification was destined to exist for almost a millennium. Only in the 19th century, two of those groups were formed - organic and inorganic substances. Chemicals of both types are built thanks to the ninety elements included in the DI Mendeleev's table.

Group of inorganic substances

Among inorganic compounds, simple and complex substances are distinguished. The group of simple substances combines metals, non-metals and noble gases. Complex substances are represented by oxides, hydroxides, acids and salts. All inorganic substances can be built from any chemical elements.

Group of organic substances

The composition of all organic compounds without fail includes carbon and hydrogen (this is their fundamental difference from mineral substances). Substances formed by C and H are called hydrocarbons - the simplest organic compounds. The derivatives of hydrocarbons contain nitrogen and oxygen. They, in turn, are classified into oxygen- and nitrogen-containing compounds.

The group of oxygen-containing substances is represented by alcohols and ethers, aldehydes and ketones, carboxylic acids, fats, waxes and carbohydrates. Nitrogen-containing compounds include amines, amino acids, nitro compounds, and proteins. For heterocyclic substances, the position is twofold - they, depending on the structure, can refer to both types of hydrocarbons.

Cell chemicals

The existence of cells is possible if they contain organic and inorganic substances. They die when there is no water or mineral salts in them. Cells die if they are severely depleted in nucleic acids, fats, carbohydrates and proteins.

They are capable of normal life activity if they contain several thousand compounds of organic and inorganic nature, capable of entering into many different chemical reactions. Biochemical processes running in a cell are the basis of its vital activity, normal development and functioning.

Chemical elements that saturate the cell

The cells of living systems contain groups of chemical elements. They are enriched with macro-, micro- and ultra-microelements.

• Macronutrients are primarily represented by carbon, hydrogen, oxygen and nitrogen. These inorganic substances of the cell form almost all of its organic compounds. And they also include vital elements. The cell is unable to live and develop without calcium, phosphorus, sulfur, potassium, chlorine, sodium, magnesium and iron.
• The group of trace elements is formed by zinc, chromium, cobalt and copper.
• Ultramicroelements are another group representing the most important inorganic substances of the cell. The group is formed by gold and silver, which has a bactericidal effect, mercury, which prevents the reabsorption of water that fills the renal tubules, which affects enzymes. It also includes platinum and cesium. A certain role in it is assigned to selenium, a deficiency of which leads to various types of cancer.

Water in the cell

The importance of water, a substance common on earth for cell life, is undeniable. Many organic and inorganic substances dissolve in it. Water is a fertile environment where an incredible number of chemical reactions take place. It is able to dissolve the products of decay and metabolism. Thanks to her, slags and toxins leave the cell.

This liquid is endowed with high thermal conductivity. This allows the heat to spread evenly throughout the tissues of the body. It has a significant heat capacity (the ability to absorb heat when its own temperature changes minimally). This ability prevents sudden temperature changes in the cell.

Water has an extremely high surface tension. Thanks to him, dissolved inorganic substances, like organic ones, easily move through the tissues. Many small organisms, using the feature of surface tension, stick to the water surface and glide freely over it.

The turgor of plant cells depends on water. It is water that copes with the support function in certain animal species, and not any other inorganic substances. Biology has identified and studied animals with hydrostatic skeletons. These include representatives of echinoderms, round and annelids, jellyfish and anemones.

Cell saturation with water

Working cells are filled with water to 80% of their total volume. The liquid is in them in a free and bound form. Protein molecules bind tightly to bound water. They, surrounded by a water shell, are isolated from each other.

Water molecules are polar. They form hydrogen bonds. Due to hydrogen bridges, water has a high thermal conductivity. Bound water allows cells to withstand colder temperatures. Free water accounts for 95%. It promotes the dissolution of substances involved in cellular metabolism.

Highly active cells in brain tissues contain up to 85% water. Muscle cells are 70% saturated with water. Less active cells that form adipose tissue need 40% water. In living cells, it not only dissolves inorganic chemicals, it is a key participant in the hydrolysis of organic compounds. Under its influence, organic substances, splitting, turn into intermediate and final substances.

The importance of mineral salts for the cell

Mineral salts are represented in cells by cations of potassium, sodium, calcium, magnesium and anions HPO 4 2-, H 2 PO 4 -, Cl -, HCO 3 -. The correct proportions of anions and cations create the acidity necessary for cell life. In many cells, a slightly alkaline environment is maintained, which practically does not change and ensures their stable functioning.

The concentration of cations and anions in cells is different from their ratio in the intercellular space. The reason for this is active regulation aimed at transporting chemical compounds. This course of processes determines the constancy of chemical compositions in living cells. After cell death, the concentration of chemical compounds in the intercellular space and the cytoplasm becomes equilibrium.

Inorganic substances in the chemical organization of the cell

The chemical composition of living cells does not contain any special elements characteristic only of them. This determines the unity of the chemical compositions of living and inanimate objects. Inorganic substances in the composition of the cell play a huge role.

Sulfur and nitrogen help proteins form. Phosphorus is involved in the synthesis of DNA and RNA. Magnesium is an important constituent of enzymes and chlorophyll molecules. Copper is essential for oxidative enzymes. Iron is the center of the hemoglobin molecule, zinc is part of the hormones produced by the pancreas.

The importance of inorganic compounds for cells

Nitrogen compounds convert proteins, amino acids, DNA, RNA and ATP. In plant cells, ammonium ions and nitrates in the process of oxidation-reduction reactions are converted into NH 2, become participants in the synthesis of amino acids. Living organisms use amino acids to form their own proteins, which are necessary for building bodies. After the death of organisms, proteins are poured into the circulation of substances; during their decay, nitrogen is released in free form.

Inorganic substances, which contain potassium, play the role of a "pump". Thanks to the "potassium pump", substances that they urgently need penetrate into the cells through the membrane. Potassium compounds lead to the activation of the vital activity of cells, thanks to them excitations and impulses are carried out. The concentration of potassium ions in cells is very high in contrast to the environment. Potassium ions after the death of living organisms easily pass into the natural environment.

Substances containing phosphorus contribute to the formation of membrane structures and tissues. In their presence, enzymes and nucleic acids are formed. Various soil layers are saturated with phosphorus salts to one degree or another. The root secretions of plants, dissolving phosphates, assimilate them. Following the dying off of organisms, the remains of phosphates undergo mineralization, turning into salts.

Inorganic substances containing calcium contribute to the formation of intercellular substance and crystals in plant cells. Calcium from them enters the blood, regulating the process of its coagulation. Thanks to it, bones, shells, calcareous skeletons, coral polyps are formed in living organisms. Cells contain calcium ions and crystals of calcium salts.

CHEMICAL ELEMENTS IN THE HUMAN ORGANISM (KUKUSHKIN Yu.N., 1998), CHEMISTRY

The role of about 30 chemical elements has been definitely established for the human body, 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 a certain content are poisons.

CHEMICAL ELEMENTS IN THE HUMAN BODY

Y. N. KUKUSHKIN

Saint Petersburg State Technological Institute

INTRODUCTION

Many chemists are familiar with the winged words spoken in the 40s of the current century by the German scientists Walter and Ida Noddack, that every cobblestone on the pavement contains all the elements of the Periodic Table. At first, these words were met with far from unanimous approval. However, as more and more accurate methods for the analytical determination of chemical elements were developed, scientists were more and more convinced of the validity of these words.

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

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

The human body consists of 60% water, 34% organic matter and 6% inorganic. The main components of organic substances are carbon, hydrogen, oxygen; they also include nitrogen, phosphorus and sulfur. 22 chemical elements are necessarily present in inorganic substances of the human body: 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's weight is 70 kg, then it contains (in grams): calcium - 1700, potassium - 250, sodium - 70, magnesium - 42, iron - 5, zinc - 3.

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

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

LIFE ELEMENTS

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

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

Figure: 1. The dependence of the response ( R) on the dose ( n) for vital elements

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

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

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

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

Impurity elements

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

Table 3.

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

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

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

These examples show that the concentration of an element in the body plays a very significant, and sometimes catastrophic role. Among the impurity elements, there are those that in small doses have effective healing properties. So, 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, in chronic cystitis and urethitis, as well as in the form of eye drops in purulent conjunctivitis and blennorrhea. Silver nitrate pencils are used for cauterization of warts, granulations. In dilute solutions (0.1-0.25%), silver nitrate is used as an astringent and antimicrobial agent for lotions, as well as eye drops. Scientists believe that the cauterizing effect of silver nitrate is due to 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, in the endocrine glands, and in the liver has already been experimentally established. Silver enters the body from plant foods, such as cucumbers and cabbage.

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

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

CONCLUSION

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

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

The question of the principles of selection by nature of chemical elements for the functioning of living organisms is very interesting. 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 possibilities of plants in this process are limited. Conscious human regulation of the content of trace elements in the soil of agricultural land is also one of the important tasks facing researchers. The knowledge gained by scientists in this direction has already taken shape in a new branch of chemical science - bioinorganic chemistry. Therefore, it is appropriate to recall the words of the outstanding scientist of the 19th century A. Ampere: "Happy are those who develop science in years when it is not completed, but when a decisive turn has already matured in it." These words can be especially useful for those facing a career choice.

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2. Kukushkin Yu.N. Higher order compounds. L .: Chemistry, 1991.

3. Kukushkin Yu.N. Chemistry around us. M .: Higher. shk., 1992.

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5. Inorganic biochemistry. Moscow: Mir, 1978.Vol. 1, 2 / Ed. G. Eichhorn.

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7. Yatsimirsky KB Introduction to Bioinorganic Chemistry. Kiev: Nauk. dumka, 1973.

8. Kaim W., Schwederski B. Bioinorganic Chemistry: Inorganic Elements in the Chemistry of Life. Chichester: John Wile and Sons, 1994.401 p.

Yuri Nikolaevich Kukushkin, Doctor of Chemistry, Professor, Head. Department of Inorganic Chemistry, St. Petersburg State Technological Institute, Honored Scientist of the Russian Federation, laureate of the L.A. Chugaeva of the USSR Academy of Sciences, academician of the Russian Academy of Natural Sciences. Research interests - coordination chemistry and chemistry of platinum metals. Author and co-author of over 600 scientific articles, 14 monographs, textbooks and popular science books, 49 inventions.

Substances such as sand, clay, various minerals, water, carbon oxides, carbonic acid, its salts and others found in "inanimate nature" are called inorganic or mineral substances.

Of about a hundred chemical elements found in the earth's crust, only sixteen are needed for life, and four of them - hydrogen (H), carbon (C), oxygen (O) and nitrogen (N) are the most common in living organisms and make up 99% the masses of the living. The biological significance of these elements is associated with their valence (1, 2, 3, 4) and the ability to form strong covalent bonds, which are stronger than bonds formed by other elements of the same valency. The next in importance are phosphorus (P), sulfur (S), sodium, magnesium, chlorine, potassium and calcium ions (Na, Mg, Cl, K, Ca). As trace elements in living organisms there are also iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), boron (B), aluminum (Al), silicon (Si), vanadium (V), molybdenum ( Mo), iodine (I), manganese (Mn).

All chemical elements in the form of ions or in the composition of certain compounds are involved in the construction of the organism. For example, carbon, hydrogen and oxygen are found in carbohydrates and fats. In the composition of proteins, nitrogen and sulfur are added to them, in the composition of nucleic acids - nitrogen, phosphorus, iron, participating in the construction of the hemoglobin molecule; magnesium is found in chlorophyll; copper is found in some oxidative enzymes; iodine is contained in the thyroxine molecule (thyroid hormone); sodium and potassium provide an electrical charge on the membranes of nerve cells and nerve fibers; zinc is included in the molecule of the pancreas hormone - insulin; cobalt is found in vitamin B12.

Compounds of nitrogen, phosphorus, calcium and other inorganic substances serve as a source of building material for the synthesis of organic molecules (amino acids, proteins, nucleic acids, etc.) and are part of a number of supporting structures of the cell and organism. Some inorganic ions (for example, calcium and magnesium ions) are activators and components of many enzymes, hormones and vitamins. With a lack of these ions, vital processes in the cell are disrupted.

Inorganic acids and their salts perform important functions in living organisms. Hydrochloric acid is part of the gastric juice of animals and humans, accelerating the process of digestion of food proteins. The remains of sulfuric acid, attaching to water-insoluble foreign substances, give them solubility, promoting excretion from the body. Inorganic sodium and potassium salts of nitrous and phosphoric acids are important components of the mineral nutrition of plants; they are introduced into the soil as fertilizers. Calcium and phosphorus salts are part of the bone tissue of animals. Carbon dioxide (CO2) is constantly formed in nature during the oxidation of organic substances (decay of plant and animal residues, respiration, fuel combustion) in large quantities, it is released from volcanic cracks and from the waters of mineral springs.

Water is a very common substance on Earth. Almost one-third of the surface of the earth is covered with water, which forms oceans and seas. Rivers, lakes. A lot of water is in a gaseous state as vapor in the atmosphere; in the form of huge masses of snow and ice, it lies all year round on the tops of high mountains and in the polar countries in the bowels of the Earth there is also water that permeates the soil and rocks.

Water is very important in the life of plants, animals and humans. According to modern ideas, the very origin of life is associated with the sea. In any organism, water is an environment in which chemical processes take place that ensure the vital activity of the organism; in addition, she herself takes part in a number of biochemical reactions.

The chemical and physical properties of water are quite unusual and are mainly associated with the small size of its molecules, with the polarity of its molecules and with their ability to bond with each other by hydrogen bonds.

Consider the biological significance of water. Water is excellent solvent for polar substances. These include ionic compounds, such as salts, in which charged particles (ions) dissociate (separate from each other) in water when the substance dissolves, as well as some non-ionic compounds, such as sugars and simple alcohols, in which charged particles are present in the molecule. (polar) groups (in sugars and alcohols, these are OH groups). When a substance goes into solution, its molecules or ions are able to move more freely and, accordingly, its reactivity increases. For this reason, most of the chemical reactions in the cell take place in aqueous solutions. Non-polar substances, for example lipids, do not mix with water and therefore can separate aqueous solutions into separate compartments, just as membranes separate them. Non-polar parts of molecules are repelled by water and, in its presence, are attracted to each other, as happens, for example, when oil droplets merge into larger droplets; in other words, non-polar molecules are hydrophobic. Such hydrophobic interactions play an important role in ensuring the stability of membranes, as well as many protein molecules, nucleic acids. The solvent properties of water also mean that water serves as a medium for the transport of various substances. It performs this role in the blood, in the lymphatic and excretory systems, in the digestive tract and in the phloem and xylem of plants.

Water has great heat capacity. This means that a significant increase in thermal energy causes only a relatively small increase in its temperature. This phenomenon is explained by the fact that a significant part of this energy is spent on breaking hydrogen bonds, which limit the mobility of water molecules, i.e., to overcome its stickiness. The high heat capacity of water minimizes the temperature changes occurring in it. Due to this, biochemical processes take place in a smaller temperature range, at a more constant rate, and the danger of disrupting these processes from sudden temperature deviations does not threaten them so much. Water serves as a habitat for many cells and organisms, which is characterized by a fairly significant constancy of conditions.

Water is characterized by a large heat of vaporization... Latent heat of vaporization (or relative latent heat of vaporization) is a measure of the amount of thermal energy that must be imparted to a liquid for its transition to vapor, i.e., to overcome the forces of molecular cohesion in a liquid. The evaporation of water requires quite significant amounts of energy. This is due to the existence of hydrogen bonds between water molecules. It is because of this that the boiling point of water - a substance with such small molecules - is unusually high.

The energy needed for water molecules to evaporate comes from their environment. Thus, evaporation is accompanied by cooling. This phenomenon is used in animals for perspiration, for thermal dyspnea in mammals or in some reptiles (for example, crocodiles), which sit in the sun with their mouths open; it may also play a significant role in the cooling of transpiring leaves. Latent heat of fusion (or relative latent heat of fusion) is a measure of the heat energy required to melt a solid (ice). Water needs a relatively large amount of energy to melt (melt). The opposite is also true: when water freezes, it must give off a large amount of thermal energy. This reduces the likelihood of freezing of the contents of the cells and their surrounding fluid. Ice crystals are especially detrimental to living things when they form inside cells.

Water is the only substance that has a greater density, than solid. Since ice floats in water, it forms when it freezes first on its surface and only finally in the bottom layers. If the freezing of ponds proceeded in the reverse order, from bottom to top, then in areas with a temperate or cold climate, life in freshwater reservoirs could not exist at all. Ice covers the water column like a blanket, which increases the chances of survival for organisms living in it. This is important in cold climates and in the cold season, but, undoubtedly, it played a particularly important role during the ice age. On the surface, ice melts faster and faster. The fact that the layers of water, the temperature of which has dropped below 4 degrees, rise up, causes their movement in large reservoirs. Along with the water, the nutrients in it circulate, due to which the reservoirs are populated by living organisms to a great depth.

The water has a large surface tension and cohesion. Cohesion - this is the adhesion of molecules of a physical body to each other under the influence of gravity. There is surface tension on the surface of the liquid - the result of cohesion forces acting between the molecules, directed inward. Due to surface tension, the liquid tends to take a shape so that its surface area is minimal (ideally, a ball shape). Of all liquids, water has the greatest surface tension. The significant cohesion characteristic of water molecules plays an important role in living cells, as well as in the movement of water through the vessels of xylem in plants. Many small organisms benefit from surface tension: it allows them to float or slide on water.

The biological significance of water is also determined by the fact that it is one of the necessary metabolites, that is, it participates in metabolic reactions. Water is used, for example, as a source of hydrogen in the process of photosynthesis, and also participates in hydrolysis reactions.

The role of water for living organisms is reflected, in particular, in the fact that one of the main factors of natural selection influencing speciation is the lack of water (limiting the spread of some plants with mobile gametes). All terrestrial organisms are adapted to extract and conserve water; in its extreme manifestations - among xerophytes, among animals living in the desert, etc. Such adaptations seem to be a true miracle of nature's ingenuity.

Biological functions of water:

In all organisms:

1) ensures the maintenance of the structure (high water content in protoplasm); 2) serves as a solvent and diffusion medium; 3) participates in hydrolysis reactions; 4) serves as the environment in which fertilization occurs;

5) ensures the spread of seeds, gametes and larval stages of aquatic organisms, as well as seeds of some terrestrial plants, such as the coconut palm.

In plants:

1) determines osmosis and turgidity (on which a lot depends: growth (cell enlargement), maintenance of structure, stomatal movement, etc.); 2) participates in photosynthesis; 3) provides the transport of inorganic ions and organic molecules; 4) ensures seed germination - swelling, rupture of the seed coat and further development.

In animals:

1) ensures the transport of substances;

2) causes osmoregulation;

3) helps to cool the body (sweating, heat shortness of breath);

4) serves as one of the components of the lubricant, for example, in the joints;

5) carries support functions (hydrostatic skeleton);

6) performs a protective function, for example, in lacrimal fluid and mucus;

7) promotes migration (sea currents).

1 Organic and inorganic substances

I. Inorganic compounds.

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

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

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, it is possible to carry out osmotic reactions in living cells.

Water is the main vehicle for the movement of substances in the body (blood circulation, ascending and descending currents of solutions through the body of a plant, etc.).

2. Minerals.

In the composition of living organisms, 80 elements of the periodic system have been found by modern methods of chemical analysis. By 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 - mainly heavy metal ions. 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 organogenic elements: oxygen, carbon, hydrogen and nitrogen, of 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 the most important compounds: pigments (chlorophyll, hemoglobin), nucleic acids, vitamins.

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

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

Sulfur is involved in the construction of sulfur-containing amino acids (cystine, cysteine), 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 contained in cells only in the form of ions. Thanks to potassium, the cytoplasm has certain colloidal properties; potassium activates enzymes of protein synthesis, determines the normal rhythm of cardiac activity, participates in the generation of bioelectric potentials, 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 the regulation of water exchange in the body. Sodium ions contribute to the polarization of the cell membrane; the normal rhythm of cardiac activity depends on the presence in the nutrient medium in the required amount of sodium, potassium, and calcium salts.

Calcium in the ionic state is a potassium antagonist. It is a part of membrane structures, in the form of salts of pectin substances it sticks together plant cells. In plant cells, it is often found in the form of simple, needle-shaped or accrete 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 participates in the biosynthesis of chlorophyll, therefore, with a lack of iron in the soil, chlorosis develops in plants. The main role of iron is participation in the processes of respiration, photosynthesis through the transfer of electrons in the composition of oxidative enzymes - catalase, ferredoxin. A certain reserve of iron in the body of animals and humans is stored in the ferritin, a gel-containing protein, 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, 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 are involved in the dark reactions of photosynthesis and other biosynthesis. Anemia, loss of appetite, and heart disease are observed in animals with a copper deficiency.

Manganese is a trace element, with an insufficient amount of which chlorosis occurs in plants. Manganese also plays an important 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 trace element in the soil, the conductive tissues, flowers, and ovary die off in plants.

Recently, trace elements are widely used in plant growing (pre-sowing seed treatment), in animal husbandry (trace element additives to feed).

Other inorganic components of the cell are most often found in the form of salts dissociated into ions in solution, 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. Carbon is the main source of energy for living organisms. In addition, they provide organisms with compounds that are later used to synthesize 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, forming 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 readily soluble in water, sweet in taste, and have a constant molecular weight. An example of oligosaccharides can be 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 to bind, adhere connective tissue cells, and protect cells from adverse factors.

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

Depending on the 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 of 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, since, due to their structure, they form clearly oriented molecular layers, and the ordered arrangement of hydrophilic and hydrophobic ends of the 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 in the process of biochemical transformations, therefore, a relatively small amount of them catalyze the reactions of a large amount of a substance. The characteristic difference between enzymes and chemical catalysts is their ability to accelerate reactions under normal conditions.

By their chemical nature, enzymes are divided into two groups - one-component (consisting only of protein, their activity is due to the active center - a specific group of amino acids in a protein molecule (pepsin, trypsin)) and two-component (consisting of a protein (apoenzyme - a protein carrier) and a protein component ( coenzyme), and the chemical nature of coenzymes is 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 impart reactivity to the molecule.

The modern classification of enzymes is based on the types of chemical reactions they catalyze. Hydrolase enzymes accelerate the cleavage reaction of 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 nitrogenous groups from one molecule to another.

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

Isomerases carry out isomerization.

Ligases catalyze the reactions of joining two molecules using the energy of ATP or another triopasphate.

Pigments are high molecular weight natural colored compounds. Of several hundreds of 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 an iron atom stands in place of magnesium, then such a metalloporphyrin is called heme.

The composition of hemoglobin of erythrocytes of human blood, all other vertebrates and some invertebrates includes iron oxide, which gives the blood a red color. Hemerithrin gives the blood a pink color (some polychaete worms). Chlorocruorin stains blood and tissue fluid green.

The most common respiratory blood pigments are hemoglobin and hemocyanin (respiratory pigment of higher crustaceans, arachnids, some octopus molluscs).

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

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 mass of the cell. Water plays an essential role in the life of cells and living organisms in general. In addition to the fact that it is included in their composition, for many organisms it is also a habitat.

The role of water in the cell is determined by its unique chemical and physical properties, associated mainly with the small size of the molecules, with 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:

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 able to move more freely; correspondingly, the reactivity of the substance increases. It is for this reason that most of the chemical reactions in the cell take place in aqueous solutions. Its molecules are involved in many chemical reactions, such as 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 non-polar substances and does not mix with them, since it cannot form hydrogen bonds with them. Substances insoluble in water are called hydrophobic. Hydrophobic molecules or their parts 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 of 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 during significant temperature changes 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, that is, the ability of molecules to carry with them a significant amount of heat while simultaneously cooling the body. Due to this property of water, which manifests itself during perspiration in mammals, heat shortness of breath in crocodiles and other animals, transpiration in plants, overheating is prevented.

Water has an extremely 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 slide on the water's surface.

Water ensures the movement of substances in the cell and the 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 annelid worms, echinoderms).

Water is a component of lubricating fluids (synovial - in the joints of vertebrates, pleural - in the pleural cavity, pericardial - in the pericardial sac) and mucus (facilitates 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, are pretsspavleva with mineral salts. Salt molecules in aqueous solution break down into cations and anions. The most important are the cations (K +, Na +, Ca2 +, Mg: +, NH4 +) and anions (C1, H2P04 -, HP042-, HC03 -, NO32--, SO4 2-) Not only the content, but also the ratio of ions 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 emergence of nervous and muscle excitement. 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.

Anions of phosphoric acid create a phosphate buffer system that maintains the pH of the intracellular environment of the body at 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.