Lesson type - combined

Methods: partially search, problem presentation, explanatory and illustrative.

Target:

Formation in students of a holistic system of knowledge about living nature, its systemic organization and evolution;

Ability to give a reasoned assessment of new information on biological issues;

Fostering civic responsibility, independence, initiative

Tasks:

Educational: about biological systems (cell, organism, species, ecosystem); history of the development of modern ideas about living nature; outstanding discoveries in biological science; the role of biological science in the formation of the modern natural science picture of the world; methods of scientific knowledge;

Development creative abilities in the process of studying the outstanding achievements of biology that have entered into universal human culture; complex and contradictory ways of developing modern scientific views, ideas, theories, concepts, various hypotheses (about the essence and origin of life, man) in the course of working with various sources of information;

Upbringing conviction in the possibility of knowing living nature, the need to take care of the natural environment, and one’s own health; respect for the opponent's opinion when discussing biological problems

Personal results of studying biology:

1. education of Russian civic identity: patriotism, love and respect for the Fatherland, a sense of pride in one’s Motherland; awareness of one's ethnicity; assimilation of humanistic and traditional values ​​of multinational Russian society; fostering a sense of responsibility and duty to the Motherland;

2. the formation of a responsible attitude towards learning, the readiness and ability of students for self-development and self-education based on motivation for learning and knowledge, conscious choice and construction of a further individual educational trajectory based on orientation in the world of professions and professional preferences, taking into account sustainable cognitive interests;

Meta-subject results of teaching biology:

1. the ability to independently determine the goals of one’s learning, set and formulate new goals for oneself in learning and cognitive activity, develop the motives and interests of one’s cognitive activity;

2. mastery of the components of research and project activities, including the ability to see a problem, pose questions, put forward hypotheses;

3. ability to work with different sources of biological information: find biological information in various sources (textbook text, popular scientific literature, biological dictionaries and reference books), analyze and

evaluate information;

Cognitive: identification of essential features of biological objects and processes; providing evidence (argumentation) of the relationship between humans and mammals; relationships between humans and the environment; dependence of human health on the state of the environment; the need to protect the environment; mastering the methods of biological science: observation and description of biological objects and processes; setting up biological experiments and explaining their results.

Regulatory: the ability to independently plan ways to achieve goals, including alternative ones, to consciously choose the most effective ways to solve educational and cognitive problems; the ability to organize educational cooperation and joint activities with the teacher and peers; work individually and in a group: find a common solution and resolve conflicts based on coordinating positions and taking into account interests; formation and development of competence in the field of use of information and communication technologies (hereinafter referred to as ICT competences).

Communicative: the formation of communicative competence in communication and cooperation with peers, understanding the characteristics of gender socialization in adolescence, socially useful, educational and research, creative and other types of activities.

Technologies : Health conservation, problem-based, developmental education, group activities

Techniques: analysis, synthesis, inference, translation of information from one type to another, generalization.

During the classes

Tasks

Introduce students to the chemical composition of cells.

Reveal the structural features of water molecules that determine its role in the life of cells and organisms.

Characterize the role of mineral salts and their constituent cations and anions in the life of a cell.

Basic provisions

Biological evolution represents a natural stage in the development of matter as a whole.

The cosmic and planetary prerequisites for the emergence of life are the size of the planet, the distance from the Sun, the circular orbit and the constancy of the star’s radiation.

The restorative nature of the atmosphere on the primitive Earth is regarded as a chemical prerequisite for the emergence of life on our planet.

Abiogenically, from the components of the Earth's primary atmosphere under the influence of the energy of lightning discharges, powerful hard ultraviolet radiation from the Sun, etc., a variety of simple organic molecules—monomers of biological polymers—could arise.

In aqueous solutions, under milder conditions, more complex compounds were formed as a result of the interaction of simple organic molecules.

Coacervates are multimolecular complexes surrounded by a common aqueous shell.

Coacervate drops have the ability to selectively absorb substances from the environment and carry out simple metabolic reactions.

During the formation of the internal environment of coacervates, the synthesis processes occurring in them led to the appearance of membranes and specific catalysts of a protein nature.

The most important event of prebiological evolution is the emergence of the genetic code in the form of a sequence of RNA codons, and then DNA, which turned out to be capable of storing information about the most successful combinations of amino acids in protein molecules.

The appearance of the first cellular forms marked the beginning of biological evolution, the initial stages of which were characterized by the appearance of eukaryotic organisms, the sexual process and the emergence of the first multicellular organisms.

Problem areas

How could the concentration barrier in the waters of the primordial ocean be overcome?

What are the principles of natural selection of coacervates under the conditions of the early Earth?

What major evolutionary transformations accompanied the first steps of biological evolution?

Inorganic substances that make up the cell

About 70 elements of the periodic table of chemical elements were discovered in the cells of different organisms D.I. Mendeleev, but only 24 of them have an established significance and are constantly found in all types of cells.

The largest share in the elemental composition of the cell is made up of oxygen, carbon, hydrogen and nitrogen. These are the so-called basic or biogenic elements. These elements account for more than 95% of the mass of cells, and their relative content in living matter is much higher than in the earth's crust.

The vital ones are calcium, phosphorus, sulfur, potassium, chlorine, sodium, magnesium and iron. Their content in the cell is calculated in tenths and hundredths of a percent. The listed elements constitute a group of macroelements.

Other chemical elements: copper, cobalt, manganese, molybdenum, zinc, boron, fluorine, chromium, selenium, aluminum, iodine, silicon - are contained exclusively in small quantities (less than 0.01% of cell mass). They belong to the group of microelements.

The percentage content of a particular element in the body in no way characterizes the degree of importance and necessity in the body. For example, many microelements are part of various biologically active substances - enzymes, vitamins, hormones; they influence growth and development, hematopoiesis, cellular respiration processes, etc.

Water. The most common inorganic compound in living organisms is water. Its content varies widely: in the cells of tooth enamel there is about 10% water, and in the cells of the developing embryo - more than 90%. On average, in a multicellular organism, water makes up about 80% of body weight.

The role of water in the cell is very important. Its functions are largely determined by its chemical nature. The dipole nature of the structure of molecules determines the ability of water to actively interact with various substances. Its molecules cause the breakdown of a number of water-soluble substances into cations and anions. As a result, the ions quickly enter into chemical reactions. Most chemical reactions involve interactions between water-soluble substances.

Water. Plays an important role in the life of cells and living organisms in general. In addition to the fact that it is part of their composition, for many organisms it is also a habitat. The role of water in a cell is determined by its properties. These properties are quite unique and are associated mainly with the small size of water molecules, with the polarity of its molecules and with their ability to connect with each other through hydrogen bonds.

Water molecules have a nonlinear spatial structure. The atoms in a water molecule are held together by polar covalent bonds that link one oxygen atom to two hydrogen atoms. The polarity of covalent bonds is explained in this case by the strong electronegativity of the oxygen atoms relative to the hydrogen atom; The oxygen atom attracts electrons from their common electron pairs.

As a result, a partially negative charge appears on the oxygen atom, and a partially positive charge on the hydrogen atoms. Hydrogen bonds occur between the oxygen and hydrogen atoms of neighboring water molecules.

Water is an excellent solvent for polar substances, such as salts, sugars, alcohols, and acids. Substances that are soluble in water are called hydrophilic.

Substances that are insoluble in water are called hydrophobic.

Water has high heat capacity. Breaking the hydrogen bonds that hold water molecules together requires the absorption of a large amount of energy. This property ensures the maintenance of the body's thermal balance during significant temperature changes in the environment. In addition, water has high thermal conductivity, which allows the body to maintain the same temperature throughout its entire volume. Water also has high heat of vaporization, i.e. the ability of molecules to carry away a significant amount of heat, cooling the body. This property of water is used in sweating in mammals, thermal shortness of breath in crocodiles, and transpiration (evaporation) in plants, preventing them from overheating.

Biological properties of water:

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

Metabolic. Water is the medium for many biochemical reactions in the cell.

Structural. The cytoplasm of cells contains from 60 to 95% water. In plants, water determines cell turgor.

Water participates in the formation of lubricating fluids and mucus. It is part of saliva, bile, tears, etc.

Mineral salts. Most of the inorganic substances of the cell are in the form of salts. In an aqueous solution, salt molecules dissociate into cations and anions. The most important cations are: K+, Na+, Ca2+, Mg2+ and anions: Cl-, H2PO4-, HPO42-, HCO3-, NO3-, SO42-. Not only the content, but also the ratio of ions in the cell is significant.

The buffering properties of the cell depend on the concentration of salts inside the cell.

Buffer call the ability of a cell to maintain the slightly alkaline reaction of its contents at a constant level.

Issues for discussion

What is the contribution of various elements to the organization of living and nonliving matter?

How do the physicochemical properties of water manifest themselves in supporting the vital processes of the cell and the entire organism?

Questions and tasks for review

1.What substance forms the basis of the internal environment of living organisms?

2. How will the lack of any necessary element affect the vital activity of the cell and organism? Give examples of such phenomena?

3.Which element cations provide the most important property of living organisms - irritability?

4. Find in the reference material the elements contained in the smallest quantities in the cell. What is their common name? What role do they perform in the cell?

Inorganicsubstancescells

Water and its role in cell life

Chemical composition of the cell. Inorganic compounds.

Resources

V. B. ZAKHAROV, S. G. MAMONTOV, N. I. SONIN, E. T. ZAKHAROVA TEXTBOOK “BIOLOGY” FOR GENERAL EDUCATIONAL INSTITUTIONS (grades 10-11).

A. P. Plekhov Biology with fundamentals of ecology. Series “Textbooks for universities. Special literature".

Book for teachers Sivoglazov V.I., Sukhova T.S. Kozlova T. A. Biology: general patterns.

Presentation hosting

Topic: “Chemical composition of the cell.”

Plan:

1. Inorganic substances of the cell.

2. Organic substances of the cell.

The cell contains about 70 chemical elements of Mendeleev's periodic table, which are also found in inanimate nature. This indicates the unity of the organic and inorganic world. However, the ratio of chemical elements in living and nonliving matter is different.

Depending on their content in a living organism, chemical elements are divided into several groups:

1 group - macronutrients(make up 98% of the cell's mass): hydrogen, oxygen, carbon and nitrogen. They are part of carbohydrates, fats and proteins.

2nd group - macronutrients(make up approximately 1.9% of the total composition of the cell): sulfur, phosphorus, chlorine, potassium, sodium, magnesium, calcium, iron. They also perform an important function in the cell. For example, sodium, potassium and calcium ensure the permeability of cell membranes for various substances and the conduction of impulses along the nerve fiber. Ca is one of the factors on which normal blood clotting depends. Fe is part of hemoglobin, a red blood cell protein involved in the transfer of oxygen from the lungs to the tissues.

3 group - microelements(0.1%): zinc, copper, iodine, fluorine, cobalt, manganese, boron, etc. They also perform an important function. Microelements are part of enzymes, vitamins, hormones - substances with great biological activity. Lack or absence of any trace elements in the body can cause disease. For example, lack iodine, which is part of the thyroid hormone - thyroxine, leads to a decrease in its formation, hypofunction of the organ and the development of the disease. Zinc is part of a number of enzymes of the pancreatic hormone - insulin; it enhances the activity of sex hormones. Cobalt– a necessary component of vitamin B 12, which is involved in the process of NK synthesis, in protein metabolism, and is very important for hematopoiesis.

4 group - ultramicroelements(less than 0.00001%): gold, silver, mercury, uranium, beryllium, radium, etc. Their role has not been fully studied.

Based on the chemical composition, the substances entering the cell are divided into inorganic(also found in inanimate nature) and organic, characteristic of living organisms.

Inorganic substances of the cell.

Water- the most common inorganic compound. On average, in a multicellular organism it makes up 80% of body weight. The function of water is largely determined by its chemical and physical properties. These properties are associated with the small size of water molecules, their polarity and ability to connect with each other through hydrogen bonds.

Water function:

1. Water is the main solvent for polar substances (salts, sugar, acids, alcohols, etc.). In relation to water, all substances are divided into 2 groups: substances that are highly soluble in water are called hydrophilic. Water does not dissolve non-polar substances (fats, oils) and does not mix with them, since it cannot form hydrogen bonds with them. Substances that are insoluble in water are called hydrophobic.

2. Water has good thermal conductivity and high heat capacity, so the temperature inside the cell remains unchanged or its fluctuations are significantly less than in the environment surrounding the cell.

3. Water has a high heat of vaporization, i.e. the ability of molecules to carry away a significant amount of heat, cooling the body (this property of water is used during sweating in mammals).

4. Water ensures both the influx of substances into the cell and the removal from it.

5. Water is a source of O 2 and H 2 during photosynthesis.

6. Water is a stabilizer of cell structure due to the polarity of molecules

7. Water – osmoregulator: provides elasticity and volume of the cell.

8. Water is a participant in the hydrolysis and oxidation of high-molecular substances.

Mineral salts. Most of the inorganic substances in the cell are in the form of salts. Salt molecules in an aqueous solution dissociate into cations and anions (NaCl = Na + + Cl - ; NaSO 4 = Na + + SO 4 2-)

The most important cations are: K +, Na +, Ca 2+, NH 4 + and anions: Cl -, H 2 PO 4 -, HCO 3 -, NO 3 -, SO 4 2-.

The difference between the amounts of cations and anions on the surface and inside the cell ensures the occurrence of an action potential, which underlies nerve and muscle excitation.

Functions:

1. Maintaining the constancy of the internal environment of the body: phosphoric acid anions (H 2 PO 4 and HPO 4 2-) create a buffer system that maintains the pH inside the cell at 6.9. In the extracellular fluid and in the blood, carbonic acid plays the role of a buffer and its anions (H 2 CO 3 and HCO 3 -) maintain pH = 7.4.

2. Ensuring constant osmotic pressure: inside the cell the concentration of salts is higher - this ensures the flow of water into the cell and creates turgor pressure.

3. Activation of enzymes.

4. Form compounds with organic substances (Hb, chlorophyll, thyroxine, vitamin B 12, oxidative enzymes).

Biology- life science. The most important task of biology is the study of the diversity, structure, life activity, individual development and evolution of living organisms, their relationships with their environment.

Alive organisms have a number of features that distinguish them from inanimate nature. Individually, each of the differences is quite arbitrary, so they should be considered in combination.

Signs that distinguish living matter from nonliving matter:

1. the ability to reproduce and transmit hereditary information to the next generation;
2. metabolism and energy;
3. excitability;
4. adaptability to specific living conditions;
5. building material - biopolymers (the most important of them are proteins and nucleic acids);
6. specialization from molecules to organs and a high degree of their organization;
7. height;
8. aging;
9. death.

Levels of organization of living matter:

1. molecular,
2. cellular,
3. fabric,
4. organ,
5. organismic,
6. population-species,
7. biogeocenotic,
8. biosphere.

Diversity of life

Nuclear-free cells were the first to appear on our planet. Most scientists accept that nuclear organisms appeared as a result of the symbiosis of ancient archaebacteria with blue-green algae and oxidizing bacteria (the theory of symbiogenesis).

Cytology

Cytology- the science of cage. Studies the structure and functions of cells of unicellular and multicellular organisms. The cell is the elementary unit of structure, functioning, growth and development of all living beings. Therefore, the processes and patterns characteristic of cytology underlie the processes studied by many other sciences (anatomy, genetics, embryology, biochemistry, etc.).

Chemical elements of the cell

Chemical element- a certain type of atom with the same positive nuclear charge. About 80 chemical elements have been found in cells. They can be divided into four groups:
Group 1 - carbon, hydrogen, oxygen, nitrogen (98% of the cell contents),
Group 2 - potassium, sodium, calcium, magnesium, sulfur, phosphorus, chlorine, iron (1.9%),
Group 3 - zinc, copper, fluorine, iodine, cobalt, molybdenum, etc. (less than 0.01%),
Group 4 - gold, uranium, radium, etc. (less than 0.00001%).

The elements of the first and second groups in most manuals are called macronutrients, elements of the third group - microelements, elements of the fourth group - ultramicroelements. For macro- and microelements, the processes and functions in which they participate have been clarified. For most ultramicroelements, a biological role has not been identified.

Atoms of chemical elements in living organisms form inorganic(water, salts) and organic compounds(proteins, nucleic acids, lipids, carbohydrates). At the atomic level, there are no differences between living and nonliving matter; differences will appear at the next, higher levels of organization of living matter.

Water

Water- the most common inorganic compound. Water content ranges from 10% (tooth enamel) to 90% of cell mass (developing embryo). Without water, life is impossible; the biological significance of water is determined by its chemical and physical properties.

The water molecule has an angular shape: hydrogen atoms form an angle of 104.5° with respect to oxygen. The part of the molecule where hydrogen is located is positively charged, the part where oxygen is located is negatively charged, and therefore the water molecule is a dipole. Hydrogen bonds are formed between water dipoles. Physical properties of water: transparent, maximum density at 4 °C, high heat capacity, practically does not compress; Pure water conducts heat and electricity poorly, freezes at 0 °C, boils at 100 °C, etc. Chemical properties of water: a good solvent, forms hydrates, undergoes hydrolytic decomposition reactions, interacts with many oxides, etc. In relation to the ability to dissolve in water, they are distinguished: hydrophilic substances- highly soluble, hydrophobic substances- practically insoluble in water.

Biological significance of water:

1. is the basis of the internal and intracellular environment,
2. ensures the maintenance of spatial structure,
3. provides transport of substances
4. hydrates polar molecules,
5. serves as a solvent and medium for diffusion,
6. participates in the reactions of photosynthesis and hydrolysis,
7. helps cool the body,
8. is a habitat for many organisms,
9. promotes migration and distribution of seeds, fruits, larval stages,
10. is the environment in which fertilization occurs,
11. in plants, ensures transpiration and seed germination,
12. promotes uniform distribution of heat in the body and much more. etc.

Other inorganic compounds of the cell

Other inorganic compounds are represented mainly by salts, which can be found either in dissolved form (dissociated into cations and anions) or solid. The cations K + , Na + , Ca 2+ , Mg 2+ (see table above) and the anions HPO 4 2 - , Cl - , HCO 3 - are important for the life of the cell, providing the buffering properties of the cell. Buffering- the ability to maintain pH at a certain level (pH is the decimal logarithm of the reciprocal of the concentration of hydrogen ions). A pH value of 7.0 corresponds to a neutral solution, below 7.0 to an acidic solution, and above 7.0 to an alkaline solution. Cells and tissues are characterized by a slightly alkaline environment. Phosphate (1) and bicarbonate (2) buffer systems are responsible for maintaining this slightly alkaline reaction.

Chemical composition of the cell

Chemical elements of the cell.

All cells, regardless of the level of organization, are similar in chemical composition. The cell contains several thousand substances that participate in various chemical reactions. About 80 chemical elements of D.I. Mendeleev’s periodic table were discovered in living organisms. For 24 elements the functions they perform in the body are known, these are biogenic elements. Based on their quantitative content in living matter, elements are divided into three categories:

Macronutrients:

O, C, H, N- about 98% of the mass of living matter, elements of the 1st group;

K, Na, Ca, Mg, S, P, Cl, F e - elements of the 2nd group. (1.9% of the mass of living matter).

Microelements (Zn, Mn, Cu, Co, Mo and many others), the share of which ranges from 0.001% to 0.000001. Microelements are part of biologically active substances - enzymes, vitamins and hormones.

Ultramicroelements (Au, U, Ra, etc.), the concentration of which does not exceed 0.000001%. The role of most elements of this group has not yet been clarified.

Macro- and microelements are present in living matter in the form of various chemical compounds, which are divided into inorganic and organic substances .

Inorganic compounds of the cell.

Inorganic substances include: water, constituting approximately 70-80% of the body’s weight; minerals - 1-1,5%.

Water. The most common inorganic compound in living organisms. Its content varies widely: in the cells of tooth enamel, water makes up about 10% by weight, and in the cells of a developing embryo - more than 90%.

Without water, life is impossible. It is not only an essential component of living cells, but also the habitat of organisms. The biological significance of water is based on its chemical and physical properties.

The chemical and physical properties of water are explained, first of all, by the small size of water molecules, their polarity and ability to connect with each other through hydrogen bonds. In a water molecule, one oxygen atom is covalently bonded to two hydrogen atoms. The molecule is polar: the oxygen atom carries a small negative charge, and the two hydrogen atoms carry small positive charges. This makes the water molecule a dipole. Therefore, when water molecules interact with each other, hydrogen bonds are established between them. They are 15-20 times weaker than covalent ones, but since each water molecule is capable of forming 4 hydrogen bonds, they significantly affect the physical properties of water. The large heat capacity, heat of fusion and heat of vaporization are explained by the fact that most of the heat absorbed by water is spent on breaking hydrogen bonds between its molecules. Water has high thermal conductivity. Water is practically incompressible and transparent in the visible part of the spectrum. Finally, water is a substance whose density in a liquid state is greater than in a solid state; at 4ºC it has a maximum density, ice has a lower density, it rises to the surface and protects the reservoir from freezing.

Physical and chemical properties make it a unique liquid and determine its biological significance. Water is a good solvent for ionic (polar) compounds, as well as some non-ionic compounds whose molecules contain charged (polar) groups. Any polar compounds in water hydrate(surrounded by water molecules), while water molecules participate in the formation of the structure of molecules of organic substances. If the energy of attraction of water molecules to molecules of a substance is greater than the energy of attraction between molecules of a substance, then the substance dissolves. In relation to water there are: hydrophilic substances - substances that are highly soluble in water; hydrophobic substances- substances that are practically insoluble in water. Most biochemical reactions can only occur in an aqueous solution; Many substances enter and leave the cell in an aqueous solution. The high heat capacity and thermal conductivity of water contribute to the uniform distribution of heat in the cell.

Due to the large loss of heat during the evaporation of water, the body cools down. Thanks to the forces of adhesion and cohesion, water is able to rise through capillaries (one of the factors ensuring the movement of water in the vessels of plants). Water is a direct participant in many chemical reactions (hydrolytic breakdown of proteins, carbohydrates, fats, etc.). Determines the stressed state of cell walls (turgor), and also performs a supporting function (hydrostatic skeleton, for example, in roundworms).

Minerals of the cell. They are mainly represented by salts that dissociate into anions and cations. For the vital processes of the cell, the most important cations are K +, Na +, Ca 2+, Mg 2+, and the anions HPO 4 2-, Cl -, HCO 3 -. The concentrations of ions in the cell and its environment are different. For example, in the external environment (blood plasma, sea water) K + is always less, and Na + is always more than in the cell. There are a number of mechanisms that allow the cell to maintain a certain ratio of ions in the protoplast and the external environment.

Various ions take part in many processes of cell life: cations K +, Na +, Cl - provide the excitability of living organisms; cations Mg 2+, Mn 2+, Zn 2+, Ca 2+, etc. are necessary for the normal functioning of many enzymes; the formation of carbohydrates during photosynthesis is impossible without Mg 2+ (a component of chlorophyll); the buffer properties of the cell (maintaining the slightly alkaline reaction of the cell contents) are supported by anions of weak acids (HCO 3 -, HPO 4 -) and weak acids (H 2 CO 3);

Phosphate buffer system:

Low pH High pH

NPO 4 2- + H + ←―――――――→H 2 PO 4 -

Hydrogen phosphate - ion Dihydrogen phosphate - ion

Bicarbonate buffer system:

Low pH High pH

HCO 3 - + H + ←―――――――→ H 2 CO 3

Bicarbonate - ion Carbonic acid

Some inorganic substances are contained in the cell not only in a dissolved state, but also in a solid state. For example, Ca and P are contained in bone tissue and in mollusk shells in the form of double carbon dioxide and phosphate salts.

Chemical elements that make up the cell.

The composition of a living cell includes about 60 chemical elements of D.I. Mendeleev’s periodic table. Moreover, many of them have the smallest serial numbers. And the lower the serial number of a chemical element, the more often it is found in living nature.

All chemical elements that make up a cell can be divided into
3 groups according to occurrence:

1) macroelements: carbon, hydrogen, oxygen and nitrogen. Their number in the cell is greatest, about 98%. These elements are part of the protein.

2) oligoelements or average in occurrence. There are 8 of them in total: 5 of them are metals (sodium, potassium, calcium, magnesium and iron) and 3 are non-metals (sulfur, phosphorus and chlorine). The share of oligoelements in the cell accounts for 1.9%.

3) microelements. There are very few of them in the cell, about 0.1% of more than 40 elements. These are iodine, zinc, copper, fluorine, etc. Lack or absence of microelements can cause serious diseases. For example, iodine deficiency causes dysfunction of the thyroid gland, resulting in the development of goiter.

Based on the chemical composition, the substances entering the cell are divided into 2 groups:

– Inorganic (also found in inanimate nature)

– Organic (characteristic only of living organisms)

Water . The amount of water in the cell is maximum and is 70–80%.

The role of water in the cell is very important:

1) Water is a universal solvent. Various organic and inorganic substances dissolve in it. Depending on how different substances dissolve in water, there are 2 groups of substances:

– hydrophilic(from the Greek hydor - water, phileo - love) - these are substances that are highly soluble in water. These include many salts, acids, proteins, carbohydrates, etc.

– hydrophobic(from the Greek hydor - water, phobos - fear) - these are insoluble or poorly soluble substances in water. These include fats and fat-like substances.

2) Most chemical processes in a cell occur only in aqueous solutions. Water is directly involved in many chemical intracellular reactions (hydrolysis, i.e. the breakdown of proteins, fats and other substances).

3) The volume and elasticity of the cell depend on the amount of water in it.

4) Water has a high heat capacity; it provides thermoregulation of the cell.

Water molecules are polar and are capable of forming complexes of several molecules due to the formation of hydrogen bonds. As the ambient temperature increases, part of the heat is spent on breaking hydrogen bonds between water molecules, while the temperature of the internal environment remains virtually unchanged. When cooled, hydrogen bonds between water molecules reappear and heat is released.

In addition to water, the cell contains weak acids, bases, and many salts.

Salts are in a dissociated state in the cell. K + , Na + Ca 2+ Mg 2+ and HPO 2- , H 2 PO 4 , HCO 3 , Cl – are important in the life of the cell. With the help of anions of weak acids, the reaction of the internal environment of the cell is maintained at an almost constant level, close to neutral (weakly alkaline).

The concentration of ions inside the cell and in the intercellular fluid is different. Particularly sharp differences are characteristic of Na + (localized mainly in the intercellular fluid) and K + (contained in high concentrations in the cell), which play an important role in the work of nerve and muscle fibers.

The content of various salts in the cell is maintained at a certain level. A significant change in their concentration can cause serious disturbances in the cell, and even its death. A decrease in Ca 2+ concentration in the blood of mammals causes convulsions and death. For normal contraction of the heart muscle, a certain ratio of K +, Na + Ca 2+ is necessary. When the balance of these ions changes, the work of the heart muscle is disrupted.

Often inorganic substances in the cell form complexes with proteins, carbohydrates and fats.