Functions of inorganic substances in the cell table. The main chemical elements of the cell and their importance for the life of organisms

About 70 chemical elements of the Periodic Table of D. I. Mendeleev are found in the cell, however, the content of these elements differs significantly from their concentrations in the environment, which proves the unity of the organic world.

The chemical elements present in the cell are divided into three large groups: macroelements, mesoelements (oligoelements) and microelements.

The content of macronutrients is about 98% of the mass of the cell. These include carbon, oxygen, hydrogen and nitrogen, which are part of the main organic substances. Mesoelements are sulfur, phosphorus, potassium, calcium, sodium, iron, magnesium, chlorine, which together make up about 1.9% of the cell mass. Sulfur and phosphorus are components of the most important organic compounds. Chemical elements, the concentration of which in the cell is about 0.1%, are microelements. These are zinc, iodine, copper, manganese, fluorine, cobalt, etc.

Substances of the cell are divided into inorganic and organic. Inorganic substances include water and mineral salts.

Due to its physicochemical properties, water in the cell is a solvent, a medium for reactions, a starting material and a product of chemical reactions, it performs transport and thermoregulatory functions, gives the cell elasticity, and provides that prop to the plant cell.

Mineral salts in the cell can be in dissolved or undissolved states. Soluble salts dissociate into ions. The most important cations are potassium and sodium, which facilitate the transfer of substances across the membrane and participate in the occurrence and conduction of a nerve impulse; calcium, which takes part in the processes of contraction of muscle fibers and blood clotting, magnesium, which is part of chlorophyll, and iron, which is part of a number of proteins, including hemoglobin. Zinc is part of the molecule of the pancreatic hormone - insulin, copper is required for the processes of photosynthesis and respiration. The most important anions are the phosphate anion, which is part of ATP and nucleic acids, and the carbonic acid residue, which softens fluctuations in the pH of the medium. Lack of calcium and phosphorus leads to rickets, lack of iron - to anemia.

Organic substances of the cell are represented by carbohydrates, lipids, proteins, nucleic acids, ATP, vitamins and hormones.

Carbohydrates consist mainly of three chemical elements: carbon, oxygen and hydrogen. Their general formula is Cm(H20)n. Distinguish between simple and complex carbohydrates. Simple carbohydrates (monosaccharides) contain a single sugar molecule. They are classified according to the number of carbon atoms, for example, pentoses (C5) and hexoses (C6). Pentoses include ribose and deoxyribose. Ribose is a constituent of RNA and ATP. Deoxyribose is a component of DNA. Hexoses are glucose, fructose, galactose, etc. They take an active part in the metabolism in the cell and are part of complex carbohydrates - oligosaccharides and polysaccharides. Oligosaccharides (disaccharides) include sucrose (glucose + fructose), lactose or milk sugar (glucose + galactose), etc.

Examples of polysaccharides are starch, glycogen, cellulose and chitin. Carbohydrates perform in the cell plastic (construction), energy (the energy value of the breakdown of 1 g of carbohydrates is 17.6 kJ), storage and support functions. Carbohydrates can also be part of complex lipids and proteins.

Lipids are a group of hydrophobic substances. These include fats, wax steroids, phospholipids, etc.

The structure of the fat molecule

Fat is an ester of the trihydric alcohol glycerol and higher organic (fatty) acids. In a fat molecule, a hydrophilic part can be distinguished - the “head” (glycerol residue) and a hydrophobic part - “tails” (fatty acid residues), therefore, in water, the fat molecule is oriented in a strictly defined way: the hydrophilic part is directed towards water, and the hydrophobic part is away from it.

Lipids perform in the cell plastic (construction), energy (the energy value of splitting 1 g of fat is 38.9 kJ), storage, protective (amortization) and regulatory (steroid hormones) functions.

Proteins are biopolymers whose monomers are amino acids. Amino acids contain an amino group, a carboxyl group and a radical. Amino acids differ only in radicals. Proteins contain 20 essential amino acids. Amino acids are linked together to form a peptide bond. A chain of more than 20 amino acids is called a polypeptide or protein. Proteins form four basic structures: primary, secondary, tertiary, and quaternary.

The primary structure is a sequence of amino acids connected by a peptide bond.

The secondary structure is a helix, or folded structure, held together by hydrogen bonds between the oxygen and hydrogen atoms of the peptide groups of different turns of the helix or folds. The tertiary structure (globule) is held by hydrophobic, hydrogen, disulfide and other bonds.

Tertiary structure of a protein

The tertiary structure is characteristic of most body proteins, such as muscle myoglobin.

Quaternary structure of the protein.

The quaternary structure is the most complex, formed by several polypeptide chains connected mainly by the same bonds as in the tertiary. The quaternary structure is characteristic of hemoglobin, chlorophyll, etc.

Proteins can be simple or complex. Simple proteins consist only of amino acids, while complex proteins (lipoproteins, chromoproteins, glycoproteins, nucleoproteins, etc.) contain protein and non-protein parts. For example, in addition to the four polypeptide chains of the globin protein, hemoglobin includes a non-protein part - heme, in the center of which there is an iron ion, which gives hemoglobin a red color.

The functional activity of proteins depends on environmental conditions. The loss of a protein molecule of its structure up to the primary is called denaturation. The reverse process of restoring secondary and higher structures is renaturation. The complete destruction of a protein molecule is called destruction.

Proteins perform a number of functions in the cell: plastic (construction), catalytic (enzymatic), energy (the energy value of splitting 1 g of protein is 17.6 kJ), signal (receptor), contractile (motor), transport, protective, regulatory, storage.

Nucleic acids are biopolymers whose monomers are nucleotides. A nucleotide consists of a nitrogenous base, a pentose sugar residue, and a phosphoric acid residue. There are two types of nucleic acids: ribonucleic (RNA) and deoxyribonucleic (DNA).

DNA includes four types of nucleotides: adenine (A), thymine (T), guanine (G) and cytosine (C). These nucleotides contain the sugar deoxyribose. For DNA, Chargaff's rules are set:

1) the number of adenyl nucleotides in DNA is equal to the number of thymidyl (A = T);

2) the number of guanyl nucleotides in DNA is equal to the number of cytidyl (G = C);

3) the sum of adenyl and guanyl nucleotides is equal to the sum of thymidyl and cytidyl (A + G = T + C).

The structure of DNA was discovered by F. Crick and D. Watson (Nobel Prize in Physiology or Medicine in 1962). The DNA molecule is a double-stranded helix. Nucleotides are connected to each other through phosphoric acid residues, forming a phosphodiester bond, while the nitrogenous bases are directed inward. The distance between nucleotides in the chain is 0.34 nm.

Nucleotides of different chains are interconnected by hydrogen bonds according to the principle of complementarity: adenine is connected to thymine by two hydrogen bonds (A \u003d T), and guanine with cytosine by three (G \u003d C).

The structure of the nucleotide

The most important property of DNA is the ability to replicate (self-doubling). The main function of DNA is the storage and transmission of hereditary information.

It is concentrated in the nucleus, mitochondria and plastids.

The composition of RNA also includes four nucleotides: adenine (A), ura-cil (U), guanine (G) and cytosine (C). The sugar-pentose residue in it is represented by ribose. RNA is mostly single-stranded molecules. There are three types of RNA: messenger (i-RNA), transport (t-RNA) and ribosomal (r-RNA).

tRNA structure

All of them take an active part in the process of realizing hereditary information, which is rewritten from DNA to mRNA, and on the latter protein synthesis is already carried out, tRNA brings amino acids to ribosomes in the process of protein synthesis, rRNA is part of the ribosomes themselves.

>> Chemistry: Chemical elements in the cells of living organisms

More than 70 elements have been found in the composition of substances that form the cells of all living organisms (humans, animals, plants). These elements are usually divided into two groups: macroelements and microelements.

Macronutrients are found in cells in large quantities. First of all, these are carbon, oxygen, nitrogen and hydrogen. In total, they make up almost 98% of the total contents of the cell. In addition to these elements, macronutrients also include magnesium, potassium, calcium, sodium, phosphorus, sulfur and chlorine. Their total content is 1.9%. Thus, the share of other chemical elements accounts for about 0.1%. These are micronutrients. These include iron, zinc, manganese, boron, copper, iodine, cobalt, bromine, fluorine, aluminum, etc.

23 trace elements were found in the milk of mammals: lithium, rubidium, copper, silver, barium, strontium, titanium, arsenic, vanadium, chromium, molybdenum, iodine, fluorine, manganese, iron, cobalt, nickel, etc.

The composition of the blood of mammals includes 24 microelements, and the composition of the human brain - 18 microelements.

As you can see, there are no special elements in the cell that are characteristic only of living nature, that is, at the atomic level there are no differences between living and inanimate nature. These differences are found only at the level of complex substances - at the molecular level. So, along with inorganic substances (water and mineral salts), the cells of living organisms contain substances that are characteristic only for them - organic substances (proteins, fats, carbohydrates, nucleic acids, vitamins, hormones, etc.). These substances are built mainly from carbon, hydrogen, oxygen and nitrogen, i.e. from macroelements. Trace elements are contained in these substances in small quantities, however, their role in the normal life of organisms is enormous. For example, compounds of boron, manganese, zinc, cobalt dramatically increase the yield of individual agricultural plants and increase their resistance to various diseases.

Man and animals receive the trace elements they need for normal life through the plants they feed on. If there is not enough manganese in the food, then growth retardation, a slowdown in the onset of puberty, and metabolic disorders during the formation of the skeleton are possible. The addition of fractions of a milligram of manganese salts to the daily diet of animals eliminates these diseases.

Cobalt is part of vitamin B12, which is responsible for the work of hematopoietic organs. The lack of cobalt in food often causes a serious illness that leads to depletion of the body and even death.

The importance of trace elements for humans was first revealed in the study of such a disease as endemic goiter, which was caused by a lack of iodine in food and water. The intake of salt containing iodine leads to recovery, and its addition to food in small quantities prevents the disease. For this purpose, iodized table salt is carried out, to which 0.001-0.01% potassium iodide is added.

The composition of most biological enzyme catalysts includes zinc, molybdenum and some other metals. These elements, contained in the cells of living organisms in very small quantities, ensure the normal operation of the finest biochemical mechanisms, and are true regulators of life processes.

Many trace elements are contained in vitamins - organic substances of various chemical nature, which enter the body with food in small doses and have a great influence on the metabolism and overall vital activity of the body. In their biological action, they are close to enzymes, but enzymes are formed by the cells of the body, and vitamins usually come from food. Plants serve as sources of vitamins: citrus fruits, rose hips, parsley, onions, garlic and many others. Some vitamins - A, B1, B2, K - are obtained synthetically. Vitamins got their name from two words: vita - life and amine - containing nitrogen.

Trace elements are also part of hormones - biologically active substances that regulate the functioning of organs and systems of human and animal organs. They take their name from the Greek word harmao - I win. Hormones are produced by the endocrine glands and enter the blood, which carries them throughout the body. Some hormones are obtained synthetically.

1. Macroelements and microelements.

2. The role of trace elements in the life of plants, animals and humans.

3. Organic substances: proteins, fats, carbohydrates.

4. Enzymes.

5. Vitamins.

6. Hormones.

At what level of forms of existence of a chemical element does the difference between animate and inanimate nature begin?

Why are individual macronutrients also called biogenic? List them.

All living organisms are made up of cells. The human body also has cellular structure, thanks to which its growth, reproduction and development is possible.

The human body consists of a huge number of cells of different shapes and sizes, which depend on the function performed. By studying structure and function of cells is engaged cytology.

Each cell is covered with a membrane consisting of several layers of molecules, which ensures the selective permeability of substances. Under the membrane in the cell is a viscous semi-liquid substance - the cytoplasm with organelles.

Mitochondria- energy stations of the cell, ribosomes - the place of protein formation, the endoplasmic reticulum, which performs the function of transporting substances, the nucleus - the place of storage of hereditary information, inside the nucleus - the nucleolus. It produces ribonucleic acid. Near the nucleus is the cell center necessary for cell division.

human cells composed of organic and inorganic substances.

Inorganic substances:
Water - makes up 80% of the mass of the cell, dissolves substances, participates in chemical reactions;
Mineral salts in the form of ions are involved in the distribution of water between cells and intercellular substance. They are necessary for the synthesis of vital organic substances.
organic matter:
Proteins are the basic substances of the cell, the most complex substances found in nature. Proteins are part of membranes, nuclei, organelles, perform a structural function in the cell. Enzymes - proteins, reaction accelerators;
Fats - perform an energy function, they are part of the membranes;
Carbohydrates - also when splitting, they form a large amount of energy, they are highly soluble in water, and therefore, when they are split, energy is generated very quickly.
Nucleic acids - DNA and RNA, they determine, store and transmit hereditary information about the composition of cell proteins from parents to offspring.
The cells of the human body have a number of vital properties and perform certain functions:

AT cells are metabolized, accompanied by the synthesis and decomposition of organic compounds; metabolism is accompanied by the transformation of energy;
When substances are formed in a cell, it grows, the growth of cells is associated with an increase in their number, this is associated with reproduction by division;
Living cells are excitable;
One of the characteristic features of the cell is movement.
Cell of the human body the following vital properties are inherent: metabolism, growth, reproduction and excitability. Based on these functions, the functioning of the whole organism is carried out.

The chemical composition of the cell.

Basic properties and levels of organization of living nature

The levels of organization of living systems reflect the subordination, hierarchy of the structural organization of life:

Molecular genetic - individual biopolymers (DNA, RNA, proteins);

Cellular - an elementary self-reproducing unit of life (prokaryotes, unicellular eukaryotes), tissues, organs;

Organismic - independent existence of a separate individual;

Population-species - an elementary evolving unit - a population;

Biogeocenotic - ecosystems consisting of different populations and their habitat;

Biospheric - all the living population of the Earth, providing the circulation of substances in nature.

Nature is the entire existing material world in all its diversity of forms.

The unity of nature is manifested in the objectivity of its existence, the common elemental composition, subordination to the same physical laws, in the systemic nature of the organization.

Various natural systems, both living and non-living, are interconnected and interact with each other. An example of systemic interaction is the biosphere.

Biology is a complex of sciences that studies the patterns of development and life of living systems, the reasons for their diversity and adaptability to the environment, the relationship with other living systems and objects of inanimate nature.

The object of biology research is wildlife.

The subject of biology research are:

General and particular patterns of organization, development, metabolism, transmission of hereditary information;

The diversity of life forms and organisms themselves, as well as their relationship with the environment.

All the diversity of life on Earth is explained by the evolutionary process and the effect of the environment on organisms.

The essence of life is determined by M.V.

Volkenstein as the existence on Earth of "living bodies, which are open self-regulating and self-reproducing systems built from biopolymers - proteins and nucleic acids."

The main properties of living systems:

Metabolism;

Self-regulation;

Irritability;

Variability;

Heredity;

reproduction;

The chemical composition of the cell.

Inorganic substances of the cell

Cytology is a science that studies the structure and functions of cells. The cell is the elementary structural and functional unit of living organisms. The cells of unicellular organisms have all the properties and functions of living systems.

The cells of multicellular organisms are differentiated in structure and function.

Atomic composition: the cell contains about 70 elements of the Mendeleev Periodic Table of Elements, and 24 of them are present in all types of cells.

Macronutrients - H, O, N, C, microelements - Mg, Na, Ca, Fe, K, P, CI, S, ultramicroelements - Zn, Cu, I, F, Mn, Co, Si, etc.

Molecular composition: the composition of the cell includes molecules of inorganic and organic compounds.

Inorganic substances of the cell

The water molecule has a non-linear spatial structure and has polarity. Hydrogen bonds are formed between individual molecules, which determine the physical and chemical properties of water.

1. Water molecule 2. Hydrogen bonds between water molecules

Physical properties of water:

Water can be in three states - liquid, solid and gaseous;

Water is a solvent. Polar water molecules dissolve polar molecules of other substances. Substances that are soluble in water are called hydrophilic. Substances that are insoluble in water are hydrophobic;

High specific heat capacity. It takes a lot of energy to break the hydrogen bonds that hold water molecules together.

This property of water ensures the maintenance of heat balance in the body;

High heat of vaporization. It takes a lot of energy to evaporate water. The boiling point of water is higher than that of many other substances. This property of water protects the body from overheating;

Water molecules are in constant motion, they collide with each other in the liquid phase, which is important for metabolic processes;

adhesion and surface tension.

Hydrogen bonds determine the viscosity of water and the adhesion of its molecules to the molecules of other substances (cohesion).

Due to the adhesion forces of molecules, a film is created on the surface of water, which is characterized by surface tension;

Density. When cooled, the movement of water molecules slows down. The number of hydrogen bonds between molecules becomes maximum. Water has the highest density at 4°C. Freezing, water expands (a place is needed for the formation of hydrogen bonds), and its density decreases, so ice floats on the surface of the water, which protects the reservoir from freezing;

The ability to form colloidal structures.

Water molecules form a shell around the insoluble molecules of some substances, preventing the formation of large particles. This state of these molecules is called dispersed (scattered). The smallest particles of substances surrounded by water molecules form colloidal solutions (cytoplasm, intercellular fluids).

Biological functions of water:

Transport - water provides the movement of substances in the cell and body, the absorption of substances and the excretion of metabolic products.

In nature, water carries waste products to soils and water bodies;

Metabolic - water is a medium for all biochemical reactions and an electron donor during photosynthesis, it is necessary for the hydrolysis of macromolecules to their monomers;

Participates in education:

1) lubricating fluids that reduce friction (synovial - in the joints of vertebrates, pleural, in the pleural cavity, pericardial - in the pericardial sac);

2) mucus, which facilitate the movement of substances through the intestines, create a humid environment on the mucous membranes of the respiratory tract;

3) secrets (saliva, tears, bile, semen, etc.) and juices in the body.

inorganic ions.

Inorganic cell ions are represented by: K+, Na+, Ca2+, Mg2+, NH3 cations and Cl-, NOi2-, H2PO4-, HCO3-, HPO42- anions.

The difference between the number of cations and anions on the surface and inside the cell provides the occurrence of an action potential, which underlies the nervous and muscle excitation.

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 create a bicarbonate buffer system and maintain the pH of the extracellular medium (blood plasma) at the level of 4-7.

Nitrogen compounds serve as a source of mineral nutrition, synthesis of proteins, nucleic acids.

Phosphorus atoms are part of the nucleic acids, phospholipids, as well as the bones of vertebrates, the chitinous cover of arthropods. Calcium ions are part of the bone substance, they are also necessary for the implementation of muscle contraction, blood clotting.

The chemical composition of the cell. inorganic substances

Atomic and molecular composition of the cell. A microscopic cell contains several thousand substances that are involved in a variety of chemical reactions. Chemical processes occurring in a cell are one of the main conditions for its life, development, and functioning.

All cells of animal and plant organisms, as well as microorganisms, are similar in chemical composition, which indicates the unity of the organic world.

The table shows data on the atomic composition of cells.

Of the 109 elements of the periodic system of Mendeleev, a significant majority of them were found in cells. Some elements are contained in the cells in a relatively large amount, others in a small amount. Especially high is the content in the cell of four elements - oxygen, carbon, nitrogen and hydrogen. In total, they make up almost 98% of the total contents of the cell. The next group consists of eight elements, the content of which in a cell is calculated in tenths and hundredths of a percent. These are sulfur, phosphorus, chlorine, potassium, magnesium, sodium, calcium, iron.

Together, they account for 1.9%. All other elements are contained in the cell in extremely small quantities (less than 0.01%).

Thus, in the cell there are no special elements characteristic only of living nature. This indicates the connection and unity of animate and inanimate nature.

At the atomic level, there are no differences between the chemical composition of the organic and inorganic worlds. Differences are found at a higher level of organization - the molecular one.

As can be seen from the table, in living bodies, along with substances common in inanimate nature, there are many substances that are characteristic only of living organisms.

Water. In the first place among the substances of the cell is water. It makes up almost 80% of the mass of the cell. Water is the most important component of the cell, not only in quantity. She has an essential and diverse role in the life of the cell.

Water determines the physical properties of the cell - its volume, elasticity.

The importance of water in the formation of the structure of molecules of organic substances, in particular the structure of proteins, which is necessary for the performance of their functions. The importance of water as a solvent is great: many substances enter the cell from the external environment in an aqueous solution, and in an aqueous solution, waste products are removed from the cell.

Finally, water is a direct participant in many chemical reactions (breakdown of proteins, carbohydrates, fats, etc.).

The adaptability of the cell to function in an aquatic environment is an argument in favor of the fact that life on Earth originated in water.

The biological role of water is determined by the peculiarity of its molecular structure: the polarity of its molecules.

Carbohydrates.

Carbohydrates are complex organic compounds, they include carbon, oxygen and hydrogen atoms.

Distinguish between simple and complex carbohydrates.

Simple carbohydrates are called monosaccharides. Complex carbohydrates are polymers in which monosaccharides play the role of monomers.

Two monosaccharides form a disaccharide, three a trisaccharide, and many a polysaccharide.

All monosaccharides are colorless substances, readily soluble in water. Almost all of them have a pleasant sweet taste. The most common monosaccharides are glucose, fructose, ribose, and deoxyribose.

2.3 Chemical composition of the cell. Macro- and microelements

The sweet taste of fruits and berries, as well as honey, depends on the content of glucose and fructose in them. Ribose and deoxyribose are components of nucleic acids (p. 158) and ATP (p.

Di- and trisaccharides, like monosaccharides, dissolve well in water and have a sweet taste. With an increase in the number of monomer units, the solubility of polysaccharides decreases, and the sweet taste disappears.

Beet (or cane) and milk sugar are important among disaccharides, starch (in plants), glycogen (in animals), fiber (cellulose) are widespread among polysaccharides.

Wood is almost pure cellulose. The monomers of these polysaccharides is glucose.

The biological role of carbohydrates. Carbohydrates play the role of a source of energy necessary for the cell to carry out various forms of activity. For the activity of the cell - movement, secretion, biosynthesis, luminescence, etc. - energy is needed. Structurally complex, energy-rich, carbohydrates undergo deep cleavage in the cell and, as a result, turn into simple, energy-poor compounds - carbon monoxide (IV) and water (CO2 AND H20).

During this process, energy is released. When splitting 1 g of carbohydrate, 17.6 kJ is released.

In addition to energy, carbohydrates also perform a building function. For example, the walls of plant cells are made of cellulose.

Lipids. Lipids are found in all cells of animals and plants. They are part of many cellular structures.

Lipids are organic substances that are insoluble in water, but soluble in gasoline, ether, and acetone.

Of the lipids, the most common and well-known are fats.

There are, however, cells in which about 90% fat. In animals, such cells are found under the skin, in the mammary glands, and in the omentum. Fat is found in the milk of all mammals. In some plants, a large amount of fat is concentrated in seeds and fruits, such as sunflower, hemp, walnut.

In addition to fats, other lipids are also present in cells, for example, lecithin, cholesterol. Lipids include some vitamins (A, O) and hormones (for example, sex hormones).

The biological significance of lipids is great and varied.

Let us first of all note their construction function. Lipids are hydrophobic. The thinnest layer of these substances is part of the cell membranes. Great is the importance of the most common of the lipids - fat - as a source of energy. Fats are able to oxidize in the cell to carbon monoxide (IV) and water. During the breakdown of fat, twice as much energy is released than when carbohydrates are broken down. Animals and plants store fat in reserve and consume it in the process of life.

It is necessary to note the following value. fat as a source of water. From 1 kg of fat during its oxidation, almost 1.1 kg of water is formed. This explains how some animals are able to go quite a long time without water. Camel people, for example, making the transition through the waterless desert-nu, may not drink for 10-12 days.

Bears, marmots and other hibernating animals do not drink for more than two months. These animals receive the water necessary for life as a result of fat oxidation. In addition to structural and energy functions, lipids perform protective functions: fat has a low thermal conductivity. It is deposited under the skin, forming significant accumulations in some animals. So, in a whale, the thickness of the subcutaneous layer of fat reaches 1 m, which allows this animal to live in the cold water of the polar seas.

Biopolymers: proteins, nucleic acids.

Of all organic substances, the bulk in the cell (50-70%) is proteins. The cell membrane and all its internal structures are built with the participation of protein molecules. Protein molecules are very large, because they consist of many hundreds of different monomers that form all sorts of combinations. Therefore, the variety of protein types and their properties is truly endless.

Proteins are part of hair, feathers, horns, muscle fibers, nutritional

nye substances of eggs and seeds and many other parts of the body.

A protein molecule is a polymer. Monomers of protein molecules are amino acids.

More than 150 different amino acids are known in nature, but only 20 are usually involved in the construction of proteins in living organisms. A long thread of amino acids sequentially attached to each other represents primary structure protein molecule (it displays its chemical formula).

Usually this long thread is tightly twisted into a spiral, the coils of which are firmly interconnected by hydrogen bonds.

The spirally twisted strand of a molecule is secondary structure, molecules squirrel. Such a protein is already hard to stretch. The coiled protein molecule is then twisted into a tighter configuration - tertiary structure. Some proteins have an even more complex form - quaternary Structure, for example, hemoglobin. As a result of such repeated twisting, the long and thin thread of the protein molecule becomes shorter, thicker and gathers into a compact lump - globule Only globular protein performs its biological functions in the cell.

If the protein structure is disturbed, for example, by heating or chemical action, then it loses its qualities and unwinds.

This process is called denaturation. If denaturation has affected only the tertiary or secondary structure, then it is reversible: it can again twist into a spiral and fit into the tertiary structure (denaturation phenomenon). At the same time, the functions of this protein are restored. This most important property of proteins underlies the irritability of living systems, i.e.

the ability of living cells to respond to external or internal stimuli.

Many proteins play a role catalysts in chemical reactions

passing through the cell.

They are called enzymes. Enzymes are involved in the transfer of atoms and molecules, in the breakdown and construction of proteins, fats, carbohydrates and all other compounds (i.e. in cellular metabolism). Not a single chemical reaction in living cells and tissues is complete without the participation of enzymes.

All enzymes have a specific action - they streamline the course of processes or accelerate reactions in the cell.

Proteins in a cell perform many functions: they participate in its structure, growth, and in all life processes. Cell life is impossible without proteins.

Nucleic acids were first discovered in the nuclei of cells, which is why they got their name (lat.

pusleus - core). There are two types of nucleic acids: deoxyribonucleic acid (DIC for short) and ribonucleic acid (RIC). Nucleic acid molecules pre-

are very long polymer chains (strands), monomers

which are nucleotides.

Each nucleotide contains one molecule of phosphoric acid and sugar (deoxyribose or ribose), as well as one of the four nitrogenous bases. The nitrogenous bases in DNA are adenine guanine and cymosine, and mi.min,.

Deoxyribonucleic acid (DNA)- the most important substance in a living cell. The DNA molecule is the carrier of the hereditary information of the cell and the organism as a whole. From a DNA molecule is formed chromosome.

Organisms of each biological species have a certain number of DNA molecules per cell. The sequence of nucleotides in a DNA molecule is also always strictly individual and. unique not only for each biological species, but also for individual individuals.

This specificity of DNA molecules serves as the basis for establishing the relatedness of organisms.

DNA molecules in all eukaryotes are located in the nucleus of the cell. Prokaryotes do not have a nucleus, so their DNA is located in the cytoplasm.

in all living beings, DNA macromolecules are built according to the same type. They consist of two polynucleotide chains (strands) held together by hydrogen bonds of nitrogenous bases of nucleotides (like a zipper).

In the form of a double (paired) helix, the DNA molecule twists in the direction from left to right.

The sequence in the arrangement of nucleotides in the dick molecule determines the hereditary information of the cell.

The structure of the DNA molecule was revealed in 1953 by an American biochemist

James Watson and English physicist Francis Crick.

For this discovery, scientists were awarded the Nobel Prize in 1962. They proved that the molecule

DNA consists of two polynucleotide chains.

At the same time, nucleotides (mono-mers) are connected to each other not randomly, but selectively and in pairs by means of nitrogenous compounds. Adenine (A) always docks with thymine (T), and guanine (g) with cytosine (C). This double chain is tightly wound into a helix. The ability of nucleotides to selectively pair up is called complementarity(lat. complementus - addition).

Replication occurs as follows.

With the participation of special cellular mechanisms (enzymes), the DNA double helix unwinds, the strands diverge (like a zipper being unzipped), and gradually a complementary half of the corresponding nucleotides is completed to each of the two chains.

As a result, instead of one DNA molecule, two new identical molecules are formed. Moreover, each newly formed double-stranded DNA molecule consists of one "old" chain of nucleotides and one "new" one.

Since DNA is the main carrier of information, its ability to duplicate allows, during cell division, to transfer that hereditary information to newly formed daughter cells.

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buffering and osmosis.
Salts in living organisms are in a dissolved state in the form of ions - positively charged cations and negatively charged anions.

The concentration of cations and anions in the cell and in its environment is not the same. The cell contains quite a lot of potassium and very little sodium. In the extracellular environment, for example, in blood plasma, in sea water, on the contrary, there is a lot of sodium and little potassium. Cell irritability depends on the ratio of concentrations of Na+, K+, Ca2+, Mg2+ ions.

The difference in ion concentrations on opposite sides of the membrane ensures the active transport of substances through the membrane.

In the tissues of multicellular animals, Ca2+ is part of the intercellular substance that ensures the cohesion of cells and their orderly arrangement.

The chemical composition of the cell

The osmotic pressure in the cell and its buffer properties depend on the concentration of salts.

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

There are two buffer systems:

1) phosphate buffer system - phosphoric acid anions maintain the pH of the intracellular environment at 6.9

2) bicarbonate buffer system - anions of carbonic acid maintain the pH of the extracellular medium at the level of 7.4.

Let us consider the equations of reactions occurring in buffer solutions.

If the concentration in the cell increases H+ , then the hydrogen cation is added to the carbonate anion:

With an increase in the concentration of hydroxide anions, their binding occurs:

H + OH– + H2O.

So the carbonate anion can maintain a constant environment.

osmotic called the phenomena occurring in a system consisting of two solutions separated by a semipermeable membrane.

In a plant cell, the role of semipermeable films is performed by the boundary layers of the cytoplasm: the plasmalemma and the tonoplast.

The plasmalemma is the outer membrane of the cytoplasm adjacent to the cell wall. The tonoplast is the inner membrane of the cytoplasm that surrounds the vacuole. Vacuoles are cavities in the cytoplasm filled with cell sap - an aqueous solution of carbohydrates, organic acids, salts, low molecular weight proteins, pigments.

The concentration of substances in the cell sap and in the external environment (in soil, water bodies) is usually not the same. If the intracellular concentration of substances is higher than in the external environment, water from the environment will enter the cell, more precisely into the vacuole, at a faster rate than in the opposite direction. With an increase in the volume of cell sap, due to the entry of water into the cell, its pressure on the cytoplasm, which is tightly adjacent to the membrane, increases. When the cell is completely saturated with water, it has a maximum volume.

The state of internal tension of the cell, due to the high water content and the developing pressure of the contents of the cell on its membrane, is called turgor Turgor ensures that organs maintain their shape (for example, leaves, non-lignified stems) and position in space, as well as their resistance to the action of mechanical factors. With the loss of water is associated with a decrease in turgor and wilting.

If the cell is in a hypertonic solution, the concentration of which is greater than the concentration of cell sap, then the rate of diffusion of water from the cell sap will exceed the rate of diffusion of water into the cell from the surrounding solution.

Due to the release of water from the cell, the volume of cell sap decreases, turgor decreases. A decrease in the volume of the cell vacuole is accompanied by the separation of the cytoplasm from the membrane - occurs plasmolysis.

During plasmolysis, the shape of the plasmolyzed protoplast changes. Initially, the protoplast lags behind the cell wall only in separate places, most often in the corners. Plasmolysis of this form is called angular.

Then the protoplast continues to lag behind the cell walls, maintaining contact with them in separate places; the surface of the protoplast between these points has a concave shape.

At this stage, plasmolysis is called concave. Gradually, the protoplast breaks away from the cell walls over the entire surface and takes on a rounded shape. Such plasmolysis is called convex

If a plasmolyzed cell is placed in a hypotonic solution, the concentration of which is less than the concentration of cell sap, water from the surrounding solution will enter the vacuole. As a result of an increase in the volume of the vacuole, the pressure of the cell sap on the cytoplasm will increase, which begins to approach the cell walls until it takes its original position - deplasmolysis

Task number 3

After reading the text provided, answer the following questions.

1) definition of buffering

2) what concentration of anions determines the buffer properties of the cell

3) the role of buffering in the cell

4) equation of reactions occurring in a bicarbonate buffer system (on a magnetic board)

5) determination of osmosis (give examples)

6) Determination of plasmolysis and deplasmolysis slides

About 70 chemical elements of the Periodic Table of D. I. Mendeleev are found in the cell, however, the content of these elements differs significantly from their concentrations in the environment, which proves the unity of the organic world.

The chemical elements present in the cell are divided into three large groups: macroelements, mesoelements (oligoelements) and microelements.

These include carbon, oxygen, hydrogen and nitrogen, which are part of the main organic substances. Mesoelements are sulfur, phosphorus, potassium, calcium, sodium, iron, magnesium, chlorine, which together make up about 1.9% of the cell mass.

Sulfur and phosphorus are components of the most important organic compounds. Chemical elements, the concentration of which in the cell is about 0.1%, are microelements. These are zinc, iodine, copper, manganese, fluorine, cobalt, etc.

Substances of the cell are divided into inorganic and organic.

Inorganic substances include water and mineral salts.

Due to its physicochemical properties, water in the cell is a solvent, a medium for reactions, a starting material and a product of chemical reactions, it performs transport and thermoregulatory functions, gives the cell elasticity, and provides that prop to the plant cell.

Mineral salts in the cell can be in dissolved or undissolved states.

Soluble salts dissociate into ions. The most important cations are potassium and sodium, which facilitate the transfer of substances across the membrane and participate in the occurrence and conduction of a nerve impulse; calcium, which takes part in the processes of contraction of muscle fibers and blood clotting, magnesium, which is part of chlorophyll, and iron, which is part of a number of proteins, including hemoglobin. Zinc is part of the molecule of the pancreatic hormone - insulin, copper is required for the processes of photosynthesis and respiration.

The most important anions are the phosphate anion, which is part of ATP and nucleic acids, and the carbonic acid residue, which softens fluctuations in the pH of the medium.

Lack of calcium and phosphorus leads to rickets, lack of iron - to anemia.

Organic substances of the cell are represented by carbohydrates, lipids, proteins, nucleic acids, ATP, vitamins and hormones.

Carbohydrates consist mainly of three chemical elements: carbon, oxygen and hydrogen.

Their general formula is Cm(H20)n. Distinguish between simple and complex carbohydrates. Simple carbohydrates (monosaccharides) contain a single sugar molecule. They are classified according to the number of carbon atoms, for example, pentoses (C5) and hexoses (C6). Pentoses include ribose and deoxyribose. Ribose is a constituent of RNA and ATP. Deoxyribose is a component of DNA. Hexoses are glucose, fructose, galactose, etc.

They take an active part in the metabolism in the cell and are part of complex carbohydrates - oligosaccharides and polysaccharides. Oligosaccharides (disaccharides) include sucrose (glucose + fructose), lactose or milk sugar (glucose + galactose), etc.

Examples of polysaccharides are starch, glycogen, cellulose and chitin.

Carbohydrates perform in the cell plastic (construction), energy (the energy value of the breakdown of 1 g of carbohydrates is 17.6 kJ), storage and support functions. Carbohydrates can also be part of complex lipids and proteins.

Lipids are a group of hydrophobic substances.

These include fats, wax steroids, phospholipids, etc.

The structure of the fat molecule

Fat is an ester of the trihydric alcohol glycerol and higher organic (fatty) acids. In a fat molecule, a hydrophilic part can be distinguished - the “head” (glycerol residue) and a hydrophobic part - “tails” (fatty acid residues), therefore, in water, the fat molecule is oriented in a strictly defined way: the hydrophilic part is directed towards water, and the hydrophobic part is away from it.

Lipids perform in the cell plastic (construction), energy (the energy value of splitting 1 g of fat is 38.9 kJ), storage, protective (amortization) and regulatory (steroid hormones) functions.

Proteins are biopolymers whose monomers are amino acids.

Amino acids contain an amino group, a carboxyl group and a radical. Amino acids differ only in radicals. Proteins contain 20 essential amino acids. Amino acids are linked together to form a peptide bond.

A chain of more than 20 amino acids is called a polypeptide or protein. Proteins form four basic structures: primary, secondary, tertiary, and quaternary.

The primary structure is a sequence of amino acids connected by a peptide bond.

The secondary structure is a helix, or folded structure, held together by hydrogen bonds between the oxygen and hydrogen atoms of the peptide groups of different turns of the helix or folds.

The tertiary structure (globule) is held by hydrophobic, hydrogen, disulfide and other bonds.

Tertiary structure of a protein

The tertiary structure is characteristic of most body proteins, such as muscle myoglobin.

Quaternary structure of the protein.

The quaternary structure is the most complex, formed by several polypeptide chains connected mainly by the same bonds as in the tertiary.

The quaternary structure is characteristic of hemoglobin, chlorophyll, etc.

Proteins can be simple or complex. Simple proteins consist only of amino acids, while complex proteins (lipoproteins, chromoproteins, glycoproteins, nucleoproteins, etc.) contain protein and non-protein parts.

For example, in addition to the four polypeptide chains of the globin protein, hemoglobin includes a non-protein part - heme, in the center of which there is an iron ion, which gives hemoglobin a red color.

The functional activity of proteins depends on environmental conditions.

The loss of a protein molecule of its structure up to the primary is called denaturation. The reverse process of restoring secondary and higher structures is renaturation. The complete destruction of a protein molecule is called destruction.

Proteins perform a number of functions in the cell: plastic (construction), catalytic (enzymatic), energy (the energy value of splitting 1 g of protein is 17.6 kJ), signal (receptor), contractile (motor), transport, protective, regulatory, storage.

Nucleic acids are biopolymers whose monomers are nucleotides.

A nucleotide consists of a nitrogenous base, a pentose sugar residue, and a phosphoric acid residue. There are two types of nucleic acids: ribonucleic (RNA) and deoxyribonucleic (DNA).

DNA includes four types of nucleotides: adenine (A), thymine (T), guanine (G) and cytosine (C). These nucleotides contain the sugar deoxyribose. For DNA, Chargaff's rules are set:

1) the number of adenyl nucleotides in DNA is equal to the number of thymidyl (A = T);

2) the number of guanyl nucleotides in DNA is equal to the number of cytidyl (G = C);

3) the sum of adenyl and guanyl nucleotides is equal to the sum of thymidyl and cytidyl (A + G = T + C).

The structure of DNA was discovered by F.

Crick and D. Watson (Nobel Prize in Physiology or Medicine 1962). The DNA molecule is a double-stranded helix.

The cell and its chemical composition

Nucleotides are connected to each other through phosphoric acid residues, forming a phosphodiester bond, while the nitrogenous bases are directed inward. The distance between nucleotides in the chain is 0.34 nm.

Nucleotides of different chains are interconnected by hydrogen bonds according to the principle of complementarity: adenine is connected to thymine by two hydrogen bonds (A \u003d T), and guanine with cytosine by three (G \u003d C).

The structure of the nucleotide

The most important property of DNA is the ability to replicate (self-doubling).

The main function of DNA is the storage and transmission of hereditary information.

It is concentrated in the nucleus, mitochondria and plastids.

The composition of RNA also includes four nucleotides: adenine (A), ura-cil (U), guanine (G) and cytosine (C). The sugar-pentose residue in it is represented by ribose.

RNA is mostly single-stranded molecules. There are three types of RNA: messenger (i-RNA), transport (t-RNA) and ribosomal (r-RNA).

tRNA structure

All of them take an active part in the process of realizing hereditary information, which is rewritten from DNA to mRNA, and on the latter protein synthesis is already carried out, tRNA brings amino acids to ribosomes in the process of protein synthesis, rRNA is part of the ribosomes themselves.

The chemical composition of a living cell

Cells contain various chemical compounds. Some of them - inorganic - are also found in inanimate nature. However, organic compounds are most characteristic of cells, the molecules of which have a very complex structure.

Inorganic compounds of the cell. Water and salts are inorganic compounds. Most of all in cells of water. It is essential for all life processes.

Water is a good solvent. In an aqueous solution, chemical interactions of various substances occur. Nutrients in the dissolved state from the intercellular substance penetrate into the cell through the membrane. Water also contributes to the removal from the cell of substances that are formed as a result of the reactions taking place in it.

The salts K, Na, Ca, Mg, etc. are most important for the life processes of cells.

Organic compounds of the cell. The main role in the implementation of cell function belongs to organic compounds. Among them, proteins, fats, carbohydrates and nucleic acids are of the greatest importance.

Proteins are the basic and most complex substances of any living cell.

The size of a protein molecule is hundreds and thousands of times larger than the molecules of inorganic compounds. There is no life without proteins. Some proteins speed up chemical reactions by acting as catalysts. Such proteins are called enzymes.

Fats and carbohydrates have a less complex structure.

They are the building material of the cell and serve as sources of energy for the vital processes of the body.

Nucleic acids are produced in the cell nucleus. Hence their name came from (lat. Nucleus - the core). As part of the chromosomes, nucleic acids are involved in the storage and transmission of the hereditary properties of the cell. Nucleic acids provide the formation of proteins.

Vital properties of the cell. The main vital property of the cell is metabolism.

From the intercellular substance, nutrients and oxygen constantly enter the cells and decay products are released. Substances that enter the cell are involved in the processes of biosynthesis. Biosynthesis is the formation of proteins, fats, carbohydrates and their compounds from simpler substances. In the process of biosynthesis, substances characteristic of certain cells of the body are formed.

For example, proteins are synthesized in muscle cells that ensure their contraction.

Simultaneously with biosynthesis in cells, the breakdown of organic compounds occurs. As a result of decomposition, substances of a simpler structure are formed. Most of the decay reaction takes place with the participation of oxygen and the release of energy.

Chemical organization of the cell

This energy is spent on the life processes taking place in the cell. The processes of biosynthesis and decay make up the metabolism, which is accompanied by energy transformations.

Cells are capable of growth and reproduction. The cells of the human body reproduce by dividing in half. Each of the resulting daughter cells grows and reaches the size of the mother. New cells perform the function of the mother cell.

The lifespan of cells varies from a few hours to tens of years.

Living cells are capable of responding to physical and chemical changes in their environment. This property of cells is called excitability. At the same time, cells go from a state of rest to a working state - excitation. When excited in cells, the rate of biosynthesis and decomposition of substances, oxygen consumption, and temperature change. In an excited state, different cells perform their own functions.

Glandular cells form and secrete substances, muscle cells contract, a weak electrical signal arises in nerve cells - a nerve impulse that can propagate along cell membranes.

The internal environment of the body.

Most cells in the body are not connected to the external environment. Their vital activity is provided by the internal environment, which consists of 3 types of fluids: intercellular (tissue) fluid, with which the cells are in direct contact, blood and lymph. The internal environment provides the cells with the substances necessary for their vital activity, and decay products are removed through it.

The internal environment of the body has a relative constancy of composition and physico-chemical properties. Only under this condition can cells function normally.

Metabolism, biosynthesis and decomposition of organic compounds, growth, reproduction, excitability are the main vital properties of cells.

The vital properties of cells are provided by the relative constancy of the composition of the internal environment of the body.

The cell contains about 70 elements of the Mendeleev Periodic Table of Elements, and 24 of them are present in all types of cells. All elements present in the cell are divided, depending on their content in the cell, into groups:

• macronutrients– H, O, N, C,. Mg, Na, Ca, Fe, K, P, Cl, S;
• trace elements– B, Ni, Cu, Co, Zn, Mb, etc.;
• ultramicroelements– U, Ra, Au, Pb, Hg, Se, etc.

• organogens(oxygen, hydrogen, carbon, nitrogen),
• macronutrients,
• trace elements.

The cell contains molecules inorganic and organic connections.

Inorganic cell compounds – water and inorganic ions.
Water- the most important inorganic substance of the cell. All biochemical reactions take place in aqueous solutions. The water molecule has a non-linear spatial structure and has polarity. Hydrogen bonds are formed between individual water molecules, which determine the physical and chemical properties of water.

inorganic ions:
cations K+, Na+, Ca2+, Mg2+ and anions Cl–, NO3-, PO4 2-, CO32-, HPO42-.

The difference between the number of cations and anions (Na + , TO + , Cl-) on the surface and inside the cell ensures the occurrence of an action potential, which underlies nervous and muscular excitation.
Phosphoric acid anions create phosphate buffer system, maintaining the pH of the intracellular environment of the body at the level of 6-9.
Carbonic acid and its anions create bicarbonate buffer system and maintain the pH of the extracellular medium (blood plasma) at the level of 7-4.
Nitrogen compounds serve source mineral nutrition, synthesis of proteins, nucleic acids.
Phosphorus atoms are part of the nucleic acids, phospholipids, as well as the bones of vertebrates, the chitinous cover of arthropods.
Calcium ions are part of the bone substance; they are also necessary for the implementation of muscle contraction, blood clotting.

Table. The role of macronutrients at the cellular and organismal levels of organization.

Table.

Thematic tasks

Part A

A1. The polarity of water determines its ability
1) conduct heat
3) dissolve sodium chloride
2) absorb heat
4) dissolve glycerin

A2. Children with rickets should be given drugs containing
1) iron
2) potassium
3) calcium
4) zinc

A3. Conduction of a nerve impulse is provided by ions:
1) potassium and sodium
2) phosphorus and nitrogen
3) iron and copper
4) oxygen and chlorine

A4. Weak bonds between water molecules in its liquid phase are called:
1) covalent
2) hydrophobic
3) hydrogen
4) hydrophilic

A5. Hemoglobin contains
1) phosphorus
2) iron
3) sulfur
4) magnesium

A6. Choose a group of chemical elements that must be part of proteins
1) Na, K, O, S
2) N, P, C, Cl
3) C, S, Fe, O
4) C, H, O, N

A7. Patients with hypothyroidism are given medications containing
1) iodine
2) iron
3) phosphorus
4) sodium

Part B

IN 1. Select the functions of the water in the cage
1) energy
2) enzymatic
3) transport
4) building
5) lubricating
6) thermoregulatory

IN 2. Select only the physical properties of water
1) the ability to dissociate
2) hydrolysis of salts
3) density
4) thermal conductivity
5) electrical conductivity
6) electron donation

Part C

C1. What physical properties of water determine its biological significance?

The cell consists of approximately 70 basic elements , which can be found in the periodic table. Of these, only 24 are found in all cells.

The main elements are hydrogen, carbon, oxygen and nitrogen. These are the main cellular elements, but elements such as potassium, iodine, magnesium, chlorine, iron, calcium and sulfur play an equally important role. These are macronutrients, which are contained in cells in a relatively small amount (up to tenths of a percent).

There are even fewer trace elements in cells (less than 0.01% of cell mass). These include copper, molybdenum, boron, fluorine, chromium, zinc, silicon and cobalt.

The value and content of elements in the cells of organisms is given in the table.