What organic substances predominate in plant cells. Cytology task

Most of the chemical elements of D.I. Mendeleev’s Periodic Table of Elements discovered to date have been found in living organisms. On the one hand, they do not contain a single element that would not be found in inanimate nature, and on the other hand, their concentrations in bodies of inanimate nature and living organisms differ significantly.

These chemical elements form inorganic and organic substances. Despite the fact that inorganic substances predominate in living organisms, it is organic substances that determine the uniqueness of their chemical composition and the phenomenon of life as a whole, since they are synthesized mainly by organisms in the process of life and play a vital role in reactions.

Science studies the chemical composition of organisms and the chemical reactions occurring in them. biochemistry.

It should be noted that the content of chemicals in different cells and tissues can vary significantly. For example, if in animal cells proteins predominate among organic compounds, then in plant cells carbohydrates predominate.

Chemical element	Earth's crust	Sea water	Alive organisms
O	49.2	85.8	65–75
C	0.4	0.0035	15–18
H	1.0	10.67	8–10
N	0.04	0.37	1.5–3.0
P	0.1	0.003	0.20–1.0
S	0.15	0.09	0.15–0.2
K	2.35	0.04	0.15–0.4
Ca	3.25	0.05	0.04–2.0
Cl	0.2	0.06	0.05–0.1
Mg	2.35	0.14	0.02–0.03
Na	2.4	1.14	0.02–0.03
Fe	4.2	0.00015	0.01–0.015
Zn	< 0.01	0.00015	0.0003
Cu	< 0.01	< 0.00001	0.0002
I	< 0.01	0.000015	0.0001
F	0.1	2.07	0.0001

Macro- and microelements

About 80 chemical elements are found in living organisms, but only 27 of these elements have their functions in the cell and organism established. The remaining elements are present in small quantities and, apparently, enter the body with food, water and air. The content of chemical elements in the body varies significantly. Depending on their concentration, they are divided into macroelements and microelements.

The concentration of each macronutrients in the body exceeds 0.01%, and their total content is 99%. Macroelements include oxygen, carbon, hydrogen, nitrogen, phosphorus, sulfur, potassium, calcium, sodium, chlorine, magnesium and iron. The first four of the listed elements (oxygen, carbon, hydrogen and nitrogen) are also called organogenic, since they are part of the main organic compounds. Phosphorus and sulfur are also components of a number of organic substances, such as proteins and nucleic acids. Phosphorus is essential for the formation of bones and teeth.

Without the remaining macroelements, normal functioning of the body is impossible. Thus, potassium, sodium and chlorine are involved in the processes of cell excitation. Potassium is also necessary for the functioning of many enzymes and the retention of water in the cell. Calcium is found in the cell walls of plants, bones, teeth, and mollusk shells and is required for muscle cell contraction and intracellular movement. Magnesium is a component of chlorophyll, a pigment that ensures photosynthesis occurs. It also takes part in protein biosynthesis. Iron, in addition to being part of hemoglobin, which carries oxygen in the blood, is necessary for the processes of respiration and photosynthesis, as well as for the functioning of many enzymes.

Microelements are contained in the body in concentrations of less than 0.01%, and their total concentration in the cell does not reach 0.1%. Microelements include zinc, copper, manganese, cobalt, iodine, fluorine, etc. Zinc is part of the molecule of the pancreatic hormone - insulin, copper is required for the processes of photosynthesis and respiration. Cobalt is a component of vitamin B12, the absence of which leads to anemia. Iodine is necessary for the synthesis of thyroid hormones, which ensure normal metabolism, and fluoride is associated with the formation of tooth enamel.

Both deficiency and excess or disturbance of the metabolism of macro- and microelements lead to the development of various diseases. In particular, a lack of calcium and phosphorus causes rickets, a lack of nitrogen - severe protein deficiency, a deficiency of iron - anemia, and a lack of iodine - a violation of the formation of thyroid hormones and a decrease in metabolic rate. A decrease in fluoride intake from water and food largely determines the disruption of tooth enamel renewal and, as a consequence, a predisposition to caries. Lead is toxic to almost all organisms. Its excess causes irreversible damage to the brain and central nervous system, which is manifested by loss of vision and hearing, insomnia, kidney failure, seizures, and can also lead to paralysis and diseases such as cancer. Acute lead poisoning is accompanied by sudden hallucinations and ends in coma and death.

The lack of macro- and microelements can be compensated by increasing their content in food and drinking water, as well as by taking medications. Thus, iodine is found in seafood and iodized salt, calcium is found in eggshells, etc.

The relationship between the structure and functions of inorganic and organic substances (proteins, nucleic acids, carbohydrates, lipids, ATP) that make up the cell. The role of chemicals in the cell and human body

Inorganic substances

The chemical elements of the cell form various compounds - inorganic and organic. The inorganic substances of the cell include water, mineral salts, acids, etc., and the organic substances include proteins, nucleic acids, carbohydrates, lipids, ATP, vitamins, etc.

Water(H 2 O) is the most common inorganic substance of the cell, which has unique physicochemical properties. It has no taste, no color, no smell. The density and viscosity of all substances is assessed using water. Like many other substances, water can exist in three states of aggregation: solid (ice), liquid and gaseous (steam). The melting point of water is 0°C, the boiling point is 100°C, however, the dissolution of other substances in water can change these characteristics. The heat capacity of water is also quite high - 4200 kJ/mol K, which gives it the opportunity to take part in thermoregulation processes. In a water molecule, the hydrogen atoms are located at an angle of 105°, with shared electron pairs pulled away by the more electronegative oxygen atom. This determines the dipole properties of water molecules (one end is positively charged and the other negatively charged) and the possibility of the formation of hydrogen bonds between water molecules. The cohesion of water molecules underlies the phenomenon of surface tension, capillarity and the properties of water as a universal solvent. As a result, all substances are divided into those soluble in water (hydrophilic) and insoluble in it (hydrophobic). Thanks to these unique properties, it is predetermined that water has become the basis of life on Earth.

The average water content in the body's cells varies and may change with age. Thus, in a one-and-a-half-month-old human embryo, the water content in the cells reaches 97.5%, in an eight-month-old - 83%, in a newborn it decreases to 74%, and in an adult it averages 66%. However, body cells differ in their water content. So, the bones contain about 20% water, the liver - 70%, and the brain - 86%. In general it can be said that the concentration of water in cells is directly proportional to the metabolic rate.

Mineral salts may be in dissolved or undissolved states. Soluble salts dissociate into ions - cations and anions. The most important cations are potassium and sodium ions, which facilitate the transfer of substances across the membrane and are involved in the occurrence and conduction of nerve impulses; as well as calcium ions, which takes part in the processes of muscle fiber contraction and blood clotting; magnesium, which is part of chlorophyll; iron, which is part of a number of proteins, including hemoglobin. 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 environment. Ions of mineral salts ensure the penetration of water itself into the cell and its retention in it. If the salt concentration in the environment is lower than in the cell, then water penetrates into the cell. Ions also determine the buffering properties of the cytoplasm, i.e. its ability to maintain a constant slightly alkaline pH of the cytoplasm, despite the constant formation of acidic and alkaline products in the cell.

Insoluble salts(CaCO 3, Ca 3 (PO 4) 2, etc.) are part of the bones, teeth, shells and shells of unicellular and multicellular animals.

In addition, organisms can produce other inorganic compounds, such as acids and oxides. Thus, the parietal cells of the human stomach produce hydrochloric acid, which activates the digestive enzyme pepsin, and silicon oxide permeates the cell walls of horsetails and forms the shells of diatoms. In recent years, the role of nitric oxide (II) in signaling in cells and the body has also been studied.

Organic matter

Answers to school textbooks

Elements found in living nature are also widespread in inanimate nature - the atmosphere, water, and the earth's crust. There are no elements that are found exclusively in living organisms. But the ratio of chemical elements, their contribution to the formation of substances that make up a living organism and a nonliving body, differ sharply. In a living organism, most of the elements are found in the form of chemical compounds - substances dissolved in water. Only living organisms contain organic substances: proteins, fats, carbohydrates and nucleic acids.

2. Is the chemical composition of plant and animal cells similar?

The chemical composition of plant and animal cells is similar. All living organisms consist of the same elements, inorganic and organic compounds. However, the content of various elements varies in different cells. Each type of cell contains different amounts of certain organic molecules. Complex carbohydrates (fiber, starch) predominate in plant cells, while in animal cells there are more proteins and fats. Each of the groups of organic substances (proteins, carbohydrates, fats, nucleic acids) in any type of cell performs its inherent functions (nucleic acid - storage and transmission of hereditary information, carbohydrates - energy, etc.).

3. List the elements most common in living organisms.

The cell contains about 80 chemical elements. Depending on the number of chemical elements contained in the substances that form a living organism, it is customary to distinguish several groups of them. One group is formed by four elements that make up about 98% of the cell's mass: oxygen, hydrogen, carbon and nitrogen. They are called macronutrients. These are the dominant constituents of all organic compounds.

Another group includes sulfur and phosphorus, potassium and sodium, calcium and magnesium, manganese, iron and chlorine. They are found in cells in smaller quantities (tenths and hundredths of a percent). Each of them performs an important function in the cell. For example, calcium and phosphorus are involved in the formation of bone tissue, determining bone strength. Iron is part of hemoglobin, a protein in red blood cells (erythrocytes) that is involved in the transfer of oxygen from the lungs to the tissues.

4. What substances are classified as organic?

Organic substances include proteins, nucleic acids, fats, carbohydrates, as well as hormones, pigments, ATP and some others. They constitute on average 20-30% of the mass of a cell in a living organism.

5. What is the role of proteins in the cell?

Among the organic substances of the cell, proteins occupy first place both in quantity and in importance. In animals they account for about 50% of the dry mass of the cell.

The role of proteins in the cell is extremely large and diverse. One of the most important functions of proteins is construction: proteins participate in the formation of membranes and organelles of non-membrane structure. Another important function is catalytic: certain proteins accelerate chemical reactions occurring in the cell by tens and hundreds of thousands of times.

The motor function of the body is provided by contractile proteins. These proteins are involved in all types of movement that animal cells and organisms are capable of.

The transport function of proteins is to attach chemical elements (for example, oxygen) or biologically active substances (hormones) and transport them to various tissues and organs of the body.

When foreign proteins or microorganisms enter the body, special proteins - antibodies - are formed in white blood cells (leukocytes). They bind and neutralize substances unusual for the body. This expresses the protective function of proteins.

Proteins also serve as one of the sources of energy in the cell, i.e., they perform an energy function.

6. What substances are the main source of energy?

The main source of energy in animal and plant cells is carbohydrates. These include glucose, sucrose, fiber, starch, etc. By “burning” glucose, the body receives the necessary energy for the metabolic processes taking place in it. Living organisms can store carbohydrates in the form of starch (in plants) and glycogen (in animals and fungi). In potato tubers, starch can make up up to 80% of the mass, and in animals there is especially a lot of carbohydrates in liver cells and muscles - up to 5%.

Carbohydrates also perform other functions, such as support and protection. Fiber is part of wood; chitin forms the exoskeleton of insects, crustaceans and other arthropods.

7. Describe the role of fats in the body.

Fats perform a number of functions in the body, such as serving as a reserve source of energy. They provide the body with up to 30% of all the energy it needs. Fats also perform a construction function, being an essential component of the cellular and nuclear membranes. In some animals, fats accumulate in large quantities and serve as a heat insulator, that is, they protect the body from heat loss (for example, in whales the thickness of the fat layer reaches 1 m).

Fats are also of great importance as an internal water reserve: as a result of the breakdown of 1 kg of fat, up to 1.1 kg of water is formed. This is very important for animals that hibernate in winter - gophers, marmots: thanks to their subcutaneous fat reserves, they can not drink at this time for up to two months. When crossing the desert, camels go without drinking for up to two weeks - they extract the water necessary for the body from their humps, which are receptacles for fat.

8. What is the role of water in the cell?

The most common inorganic compound in living organisms is water. Its content varies widely: in the cells of tooth enamel - about 10%, 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. First of all, water determines the physical properties of the cell, its volume, elasticity. Numerous chemical reactions take place in an aqueous environment, since water is a good solvent. And water itself is involved in many chemical transformations.

Water helps remove unnecessary and harmful substances from the body resulting from metabolism (excretory function), and promotes the movement of oxygen, carbon dioxide and nutrients throughout the body (transport function).

Water has good thermal conductivity and high heat capacity. When the ambient temperature changes, water absorbs or releases heat. As a result, the temperature inside the cell remains unchanged or its fluctuations are significantly less than in the environment surrounding the cell (thermoregulatory function).

9. Name the carbohydrates you know.

Carbohydrates include the following natural organic compounds: glucose, fructose, sucrose, maltose, lactose, chitin, starch, glycogen and cellulose.

10. What role do nucleic acids play in a cell?

Nucleic acids are responsible for the storage and transmission of hereditary characteristics from parents to offspring. They are part of chromosomes - special structures located in the cell nucleus. Nucleic acids are also found in the cytoplasm and its organelles.

11. What is the chemical composition of living organisms?

The most common elements in living organisms are oxygen, carbon, hydrogen and nitrogen. Living organisms include organic substances (proteins, fats, carbohydrates, nucleic acids) and inorganic substances (water, mineral salts).

Animals, fungi and bacteria

Sign	Bacteria	Animals	Mushrooms	Plants
Nutrition method	Heterotrophic or autotrophic	Heterotrophic	Heterotrophic	Autotrophic
Organization hereditary information	Prokaryotes	Eukaryotes	Eukaryotes	Eukaryotes
DNA localization	Nucleoid, plasmids	Nucleus, mitochondria	Nucleus, mitochondria	Nucleus, mitochondria, plastids
Plasma membrane	Eat	Eat	Eat	Eat
Cell wall	Mureinovaya	-	Chitinous	Pulp
Cytoplasm	Eat	Eat	Eat	Eat
Organoids	Ribosomes	Membrane and non-membrane, including the cell center	Membrane and non-membrane	Membrane and non-membrane, including plastids
Organoids of movement	Flagella and villi	Flagella and cilia	Flagella and cilia	Flagella and cilia
Vacuoles	Rarely	Contractile, digestive	Sometimes	Central vacuole with cell sap
Inclusions	Volyutin	Glycogen	Glycogen	Starch

Differences in the structure of cells of representatives of different kingdoms of living nature are shown in Fig. 2.3.

Rice. 2.3. The structure of bacterial cells (A), animals (B), fungi (C) and plants (D)
2.3. Chemical organization of the cell. The relationship between the structure and functions of inorganic and organic substances (proteins, nucleic acids, carbohydrates, lipids, ATP) that make up the cell. Justification of the relationship of organisms based on an analysis of the chemical composition of their cells.
Chemical composition of the cell.

Most of the chemical elements of D.I. Mendeleev’s Periodic Table of Elements discovered to date have been found in living organisms. On the one hand, they do not contain a single element that would not be found in inanimate nature, and on the other hand, their concentrations in bodies of inanimate nature and living organisms differ significantly (Table 2.2).

These chemical elements form inorganic and organic substances. Despite the fact that inorganic substances predominate in living organisms (Fig. 2.4), it is organic substances that determine the uniqueness of their chemical composition and the phenomenon of life as a whole, since they are synthesized mainly by organisms in the process of life and play a vital role in reactions.

Science studies the chemical composition of organisms and the chemical reactions occurring in them. biochemistry.

It should be noted that the content of chemicals in different cells and tissues can vary significantly. For example, if in animal cells proteins predominate among organic compounds, then in plant cells carbohydrates predominate.

Table 2.2

Content of some chemical elements in inanimate nature and living organisms, %

Chemical element	Earth's crust	Sea water	Alive organisms
ABOUT	49,2	85,8	65-75
WITH	0,4	0,0035	15-18
N	1,0	10,67	8-10
N	0,04	0,37	1,5-3,0
R	0,1	0,003	0,20-1,0
S	0,15	0,09	0,15-0,2
TO	2,35	0,04	0,15-0,4
Ca	3,25	0,05	0,04-2,0
C1	0,2	0,06	0,05-0,1
Mg	2,35	0,14	0,02-0,03
Na	2,4	1.14	0,02-0,03
Fe	4,2	0,00015	0,01-0,015
Zn		0,00015	0,0003
Cu			0,0002
I		0,000015	0,0001
F	0,1	2,07	0,0001

Macro- and microelements

About 80 chemical elements are found in living organisms, but only 27 of these elements have their functions in the cell and organism established. The remaining elements are present in small quantities and, apparently, enter the body with food, water and air. The content of chemical elements in the body varies significantly (see Table 2.2). Depending on their concentration, they are divided into macroelements and microelements.

The concentration of each macronutrients in the body exceeds 0.01%, and their total content is 99%. Macroelements include oxygen, carbon, hydrogen, nitrogen, phosphorus, sulfur, potassium, calcium, sodium, chlorine, magnesium and iron. The first four of the listed elements (oxygen, carbon, hydrogen and nitrogen) are also called organogenic, since they are part of the main organic compounds. Phosphorus and sulfur are also components of a number of organic substances, such as proteins and nucleic acids. Phosphorus is essential for the formation of bones and teeth.

Without the remaining macroelements, normal functioning of the body is impossible. Thus, potassium, sodium and chlorine are involved in the processes of cell excitation. Potassium is also necessary for the functioning of many enzymes and the retention of water in the cell. Calcium is found in the cell walls of plants, bones, teeth, and mollusk shells and is required for muscle cell contraction and intracellular movement. Magnesium is a component of chlorophyll, a pigment that ensures photosynthesis occurs. It also takes part in protein biosynthesis. Iron, in addition to being part of hemoglobin, which carries oxygen in the blood, is necessary for the processes of respiration and photosynthesis, as well as for the functioning of many enzymes.

Microelements are contained in the body in concentrations of less than 0.01%, and their total concentration in the cell does not reach 0.1%. Microelements include zinc, copper, manganese, cobalt, iodine, fluorine, etc. Zinc is part of the molecule of the pancreatic hormone - insulin, copper is required for the processes of photosynthesis and respiration. Cobalt is a component of vitamin B 12, the absence of which leads to anemia. Iodine is necessary for the synthesis of thyroid hormones, which ensure normal metabolism, and fluoride is associated with the formation of tooth enamel.

Both deficiency and excess or disturbance of the metabolism of macro- and microelements lead to the development of various diseases. In particular, a lack of calcium and phosphorus causes rickets, a lack of nitrogen - severe protein deficiency, a deficiency of iron - anemia, and a lack of iodine - a violation of the formation of thyroid hormones and a decrease in metabolic rate. A decrease in fluoride intake from water and food largely determines the disruption of tooth enamel renewal and, as a consequence, a predisposition to caries. Lead is toxic to almost all organisms. Its excess causes irreversible damage to the brain and central nervous system, which is manifested by loss of vision and hearing, insomnia, kidney failure, seizures, and can also lead to paralysis and diseases such as cancer. Acute lead poisoning is accompanied by sudden hallucinations and ends in coma and death.


Rice. 2.4. Content of chemicals in the cell
The lack of macro- and microelements can be compensated by increasing their content in food and drinking water, as well as by taking medications. Thus, iodine is found in seafood and iodized salt, calcium is found in eggshells, etc.

2.3.1. Inorganic substances of the cell.
The chemical elements of the cell form various compounds - inorganic and organic. The inorganic substances of the cell include water, mineral salts, acids, etc., and the organic substances include proteins, nucleic acids, carbohydrates, lipids, ATP, vitamins, etc. (Fig. 2.4).

Water (H 2 0) is the most common inorganic substance of the cell, which has unique physicochemical properties. It has no taste, no color, no smell. The density and viscosity of all substances is assessed using water. Like many other substances, water can exist in three states of aggregation: solid (ice), liquid and gaseous (steam). The melting point of water is 0°C, the boiling point is 100°C, however, the dissolution of other substances in water can change these characteristics. The heat capacity of water is also quite high - 4200 kJ/mol. K, which gives it the opportunity to take part in thermoregulation processes. In a water molecule, the hydrogen atoms are located at an angle of 105°, with shared electron pairs pulled away by the more electronegative oxygen atom. This determines the dipole properties of water molecules (one end is positively charged and the other negatively charged) and the possibility of the formation of hydrogen bonds between water molecules (Fig. 2.5). The cohesion of water molecules underlies the phenomenon of surface tension, capillarity and the properties of water as a universal solvent. As a result, all substances are divided into soluble in water (hydrophilic) and insoluble in it (hydrophobic). Thanks to these unique properties, it is predetermined that water has become the basis of life on Earth.

The average water content in the body's cells varies and may change with age. Thus, in a one-and-a-half-month-old human embryo, the water content in the cells reaches 97.5%, in an eight-month-old - 83%, in a newborn it decreases to 74%, and in an adult it averages 66%. However, body cells differ in their water content. So, the bones contain about 20% water, the liver - 70%, and the brain - 86%. In general it can be said that the concentration of water in cells is directly proportional to the metabolic rate.

Mineral salts can be in dissolved or undissolved states. Soluble salts dissociate into ions - cations and anions. The most important cations are potassium and sodium ions, which facilitate the transfer of substances across the membrane and are involved in the occurrence and conduction of nerve impulses; as well as calcium ions, which takes part in the processes of muscle fiber contraction and blood clotting; magnesium, which is part of chlorophyll; iron, which is part of a number of proteins, including hemoglobin. 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 environment. Ions of mineral salts ensure the penetration of water itself into the cell and its retention in it. If the salt concentration in the environment is lower than in the cell, then water penetrates into the cell. Ions also determine the buffering properties of the cytoplasm, i.e. its ability to maintain a constant slightly alkaline pH of the cytoplasm, despite the constant formation of acidic and alkaline products in the cell.

Insoluble salts(CaC0 3, Ca 3 (P0 4) 2, etc.) are part of the bones, teeth, shells and shells of unicellular and multicellular animals.

In addition, organisms can produce other inorganic compounds, such as acids and oxides. Thus, the parietal cells of the human stomach produce hydrochloric acid, which activates the digestive enzyme pepsin, and silicon oxide permeates the cell walls of horsetails and forms the shells of diatoms. In recent years, the role of nitric oxide (II) in signaling in cells and the body has also been studied.

Organic substances that make up a cell.
Organic compounds make up on average 20-30% of the cell mass of a living organism. These include biological polymers - proteins, nucleic acids and carbohydrates, as well as fats and a number of small molecules - hormones, pigments, ATP and many others. Different types of cells contain different amounts of organic compounds. Complex carbohydrates - polysaccharides - predominate in plant cells; in animals there are more proteins and fats. However, each of the groups of organic substances in any type of cell performs similar functions.
Squirrels. Among the organic substances of cells, proteins occupy first place both in quantity and in importance. In animals they account for about 50% of the dry mass of the cell. In the human body, there are 5 million types of protein molecules that differ not only from each other, but also from proteins of other organisms.
Despite such diversity and complexity of structure, they are built from only 20 different amino acids.
Proteins isolated from living organisms - animals, plants and microorganisms - include several hundred and sometimes thousands of combinations of 20 basic amino acids. The order of their alternation is very diverse, which makes it possible for the existence of a huge number of protein molecules that differ from each other. For example, for a protein consisting of only 20 amino acid residues, about 2,1018 variants are theoretically possible, differing in the alternation of amino acids, and therefore in the properties of different protein molecules. The sequence of amino acids in a polypeptide chain is usually called the primary structure of a protein. However, a protein molecule in the form of a chain of amino acids sequentially connected to each other by peptide bonds is not yet capable of performing specific functions. This requires a higher structural organization. By forming hydrogen bonds between the carboxyl and amino group residues of different amino acids, the protein molecule takes the form of a helix. This is the secondary structure of the protein. But this is often not enough to acquire characteristic activity. Only a molecule with a tertiary structure can serve as a catalyst or any other. The tertiary structure is formed due to the interaction of radicals, in particular radicals of the amino acid cysteine, which contain sulfur. The sulfur atoms of two amino acids located at some distance from each other in the polypeptide chain are connected to form so-called disulfide, or 5-3 bonds. Thanks to these interactions, as well as other weaker bonds, the protein helix folds and takes the shape of a ball, or globule. The method of packing polypeptide helices into globules is called the tertiary structure of a protein. Many proteins with tertiary structure can perform their biological role in the cell. However, some body functions require the participation of proteins with an even higher level of organization. This organization is called a quaternary structure. It is a functional association of several (two, three or more) protein molecules with tertiary organization. An example of such a complex protein is hemoglobin. Its molecule consists of four interconnected molecules.
The loss of a protein molecule's structural organization is called denaturation.
Denaturation can be caused by temperature changes, dehydration, X-ray exposure and other influences. First, the weakest structure is destroyed - the quaternary, then the tertiary, secondary and, under the most severe conditions, the primary. If a change in environmental conditions does not lead to destruction of the primary structure of the molecule, then when normal environmental conditions are restored, the structure of the protein is completely recreated. This process is called renaturation. This property of proteins to completely restore the lost structure is widely used in the medical and food industries for the preparation of certain medical preparations, such as antibiotics, to obtain food concentrates that retain their nutritional properties for a long time in dried form.
The functions of proteins in a cell are extremely diverse. One of the most important is the construction function: proteins are involved in the formation of all cell membranes and cell organelles, as well as extracellular structures. The catalytic role of proteins is extremely important. All enzymes are substances of protein nature; they accelerate chemical reactions occurring in the cell tens and hundreds of thousands of times.
The motor function of living organisms is ensured by special contractile proteins. These proteins are involved in all types of movement that cells and organisms are capable of: the flickering of cilia and the beating of flagella in protozoa, muscle contraction in multicellular animals, the movement of leaves in plants, etc.
The transport function of proteins is to attach chemical elements (for example, oxygen) or biologically active substances (hormones) and transport them to various tissues and organs of the body.
When foreign proteins or microorganisms enter the body, special proteins - antibodies - are formed in white blood cells - leukocytes. They bind and neutralize substances that are not characteristic of the body - this is a protective function.
Proteins also serve as one of the sources of energy in the cell, i.e., they perform an energy function. When 1 g of protein is completely broken down, 17.6 kJ of energy is released.
Carbohydrates. Carbohydrates, or saccharides, are organic substances. Most carbohydrates have twice the number of hydrogen atoms as oxygen atoms. That's why these substances were called carbohydrates.
In an animal cell, carbohydrates are found in quantities not exceeding 1-2, sometimes 5%. Plant cells are the richest in carbohydrates, where their content in some cases reaches 90% of dry mass (potato tubers, seeds, etc.).
Carbohydrates are simple and complex. Simple carbohydrates are called monosaccharides. Depending on the number of carbon atoms in the molecule, monosaccharides are called trioses - 3 atoms, tetroses - 4, pentoses - 5 and hexoses - 6 carbon atoms. Of the six-carbon monosaccharides - hexoses, the most important are glucose, fructose and galactose. Glucose is contained in the blood (0.1-0.12%). Pentoses - ribose and deoxyribose - are part of nucleic acids and ATP. If two monosaccharides are combined in one molecule, such a compound is called a disaccharide. Table sugar, obtained from cane or sugar beets, consists of one molecule of glucose and one molecule of fructose, milk sugar - of glucose and galactose.
Complex carbohydrates formed from many monosaccharides are called polysaccharides. The monomer of such polysaccharides as starch, glycogen, cellulose is glucose.
Carbohydrates perform two main functions: construction and energy. For example, cellulose forms the walls of plant cells; the complex polysaccharide chitin is the main structural component of the exoskeleton of arthropods. Chitin also performs a construction function in fungi. Carbohydrates play the role of the main source of energy in the cell. During the oxidation process, 1 g of carbohydrates releases 17.6 kJ. Starch in plants and glycogen in animals, deposited in cells, serve as an energy reserve.
Fats and lipoids. Fats (lipids) are compounds of high molecular weight fatty acids and trihydric alcohol glycerol. Fats do not dissolve in water - they are hydrophobic. Cells always contain other complex hydrophobic fat-like substances called lipoids.
One of the main functions of fats is energy. During the breakdown of 1 g of fat, a large amount of energy is released - 38.9 kJ. The fat content in the cell ranges from 5-15% of the dry matter weight. In adipose tissue cells, the amount of fat increases to 90%. Accumulating in the cells of adipose tissue of animals, in the seeds and fruits of plants, fat serves as a reserve source of energy.
Fats and lipids also perform a construction function; they are part of cell membranes. Due to its poor thermal conductivity, fat can act as a heat insulator. In some animals (seals, whales) it is deposited in the subcutaneous adipose tissue, which in whales forms a layer up to 1 m thick. The formation of some lipoids precedes the synthesis of a number of hormones. Consequently, these substances also have the function of regulating metabolic processes.
Nucleic acids. The importance of nucleic acids in a cell is very great. The peculiarities of their chemical structure provide the possibility of storing, transferring and inheriting to daughter cells information about the structure of protein molecules that are synthesized in each tissue at a certain stage of individual development. Since most of the properties and characteristics of cells are determined by proteins, it is clear that the stability of nucleic acids is the most important condition for the normal functioning of cells and entire organisms. Any changes in the structure of nucleic acids entail changes in the structure of cells or the activity of physiological processes in them, thus affecting viability. The study of the structure of nucleic acids, which was first established by the American biologist Watson and the English physicist Crick, is extremely important for understanding the inheritance of traits in organisms and the patterns of functioning of both individual cells and cellular systems - tissues and organs.
There are two types of nucleic acids: DNA and RNA. DNA (deoxyribonucleic acid) is a biological polymer consisting of two polynucleotide chains connected to each other. The monomers that make up each of the DNA chains are complex organic compounds, including nitrogenous bases - adenine (A) or thymine (T), cytosine (C) or guanine (G); pentaatomic sugar pentose - deoxyribose, from which the DNA itself was named, as well as the phosphoric acid residue. These compounds are called nucleotides. In each chain, nucleotides are connected to each other to form coballetic bonds between the desocaribose of one nucleotide and the phosphoric acid residue of the other. Nucleotides can only join in pairs: the nitrogenous base A of one chain of polynucleotides is always connected by two hydrogen bonds with the nitrogenous base T of the opposite polynucleotide chain, and D by three hydrogen bonds with C. This ability to selectively combine nucleotides, resulting in the formation of A-T pairs and G-C is called complementarity.
RNA (ribonucleic acid), like DNA, is a polymer whose monomers are nucleotides. The nitrogenous bases of three nucleotides are the same as those that make up DNA (adenine, guanine, cytosine), the fourth - ura-cil - is present in the RNA molecule instead of thymine. RNA nucleotides differ from DNA nucleotides in the structure of the carbohydrate they contain: they include another pentose - ribose (instead of deoxyribose). In an RNA chain, nucleotides are connected by forming covalent bonds between the deoxyribose of one nucleotide and the phosphoric acid residue of another.
RNAs carry information about the sequence of amino acids in proteins, i.e., about the structure of proteins from chromosomes to the place of their synthesis, and participate in protein synthesis.
There are several types of RNA. Their names are determined by their function or location in the cell. The majority of the RNA in the cytoplasm (up to 80-90%) is ribosomal RNA (rRNA), contained in ribosomes. rRNA molecules are relatively small and consist of 3-5 thousand nucleotides. Another type of RNA is messenger RNA (mRNA), which carries information about the sequence of amino acids in proteins that must be synthesized to ribosomes. The size of these RNAs depends on the length of the DNA region from which they were synthesized. mRNA molecules can consist of 300-30,000 nucleotides. Transport P/-//((tRNAs) include 76-85 nucleotides and perform several functions. They deliver amino acids to the site of protein synthesis, “recognize” (by the principle of complementarity) the mRNA triplet corresponding to the transferred amino acid, and carry out the exact orientation of the amino acid to ribosome.

And look at 33 at 31.

In addition to the features characteristic of prokaryotes and eukaryotes, the cells of plants, animals, fungi and bacteria also have a number of features. Thus, plant cells contain specific organelles - chloroplasts, which determine their ability to photosynthesize, whereas these organelles are not found in other organisms. Of course, this does not mean that other organisms are not capable of photosynthesis, since, for example, in bacteria it occurs on invaginations of the plasma membrane and individual membrane vesicles in the cytoplasm.

Plant cells, as a rule, contain large vacuoles filled with cell sap. They are also found in the cells of animals, fungi and bacteria, but have a completely different origin and perform different functions. The main reserve substance found in the form of solid inclusions in plants is starch, in animals and fungi it is glycogen, and in bacteria it is glycogen or volutin.

Another distinctive feature of these groups of organisms is the organization of the surface apparatus: the cells of animal organisms do not have a cell wall, their plasma membrane is covered only with a thin glycocalyx, while all others have it. This is entirely understandable, since the way animals feed is associated with the capture of food particles during the process of phagocytosis, and the presence of a cell wall would deprive them of this opportunity. The chemical nature of the substance that makes up the cell wall is different in different groups of living organisms: if in plants it is cellulose, then in fungi it is chitin, and in bacteria it is murein. Comparative characteristics of the structure of cells of plants, animals, fungi and bacteria

Sign	Bacteria	Animals	Mushrooms	Plants
Nutrition method	Heterotrophic or autotrophic	Heterotrophic	Heterotrophic	Autotrophic
Organization of hereditary information	Prokaryotes	Eukaryotes	Eukaryotes	Eukaryotes
DNA localization	Nucleoid, plasmids	Nucleus, mitochondria	Nucleus, mitochondria	Nucleus, mitochondria, plastids
Plasma membrane	Eat	Eat	Eat	Eat
Cell wall	Mureinovaya	-	Chitinous	Pulp
Cytoplasm	Eat	Eat	Eat	Eat
Organoids	Ribosomes	Membrane and non-membrane, including the cell center	Membrane and non-membrane	Membrane and non-membrane, including plastids
Organoids of movement	Flagella and villi	Flagella and cilia	Flagella and cilia	Flagella and cilia
Vacuoles	Rarely	Contractile, digestive	Sometimes	Central vacuole with cell sap
Inclusions	Glycogen, volutin	Glycogen	Glycogen	Starch

The differences in the structure of cells of representatives of different kingdoms of living nature are shown in the figure.

Chemical composition of the cell. Macro- and microelements. The relationship between the structure and functions of inorganic and organic substances (proteins, nucleic acids, carbohydrates, lipids, ATP) that make up the cell. The role of chemicals in the cell and human body

Chemical composition of the cell

Most of the chemical elements of D.I. Mendeleev’s Periodic Table of Elements discovered to date have been found in living organisms. On the one hand, they do not contain a single element that would not be found in inanimate nature, and on the other hand, their concentrations in bodies of inanimate nature and living organisms differ significantly.

These chemical elements form inorganic and organic substances. Despite the fact that inorganic substances predominate in living organisms, it is organic substances that determine the uniqueness of their chemical composition and the phenomenon of life as a whole, since they are synthesized mainly by organisms in the process of life and play a vital role in reactions.

Science studies the chemical composition of organisms and the chemical reactions occurring in them. biochemistry.

It should be noted that the content of chemicals in different cells and tissues can vary significantly. For example, if in animal cells proteins predominate among organic compounds, then in plant cells carbohydrates predominate.

Chemical element	Earth's crust	Sea water	Alive organisms
O	49.2	85.8	65–75
C	0.4	0.0035	15–18
H	1.0	10.67	8–10
N	0.04	0.37	1.5–3.0
P	0.1	0.003	0.20–1.0
S	0.15	0.09	0.15–0.2
K	2.35	0.04	0.15–0.4
Ca	3.25	0.05	0.04–2.0
Cl	0.2	0.06	0.05–0.1
Mg	2.35	0.14	0.02–0.03
Na	2.4	1.14	0.02–0.03
Fe	4.2	0.00015	0.01–0.015
Zn	< 0.01	0.00015	0.0003
Cu	< 0.01	< 0.00001	0.0002
I	< 0.01	0.000015	0.0001
F	0.1	2.07	0.0001

Macro- and microelements

About 80 chemical elements are found in living organisms, but only 27 of these elements have their functions in the cell and organism established. The remaining elements are present in small quantities and, apparently, enter the body with food, water and air. The content of chemical elements in the body varies significantly. Depending on their concentration, they are divided into macroelements and microelements.

The concentration of each macronutrients in the body exceeds 0.01%, and their total content is 99%. Macroelements include oxygen, carbon, hydrogen, nitrogen, phosphorus, sulfur, potassium, calcium, sodium, chlorine, magnesium and iron. The first four of the listed elements (oxygen, carbon, hydrogen and nitrogen) are also called organogenic, since they are part of the main organic compounds. Phosphorus and sulfur are also components of a number of organic substances, such as proteins and nucleic acids. Phosphorus is essential for the formation of bones and teeth.

Without the remaining macroelements, normal functioning of the body is impossible. Thus, potassium, sodium and chlorine are involved in the processes of cell excitation. Potassium is also necessary for the functioning of many enzymes and the retention of water in the cell. Calcium is found in the cell walls of plants, bones, teeth, and mollusk shells and is required for muscle cell contraction and intracellular movement. Magnesium is a component of chlorophyll, a pigment that ensures photosynthesis occurs. It also takes part in protein biosynthesis. Iron, in addition to being part of hemoglobin, which carries oxygen in the blood, is necessary for the processes of respiration and photosynthesis, as well as for the functioning of many enzymes.

Microelements are contained in the body in concentrations of less than 0.01%, and their total concentration in the cell does not reach 0.1%. Microelements include zinc, copper, manganese, cobalt, iodine, fluorine, etc. Zinc is part of the molecule of the pancreatic hormone - insulin, copper is required for the processes of photosynthesis and respiration. Cobalt is a component of vitamin B12, the absence of which leads to anemia. Iodine is necessary for the synthesis of thyroid hormones, which ensure normal metabolism, and fluoride is associated with the formation of tooth enamel.

Both deficiency and excess or disturbance of the metabolism of macro- and microelements lead to the development of various diseases. In particular, a lack of calcium and phosphorus causes rickets, a lack of nitrogen - severe protein deficiency, a deficiency of iron - anemia, and a lack of iodine - a violation of the formation of thyroid hormones and a decrease in metabolic rate. A decrease in fluoride intake from water and food largely determines the disruption of tooth enamel renewal and, as a consequence, a predisposition to caries. Lead is toxic to almost all organisms. Its excess causes irreversible damage to the brain and central nervous system, which is manifested by loss of vision and hearing, insomnia, kidney failure, seizures, and can also lead to paralysis and diseases such as cancer. Acute lead poisoning is accompanied by sudden hallucinations and ends in coma and death.

The lack of macro- and microelements can be compensated by increasing their content in food and drinking water, as well as by taking medications. Thus, iodine is found in seafood and iodized salt, calcium is found in eggshells, etc.

The relationship between the structure and functions of inorganic and organic substances (proteins, nucleic acids, carbohydrates, lipids, ATP) that make up the cell. The role of chemicals in the cell and human body

Inorganic substances

The chemical elements of the cell form various compounds - inorganic and organic. The inorganic substances of the cell include water, mineral salts, acids, etc., and the organic substances include proteins, nucleic acids, carbohydrates, lipids, ATP, vitamins, etc.

Water(H 2 O) is the most common inorganic substance of the cell, which has unique physicochemical properties. It has no taste, no color, no smell. The density and viscosity of all substances is assessed using water. Like many other substances, water can exist in three states of aggregation: solid (ice), liquid and gaseous (steam). The melting point of water is 0°C, the boiling point is 100°C, however, the dissolution of other substances in water can change these characteristics. The heat capacity of water is also quite high - 4200 kJ/mol K, which gives it the opportunity to take part in thermoregulation processes. In a water molecule, the hydrogen atoms are located at an angle of 105°, with shared electron pairs pulled away by the more electronegative oxygen atom. This determines the dipole properties of water molecules (one end is positively charged and the other negatively charged) and the possibility of the formation of hydrogen bonds between water molecules. The cohesion of water molecules underlies the phenomenon of surface tension, capillarity and the properties of water as a universal solvent. As a result, all substances are divided into those soluble in water (hydrophilic) and insoluble in it (hydrophobic). Thanks to these unique properties, it is predetermined that water has become the basis of life on Earth.

The average water content in the body's cells varies and may change with age. Thus, in a one-and-a-half-month-old human embryo, the water content in the cells reaches 97.5%, in an eight-month-old - 83%, in a newborn it decreases to 74%, and in an adult it averages 66%. However, body cells differ in their water content. So, the bones contain about 20% water, the liver - 70%, and the brain - 86%. In general it can be said that the concentration of water in cells is directly proportional to the metabolic rate.

Mineral salts may be in dissolved or undissolved states. Soluble salts dissociate into ions - cations and anions. The most important cations are potassium and sodium ions, which facilitate the transfer of substances across the membrane and are involved in the occurrence and conduction of nerve impulses; as well as calcium ions, which takes part in the processes of muscle fiber contraction and blood clotting; magnesium, which is part of chlorophyll; iron, which is part of a number of proteins, including hemoglobin. 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 environment. Ions of mineral salts ensure the penetration of water itself into the cell and its retention in it. If the salt concentration in the environment is lower than in the cell, then water penetrates into the cell. Ions also determine the buffering properties of the cytoplasm, i.e. its ability to maintain a constant slightly alkaline pH of the cytoplasm, despite the constant formation of acidic and alkaline products in the cell.

Insoluble salts(CaCO 3, Ca 3 (PO 4) 2, etc.) are part of the bones, teeth, shells and shells of unicellular and multicellular animals.

In addition, organisms can produce other inorganic compounds, such as acids and oxides. Thus, the parietal cells of the human stomach produce hydrochloric acid, which activates the digestive enzyme pepsin, and silicon oxide permeates the cell walls of horsetails and forms the shells of diatoms. In recent years, the role of nitric oxide (II) in signaling in cells and the body has also been studied.

Organic matter