The cell contains about 70 elements of Mendeleev's 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 group:

• 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 compounds cells – 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 nonlinear spatial structure and polarity. Hydrogen bonds are formed between individual water molecules, which determine the physical and Chemical properties water.

Physical properties of water	Significance for biological processes
High heat capacity (due to hydrogen bonds between molecules) and thermal conductivity (due to the small size of the molecules)	Transpiration Sweating Periodic precipitation
Transparency in the visible part of the spectrum	Highly productive biocenoses of ponds, lakes, rivers (due to the possibility of photosynthesis at shallow depths)
Almost complete incompressibility (due to intermolecular bonding forces)	Maintaining the shape of organisms: the shape of the succulent organs of plants, the position of herbs in space, the hydrostatic skeleton roundworms, jellyfish, amniotic fluid supports and protects the mammalian fetus
Molecular mobility (due to weakness of hydrogen bonds)	Osmosis: the flow of water from the soil; plasmolysis
Viscosity (hydrogen bonds)	Lubricating properties: synovial fluid in joints, pleural fluid
Solvent (molecular polarity)	Blood, tissue fluid, lymph, gastric juice, saliva, in animals; cell sap in plants; aquatic organisms use oxygen dissolved in water
The ability to form a hydration shell around macromolecules (due to the polarity of the molecules)	Dispersion medium in the colloidal system of the cytoplasm
Optimal for biological systems the value of the surface tension forces (due to the forces of intermolecular adhesion)	Water solutions - a means of transport of substances in the body
Freezing expansion (due to the formation of each molecule of the maximum number - 4 - hydrogen bonds_	Ice is lighter than water, performs the function of a heat insulator in reservoirs

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 + , Сl-) on the surface and inside the cell provides the emergence of an action potential, which underlies nervous and muscle excitement.
Phosphoric acid anions create phosphate buffer system, which maintains 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 environment (blood plasma) at 7-4.
Nitrogen compounds serve source mineral nutrition, synthesis of proteins, nucleic acids.
Phosphorus atoms are part of 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 muscle contraction and blood clotting.

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

Table.

Thematic assignments

Part A

A1. The polarity of water is due to 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... The composition of hemoglobin includes
1) phosphorus
2) iron
3) sulfur
4) magnesium

A6... Select a group chemical elements, necessarily included in the composition 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 drugs containing
1) iodine
2) iron
3) phosphorus
4) sodium

Part B

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

AT 2... Select only physical properties 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 it biological significance?

The cell contains several thousand substances that are involved in a variety of chemical reactions. Chemical processes flowing in the cell is one of the basic conditions of its life, development and functioning.

The main substances of the cell = Nucleic acids + Proteins + Fats (lipids) + Carbohydrates + Water + Oxygen + Carbon dioxide.

In inanimate nature, these substances are nowhere to be found together.
According to the quantitative content in living systems, all chemical elements are divided into three groups.

1. Macronutrients... Basic or biogenic elements, which account for more than 95% of the cell mass, are part of almost all organic substances of the cell: carbon, oxygen, hydrogen, nitrogen. And also vital elements, the amount of which is up to 0.001% of the body weight - calcium, phosphorus, sulfur, potassium, chlorine, sodium, magnesium and iron.

2. Trace elements - elements, the amount of which ranges from 0.001% to 0, 000001% of the body weight: zinc, copper.

3. Ultramicroelements - chemical elements, the amount of which does not exceed 0.000001% of body weight. These include gold, silver has a bactericidal effect, mercury inhibits the reabsorption of water in the renal tubules, affecting enzymes. Platinum and cesium are also included here. Some also include selenium in this group, with a lack of it, cancers develop.

Chemicals that make up the cell:

Inorganic - compounds that are found in inanimate nature: in minerals, natural waters;
- organic - chemical compounds, which include carbon atoms. Organic compounds extremely diverse, but only four of their classes have universal biological significance: proteins, lipids (fats), carbohydrates, nucleic acids, ATP.

Inorganic compounds

Water is one of the most abundant and important substances on earth. More substances dissolve in water than in any other liquid. That is why in the aquatic environment of the cell, many chemical reactions... Water dissolves metabolic products and removes them from the cell and the body as a whole. Water has a high thermal conductivity, which makes it possible to evenly distribute heat between the tissues of the body.
Water has a high heat capacity, i.e. the ability to absorb heat with a minimum change in its own temperature. Thanks to this, it protects the cell from sudden temperature changes.

Mineral salts are in the cell, as a rule, in the form of cations (K +, Na +, Ca2 +, Mg2 +) and anions (HPO42-, H2PO4-, Cl-, HCO3), the ratio of which determines the acidity of the environment, which is important for the vital activity of cells. (In many cells, the medium is weakly alkaline and its pH hardly changes, since a certain ratio of cations and anions is constantly maintained in it.)

Organic compounds

Carbohydrates are abundant in living cells. The carbohydrate molecule contains carbon, hydrogen and oxygen.
Lipids include fats, fat-like substances. In the cell, during the oxidation of fats, a large number of energy that is used in various processes. Fats can accumulate in cells and serve as a store of energy.

Proteins are an essential part of all cells. These biopolymers contain 20 types of monomers. Amino acids are such monomers. The formation of linear protein molecules occurs as a result of the combination of amino acids with each other. The carboxyl group of one amino acid approaches the amino group of another, and when a water molecule is cleaved between the amino acid residues, a strong covalent bond, called a peptide bond, arises. A compound composed of a large number of amino acids is called a polypeptide. Each protein is a polypeptide in composition.

Nucleic acids. There are two types of nucleic acids in cells: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleic acids perform the most important biological functions... DNA stores hereditary information about all properties of the cell and the organism as a whole. Various types of RNA are involved in the implementation hereditary information through protein synthesis.

A particularly important role in the bioenergetics of the cell is played by the adenyl nucleotide, to which two phosphoric acid residues, adenosine triphosphoric acid (ATP), are attached. Energy ATP all cells are used for the processes of biosynthesis, movement, heat production, nerve impulses, that is, for all vital processes. ATP is a universal biological energy accumulator. The light energy of the Sun and the energy contained in the consumed food are stored in ATP molecules.

Textbook for grades 10-11

Section I. Cell - a unit of living
Chapter I. Chemical composition of the cell

Living organisms contain a large number of chemical elements. They form two classes of compounds - organic and inorganic. Chemical compounds, the basis of the structure of which are carbon atoms, make up distinctive feature alive. These compounds are called organic. Organic compounds are extremely diverse, but only four of their classes have universal biological significance: proteins, nucleic acids, carbohydrates and lipids.

§ 1. Inorganic compounds

Biologically important chemical elements. Of the more than 100 chemical elements known to us, about 80 are included in the composition of living organisms, and only in relation to 24 it is known what functions they perform in the cell. The set of these elements is not accidental. Life originated in the waters of the oceans, and living organisms consist mainly of those elements that form compounds readily soluble in water. Most of these elements are light, their feature is the ability to enter into strong (covalent) bonds and form many different complex molecules.

As part of cells human body dominated by oxygen (over 60%), carbon (about 20%) and hydrogen (about 10%). Nitrogen, calcium, phosphorus, chlorine, potassium, sulfur, sodium, magnesium, taken together, account for about 5%. The remaining 13 elements make up no more than 0.1%. Cells of most animals have a similar elemental composition; only the cells of plants and microorganisms differ. Even those elements that are contained in cells in negligible quantities cannot be replaced by anything and are absolutely necessary for life. Thus, the iodine content in cells does not exceed 0.01%. However, with a lack of it in the soil (because of this and in food), the growth and development of children is delayed. The copper content in animal cells does not exceed 0.0002%. But with a lack of copper in the soil (hence in plants), massive diseases of farm animals occur.

The meaning for a cell of basic elements is given at the end of this paragraph.

Inorganic (mineral) compounds. The composition of living cells includes a number of relatively simple compounds that are also found in inanimate nature - in minerals, natural waters. These are inorganic compounds.

Water is one of the most abundant substances on Earth. She covers most of the earth's surface... Almost all living things are composed primarily of water. In humans, the water content in organs and tissues varies from 20% (in bone tissue) to 85% (in the brain). About 2/3 of the mass of a person is water, in the body of a jellyfish up to 95% of water, even in dry seeds of plants, water is 10-12%.

Water has some unique properties... These properties are so important for living organisms that it is impossible to imagine life without this combination of hydrogen and oxygen.

The unique properties of water are determined by the structure of its molecules. In a water molecule, one oxygen atom is covalently bonded to two hydrogen atoms (Fig. 1). The water molecule is polar (dipole). Positive charges are concentrated at hydrogen atoms, since oxygen is more electronegative than hydrogen.

Rice. 1. Formation of hydrogen bonds in water

A negatively charged oxygen atom of one water molecule is attracted to a positively charged hydrogen atom of another molecule to form a hydrogen bond (Fig. 1).

In terms of strength, a hydrogen bond is about 15-20 times weaker than a covalent bond. Therefore, the hydrogen bond is easily broken, which is observed, for example, during the evaporation of water. Due to the thermal motion of molecules in water, some hydrogen bonds are broken, others are formed.

Thus, molecules in liquid water are mobile, which is important for metabolic processes. Water molecules easily penetrate cell membranes.

Due to the high polarity of the molecules, water is a solvent for other polar compounds. More substances dissolve in water than in any other liquid. That is why many chemical reactions take place in the aquatic environment of the cell. Water dissolves metabolic products and removes them from the cell and the body as a whole.

Water has a high heat capacity, that is, the ability to absorb heat with a minimum change in its own temperature. Thanks to this, it protects the cell from sudden temperature changes. Since the evaporation of water consumes a lot of heat, then by evaporating water, organisms can protect themselves from overheating (for example, during perspiration).

Water has a high thermal conductivity. This property creates the possibility of an even distribution of heat between the tissues of the body.

Water acts as a solvent for the "lubricants" needed wherever there are rubbing surfaces (eg joints).

Water has a maximum density at 4 ° C. Therefore, ice, which has a lower density, is lighter than water and floats on its surface, which protects the reservoir from freezing.

In relation to water, all cell substances are divided into two groups: hydrophilic - "loving water" and hydrophobic - "afraid of water" (from the Greek. "Hydro" - water, "phileo" - to love and "phobos" - fear).

Hydrophilic substances are readily soluble in water. These are salts, sugars, amino acids. Hydrophobic substances, on the other hand, are practically insoluble in water. These include, for example, fats.

Cell surfaces that separate the cell from the external environment, and some other structures are composed of water-insoluble (hydrophobic) compounds. This preserves the structural integrity of the cell. Figuratively, a cell can be represented as a vessel with water, where biochemical reactions that provide life take place. The walls of this vessel are insoluble in water. However, they are capable of selectively passing water-soluble compounds.

In addition to water, among the inorganic substances of the cell, it is necessary to name salts, which are ionic compounds. They are formed by cations of potassium, sodium, magnesium and other metals and anions of hydrochloric, carbonic, sulfuric, phosphoric acids. During the dissociation of such salts, cations (K +, Na +, Ca 2+, Mg 2+, etc.) and anions (CI -, HCO 3 -, HS0 4 -, etc.) appear in solutions. The concentration of ions on the outer surface of the cell differs from their concentration on the inner surface. Different number potassium and sodium ions on the inner and outer surfaces of the cell creates a charge difference on the membrane. On the outer surface of the cell membrane there is a very high concentration of sodium ions, and on the inner surface there is a very high concentration of potassium ions and a low concentration of sodium. As a result, a potential difference is formed between the inner and outer surfaces of the cell membrane, which causes the transmission of excitation along a nerve or muscle.

Calcium and magnesium ions are activators of many enzymes, and when they are lacking, vital processes in cells are disrupted. Inorganic acids and their salts perform a number of important functions in living organisms. Hydrochloric acid creates an acidic environment in the stomach of animals and humans and in the special organs of insectivorous plants, accelerating the digestion of food proteins. Residues of phosphoric acid (H 3 PO 4), attaching to a number of enzyme and other proteins of the cell, change their physiological activity. The remains of sulfuric acid, attaching to water-insoluble foreign substances, give them solubility and thus contribute to their removal from cells and organisms. Sodium and potassium salts of nitrous and phosphoric acids, calcium salt of sulfuric acid are important constituent parts mineral nutrition of plants, they are introduced into the soil as fertilizers for plant nutrition. In more detail the meaning of chemical elements for a cell is given below.

Biologically important chemical elements of the cell

1. What is biological role water in the cage?
2. What ions are in the cell? What is their biological role?
3. What is the role of the cations contained in the cell?

Chemical composition cells.

The cells of living organisms contain the same chemical. el., as in the surrounding inanimate nature. More than 80 e-mails were found in the cells. from the table D.I. Mendeleev. The functions of 27 of them have been defined.

Macro email about 99% of the cell mass O, C, H, N. F, K, S, Fe, Mg, Na, Ca.

Micro el. from 0.001% to 0.000001% of body weight B, Cobalt, Cu, Molybdenum, Zn, vanadium, I, Br.

Ultra micro el. less than 0.000001% radium, gold, beryllium, cesium, strong, etc.

All these e-mails. are part of organic and inorganic compounds.

Not organic matter.

I. Water (H2O). A living cell contains about 70% H2O by weight.

1) Universal solvent.

2) Participates in bio-chemistry. reactions (hydrolysis, redox, photosynthesis)

3) Participates in the phenomena of osmosis.

4) Transport.

5) Water is practically not compressed, thus determining turgor.

6) Has a surface tension force.

7) Possesses high heat capacity, thermal conductivity.

II. Minerals. Mineral substances in the cell are in the form of salts.

2) Regulate bio. - chem. processes.

Organic matter.

I. Carbohydrates (saccharides). In animal cells, 1-5% carbohydrates, in plant cells up to 90% (photosynthesis). The monomer is glucose.

Functions: structural, protective, storage, construction, energy.

II. Lipids are fats, fat-like compounds. Monomer - glycerin and high molecular weight fatty acids.

Functions: structural (construction), storage, protective, regulatory, energy.

III. Proteins are high molecular weight polymeric organic compounds. The protein content in various cells is from 50-80%. Monomers are amino acids.

Functions: structural, receptor, transport, protective, motor, regulatory, energy.

IV. DNA is deoxyribonucleic acid.

Functions: storage of hereditary information, gene transfer. information, structural component.

V. ATP - adenosine triphosphoric acid.

Functions: universal keeper and carrier of energy in the cell.

Water and minerals

A living cell contains about 70% H2O by weight. H2O is in two forms:

1) Free (95%) - in the intercellular space, vessels, vacuoles, organ cavities.

2) Associated (5%) - with high-molecular organic substances.

Property:

8) Universal solvent. By solubility in water, substances are divided into hydrophilic - soluble and hydrophobic - insoluble (fats, nucleic acids, some proteins).

9) Participates in bio-chemistry. reactions (hydrolysis, redox, photosynthesis)

10) Participates in the phenomena of osmosis - the passage of a solvent through a semi-permeable shell towards a soluble substance due to the force of osmotic pressure. Osmotic pressure in mammals is 0.9% NaCl solution.

11) Transport - substances soluble in water are transported into or out of the cell by diffusion.

12) Water is practically not compressed, thus determining turgor.

13) Has a surface tension force - this force carries out capillary blood flow ascending and descending in plants.

14) Possesses high heat capacity, thermal conductivity, which maintains thermal equilibrium.

With a lack of H2O, metabolic processes are disrupted, the loss of 20% H2O leads to death.

Minerals.

Minerals in the cell are in the form of salts. According to the reaction, solutions can be acidic, basic, neutral. This concentration is expressed using the pH value.

pH = 7 neutral liquid reaction

NS< 7 кислая

pH> 7 basic

A change in pH by 1-2 units is detrimental to the cell.

Function of mineral salts:

1) Maintain cell turgor.

2) Regulate bio-chemical. processes.

3) Maintain a constant composition of the internal environment.

1) Calcium ions stimulate muscle contraction. A decrease in blood concentration causes seizures.

2) Salts of potassium, sodium, calcium. The ratio of these ions ensures the normal contraction of the cardiac system.

3) Iodine is a component of the thyroid gland.

9) Organic compounds of the cell: carbohydrates, lipids, proteins, amino acids, enzymes.

I. Carbohydrates

They are part of the cells of all living organisms. In animal cells, 1-5% carbohydrates, in plant cells up to 90% (photosynthesis).

Chem. composition: C, H, O. Monomer - glucose.

Carbohydrate groups:

1) Monosaccharides - colorless, sweet, readily soluble in water (glucose, fructose, galactose, ribose, deoxyribose).

2) Oligosaccharides (disaccharides) - sweet, soluble (sucrose, maltose, lactose).

3) Polysaccharides - unsweetened, poorly soluble in water (starch, cellulose - in plant cells, chitin in fungi and arthropods, glycogen in animals and humans). Glycogen is stored in muscles and liver. When it breaks down, glucose is released.

Functions of carbohydrates:

1) Structural - is part of the membranes of plant cells.

2) Protective - the secretions secreted by the glands contain carbohydrates that protect the hollow organs (bronchi, stomach, intestines) from fur. Damage, and plants from the penetration of pathogenic bacteria

3) Storing. Nutrients (starch, glycogen) are stored in cells in reserve.

4) Construction. Monosaccharides serve as the starting material for the construction of organic substances.

5) Energy. The body receives 60% of its energy from the breakdown of carbohydrates. When 1 gram of carbohydrate is broken down, 17.6 kJ of energy is released.

II. Lipids (fats, fat-like compounds).

Chem. compound

C, O, H. Monomer - glycerin and high molecular weight fatty acids.

Properties: insoluble in water, soluble in organic solvents (gasoline, chloroform, ether, acetone).

By chem. structure, lipids are divided into a trace of the group:

1) Neutral. They are divided into solid (at 20 degrees they remain solid), soft (butter and human body fat), liquid (vegetable oils).

2) Wax. Cover: leather, wool, animal feathers, stems, leaves, fruits of plants.

Esters formed by fatty acids and polyhydric alcohol.

3) Phospholipids. One, two leftovers fatty acids, are replaced by a phosphoric acid residue. The main component of the cell membrane.

4) Steroids are fatty acid-free lipids. Steroids include hormones (cortisone, sex), vitamins (A, D, E).

Steroid cholesterol: an important component of the cell membrane. Excess cholesterol can lead to cardiovascular disease and the formation of gallstones.

Lipid functions:

1) Structural (building) - part of the cell membranes.

2) Storage - deposited in the reserve in plants in fruits and seeds, in animals in subcutaneous adipose tissue. When 1 g of fat is oxidized, more than 1 g of water is produced.

3) Protective - serve for thermal insulation of organisms, because has poor thermal conductivity.

4) Regulatory - hormones (corticosterone, androgens, estrogens, etc.) regulate metabolic processes in the body.

5) Energy: during the oxidation of 1 g of fat, 38.9 kJ is released.

III. Proteins.

High molecular weight polymeric organic compounds. The protein content in various cells is from 50-80%. Each person. on Earth has its own non-repeatable set of proteins inherent only to it (with the exception of identical twins). The specificity of protein kits ensures the immune status of each person.

Chem. compound: C, O, N, H, S, P, Fe.

Monomers. There are 20 of them, 9 of them are irreplaceable. They enter the body with food ready-made.

Properties:

1) Denaturation - the destruction of protein molecules under the influence of high temperature, acids, chemical. substances, dehydration, radiation.

2) Renaturation - restoration of the previous structure upon the return of normal environmental conditions (except for the primary one).

Structure (levels of organization of a protein molecule):

1) Primary structure.

It is a polypeptide chain composed of a sequence of amino acids.

2) Secondary structure.

Spiral twisted polypeptide chain.

3) Tertiary structure.

The spiral takes on a bizarre configuration - a globule.

4) Quaternary structure.

Several globules are combined into a complex complex.

Protein functions:

1) Catalytic (enzymatic) - proteins serve as catalysts (accelerators of bio-chemical reactions).

2) Structural - they are part of membranes, organelles of cells, bones, hair, tendons, etc.

3) Receptor - receptor proteins perceive signals from the external environment and transmit them to the cell.

4) Transport - carrier proteins carry out the transfer of substances through cell membranes (the hemoglobin protein transfers oxygen from the lungs to the cells of other tissues).

5) Protective - proteins protect the body from damage and invasion of foreign organisms (immunoglobulin proteins neutralize foreign proteins. Interferon inhibits the development of viruses).

6) Motor - the proteins actin and lysine are involved in the contraction of muscle fibers.

7) Regulatory - proteins hormones regulate physiological processes. For example insulin, glucagon regulate blood glucose levels.

8) Energy - when 1 g of protein is broken down, 17.6 kJ of energy is released.

IV. Amino acids.

It is a monomer of proteins.

Formula:

The amino acid contains the amino groups H2N and the carboxyl group COOH. Amino acids differ from each other by their R radicals.

Amino acids are linked by peptide bonds to form polypeptide chains.

NH-CO --- NH-CO --- NH-CO

Polypeptide bond.

The carboxyl group of one amino acid is attached to the amino group of the adjacent amino acid.

V. Enzymes.

These are protein molecules capable of catalyzing (accelerating bio-chemical reactions in a cell in a dormouse, millions of times).

Functions and properties:

Enzymes are specific, that is, they catalyze only a certain chemical. reaction or similar.

They act in a strictly defined sequence.

The activity of enzymes depends on temperature, the reaction of the environment, the presence of coenzymes - non-protein compounds, they can be vitamins, ions, various Me. The optimum temperature for enzymes is 37-40 degrees.

Enzyme activity is regulated by:

When the temperature rises, it increases, under the influence of drugs, poisons, it is suppressed.

The absence or lack of enzymes leads to serious diseases (hemophilia is caused by a lack of an enzyme responsible for blood clotting).

Enzymes are used in medicine to make vaccines. In industry for the production of sugar from starch, alcohol from sugar and other substances.

Structure:

In the active center, the substrate interacts with an enzyme that fit together like a “key to a lock”.

10) Nucleic acids: DNA, RNA, ATP.

DNA, RNA were first isolated from the cell nucleus in 1869 by the Swiss scientist Mischer. Nucleic acids are polymers whose monomers are nucleotides consisting of 2 nucleic bases adenine and guanine and 3 pyrimidine cytosine, uracil, thymine.

I) DNA (deoxyribonucleic acid).

Deciphered in 1953 by Watson and Creek. 2 strands spirally wrapped around each other. DNA is in the nucleus.

The nucleotide consists of 3 residues:

1) Carbohydrate - deoxyribose.

2) Phosphoric acid.

3) Nitrogenous bases.

Nucleotides differ from each other only in nitrogenous bases.

C - cytidyl, G - guanine, T - thymidyl, A - adenine.

Assembly of DNA molecules.

The connection of nucleotides in a DNA strand occurs through covalent bonds through a carbohydrate of one nucleotide and a phosphoric acid residue of a neighboring one.

The connection of two strands.

The two strands are connected to each other by hydrogen bonds between nitrogenous bases. Nitrogenous bases are connected according to the principle of complementarity A-T, G-C. Complementarity (addition) is a strict correspondence of nucleotides located in paired DNA strands. The genetic code is in the nitrogenous bases.

Properties and functions of DNA:

I) Replication (reduplication) - doubling itself. Occurs during the synthetic period of the interphase.

1) The enzyme breaks hydrogen bonds and the spirals unwind.

2) One strand is separated from another part of the DNA molecule (each strand is used as a template).

3) The molecules are affected by the DNA enzyme - polymerase.

4) Attachment of each DNA strand of complementary nucleotides.

5) Formation of two DNA molecules.

II) Storage of hereditary information in the form of a sequence of nucleotides.

III) Transfer to gene. inf.

Iv) Structural DNA is present in the chromosome as a structural component.

II) RNA (ribonucleic acid).

Single chain polymer. They are: in the nucleolus, cytoplasm, ribosomes, mitochondria, plastids.

Monomer - a nucleotide consisting of 3 residues:

1) Carbohydrate - ribose.

2) The remainder of the phosphoric acid.

3) Nitrogen base (unpaired) (A, G, C, U - instead of thymine).

RNA functions: transmission and implementation of hereditary information through protein synthesis.

RNA types:

1) Informational (mRNA) or messenger (mRNA) 5% of all RNA.

It is synthesized in the process of transcription at a certain part of the DNA molecule - a gene. mRNA carries inf. The structure of the protein (sequence of nucleotides) from the nucleus to the cytoplasm to the ribosomes and becomes the matrix for protein synthesis.

2) Ribosomal (ribosomal rRNA) 85% of all RNA, synthesized in the nucleolus, are part of chromosomes, form the active center of the ribosome where protein biosynthesis takes place.

3) Transport (tRNA) 10% of all RNA is formed in the nucleus and passes into the cytoplasm and transport amino acids to the site of protein synthesis, that is, to the ribosomes. Therefore, it has the shape of a clover leaf:

III) ATP (adenosine triphosphoric acid).

A nucleotide consisting of 3 residues:

1) The nitrogenous base is adenine.

2) Carbohydrate residue - ribose.

3) Three residues of phosphoric acid.

The bonds between phosphoric acid residues are energy-rich and are called macronutrients. When 1 molecule of phosphoric acid is cleaved off, ATP transforms into ADP, two molecules into AMP. In this case, an energy of 40 kJ is released.

ATP (three)> ADP (di)> AMP (mono).

ATP is synthesized in mitochondria as a result of the phosphorylation reaction.

One phosphoric acid residue is attached to ADP. They are always in the cell, as a product of its vital activity.

Functions of ATP: universal keeper and carrier of information.

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

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

Group of inorganic substances

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

Group of organic substances

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

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

Cell chemicals

The existence of cells is possible if they contain organic and inorganic substances. They die when they lack water, mineral salts. Cells die if they are severely depleted in nucleic acids, fats, carbohydrates, and proteins.

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

Chemical elements that saturate the cell

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

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

Water in the cell

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

This liquid is endowed with high thermal conductivity. This allows the heat to spread evenly through the tissues of the body. It has a significant heat capacity (the ability to absorb heat when its own temperature changes minimally). This ability does not allow sudden temperature changes to occur in the cell.

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

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

Cell saturation with water

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

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

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

The importance of mineral salts for the cell

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

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

Inorganic substances in the chemical organization of the cell

In the chemical composition of living cells, there are no special elements characteristic only of them. This determines the unity of the chemical compositions of living and nonliving objects. Inorganic substances in the composition of the cell play a huge role.

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

The importance of inorganic compounds for cells

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

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

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

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