Inorganic compounds in cell biology. Inorganic substances and their role in the cell

From the inorganic substances of the cell water makes up about 65% of its mass: in young rapidly growing cells up to 95%, in old cells - about 60%. The role of water in cells is very large, it is a medium and a solvent, participates in most chemical reactions, the movement of substances, thermoregulation, the formation of cellular structures, determines the volume and elasticity of the cell. Most substances enter the body and are excreted from it in an aqueous solution.

organic matter- make up 20-30% of the cell composition. They can be simple(amino acids, glucose, fatty acids) and complex(proteins, polysaccharides, nucleic acids, lipids). Most importance have proteins, fats, carbohydrates, nucleic acids.

Proteins are the basic and most complex substances of any cell. The size of a protein molecule is hundreds and thousands of times larger than the molecules of inorganic compounds. Protein molecules are formed from simple compounds - amino acids (natural proteins contain 20 amino acids). Combining in different sequences and quantities, they form a wide variety (up to 1000) of proteins. Their role in the life of the cell is enormous: construction material organism, catalysts (enzyme proteins accelerate chemical reactions), transport (blood hemoglobin delivers oxygen and nutrients to cells and carries away carbon dioxide and decay products). Proteins perform protective function, energetic. Carbohydrates are organic substances composed of carbon, hydrogen and oxygen. The simplest of these are monosaccharides - hexose, fructose, glucose (found in fruits, honey), galactose (in milk) and polysaccharides - consisting of several simple carbohydrates. These include starch and glycogen. Carbohydrates are the main source of energy for all forms of cellular activity (movement, biosynthesis, secretion, etc.) and play the role of reserve substances. Lipids are water-insoluble fats and fat-like substances. They are the main structural component of biological membranes. Lipids perform an energy function, they contain fat-soluble vitamins. Nucleic acids - (from the Latin word "nucleus" - nucleus) - are formed in the nucleus of the cell. They are of two types: deoxyribonucleic acids (DNA) and ribonucleic acids (RNA). Biological role their very large. They determine the synthesis of proteins and the transmission of hereditary information.

The chemical composition of the cell.

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

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

Micro email 0.001% to 0.000001% 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. are part of organic and inorganic compounds.

inorganic substances.

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

1) Universal solvent.

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

3) Participates in the phenomena of osmosis.

4) Transport.

5) Water practically does not compress, thus determining turgor.

6) Has surface tension.

7) It has a high heat capacity, thermal conductivity.

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

2) Regulate the bio. - chem. processes.

organic substances.

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. The monomer is glycerol and high molecular weight fatty acids.

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

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

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

IV. DNA - deoxy ribonucleic 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 exists 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-chemical. 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. The osmotic pressure in mammals is 0.9% solution of NaCl.

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

12) Water practically does not compress, which determines the turgor.

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

14) It has a high heat capacity, thermal conductivity, which maintains thermal equilibrium.

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

Minerals.

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

pH = 7 neutral liquid reaction

pH< 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 convulsions.

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, highly soluble in water (glucose, fructose, galactose, ribose, deoxyribose).

2) Oligosaccharide (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 the muscles and liver. When it is broken down, glucose is released.

Functions of carbohydrates:

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

2) Protective - the secrets 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) Reserve. Nutrients (starch, glycogen) are stored in the cells in reserve.

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

5) Energy. 60% of the body's energy comes from the breakdown of carbohydrates. When splitting 1 gram of carbohydrate, 17.6 kJ of energy is released.

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

Chem. compound

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

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

According to chem. The structure of lipids is divided into the following groups:

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

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

Esters formed by fatty acids and polyhydric alcohol.

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

4) Steroids are lipids that do not contain fatty acids. Steroids include hormones (cortisone, sex), vitamins (A, D, E).

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

Lipid functions:

1) Structural (construction) - being a part of cell membranes.

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

3) Protective - serve for thermal insulation of organisms, tk. 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 are released.

III. Squirrels.

High-molecular polymeric organic compounds. The content of proteins in various cells is from 50-80%. Every pers. on Earth has its own unique set of proteins peculiar to it only (with the exception of identical twins). The specificity of protein sets 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 in finished form.

Properties:

1) Denaturation - the destruction of protein molecules under the influence of high temperature, acids, chemicals. 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 consisting 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 - are part of the membranes, cell organelles, bones, hair, tendons, etc.

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

4) Transport - carrier proteins carry out the transfer of substances through cell membranes(The protein hemoglobin carries 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 - actin and lysine proteins are involved in the contraction of muscle fibers.

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

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

IV. Amino acids.

It is a protein monomer.

Formula:

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

Amino acids are connected 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 (accelerate the bio-chemical reactions in the 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 operate in a strictly defined sequence.

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

Enzyme activity is regulated by:

With increasing temperatures, it increases, under the influence of drugs, poisons, it is suppressed.

The absence or deficiency 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 produce vaccines. In industry, for the production of sugar from starch, alcohol from sugar, and other substances.

Structure:

In the active site, the substrate interacts with the enzyme, which fit together like a "key to a lock".

10) Nucleic acids: DNA, RNA, ATP.

DNA, RNA were first isolated from the nucleus of cells in 1869 by the Swiss scientist Miescher. 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 Crick. 2 threads spirally wrapped around each other. DNA is in the nucleus.

A nucleotide is made up 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 the carbohydrate of one nucleotide and the phosphoric acid residue of the adjacent one.

The connection of two threads.

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 strands of DNA. The nitrogenous bases contain the genetic code.

Properties and functions of DNA:

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

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

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

3) 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 the gene. inf.

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

II) RNA (ribonucleic acid).

Polymer consisting of one chain. They are: in the nucleolus, cytoplasm, ribosomes, mitochondria, plastids.

A monomer is a nucleotide consisting of 3 residues:

1) Carbohydrate - ribose.

2) The rest of phosphoric acid.

3) Nitrogenous 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 template (mRNA) 5% of all RNA.

It is synthesized during transcription at a specific site of the DNA molecule - the gene. mRNA carries inf. On the structure of the protein (sequence of nucleotides) from the nucleus to the cytoplasm to the ribosomes and becomes a matrix for protein synthesis.

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

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

III) ATP (adenosine triphosphoric acid).

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 rich in energy and are called macronutrients. With the elimination of 1 molecule of phosphoric acid, ATP passes into ADP, two molecules into AMP. In this case, energy of 40 kJ is released.

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

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

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

Functions of ATP: universal custodian and carrier of information.

lesson type - combined

Methods: partially exploratory, problematic presentation, explanatory and illustrative.

Target:

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

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

Education of civic responsibility, independence, initiative

Tasks:

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

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

Upbringing conviction in the possibility of knowing wildlife, the need for careful attitude to natural environment, own health; respect for the opinion of the opponent when discussing biological problems

Personal Outcomes of Learning Biology:

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

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

Meta-subject learning outcomes in biology:

1. the ability to independently determine the goals of their learning, set and formulate new tasks for themselves in their studies and cognitive activity, to develop the motives and interests of their cognitive activity;

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

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

evaluate information;

cognitive: selection of essential features of biological objects and processes; bringing evidence (argumentation) of human kinship with mammals; the relationship between man and the environment; dependence of human health on the state of the environment; the need to protect the environment; mastering the methods of biological science: observation and description of biological objects and processes; setting up biological experiments and explaining their results.

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

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

Technology : Health saving, problematic, developmental education, group activities

Receptions: analysis, synthesis, conclusion, transfer of information from one type to another, generalization.

During the classes

Tasks

Introduce students to the chemical composition of cells.

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

To characterize the role of mineral salts and their constituent cations and anions in the life of the cell.

Key points

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

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

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

In an abiogenic way, from the components of the Earth's primary atmosphere under the influence of the energy of lightning discharges, powerful hard ultraviolet radiation Sun, etc., various simple organic molecules could arise - monomers of biological polymers.

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

Coacervates are multimolecular complexes surrounded by a common aqueous shell.

Coacervate drops have the ability to selectively absorb substances from the environment and the simplest metabolic reactions.

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

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

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

Problem areas

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

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

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

Inorganic substances that make up the cell

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

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

Vital are calcium, phosphorus, sulfur, potassium, chlorine, sodium, magnesium and iron. Their content in the cell is calculated in tenths and hundredths of a percent. The listed elements make up a group of macronutrients.

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

The percentage of one or another element in the body in no way characterizes the degree of importance and necessity in the body. So, for example, many microelements are part of various biologically active substances - enzymes, vitamins, hormones, they affect growth and development, hematopoiesis, cellular respiration processes, etc.

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

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

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

Water molecules have a non-linear spatial structure. The atoms in a water molecule are held together by polar covalent bonds that link one oxygen atom to two hydrogen atoms. The polarity of covalent bonds is explained in this case by the strong electronegativity of the oxygen atoms with respect to the hydrogen atom; the oxygen atom pulls on itself the electrons of their common electron pairs.

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

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

Substances that are insoluble in water are called hydrophobic.

Water has high heat capacity. It takes a lot of energy to break the hydrogen bonds that hold water molecules together. This property maintains heat balance organisms during significant temperature fluctuations in the environment. In addition, water has high thermal conductivity, which allows the body to maintain the same temperature throughout its volume. Water also has a high heat of vaporization, i.e. the ability of molecules to carry away a significant amount of heat, cooling the body. This property of water is used in sweating in mammals, heat panting in crocodiles, and transpiration (evaporation) in plants, preventing them from overheating.

Biological properties water:

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

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

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

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

mineral salts. Most of the inorganic substances of the cell are in the form of salts. In an aqueous solution, salt molecules dissociate into cations and anions. Highest value have cations: K+, Na+, Ca2+, Mg2+ and anions: Cl-, H2PO4-, HPO42-, HCO3-, NO3-, SO42-. Essential is not only the content, but also the ratio of ions in the cell.

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

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

Issues for discussion

What is the contribution various elements in the organization of living and inanimate matter?

How do they manifest physiochemical properties water in ensuring the processes of vital activity of the cell and the whole organism?

Questions and tasks for repetition

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

2. How will the lack of any required element? Give examples of such phenomena?

3. Cations of which elements provide the most important property of living organisms - irritability?

4. Find in the reference material the elements contained in the least amount in the cell. What is their common name? What role do they play in the cell?

Inorganicsubstancescells

Water and its role in cell life

The chemical composition of the cell. inorganic compounds.

Resources

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

AP Plekhov Biology with fundamentals of ecology. Series “Textbooks for universities. Special Literature.

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

Presentation Hosting

Of the inorganic substances, the cell contains 86 elements. Periodic table, about 16-18 elements are vital for the normal existence of a living cell.

Among the elements are: organogens, macroelements, microelements and ultramicroelements.

Organogens

These are the substances that make up organic matter: oxygen, carbon, hydrogen and nitrogen.

Oxygen(65-75%) - contained in huge number organic molecules - proteins, fats, carbohydrates, nucleic acids Oh. In the form of a simple substance (O2) it is formed in the process of oxygenic photosynthesis (cyanobacteria, algae, plants).

Functions: 1. Oxygen is a strong oxidizing agent (oxidizes glucose during cellular respiration, energy is released in the process)

2. Included in the organic substances of the cell

3. Included in the water molecule

Carbon(15-18%) - is the basis of the structure of all organic substances. As carbon dioxide released during respiration and absorbed during photosynthesis. May be in the form of CO - carbon monoxide. In the form of calcium carbonate (CaCO3) is part of the bones.

Hydrogen(8 - 10%) - like carbon, it is part of any organic compound. It also contains water.

Nitrogen(2 - 3%) - is part of amino acids, and hence proteins, nucleic acids, some vitamins and pigments. Fixed by bacteria from the atmosphere.

Macronutrients

Magnesium (0,02 - 0,03%)

1. In the cell - is part of enzymes, participates in the synthesis of DNA and energy exchange

2. In plants - is part of chlorophyll

3. In animals - it is part of the enzymes involved in the functioning of muscle, nervous and bone tissues.

Sodium (0,02 - 0,03%)

1. In the cell - is part of the potassium-sodium channels and pumps

2. In plants - participates in osmosis, which ensures the absorption of water from the soil

3. In animals - participates in the work of the kidneys, maintaining heart rate, is part of the blood (NaCl), helps maintain acid-base balance

Calcium (0,04 - 2,0%)

1. In the cell - participates in the selective permeability of the membrane, in the process of connecting DNA to proteins

2. In plants - forms salts of pectin substances, gives hardness to the intercellular substance connecting plant cells, and also participates in the formation of intercellular contacts

3. In animals, it is part of the bones of vertebrates, shells of mollusks and coral polyps, participates in the formation of bile, increases the reflex excitability of the spinal cord and the center of salivation, participates in the synaptic transmission of a nerve impulse, in the processes of blood coagulation, is a necessary factor in reducing the striated muscles

Iron (0,02%)

1. In the cell - is part of the cytochromes

2. In plants - participates in the synthesis of chlorophyll, is part of the enzymes involved in respiration, are part of cytochromes

3. In animals - is part of hemoglobin

Potassium (0,15 - 0,4%)

1. In the cell - maintains the colloidal properties of the cytoplasm, is part of the potassium-sodium pumps and channels, activates enzymes involved in protein synthesis during glycolysis

2. In plants - participates in the regulation of water metabolism and photosynthesis

3. Necessary for the correct heart rhythm, participates in the conduction of a nerve impulse

Sulfur (0,15 - 0,2%)

1. In the cell - is part of some amino acids - cytine, cysteine ​​and methionine, forms disulfide bridges in the tertiary structure of the protein, is part of some enzymes and coenzyme A, is part of bacteriochlorophyll, some chemosynthetics use sulfur compounds to generate energy

2. In animals - is part of insulin, vitamin B1, biotin

Phosphorus (0,2 - 1,0%)

1. In the cell - in the form of phosphoric acid residues, it is part of DNA, RNA, ATP, nucleotides, coenzymes NAD, NADP, FAD, phosphorylated sugars, phospholipids and many enzymes, forms membranes as part of phospholipids

2. In animals - it is part of the bones, teeth, in mammals it is a component of the buffer system, maintains the acid balance of the tissue fluid relatively constant

Chlorine (0,05 - 0,1%)

1. In the cell - participates in maintaining the electrical neutrality of the cell

2. In plants - participates in the regulation of turgor pressure

3. In animals - participates in the formation of the osmotic potential of blood plasma, as well as in the processes of excitation and inhibition in nerve cells present in gastric juice as hydrochloric acid

trace elements

Copper

1. In the cell - is part of the enzymes involved in the synthesis of cytochromes

2. In plants - it is part of the enzymes involved in the reactions of the dark phase of photosynthesis

3. In animals - it is involved in the synthesis of hemoglobin, in invertebrates it is part of hemocyanins - oxygen carriers, in humans - it is part of the skin pigment - melanin

Zinc

1. Participates in alcoholic fermentation

2. In plants - it is part of the enzymes involved in the breakdown of carbonic acid and in the synthesis of plant hormones-auxins

Iodine

1. In vertebrates - is part of the thyroid hormones (thyroxine)

Cobalt

1. In animals - it is part of vitamin B12 (takes part in the synthesis of hemoglobin), its deficiency leads to anemia

Fluorine

1. In animals - gives strength to bones and tooth enamel

Manganese

1. In the cell - is part of the enzymes involved in respiration, oxidation of fatty acids, increases the activity of carboxylase

2. In plants - as part of enzymes, it participates in dark reactions of photosynthesis and in the reduction of nitrates

3. In animals - it is part of the phosphatase enzymes necessary for bone growth

Bromine

1. In the cell - is part of vitamin B1, which is involved in the breakdown of pyruvic acid

Molybdenum

1. In the cell - as part of enzymes, it participates in the fixation of atmospheric nitrogen

2. In plants - as part of enzymes, it participates in the work of stomata and enzymes involved in the synthesis of amino acids

Bor

1. Affects plant growth

Functions of mineral salts

Mineral salts in aqueous solutions dissociate into cations (positive ions) and anions (negative ions).

1. Maintaining acid-base balance

Due to the buffer systems, the pH of the medium is regulated. The phosphate buffer system maintains the pH of the intracellular environment within 6.9-7.4. Bicarbonate - at the level of 7.4.

2. Enzyme activation

Some cations are activators and components of various enzymes, vitamins and hormones.

3. Structural

Various inorganic substances serve as a source for the synthesis of organic molecules or participate in the formation of the internal and external skeleton of organisms.

4. Creation of cell membrane potentials

Potassium ions predominate inside the cell, while sodium and chloride ions predominate outside. As a result, a potential difference is formed between the external and inner surface cell membranes.

5. Creation of osmotic pressure

Inside the cell, the concentration of salt ions is higher, which ensures the entry of water into the cell, creates turgor pressure.

Kirilenko A. A. Biology. USE. Section "Molecular Biology". Theory, training tasks. 2017.

Organisms are made up of cells. Cells of different organisms have similar chemical composition. Table 1 presents the main chemical elements found in the cells of living organisms.

Table 1. The content of chemical elements in a cell

According to the content in the cell, three groups of elements can be distinguished. The first group includes oxygen, carbon, hydrogen and nitrogen. They account for almost 98% of the total composition of the cell. The second group includes potassium, sodium, calcium, sulfur, phosphorus, magnesium, iron, chlorine. Their content in the cell is tenths and hundredths of a percent. The elements of these two groups belong to macronutrients(from Greek. macro- big).

The remaining elements, represented in the cell by hundredths and thousandths of a percent, are included in the third group. it trace elements(from Greek. micro- small).

No elements inherent only in living nature were found in the cell. All of the above chemical elements are included in inanimate nature. This indicates the unity of animate and inanimate nature.

The lack of any element can lead to illness, and even death of the body, since each element plays a certain role. Macronutrients of the first group form the basis of biopolymers - proteins, carbohydrates, nucleic acids, and lipids, without which life is impossible. Sulfur is part of some proteins, phosphorus is part of nucleic acids, iron is part of hemoglobin, and magnesium is part of chlorophyll. Calcium plays an important role in metabolism.

Part of the chemical elements contained in the cell is part of inorganic substances - mineral salts and water.

mineral salts are in the cell, as a rule, in the form of cations (K +, Na +, Ca 2+, Mg 2+) and anions (HPO 2-/4, H 2 PO -/4, CI -, HCO 3), the ratio of which determines the acidity of the medium, which is important for the life of cells.

(In many cells, the medium is slightly alkaline and its pH hardly changes, since a certain ratio of cations and anions is constantly maintained in it.)

Of the inorganic substances in wildlife, a huge role is played by water.

Life is impossible without water. It makes up a significant mass of most cells. A lot of water is contained in the cells of the brain and human embryos: more than 80% of water; in adipose tissue cells - only 40%. By old age, the water content in the cells decreases. A person who loses 20% of water dies.

The unique properties of water determine its role in the body. It is involved in thermoregulation, which is due to the high heat capacity of water - consumption a large number energy when heated. What determines the high heat capacity of water?

In a water molecule, an oxygen atom is covalently bonded to two hydrogen atoms. The water molecule is polar because the oxygen atom has a partially negative charge, and each of the two hydrogen atoms has

Partially positive charge. A hydrogen bond is formed between the oxygen atom of one water molecule and the hydrogen atom of another molecule. Hydrogen bonds provide the connection of a large number of water molecules. When water is heated, a significant part of the energy is spent on breaking hydrogen bonds, which determines its high heat capacity.

Water - good solvent. Due to the polarity, its molecules interact with positively and negatively charged ions, thereby contributing to the dissolution of the substance. In relation to water, all substances of the cell are divided into hydrophilic and hydrophobic.

hydrophilic(from Greek. hydro- water and fileo- love) are called substances that dissolve in water. These include ionic compounds (eg salts) and some non-ionic compounds (eg sugars).

hydrophobic(from Greek. hydro- water and phobos- fear) are called substances that are insoluble in water. These include, for example, lipids.

Water plays big role in chemical reactions occurring in the cell in aqueous solutions. It dissolves metabolic products that are unnecessary to the body and thereby contributes to their removal from the body. The high water content in the cell gives it elasticity. Water facilitates the movement of various substances within the cell or from cell to cell.

Bodies of animate and inanimate nature consist of the same chemical elements. The composition of living organisms includes inorganic substances - water and mineral salts. The vital numerous functions of water in a cell are due to the peculiarities of its molecules: their polarity, the ability to form hydrogen bonds.

INORGANIC COMPONENTS OF THE CELL

About 90 elements are found in the cells of living organisms, and approximately 25 of them are found in almost all cells. According to the content in the cell, chemical elements are divided into three large groups: macronutrients (99%), micronutrients (1%), ultramicronutrients (less than 0.001%).

Macronutrients include oxygen, carbon, hydrogen, phosphorus, potassium, sulfur, chlorine, calcium, magnesium, sodium, and iron.
Microelements include manganese, copper, zinc, iodine, fluorine.
Ultramicroelements include silver, gold, bromine, selenium.

ORGANIC COMPONENTS OF A CELL

Enzymes.

The most important function of proteins is catalytic. Protein molecules that increase the rate of chemical reactions in a cell by several orders of magnitude are called enzymes. Not a single biochemical process in the body occurs without the participation of enzymes.

Over 2000 enzymes have been discovered so far. Their efficiency is many times higher than the efficiency of inorganic catalysts used in production. So, 1 mg of iron in the composition of the catalase enzyme replaces 10 tons of inorganic iron. Catalase increases the rate of decomposition of hydrogen peroxide (H 2 O 2) by 10 11 times. The enzyme catalyzing the formation of carbonic acid (CO 2 + H 2 O \u003d H 2 CO 3) accelerates the reaction by 10 7 times.

An important property of enzymes is the specificity of their action; each enzyme catalyzes only one or a small group of similar reactions.

The substance that an enzyme acts on is called substrate. The structures of the enzyme molecule and the substrate must exactly match each other. This explains the specificity of the action of enzymes. When a substrate is combined with an enzyme, the spatial structure of the enzyme changes.

The sequence of interaction between the enzyme and the substrate can be depicted schematically:

Substrate+Enzyme - Enzyme-substrate complex - Enzyme+Product.

It can be seen from the diagram that the substrate combines with the enzyme to form an enzyme-substrate complex. In this case, the substrate is transformed into a new substance - the product. At the final stage, the enzyme is released from the product and again interacts with the next substrate molecule.

Enzymes function only at a certain temperature, concentration of substances, acidity of the environment. A change in conditions leads to a change in the tertiary and quaternary structure of the protein molecule, and, consequently, to the suppression of enzyme activity. How does this happen? Only a certain part of the enzyme molecule has catalytic activity, called active center. The active center contains from 3 to 12 amino acid residues and is formed as a result of the bending of the polypeptide chain.

Under the influence of various factors, the structure of the enzyme molecule changes. In this case, the spatial configuration of the active center is disturbed, and the enzyme loses its activity.

Enzymes are proteins that act as biological catalysts. Thanks to enzymes, the rate of chemical reactions in cells increases by several orders of magnitude. An important property of enzymes is the specificity of action under certain conditions.

Nucleic acids.

Nucleic acids were discovered in the second half of the 19th century. Swiss biochemist F. Miescher, who isolated a substance with a high content of nitrogen and phosphorus from the nuclei of cells and called it "nuclein" (from lat. nucleus- nucleus).

Nucleic acids store hereditary information about the structure and functioning of every cell and all living beings on Earth. There are two types of nucleic acids - DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Nucleic acids, like proteins, are species-specific, that is, organisms of each species have their own type of DNA. To find out the reasons for species specificity, consider the structure of nucleic acids.

Nucleic acid molecules are very long chains consisting of many hundreds and even millions of nucleotides. Any nucleic acid contains only four types of nucleotides. The functions of nucleic acid molecules depend on their structure, their constituent nucleotides, their number in the chain, and the sequence of the compound in the molecule.

Each nucleotide is made up of three components: a nitrogenous base, a carbohydrate, and phosphoric acid. Each DNA nucleotide contains one of the four types of nitrogenous bases (adenine - A, thymine - T, guanine - G or cytosine - C), as well as a deoxyribose carbohydrate and a phosphoric acid residue.

Thus, DNA nucleotides differ only in the type of nitrogenous base.

The DNA molecule consists of a huge number of nucleotides connected in a chain in a certain sequence. Each type of DNA molecule has its own number and sequence of nucleotides.

DNA molecules are very long. For example, to write down the sequence of nucleotides in DNA molecules from one human cell (46 chromosomes), one would need a book of about 820,000 pages. The alternation of four types of nucleotides can form an infinite number of variants of DNA molecules. These features of the structure of DNA molecules allow them to store a huge amount of information about all the signs of organisms.

In 1953, the American biologist J. Watson and the English physicist F. Crick created a model for the structure of the DNA molecule. Scientists have found that each DNA molecule consists of two strands interconnected and spirally twisted. It looks like a double helix. In each chain, four types of nucleotides alternate in a specific sequence.

The nucleotide composition of DNA is different different types bacteria, fungi, plants, animals. But it does not change with age, it depends little on changes in the environment. Nucleotides are paired, that is, the number of adenine nucleotides in any DNA molecule is equal to the number of thymidine nucleotides (A-T), and the number of cytosine nucleotides is equal to the number of guanine nucleotides (C-G). This is due to the fact that the connection of two chains to each other in a DNA molecule obeys a certain rule, namely: adenine of one chain is always connected by two hydrogen bonds only with Thymine of the other chain, and guanine by three hydrogen bonds with cytosine, that is, the nucleotide chains of one molecule DNA is complementary, complement each other.

Nucleic acid molecules - DNA and RNA are made up of nucleotides. The composition of DNA nucleotides includes a nitrogenous base (A, T, G, C), a deoxyribose carbohydrate and a residue of a phosphoric acid molecule. The DNA molecule is a double helix, consisting of two strands connected by hydrogen bonds according to the principle of complementarity. The function of DNA is to store hereditary information.

In the cells of all organisms there are molecules of ATP - adenosine triphosphoric acid. ATP is a universal cell substance, the molecule of which has energy-rich bonds. The ATP molecule is one kind of nucleotide, which, like other nucleotides, consists of three components: a nitrogenous base - adenine, a carbohydrate - ribose, but instead of one it contains three residues of phosphoric acid molecules (Fig. 12). The bonds indicated by the icon in the figure are rich in energy and are called macroergic. Each ATP molecule contains two macroergic bonds.

When the high-energy bond is broken and one molecule of phosphoric acid is cleaved off with the help of enzymes, 40 kJ / mol of energy is released, and ATP is converted into ADP - adenosine diphosphoric acid. With the elimination of one more phosphoric acid molecule, another 40 kJ / mol is released; AMP is formed - adenosine monophosphoric acid. These reactions are reversible, that is, AMP can turn into ADP, ADP - into ATP.

ATP molecules are not only broken down, but also synthesized, so their content in the cell is relatively constant. The importance of ATP in the life of the cell is enormous. These molecules play a leading role in the energy metabolism necessary to ensure the vital activity of the cell and the organism as a whole.

An RNA molecule, as a rule, is a single chain consisting of four types of nucleotides - A, U, G, C. Three main types of RNA are known: mRNA, rRNA, tRNA. The content of RNA molecules in the cell is not constant, they are involved in protein biosynthesis. ATP is the universal energy substance of the cell, in which there are energy-rich bonds. ATP plays a central role in the exchange of energy in the cell. RNA and ATP are found both in the nucleus and in the cytoplasm of the cell.

Tasks and tests on the topic "Topic 4. "Chemical composition of the cell.""

• polymer, monomer;
• carbohydrate, monosaccharide, disaccharide, polysaccharide;
• lipid, fatty acid, glycerol;
• amino acid, peptide bond, protein;
• catalyst, enzyme, active site;
• nucleic acid, nucleotide.

Algorithm for solving problems.

Type 1. DNA self-copying.

One of the DNA chains has the following nucleotide sequence:
AGTACCGATACCGATTTCG...
What sequence of nucleotides does the second chain of the same molecule have?

To write the nucleotide sequence of the second strand of a DNA molecule, when the sequence of the first strand is known, it is enough to replace thymine with adenine, adenine with thymine, guanine with cytosine, and cytosine with guanine. Making this substitution, we get the sequence:
TACTGGCTATGAGCTAAATG...

Type 2. Protein coding.

The amino acid chain of the ribonuclease protein has the following beginning: lysine-glutamine-threonine-alanine-alanine-alanine-lysine ...
What sequence of nucleotides starts the gene corresponding to this protein?

To do this, use the table of the genetic code. For each amino acid, we find its code designation in the form of the corresponding trio of nucleotides and write it out. Arranging these triplets one after another in the same order as the corresponding amino acids go, we obtain the formula for the structure of the messenger RNA section. As a rule, there are several such triples, the choice is made according to your decision (but only one of the triples is taken). There may be several solutions, respectively.
AAACAAAATSUGTSGGTSUGTSGAAG

What amino acid sequence does a protein begin with if it is encoded by such a sequence of nucleotides:
ACGCCATGGCCGGT...

According to the principle of complementarity, we find the structure of the informational RNA section formed on a given segment of the DNA molecule:
UGCGGGUACCCGCCCA...

Then we turn to the table of the genetic code and for each trio of nucleotides, starting from the first, we find and write out the amino acid corresponding to it:
Cysteine-glycine-tyrosine-arginine-proline-...

Ivanova T.V., Kalinova G.S., Myagkova A.N. " General biology". Moscow, "Enlightenment", 2000

• Topic 4. "Chemical composition of the cell." §2-§7 pp. 7-21
• Topic 5. "Photosynthesis." §16-17 pp. 44-48
• Topic 6. "Cellular respiration." §12-13 pp. 34-38
• Topic 7. "Genetic information." §14-15 pp. 39-44