Organic substances that make up a cell table. Water and inorganic compounds, their role in the cell

These include water and mineral salts.

Water necessary for the implementation of life processes in the cell. Its content is 70-80% of the cell mass. Main functions of water:

is a universal solvent;

is the environment in which biochemical reactions occur;

determines the physiological properties of the cell (elasticity, volume);

participates in chemical reactions;

maintains thermal balance of the body due to high heat capacity and thermal conductivity;

is the main means for transporting substances.

Mineral salts present in the cell in the form of ions: cations K +, Na +, Ca 2+, Mg 2+; anions – Cl -, HCO 3 -, H 2 PO 4 -.

3. Organic substances of the cell.

The organic compounds of a cell consist of many repeating elements (monomers) and are large molecules - polymers. These include proteins, fats, carbohydrates and nucleic acids. Their content in the cell: proteins -10-20%; fats - 1-5%; carbohydrates - 0.2-2.0%; nucleic acids - 1-2%; low molecular weight organic substances – 0.1-0.5%.

Squirrels – high molecular weight (high molecular weight) organic matter. The structural unit of their molecule is an amino acid. 20 amino acids take part in the formation of proteins. The molecule of each protein contains only certain amino acids in the order of arrangement characteristic of this protein. The amino acid has the following formula:

H 2 N – CH – COOH

The composition of amino acids includes NH 2 - an amino group with basic properties; COOH – carboxyl group with acidic properties; radicals that distinguish amino acids from each other.

There are primary, secondary, tertiary and quaternary protein structures. Amino acids connected to each other by peptide bonds determine its primary structure. Proteins of the primary structure are connected into a helix using hydrogen bonds and form a secondary structure. Polypeptide chains, twisting in a certain way into a compact structure, form a globule (ball) - the tertiary structure of the protein. Most proteins have a tertiary structure. It should be noted that amino acids are active only on the surface of the globule. Proteins with a globular structure combine to form a quaternary structure (for example, hemoglobin). When exposed to high temperature, acids and other factors, complex protein molecules are destroyed - protein denaturation. When conditions improve, a denatured protein is able to restore its structure if its primary structure is not destroyed. This process is called renaturation.

Proteins are species specific: each animal species is characterized by a set of specific proteins.

There are simple and complex proteins. Simple ones consist only of amino acids (for example, albumins, globulins, fibrinogen, myosin, etc.). Part complex proteins In addition to amino acids, there are also other organic compounds, for example, fats and carbohydrates (lipoproteins, glycoproteins, etc.).

Proteins perform the following functions:

enzymatic (for example, the enzyme amylase breaks down carbohydrates);

structural (for example, they are part of membranes and other cell organelles);

receptor (for example, the protein rhodopsin promotes better vision);

transport (for example, hemoglobin carries oxygen or carbon dioxide);

protective (for example, immunoglobulin proteins are involved in the formation of immunity);

motor (for example, actin and myosin are involved in the contraction of muscle fibers);

hormonal (for example, insulin converts glucose into glycogen);

energy (when 1 g of protein is broken down, 4.2 kcal of energy is released).

Fats (lipids) - compounds of trihydric alcohol glycerol and high molecular weight fatty acids. Chemical formula fat:

CH 2 -O-C(O)-R¹

CH 2 -O-C(O)-R³, where the radicals can be different.

Functions of lipids in the cell:

structural (take part in the construction of the cell membrane);

energy (when 1 g of fat breaks down in the body, 9.2 kcal of energy is released);

protective (protects from heat loss, mechanical damage);

fat is a source of endogenous water (with the oxidation of 10 g of fat, 11 g of water is released);

regulation of metabolism.

Carbohydrates – their molecule can be represented by the general formula C n (H 2 O) n – carbon and water.

Carbohydrates are divided into three groups: monosaccharides (include one sugar molecule - glucose, fructose, etc.), oligosaccharides (include from 2 to 10 monosaccharide residues: sucrose, lactose) and polysaccharides (high molecular weight compounds - glycogen, starch, etc.).

Functions of carbohydrates:

serve as starting elements for the construction of various organic substances, for example, during photosynthesis - glucose;

the main source of energy for the body; during their decomposition using oxygen, more energy is released than during the oxidation of fat;

protective (for example, mucus secreted by various glands contains a lot of carbohydrates; it protects the walls of hollow organs (bronchial tubes, stomach, intestines) from mechanical damage; having antiseptic properties);

structural and support functions: included in plasma membrane.

Nucleic acids are phosphorus-containing biopolymers. These include deoxyribonucleic acid (DNA) And ribonucleic (RNA) acids.

DNA - the largest biopolymers, their monomer is nucleotide. It consists of residues of three substances: a nitrogenous base, the carbohydrate deoxyribose and phosphoric acid. There are 4 known nucleotides involved in the formation of a DNA molecule. Two nitrogenous bases are derivatives of pyrimidine - thymine and cytosine. Adenine and guanine are classified as purine derivatives.

According to the DNA model proposed by J. Watson and F. Crick (1953), the DNA molecule consists of two strands spiraling around each other.

The two strands of a molecule are held together by hydrogen bonds that occur between them. complementary nitrogenous bases. Adenine is complementary to thymine, and guanine is complementary to cytosine. DNA in cells is located in the nucleus, where it, together with proteins, forms chromosomes. DNA is also found in mitochondria and plastids, where their molecules are arranged in a ring. Main DNA function– storage of hereditary information contained in the sequence of nucleotides that form its molecule, and transmission of this information to daughter cells.

Ribonucleic acid single-stranded. An RNA nucleotide consists of one of the nitrogenous bases (adenine, guanine, cytosine or uracil), the carbohydrate ribose and a phosphoric acid residue.

There are several types of RNA.

Ribosomal RNA(r-RNA) in combination with protein is part of ribosomes. Ribosomes carry out protein synthesis. Messenger RNA(i-RNA) carries information about protein synthesis from the nucleus to the cytoplasm. Transfer RNA(tRNA) is located in the cytoplasm; attaches certain amino acids to itself and delivers them to ribosomes, the site of protein synthesis.

RNA is found in the nucleolus, cytoplasm, ribosomes, mitochondria and plastids. There is another type of RNA in nature – viral. In some viruses, it performs the function of storing and transmitting hereditary information. In other viruses, this function is performed by viral DNA.

Adenosine triphosphoric acid (ATP) is a special nucleotide formed by the nitrogenous base adenine, the carbohydrate ribose and three phosphoric acid residues.

ATP is a universal source of energy necessary for biological processes occurring in the cell. The ATP molecule is very unstable and is capable of splitting off one or two phosphate molecules, releasing a large amount of energy. This energy is spent to ensure all the vital functions of the cell - biosynthesis, movement, generation of an electrical impulse, etc. The bonds in the ATP molecule are called macroergic. The cleavage of phosphate from an ATP molecule is accompanied by the release of 40 kJ of energy. ATP synthesis occurs in mitochondria.

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

Table 1. Contents chemical elements in a cage

Based on 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. Elements of these two groups are classified as 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. This microelements(from Greek micro- small).

No elements unique to living nature were found in the cell. All of the listed chemical elements are also part of inanimate nature. This indicates the unity of living and inanimate nature.

A deficiency of any element can lead to illness and even death of the body, since each element plays a specific role. Macroelements of the first group form the basis of biopolymers - proteins, carbohydrates, nucleic acids, as well as 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.

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

Mineral salts are found 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 environment, which is important for the life of cells.

(In many cells, the environment is slightly alkaline and its pH almost does not change, since a certain ratio of cations and anions is constantly maintained in it.)

Of the inorganic substances in living nature, plays a huge role water.

Without water, life is impossible. 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% water; in adipose tissue cells - only 40.% By old age, the water content in cells decreases. A person who has lost 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 - the consumption of a large amount of energy when heating. 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 is 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 connection large number 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 their polarity, its molecules interact with positively and negatively charged ions, thereby promoting the dissolution of the substance. In relation to water, all cell substances are divided into hydrophilic and hydrophobic.

Hydrophilic(from Greek hydro- water and filleo- love) are called substances that dissolve in water. These include ionic compounds (for example, salts) and some non-ionic compounds (for example, sugars).

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

Water plays an important role in the chemical reactions that take place in the cell. aqueous solutions. It dissolves metabolic products that the body does not need and thereby promotes their removal from the body. The high water content in the cell gives it elasticity. Water promotes movement various substances within a cell or from cell to cell.

Bodies of living and inanimate nature consist of the same chemical elements. Living organisms contain inorganic substances - water and mineral salts. The vitally important numerous functions of water in a cell are determined by the characteristics 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 about 25 of them are found in almost all cells. According to their content in the cell, chemical elements are divided into three large groups: macroelements (99%), microelements (1%), ultramicroelements (less than 0.001%).

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

ORGANIC COMPONENTS OF CELLS

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.

Currently, over 2000 enzymes have been discovered. Their efficiency is many times higher than the efficiency of inorganic catalysts used in production. Thus, 1 mg of iron in 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 that catalyzes the reaction of carbonic acid formation (CO 2 + H 2 O = H 2 CO 3) accelerates the reaction 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 the enzyme acts on is called substrate. The structures of the enzyme and substrate molecules 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 enzyme and substrate can be depicted schematically:

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

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

Enzymes function only at a certain temperature, concentration of substances, and acidity of the environment. Changing conditions leads to changes 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, called active center. The active center contains from 3 to 12 amino acid residues and is formed as a result of 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 disrupted, 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 their 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 from cell nuclei with high content nitrogen and phosphorus and called it “nuclein” (from lat. core- core).

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, the nucleotides they contain, their number in the chain and the sequence of the compound in the molecule.

Each nucleotide consists of three components: a nitrogenous base, a carbohydrate and a phosphoric acid. Each DNA nucleotide contains one of four types of nitrogenous bases (adenine - A, thymine - T, guanine - G or cytosine - C), as well as deoxyribose carbon 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) in letters would require 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 structural features of DNA molecules allow them to store a huge amount of information about all the characteristics of organisms.

In 1953, the American biologist J. Watson and the English physicist F. Crick created a model of the structure of the DNA molecule. Scientists have found that each DNA molecule consists of two chains 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 varies among different types bacteria, fungi, plants, animals. But it does not change with age, it depends little on changes 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 DNA molecule are complementary, complement each other.

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

The cells of all organisms contain 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 unique 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 connections indicated in the figure with an icon are rich in energy and are called macroergic. Each ATP molecule contains two high-energy bonds.

When a high-energy bond is broken and one molecule of phosphoric acid is removed with the help of enzymes, 40 kJ/mol of energy is released, and ATP is converted into ADP - adenosine diphosphoric acid. When another molecule of phosphoric acid is removed, another 40 kJ/mol is released; AMP is formed - adenosine monophosphoric acid. These reactions are reversible, that is, AMP can be converted 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 a cell is enormous. These molecules play a leading role in energy metabolism necessary to ensure the life of the cell and the organism as a whole.

An RNA molecule is usually 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 a cell is not constant; they participate in protein biosynthesis. ATP is a universal energy substance of the cell, which contains energy-rich bonds. ATP plays a central role in cellular energy metabolism. RNA and ATP are found in both the nucleus and 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. Self-copying of DNA.

One of the DNA chains has the following nucleotide sequence:
AGTACCGATACCGATTTACCG...
What nucleotide sequence 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. Having made this replacement, we get the sequence:
TATTGGGCTATGAGCTAAAATG...

Type 2. Protein coding.

The chain of amino acids of the ribonuclease protein has the following beginning: lysine-glutamine-threonine-alanine-alanine-alanine-lysine...
What nucleotide sequence does the gene corresponding to this protein begin with?

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

What sequence of amino acids does a protein begin with if it is encoded by the following sequence of nucleotides:
ACCTTCCATGGCCGGT...

Using the principle of complementarity, we find the structure of a section of messenger RNA formed on a given segment of a DNA molecule:
UGCGGGGUACCGGCCCA...

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

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

• Topic 4. " Chemical composition cells." §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

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 groups:

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

• organogens(oxygen, hydrogen, carbon, nitrogen),
• macroelements,
• microelements.

Molecules that make up a cell inorganic And organic connections.

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

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

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

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

Table.

Thematic assignments

Part A

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

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

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

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

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

A6. Select a group of chemical elements that are necessarily included in proteins
1) Na, K, O, S
2) N, P, C, Cl
3) C, S, Fe, O
4) C, H, O, N

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

Part B

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

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

Part C

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

As we already know, a cell consists of organic and inorganic chemicals. The main inorganic substances that make up the cell are salts and water.

Water as a component of living things

Water is the dominant component of all organisms. Important biological functions water are carried out due to the unique properties of its molecules, in particular the presence of dipoles that make possible occurrence hydrogen bonds between cells.

Thanks to water molecules, the processes of thermostabilization and thermoregulation occur in the body of living beings. The process of thermoregulation occurs due to the high heat capacity of water molecules: external temperature changes do not affect temperature changes inside the body.

Thanks to water, the organs of the human body retain their elasticity. Water is one of the main components of the lubricating fluids necessary for the joints of vertebrates or the pericardial sac.

It is part of the mucus, which facilitates the movement of substances through the intestines. Water is a component of bile, tears and saliva.

Salts and other inorganic substances

In addition to water, the cells of a living organism contain inorganic substances such as acids, bases and salts. The most important in the life of the body are Mg2+, H2PO4, K, CA2, Na, C1-. Weak acids guarantee a stable internal cell environment (weakly alkaline).

Ion concentration in intercellular substance and inside the cell can be different. For example, Na+ ions are concentrated only in the intercellular fluid, while K+ is found exclusively in the cell.

A sharp reduction or increase in the number of certain ions in the cell composition not only leads to its dysfunction, but also to death. For example, a decrease in the amount of Ca+ in a cell causes convulsions inside the cell and its further death.

Some inorganic substances often interact with fats, proteins and carbohydrates. So a shining example are organic compounds with phosphorus and sulfur.

Sulfur, which is part of protein molecules, is responsible for the formation of molecular bonds in the body. Thanks to the synthesis of phosphorus and organic substances, energy is released from protein molecules.

Calcium salts

Normal development of bone tissue, as well as the functioning of the brain and spinal cord calcium salts contribute. Calcium metabolism in the body is carried out due to vitamin D. An excess or deficiency of calcium salts leads to dysfunction of the body.

Plant and animal cells contain inorganic and organic substances. Inorganic substances include water and minerals. Organic substances include proteins, fats, carbohydrates, and nucleic acids.

Inorganic substances

Wateris a connection that living cell contains in the greatest number. Water makes up about 70% of the cell's mass. Most intracellular reactions occur in aquatic environment. Water in the cell is in a free and bound state.

The importance of water for the life of a cell is determined by its structure and properties. The water content in cells can vary. 95% of water is free in the cell. It is necessary as a solvent for organic and inorganic substances. All biochemical reactions in a cell occur with the participation of water. Water is used to remove various substances from the cell. Water has high thermal conductivity and prevents sudden temperature fluctuations. 5% of water is in a bound state, forming weak compounds with proteins.

Minerals in the cell they can be in a dissociated state or in combination with organic substances.

Chemical elements, that participate in metabolic processes and have biological activity are called biogenic.

Cytoplasmcontains about 70% oxygen, 18% carbon, 10% hydrogen, calcium, nitrogen, potassium, phosphorus, magnesium, sulfur, chlorine, sodium, aluminum, iron. These elements make up 99.99% of the composition of the cell and are called macroelements. For example, calcium and phosphorus are part of bones. Iron is a component of hemoglobin.

Manganese, boron, copper, zinc, iodine, cobalt - microelements. They make up thousandths of a percent of the cell mass. Microelements are needed for the formation of hormones, enzymes, and vitamins. They influence metabolic processes in organism. For example, iodine is part of the thyroid hormone, cobalt is part of vitamin B 12.

Gold, mercury, radium, etc. - ultramicroelements- constitute millionths of a percent of the composition of the cell.

A lack or excess of mineral salts disrupts the vital functions of the body.

Organic matter

Oxygen, hydrogen, carbon, nitrogen are part of organic substances. Organic compounds are large molecules called polymers. Polymers are made up of many repeating units (monomers). Organic polymer compounds include carbohydrates, fats, proteins, nucleic acids, and ATP.

Carbohydrates

Carbohydratesconsist of carbon, hydrogen, oxygen.

Monomerscarbohydrates are monosaccharides. Carbohydrates are divided into monosaccharides, disaccharides and polysaccharides.

Monosaccharides- simple sugars with the formula (CH 2 O) n, where n is any integer from three to seven. Depending on the number of carbon atoms in the molecule, trioses (3C), tetroses (4C), pentoses (5C), hexoses (6C), and heptoses (7C) are distinguished.

TriosesC 3 H 6 O 3 - for example, glyceraldehyde and dihydroxyacetone - play the role of intermediate products in the process of respiration and are involved in photosynthesis. Tetroses C 4 H 8 O 4 are found in bacteria. Pentoses C 5 H 10 O 5 - for example, ribose - is part of RNA, deoxyribose is part of DNA. Hexoses - C 6 H 12 O 6 - for example glucose, fructose, galactose. Glucose is the source of energy for the cell. Together with fructose and galactose, glucose can participate in the formation of disaccharides.

Disaccharidesare formed as a result of a condensation reaction between two monosaccharides (hexoses) with the loss of a water molecule.

The formula of disaccharides is C 12 H 22 O 11 Among the disaccharides, the most widespread are maltose, lactose and sucrose.

Sucrose, or cane sugar, is synthesized in plants. Maltose is formed from starch during its digestion in animals. Lactose, or milk sugar, is found only in milk.

Polysaccharides (simple) are formed as a result of the condensation reaction of a large number of monosaccharides. Simple polysaccharides include starch (synthesized in plants), glycogen (found in liver cells and muscles of animals and humans), cellulose (forms cell wall in plants).

Complex polysaccharides are formed as a result of the interaction of carbohydrates with lipids. For example, glycolipids are part of membranes. Complex polysaccharides also include compounds of carbohydrates with proteins (glycoproteins). For example, glycoproteins are part of the mucus secreted by the glands of the gastrointestinal tract.

Functions of carbohydrates:

1. Energy: The body receives 60% of its energy from the breakdown of carbohydrates. When 1 g of carbohydrates is broken down, 17.6 kJ of energy is released.

2. Structural and support: carbohydrates are part of the plasma membrane, the membrane of plant and bacterial cells.

3. Storage: nutrients (glycogen, starch) are stored in cells.

4. Protective: secretions (mucus) secreted by various glands protect the walls of hollow organs, bronchi, stomach, and intestines from mechanical damage, harmful bacteria and viruses.

5. Participate in photosynthesis.

Fats and fat-like substances

Fatsconsist of carbon, hydrogen, oxygen. Monomers fats are fatty acid And glycerol. The properties of fats are determined by the qualitative composition of fatty acids and their quantitative ratio. Vegetable fats are liquid (oils), animal fats are solid (for example, lard). Fats are insoluble in water - they are hydrophobic compounds. Fats combine with proteins to form lipoproteins, and combine with carbohydrates to form glycolipids. Glycolipids and lipoproteins are fat-like substances.

Fat-like substances are part of cell membranes, membrane organelles, and nervous tissue. Fats can combine with glucose and form glycosides. For example, digitoxin glycoside is a substance used in the treatment of heart disease.

Functions of fats:

1. Energy: with complete breakdown 1 g of fat to carbon dioxide and water, 38.9 kJ of energy is released.

2. Structural: are part of the cell membrane.

3. Protective: a layer of fat protects the body from hypothermia, mechanical shocks and shocks.

4. Regulatory: Steroid hormones regulate metabolic processes and reproduction.

5. Fat- source endogenous water. When 100 g of fat is oxidized, 107 ml of water is released.

Squirrels

Proteins contain carbon, oxygen, hydrogen, and nitrogen. Monomers squirrels are amino acids. Proteins are built from twenty different amino acids. Amino acid formula:

The composition of amino acids includes: NH 2 - an amino group with basic properties; COOH is a carboxyl group and has acidic properties. Amino acids differ from each other by their radicals - R. Amino acids are amphoteric compounds. They are connected to each other in the protein molecule using peptide bonds.

Scheme of amino acid condensation (formation of peptide bond)

There are primary, secondary, tertiary and quaternary protein structures. The order, quantity and quality of amino acids that make up a protein molecule determine its primary structure. Proteins with a primary structure can join into a helix using hydrogen bonds and form a secondary structure. Polypeptide chains are twisted in a certain way into a compact structure, forming a globule (ball) - this is the tertiary structure of the protein. Most proteins have a tertiary structure. Amino acids are active only on the surface of the globule. Proteins that have a globular structure combine together to form a quaternary structure. Replacing one amino acid leads to a change in the properties of the protein (Fig. 30).

When exposed to high temperature, acids and other factors, destruction of the protein molecule can occur. This phenomenon is called denaturation (Fig. 31). Sometimes denatured

Rice. thirty.Various structures of protein molecules.

1 - primary; 2 - secondary; 3 - tertiary; 4 - quaternary (using the example of blood hemoglobin).

Rice. 31.Protein denaturation.

1 - protein molecule before denaturation;

2 - denatured protein;

3 - restoration of the original protein molecule.

When conditions change, the bathed protein can again restore its structure. This process is called renaturation and is possible only when the primary structure of the protein is not destroyed.

Proteins can be simple or complex. Simple proteins consist only of amino acids: for example, albumins, globulins, fibrinogen, myosin.

Complex proteins consist of amino acids and other organic compounds: for example, lipoproteins, glycoproteins, nucleoproteins.

Functions of proteins:

1. Energy. The breakdown of 1 g of protein releases 17.6 kJ of energy.

2. Catalytic. Serve as catalysts for biochemical reactions. Catalysts are enzymes. Enzymes speed up biochemical reactions, but are not part of the final products. Enzymes are strictly specific. Each substrate has its own enzyme. The name of the enzyme includes the name of the substrate and the ending “ase”: maltase, ribonuclease. Enzymes are active at a certain temperature (35 - 45 O C).

3. Structural. Proteins are part of membranes.

4. Transport. For example, hemoglobin carries oxygen and CO 2 in the blood of vertebrates.

5. Protective. Protecting the body from harmful effects: antibody production.

6. Contractile. Due to the presence of actin and myosin proteins in muscle fibers, muscle contraction occurs.

Nucleic acids

There are two types of nucleic acids: DNA(deoxyribonucleic acid) and RNA(ribonucleic acid). Monomers nucleic acids are nucleotides.

DNA (deoxyribonucleic acid). The DNA nucleotide contains one of the nitrogenous bases: adenine (A), guanine (G), thymine (T) or cytosine (C) (Fig. 32), the carbohydrate deoxyribose and a phosphoric acid residue. The DNA molecule is a double helix built according to the principle of complementarity. The following nitrogenous bases are complementary in a DNA molecule: A = T; G = C. Two DNA helices are connected by hydrogen bonds (Fig. 33).

Rice. 32.Nucleotide structure.

Rice. 33.Section of a DNA molecule. Complementary connection of nucleotides of different chains.

DNA is capable of self-duplication (replication) (Fig. 34). Replication begins with the separation of two complementary strands. Each strand is used as a template to form a new DNA molecule. Enzymes are involved in the process of DNA synthesis. Each of the two daughter molecules necessarily includes one old helix and one new one. The new DNA molecule is absolutely identical to the old one in terms of nucleotide sequence. This method of replication ensures accurate reproduction in daughter molecules of the information that was recorded in the mother DNA molecule.

Rice. 34.Duplication of a DNA molecule.

1 - template DNA;

2 - formation of two new chains based on the matrix;

3 - daughter DNA molecules.

Functions of DNA:

1. Storage of hereditary information.

2. Ensuring the transfer of genetic information.

3. Presence in the chromosome as a structural component.

DNA is found in the cell nucleus, as well as in cell organelles such as mitochondria and chloroplasts.

RNA (ribonucleic acid). There are 3 types of ribonucleic acids: ribosomal, transport And informational RNA. An RNA nucleotide consists of one of the nitrogenous bases: adenine (A), guanine (G), cytosine (C), uracil (U), the carbohydrate ribose and a phosphoric acid residue.

Ribosomal RNA (rRNA) in combination with protein it is part of ribosomes. rRNA makes up 80% of all RNA in a cell. Protein synthesis occurs on ribosomes.

Messenger RNA (mRNA) constitutes from 1 to 10% of all RNA in the cell. The structure of mRNA is complementary to the section of the DNA molecule that carries information about the synthesis of a specific protein. The length of the mRNA depends on the length of the DNA section from which the information was read. mRNA carries information about protein synthesis from the nucleus to the cytoplasm to the ribosome.

Transfer RNA (tRNA) makes up about 10% of all RNA. It has a short chain of nucleotides in the shape of a trefoil and is found in the cytoplasm. At one end of the trefoil is a triplet of nucleotides (an anticodon) that codes for a specific amino acid. At the other end is a triplet of nucleotides to which an amino acid is attached. Each amino acid has its own tRNA. tRNA transports amino acids to the site of protein synthesis, i.e. to ribosomes (Fig. 35).

RNA is found in the nucleolus, cytoplasm, ribosomes, mitochondria and plastids.

ATP - Adenazine triphosphoric acid. Adenazine triphosphoric acid (ATP) consists of a nitrogenous base - adenine, sugar - ribose, And three phosphoric acid residues(Fig. 36). The ATP molecule accumulates a large amount of energy necessary for the biochemical processes occurring in the cell. ATP synthesis occurs in mitochondria. The ATP molecule is very unstable

active and capable of splitting off one or two phosphate molecules, releasing a large amount of energy. The bonds in an ATP molecule are called macroergic.

ATP → ADP + P + 40 kJ ADP → AMP + P + 40 kJ

Rice. 35. Structure of tRNA.

A, B, C and D - areas of complementary connection within one RNA chain; D - site (active center) of connection with an amino acid; E - site of complementary connection with the molecule.

Rice. 36.The structure of ATP and its conversion to ADP.

Questions for self-control

1. What substances in a cell are classified as inorganic?

2. What substances in a cell are classified as organic?

3. What is the monomer of carbohydrates?

4. What structure do carbohydrates have?

5. What functions do carbohydrates perform?

6. What is the monomer of fats?

7. What structure do fats have?

8. What functions do fats perform?

9. What is a protein monomer? 10.What structure do proteins have? 11.What structures do proteins have?

12.What happens when a protein molecule denatures?

13.What functions do proteins perform?

14.What nucleic acids are known?

15.What is a monomer of nucleic acids?

16.What is included in the DNA nucleotide?

17.What is the structure of an RNA nucleotide?

18.What is the structure of a DNA molecule?

19.What functions does the DNA molecule perform?

20. What is the structure of rRNA?

21.What is the structure of mRNA?

22.What is the structure of tRNA?

23.What functions do ribonucleic acids perform?

24.What is the structure of ATP?

25.What functions does ATP perform in a cell?

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