All carbohydrates are made up of individual "units", which are saccharides. By ability tohydrolysison themonomerscarbohydrates are dividedinto two groups: simple and complex. Carbohydrates containing one unit are calledmonosaccharides, two units -disaccharides, two to ten unitsoligosaccharides, and more than tenpolysaccharides.

Monosaccharides quickly increase blood sugar, and have a high glycemic index, so they are also called fast carbohydrates. They dissolve easily in water and are synthesized in green plants.

Carbohydrates consisting of 3 or more units are calledcomplex. Foods rich in complex carbohydrates gradually increase their glucose content and have a low glycemic index, which is why they are also called slow carbohydrates. Complex carbohydrates are products of the polycondensation of simple sugars (monosaccharides) and, unlike simple ones, in the process of hydrolytic cleavage they are able to decompose into monomers, with the formation of hundreds and thousandsmoleculesmonosaccharides.

Stereoisomerism of monosaccharides: isomerglyceraldehydein which, when the model is projected onto the plane, the OH group at the asymmetric carbon atom is located on the right side, it is considered to be D-glyceraldehyde, and the mirror image is L-glyceraldehyde. All isomers of monosaccharides are divided into D- and L-forms according to the similarity of the location of the OH group at the last asymmetric carbon atom near CH 2 OH groups (ketoses contain one asymmetric carbon atom less than aldoses with the same number of carbon atoms). Naturalhexoses – glucose, fructose, mannoseandgalactose- according to stereochemical configurations, they are classified as D-series compounds.

Polysaccharides - the general name of the class of complex high-molecular carbohydrates,moleculesconsisting of tens, hundreds or thousandsmonomers – monosaccharides. From the point of view of the general principles of structure in the group of polysaccharides, it is possible to distinguish between homopolysaccharides synthesized from the same type of monosaccharide units and heteropolysaccharides, which are characterized by the presence of two or more types of monomeric residues.

https :// en . wikipedia . org / wiki /Carbohydrates

1.6. Lipids - nomenclature and structure. Lipid polymorphism.

Lipids - an extensive group of natural organic compounds, including fats and fat-like substances. Simple lipid molecules are composed of alcohol andfatty acids, complex - from alcohol, high molecular weight fatty acids and other components.

Lipid classification

Simple lipids are lipids that include carbon (C), hydrogen (H) and oxygen (O) in their structure.

Complex lipids - These are lipids that include in their structure, in addition to carbon (C), hydrogen (H) and oxygen (O), and other chemical elements. Most often: phosphorus (P), sulfur (S), nitrogen (N).

https:// en. wikipedia. org/ wiki/Lipids

Literature:

1) Cherkasova L. S., Merezhinsky M. F., Metabolism of fats and lipids, Minsk, 1961;

2) Markman A. L., Chemistry of lipids, v. 12, Tash., 1963 - 70;

3) Tyutyunnikov B. N., Chemistry of fats, M., 1966;

4) Mahler G., Kordes K., Fundamentals of biological chemistry, trans. from English, M., 1970.

1.7. biological membranes. Forms of lipid aggregation. The concept of the liquid-crystal state. Lateral diffusion and flip flops.

membranes delimit the cytoplasm from the environment, and also form the membranes of the nuclei, mitochondria and plastids. They form a labyrinth of the endoplasmic reticulum and flattened stacked vesicles that make up the Golgi complex. The membranes form lysosomes, large and small vacuoles of plant and fungal cells, pulsating vacuoles of protozoa. All these structures are compartments (compartments) designed for certain specialized processes and cycles. Therefore, without membranes, the existence of a cell is impossible.

Diagram of the structure of the membrane: a – three-dimensional model; b - planar image;

1 - proteins adjacent to the lipid layer (A), immersed in it (B) or penetrating it through (C); 2 - layers of lipid molecules; 3 - glycoproteins; 4 - glycolipids; 5 - hydrophilic channel functioning as a pore.

The functions of biological membranes are as follows:

1) Delimit the contents of the cell from the external environment and the contents of the organelles from the cytoplasm.

2) Provide transport of substances into and out of the cell, from the cytoplasm to the organelles and vice versa.

3) They act as receptors (receiving and converting signals from the environment, recognition of cell substances, etc.).

4) They are catalysts (ensuring near-membrane chemical processes).

5) Participate in the transformation of energy.

http:// sbio. info/ page. php? id=15

Lateral diffusion is the chaotic thermal movement of lipid and protein molecules in the plane of the membrane. With lateral diffusion, adjacent lipid molecules jump around, and as a result of such successive jumps from one place to another, the molecule moves along the membrane surface.

The movement of molecules along the surface of the cell membrane during time t was determined experimentally by the method of fluorescent labels - fluorescent molecular groups. Fluorescent labels make fluorescent molecules, the movement of which on the cell surface can be studied, for example, by examining under a microscope the spreading rate of the fluorescent spot created by such molecules on the cell surface.

flip flop is the diffusion of membrane phospholipid molecules across the membrane.

The rate of jumps of molecules from one membrane surface to another (flip-flop) was determined by the spin label method in experiments on model lipid membranes - liposomes.

Some of the phospholipid molecules from which liposomes were formed were labeled with spin labels attached to them. Liposomes were exposed to ascorbic acid, as a result of which unpaired electrons on the molecules disappeared: paramagnetic molecules became diamagnetic, which could be detected by a decrease in the area under the curve of the EPR spectrum.

Thus, jumps of molecules from one surface of the bilayer to another (flip-flop) occur much more slowly than jumps during lateral diffusion. The average time for a phospholipid molecule to flip-flop (T ~ 1 hour) is tens of billions of times longer than the average time for a molecule to jump from one place to another in the membrane plane.

The concept of the liquid-crystal state

The solid body can becrystalline , andamorphous. In the first case, there is a long-range order in the arrangement of particles at distances much greater than the intermolecular distances (crystal lattice). In the second, there is no long-range order in the arrangement of atoms and molecules.

The difference between an amorphous body and a liquid is not in the presence or absence of long-range order, but in the nature of particle motion. The molecules of a liquid and a solid make oscillatory (sometimes rotational) motions around the equilibrium position. After some average time (“time of settled life”), the molecules jump to another equilibrium position. The difference is that the "settled time" in a liquid is much shorter than in a solid state.

Lipid bilayer membranes are liquid under physiological conditions, the “settled life time” of a phospholipid molecule in the membrane is 10 −7 – 10 −8 With.

Molecules in the membrane are not randomly arranged; long-range order is observed in their arrangement. Phospholipid molecules are in a double layer, and their hydrophobic tails are approximately parallel to each other. There is also order in the orientation of the polar hydrophilic heads.

The physiological state in which there is a long-range order in the mutual orientation and arrangement of molecules, but the state of aggregation is liquid, is calledliquid crystal state. Liquid crystals can form not in all substances, but in substances from "long molecules" (the transverse dimensions of which are smaller than the longitudinal ones). There may be various liquid crystal structures: nematic (filamentous), when long molecules are oriented parallel to each other; smectic - molecules are parallel to each other and arranged in layers; cholestic - the molecules are parallel to each other in the same plane, but in different planes the orientations of the molecules are different.

http:// www. studfiles. en/ preview/1350293/

Literature: ON THE. Lemeza, L.V. Kamlyuk, N.D. Lisov. "Biology manual for applicants to universities."

1.8. Nucleic acids. Heterocyclic bases, nucleosides, nucleotides, nomenclature. Spatial structure of nucleic acids - DNA, RNA (tRNA, rRNA, mRNA). Ribosomes and the cell nucleus. Methods for determining the primary and secondary structure of nucleic acids (sequencing, hybridization).

Nucleic acids - phosphorus-containing biopolymers of living organisms that provide storage and transmission of hereditary information.

Nucleic acids are biopolymers. Their macromolecules consist of repeatedly repeating units, which are represented by nucleotides. And they are logically namedpolynucleotides. One of the main characteristics of nucleic acids is their nucleotide composition. The composition of a nucleotide (a structural unit of nucleic acids) includesthree components:

– nitrogenous base. May be pyrimidine or purine. Nucleic acids contain 4 different types of bases: two of them belong to the class of purines and two belong to the class of pyrimidines.

– rest of phosphoric acid.

– Monosaccharide - ribose or 2-deoxyribose. Sugar, which is part of the nucleotide, contains five carbon atoms, i.e. is a pentose. Depending on the type of pentose present in the nucleotide, two types of nucleic acids are distinguished- ribonucleic acids (RNA), which contain ribose, anddeoxyribonucleic acids (DNA), containing deoxyribose.

Nucleotide at its core, it is the phosphate ester of the nucleoside.The composition of the nucleoside There are two components: a monosaccharide (ribose or deoxyribose) and a nitrogenous base.

http :// sbio . info / page . php ? id =11

Nitrogenous bases – heterocyclicorganic compounds, derivativespyrimidineandpurine, included innucleic acids. For the abbreviated designation, capital Latin letters are used. The nitrogenous bases areadenine(A)guanine(G)cytosine(C) which are part of both DNA and RNA.Timin(T) is only part of DNA, anduracil(U) occurs only in RNA.

Remember!

What substances are called biological polymers?

These are polymers - high-molecular compounds that are part of living organisms. Proteins, some carbohydrates, nucleic acids.

What is the importance of carbohydrates in nature?

Fructose is widely distributed in nature - fruit sugar, which is much sweeter than other sugars. This monosaccharide imparts a sweet taste to plant fruits and honey. The most common disaccharide in nature - sucrose, or cane sugar - consists of glucose and fructose. It is obtained from sugar cane or sugar beets. Starch for plants and glycogen for animals and fungi are a reserve of nutrients and energy. Cellulose and chitin perform structural and protective functions in organisms. Cellulose, or fiber, forms the walls of plant cells. In terms of total mass, it ranks first on Earth among all organic compounds. In its structure, chitin is very close to cellulose, which forms the basis of the external skeleton of arthropods and is part of the cell wall of fungi.

Name the proteins you know. What functions do they perform?

Hemoglobin is a blood protein that transports gases in the blood

Myosin - muscle protein, muscle contraction

Collagen - protein of tendons, skin, elasticity, extensibility

Casein is a milk protein

Review questions and assignments

1. What chemical compounds are called carbohydrates?

This is an extensive group of natural organic compounds. In animal cells, carbohydrates make up no more than 5% of the dry mass, and in some plant cells (for example, tubers or potatoes), their content reaches 90% of the dry residue. Carbohydrates are divided into three main classes: monosaccharides, disaccharides and polysaccharides.

2. What are mono- and disaccharides? Give examples.

Monosaccharides are composed of monomers, low molecular weight organic substances. The monosaccharides ribose and deoxyribose are constituents of nucleic acids. The most common monosaccharide is glucose. Glucose is present in the cells of all organisms and is one of the main sources of energy for animals. If two monosaccharides combine in one molecule, such a compound is called a disaccharide. The most common disaccharide in nature is sucrose, or cane sugar.

3. What simple carbohydrate serves as a monomer of starch, glycogen, cellulose?

4. What organic compounds do proteins consist of?

Long protein chains are built from only 20 different types of amino acids that have a common structural plan, but differ from each other in the structure of the radical. Connecting, amino acid molecules form so-called peptide bonds. The two polypeptide chains that make up the pancreatic hormone insulin contain 21 and 30 amino acid residues. These are some of the shortest "words" in the protein "language". Myoglobin is a protein that binds oxygen in muscle tissue and consists of 153 amino acids. The collagen protein, which forms the basis of the collagen fibers of the connective tissue and ensures its strength, consists of three polypeptide chains, each of which contains about 1000 amino acid residues.

5. How are secondary and tertiary protein structures formed?

Twisting in the form of a spiral, the protein thread acquires a higher level of organization - a secondary structure. Finally, the polypeptide coils up to form a coil (globule). It is this tertiary structure of the protein that is its biologically active form, which has individual specificity. However, for a number of proteins, the tertiary structure is not final. The secondary structure is a polypeptide chain twisted into a helix. For a stronger interaction in the secondary structure, an intramolecular interaction occurs with the help of –S–S– sulfide bridges between the turns of the helix. This ensures the strength of this structure. The tertiary structure is a secondary spiral structure twisted into globules - compact lumps. These structures provide maximum strength and greater abundance in cells compared to other organic molecules.

6. Name the functions of proteins known to you. How can you explain the existing diversity of protein functions?

One of the main functions of proteins is enzymatic. Enzymes are proteins that catalyze chemical reactions in living organisms. An enzymatic reaction is a chemical reaction that takes place only in the presence of an enzyme. Without an enzyme, not one reaction occurs in living organisms. The work of enzymes is strictly specific, each enzyme has its own substrate, which it cleaves. The enzyme approaches its substrate like a "key to a lock". So, the urease enzyme regulates the breakdown of urea, the amylase enzyme regulates starch, and the protease enzymes regulate proteins. Therefore, for enzymes, the expression "specificity of action" is used.

Proteins also perform various other functions in organisms: structural, transport, motor, regulatory, protective, energy. The functions of proteins are quite numerous, since they underlie the variety of manifestations of life. It is a component of biological membranes, the transport of nutrients, such as hemoglobin, muscle function, hormonal function, body defense - the work of antigens and antibodies, and other important functions in the body.

7. What is protein denaturation? What can cause denaturation?

Denaturation is a violation of the tertiary spatial structure of protein molecules under the influence of various physical, chemical, mechanical and other factors. Physical factors are temperature, radiation. Chemical factors are the action of any chemicals on proteins: solvents, acids, alkalis, concentrated substances, and so on. Mechanical factors - shaking, pressure, stretching, twisting, etc.

Think! Remember!

1. Using the knowledge gained in the study of plant biology, explain why there are significantly more carbohydrates in plant organisms than in animals.

Since the basis of life - plant nutrition is photosynthesis, this is the process of formation of complex organic compounds of carbohydrates from simpler inorganic carbon dioxide and water. The main carbohydrate synthesized by plants for air nutrition is glucose, it can also be starch.

2. What diseases can lead to a violation of the conversion of carbohydrates in the human body?

The regulation of carbohydrate metabolism is mainly carried out by hormones and the central nervous system. Glucocorticosteroids (cortisone, hydrocortisone) slow down the rate of glucose transport into tissue cells, insulin accelerates it; adrenaline stimulates the process of sugar formation from glycogen in the liver. The cerebral cortex also plays a certain role in the regulation of carbohydrate metabolism, since psychogenic factors increase the formation of sugar in the liver and cause hyperglycemia.

The state of carbohydrate metabolism can be judged by the content of sugar in the blood (normally 70-120 mg%). With a sugar load, this value increases, but then quickly reaches the norm. Carbohydrate metabolism disorders occur in various diseases. So, with a lack of insulin, diabetes mellitus occurs.

A decrease in the activity of one of the enzymes of carbohydrate metabolism - muscle phosphorylase - leads to muscular dystrophy.

3. It is known that if there is no protein in the diet, even despite the sufficient calorie content of food, growth stops in animals, the composition of the blood changes and other pathological phenomena occur. What is the reason for such violations?

There are only 20 different types of amino acids in the body that have a common structural plan, but differ from each other in the structure of the radical, they form different protein molecules if you do not use proteins, for example, essential ones that cannot be formed in the body on their own, but must be consumed with food . Thus, if there are no proteins, many protein molecules cannot form within the body itself and pathological changes cannot occur. Growth is controlled by the growth of bone cells, the basis of any cell is protein; hemoglobin is the main protein in the blood, which ensures the transport of the main gases in the body (oxygen, carbon dioxide).

4. Explain the difficulties that arise during organ transplantation, based on the knowledge of the specificity of protein molecules in each organism.

Proteins are the genetic material, since they contain the structure of the DNA and RNA of the body. Thus, proteins have genetic characteristics in each organism, the information of genes is encrypted in them, this is the difficulty when transplanting from alien (unrelated) organisms, since they have different genes, and hence proteins.

General characteristics, structure and properties of carbohydrates.

Carbohydrates - These are polyhydric alcohols that contain, in addition to alcohol groups, an aldehyde or keto group.

Depending on the type of group in the composition of the molecule, aldoses and ketoses are distinguished.

Carbohydrates are very widespread in nature, especially in the plant world, where they make up 70-80% of the dry matter mass of cells. In the animal body, they account for only about 2% of body weight, but here their role is no less important.

Carbohydrates can be stored as starch in plants and glycogen in animals and humans. These reserves are used as needed. In the human body, carbohydrates are deposited mainly in the liver and muscles, which are its depot.

Among other components of the organism of higher animals and humans, carbohydrates account for 0.5% of body weight. However, carbohydrates are of great importance for the body. These substances, together with proteins in the form proteoglycans underlie connective tissue. Carbohydrate-containing proteins (glycoproteins and mucoproteins) are an integral part of the body's mucus (protective, enveloping functions), plasma transport proteins and immunologically active compounds (group-specific blood substances). Part of the carbohydrates acts as a "reserve fuel" for energy organisms.

Functions of carbohydrates:

• Energy - Carbohydrates are one of the main sources of energy for the body, providing at least 60% of energy costs. For the activity of the brain, blood cells, medulla of the kidneys, almost all the energy is supplied by the oxidation of glucose. With the complete breakdown of 1 g of carbohydrates, 4.1 kcal/mol(17.15 kJ/mol) energy.

• Plastic Carbohydrates or their derivatives are found in all cells of the body. They are part of the biological membranes and organelles of cells, participate in the formation of enzymes, nucleoproteins, etc. In plants, carbohydrates serve mainly as a supporting material.

• Protective - viscous secrets (mucus) secreted by various glands are rich in carbohydrates or their derivatives (mucopolysaccharides, etc.). They protect the inner walls of the hollow organs of the gastrointestinal tract, airways from mechanical and chemical influences, the penetration of pathogenic microbes.

• Regulatory - human food contains a significant amount of fiber, the rough structure of which causes mechanical irritation of the mucous membrane of the stomach and intestines, thus participating in the regulation of the act of peristalsis.

• specific - individual carbohydrates perform special functions in the body: they are involved in the conduction of nerve impulses, the formation of antibodies, ensuring the specificity of blood groups, etc.

The functional significance of carbohydrates determines the need to provide the body with these nutrients. The daily requirement for carbohydrates for a person is on average 400 - 450 g, taking into account age, type of work, gender and some other factors.

elemental composition. Carbohydrates are made up of the following chemical elements: carbon, hydrogen and oxygen. Most carbohydrates have the general formula C n (H 2 O ) n. Carbohydrates are compounds composed of carbon and water, which is the basis for their name. However, among carbohydrates there are substances that do not correspond to the above formula, for example, rhamnose C 6 H 12 O 5, etc. At the same time, substances are known whose composition corresponds to the general formula of carbohydrates, but by their properties they do not belong to them (acetic acid C 2 H 12 O 2). Therefore, the name "carbohydrates" is rather arbitrary and does not always correspond to the chemical structure of these substances.

Carbohydrates- These are organic substances that are aldehydes or ketones of polyhydric alcohols.

Monosaccharides

Monosaccharides - These are polyhydric aliphatic alcohols that contain in their composition an aldehyde group (aldoses) or a keto group (ketoses).

Monosaccharides are solid, crystalline substances, soluble in water and sweet in taste. Under certain conditions, they are easily oxidized, as a result of which aldehyde alcohols are converted into acids, as a result of which aldehyde alcohols are converted into acids, and upon reduction, into the corresponding alcohols.

Chemical properties of monosaccharides :

• Oxidation to mono-, dicarboxylic and glycuronic acids;

• Recovery to alcohols;

• Esters formation;

• The formation of glycosides;

• Fermentation: alcohol, lactic acid, citric acid and butyric.

Monosaccharides that cannot be hydrolyzed into simpler sugars. The type of monosaccharide depends on the length of the hydrocarbon chain. Depending on the number of carbon atoms, they are divided into trioses, tetroses, pentoses, hexoses.

Trioses: glyceraldehyde and dihydroxyacetone, they are intermediate products of glucose breakdown and are involved in the synthesis of fats. both trioses can be obtained from the alcohol glycerol by its dehydrogenation or hydrogenation.

Tetroses: erythrosis - actively involved in metabolic processes.

Pentoses: ribose and deoxyribose are components of nucleic acids, ribulose and xylulose are intermediate products of glucose oxidation.

Hexoses: they are most widely represented in the animal and plant world and play an important role in metabolic processes. These include glucose, galactose, fructose, etc.

Glucose (grape sugar) . It is the main carbohydrate in plants and animals. The important role of glucose is explained by the fact that it is the main source of energy, forms the basis of many oligo- and polysaccharides, and is involved in maintaining osmotic pressure. The transport of glucose into cells is regulated in many tissues by the pancreatic hormone insulin. In the cell, in the course of multi-stage chemical reactions, glucose is converted into other substances (the intermediate products formed during the breakdown of glucose are used to synthesize amino acids and fats), which are ultimately oxidized to carbon dioxide and water, while releasing energy used by the body to ensure life. The level of glucose in the blood is usually judged on the state of carbohydrate metabolism in the body. With a decrease in the level of glucose in the blood or its high concentration and the impossibility of using it, as happens with diabetes, drowsiness occurs, loss of consciousness (hypoglycemic coma) may occur. The rate of glucose entry into the brain and liver tissues does not depend on insulin and is determined only by its concentration in the blood. These tissues are called insulin-independent. Without the presence of insulin, glucose will not enter the cell and will not be used as fuel..

Galactose. A spatial isomer of glucose, characterized by the location of the OH group at the fourth carbon atom. It is part of lactose, some polysaccharides and glycolipids. Galactose can isomerize to glucose (in the liver, mammary gland).

Fructose (fruit sugar). It is found in large quantities in plants, especially in fruits. A lot of it in fruits, sugar beets, honey. Easily isomerizes to glucose. The pathway of fructose breakdown is shorter and more energetically favorable than that of glucose. Unlike glucose, it can penetrate from the blood into tissue cells without the participation of insulin. For this reason, fructose is recommended as the safest carbohydrate source for diabetics. Part of the fructose gets into the liver cells, which turn it into a more versatile "fuel" - glucose, so fructose is also able to increase blood sugar levels, although to a much lesser extent than other simple sugars.

According to the chemical structure, glucose and galactose are aldehyde alcohols, fructose is a keto alcohol. Differences in the structure of glucose and fructose characterize both the differences and some of their properties. Glucose restores metals from their oxides, fructose does not have this property. Fructose is approximately 2 times more slowly absorbed from the intestine compared to glucose.

When the sixth carbon atom in the hexose molecule is oxidized, hexuronic (uronic) acids : from glucose - glucuronic, from galactose - galacturonic.

Glucuronic acid takes an active part in metabolic processes in the body, for example, in the neutralization of toxic products, is part of mucopolysaccharides, etc. Its function is that it combines in the organ with substances that are poorly soluble in water. As a result, the binder becomes water soluble and is excreted in the urine. This route of excretion is especially important for water soluble steroid hormones, their degradation products, and also for the isolation of degradation products of medicinal substances. Without interaction with glucuronic acid, further breakdown and excretion of bile pigments from the body are disrupted.

Monosaccharides can have an amino group .

When the hexose molecule of the OH group of the second carbon atom is replaced by an amino group, amino sugars - hexosamines are formed: glucosamine is synthesized from glucose, galactosamine is synthesized from galactose, which are part of the cell membranes and muco- polysaccharides both in free form and in combination with acetic acid.

Amino sugars called monosaccharides, whichplace of the OH group carry an amino group (- N H 2).

Amino sugars are the most important constituent glycosaminoglycans.

Monosaccharides form esters . OH group of a monosaccharide molecule; like any alcohol group, can interact with acid. In the intermediate exchangesugar esters are of great importance. To enableto be metabolized, sugar must becomephosphoric ether. In this case, the terminal carbon atoms are phosphorylated. For hexoses, these are C-1 and C-6, for pentoses, C-1 and C-5, etc. PainMore than two OH groups are not subject to phosphorylation. Therefore, the main role is played by mono- and diphosphates of sugars. In the title phosphorus ester usually indicate the position of the ester bond.

Oligosaccharides

Oligosaccharides have two or more monosaccharide. They are found in cells and biological fluids, both in free form and in combination with proteins. Disaccharides are of great importance for the body: sucrose, maltose, lactose, etc. These carbohydrates perform an energy function. It is assumed that, being part of the cells, they participate in the process of "recognition" of cells.

sucrose(beet or cane sugar). Consists of glucose and fructose molecules. She is is a vegetable product and the most important component nutritive food, has the sweetest taste compared to other disaccharides and glucose.

The content of sucrose in sugar is 95%. Sugar is rapidly broken down in the gastrointestinal tract, glucose and fructose are absorbed into the blood and serve as a source of energy and the most important precursor of glycogen and fats. It is often referred to as an "empty calorie carrier" since sugar is a pure carbohydrate and does not contain other nutrients such as vitamins, mineral salts, for example.

Lactose(milk sugar) consists of glucose and galactose, synthesized in the mammary glands during lactation. In the gastrointestinal tract, it is broken down by the action of the enzyme lactase. Deficiency of this enzyme in some people leads to milk intolerance. Deficiency of this enzyme is observed in approximately 40% of the adult population. Undigested lactose serves as a good nutrient for the intestinal microflora. At the same time, abundant gas formation is possible, the stomach "swells". In fermented milk products, most of the lactose is fermented to lactic acid, so people with lactase deficiency can tolerate fermented milk products without unpleasant consequences. In addition, lactic acid bacteria in fermented milk products inhibit the activity of the intestinal microflora and reduce the adverse effects of lactose.

Maltose consists of two glucose molecules and is the main structural component of starch and glycogen.

Polysaccharides

Polysaccharides - high molecular weight carbohydrates, composed of a large number of monosaccharides. They have hydrophilic properties and form colloidal solutions when dissolved in water.

Polysaccharides are divided into homo- and gete roposaccharides.

Homopolysaccharides. Contains monosaccharides only one kind. Gak, starch and glycogen fasting swarms only from glucose molecules, inulin - fructose. Homopolysaccharides are highly branched structure and are a mixture of two polymers - amylose and amylopectin. Amylose consists of 60-300 glucose residues connected in chain via an oxygen bridge, formed between the first carbon atom of one molecule and the fourth carbon atom of another (bond 1,4).

amylose soluble in hot water and gives a blue color with iodine.

Amylopectin - a branched polymer consisting of both straight chains (bond 1.4) and branched chains, which are formed due to bonds between the first carbon atom of one glucose molecule and the sixth carbon atom of another with the help of an oxygen bridge (bond 1.6).

Representatives of homopolysaccharides are starch, fiber and glycogen.

Starch(plant polysaccharide)- consists of several thousand glucose residues, 10-20% of which is represented by amylose, and 80-90% by amylopectin. Starch is insoluble in cold water, but in hot water it forms a colloidal solution, commonly called starch paste. Starch accounts for up to 80% of carbohydrates consumed with food. The source of starch is vegetable products, mainly cereals: cereals, flour, bread, and potatoes. Cereals contain the most starch (from 60% in buckwheat (kernel) and up to 70% in rice).

Cellulose, or cellulose,- the most common plant carbohydrate on earth, formed in an amount of approximately 50 kg per inhabitant of the Earth. Cellulose is a linear polysaccharide consisting of 1000 or more glucose residues. In the body, fiber is involved in the activation of the motility of the stomach and intestines, stimulates the secretion of digestive juices, and creates a feeling of satiety.

Glycogen(animal starch) is the main storage carbohydrate of the human body. It consists of approximately 30,000 glucose residues, which form a branched structure. In the most significant amount, glycogen accumulates in the liver and muscle tissue, including the heart muscle. The function of muscle glycogen is that it is a readily available source of glucose used in energy processes in the muscle itself. Liver glycogen is used to maintain physiological blood glucose concentrations, primarily between meals. After 12-18 hours after a meal, the store of glycogen in the liver is almost completely depleted. The content of muscle glycogen decreases markedly only after prolonged and strenuous physical work. With a lack of glucose, it quickly breaks down and restores its normal level in the blood. In cells, glycogen is associated with cytoplasmic protein and partially with intracellular membranes.

Heteropolysaccharides (glycosaminoglycans or mucopolysaccharides) (the prefix "muco-" indicates that they were first obtained from mucin). They consist of various types of monosaccharides (glucose, galactose) and their derivatives (amino sugars, hexuronic acids). Other substances were also found in their composition: nitrogenous bases, organic acids and some others.

Glycosaminoglycans are jelly-like, sticky substances. They perform various functions, including structural, protective, regulatory, etc. Glycosaminoglycans, for example, make up the bulk of the intercellular substance of tissues, are part of the skin, cartilage, synovial fluid, and the vitreous body of the eye. In the body, they are found in combination with proteins (proteoglycans and glycoproteins) and fats (glycolipids), in which polysaccharides account for the bulk of the molecule (up to 90% or more). The following are important for the body.

Hyaluronic acid- the main part of the intercellular substance, a kind of "biological cement" that connects the cells, filling the entire intercellular space. It also acts as a biological filter that traps microbes and prevents their penetration into the cell, and is involved in the exchange of water in the body.

It should be noted that hyaluronic acid decomposes under the action of a specific enzyme hyaluronidase. In this case, the structure of the intercellular substance is disturbed, “cracks” are formed in its composition, which leads to an increase in its permeability to water and other substances. This is important in the process of fertilization of the egg by spermatozoa, which are rich in this enzyme. Some bacteria also contain hyaluronidase, which greatly facilitates their penetration into the cell.

X ondroitin sulfates- chondroitin sulfuric acids, serve as structural components of cartilage, ligaments, heart valves, umbilical cord, etc. They contribute to the deposition of calcium in the bones.

Heparin is formed in mast cells, which are found in the lungs, liver and other organs, and is released by them into the blood and intercellular environment. In the blood, it binds to proteins and prevents blood clotting, acting as an anticoagulant. In addition, heparin has an anti-inflammatory effect, affects the exchange of potassium and sodium, and performs an antihypoxic function.

A special group of glycosaminoglycans are compounds containing neuraminic acids and carbohydrate derivatives. Compounds of neuraminic acid with acetic acid are called opal acids. They are found in cell membranes, saliva and other biological fluids.

Carbohydrates are organic compounds made up of carbon and oxygen. There are simple carbohydrates, or monosaccharides, such as glucose, and complex, or polysaccharides, which are divided into lower, containing few simple carbohydrate residues, such as disaccharides, and higher, having very large molecules of many simple carbohydrate residues. In animal organisms, the carbohydrate content is about 2% dry weight.

The average daily requirement of an adult in carbohydrates is 500 g, and with intensive muscular work - 700-1000 g.

The amount of carbohydrates per day should be 60% by weight, and 56% by weight of the total amount of food.

Glucose is contained in the blood, in which its amount is maintained at a constant level (0.1-0.12%). After absorption in the intestine, monosaccharides are delivered by the blood to where synthesis of glycogen from monosaccharides, which is part of the cytoplasm, takes place. Glycogen stores are stored mainly in the muscles and in the liver.

The total amount of glycogen in the body of a person weighing 70 kg is approximately 375 g, of which 245 g is contained in the muscles, 110 g (up to 150 g) in the liver, 20 g in the blood and other body fluids. In the body of a trained person, glycogen is 40 -50% more than untrained.

Carbohydrates are the main source of energy for the life and work of the body.

In the body, under oxygen-free (anaerobic) conditions, carbohydrates break down into lactic acid, releasing energy. This process is called glycolysis. With the participation of oxygen (aerobic conditions), they are split into carbon dioxide and, while releasing much more energy. Of great biological importance is the anaerobic breakdown of carbohydrates with the participation of phosphoric acid - phosphorylation.

Phosphorylation of glucose occurs in the liver with the participation of enzymes. The source of glucose can be amino acids and fats. In the liver, from pre-phosphorylated glucose, huge polysaccharide molecules, glycogen, are formed. The amount of glycogen in the human liver depends on the nature of nutrition and muscle activity. With the participation of other enzymes in the liver, glycogen is broken down to glucose - sugar formation. The breakdown of glycogen in the liver and skeletal muscles during fasting and muscular work is accompanied by simultaneous synthesis of glycogen. Glucose, formed in the liver, enters and is delivered with it to all cells and tissues.

Only a small part of proteins and fats releases energy in the process of desmolytic breakdown and, therefore, serves as a direct source of energy. A significant part of the proteins and fats, even before complete disintegration, is first converted into carbohydrates in the muscles. In addition, from the digestive canal, the products of hydrolysis of proteins and fats enter the liver, where amino acids and fats are converted into glucose. This process is referred to as gluconeogenesis. The main source of glucose formation in the liver is glycogen, a much smaller part of glucose is obtained by gluconeogenesis, during which the formation of ketone bodies is delayed. Thus, carbohydrate metabolism significantly affects the metabolism, and water.

When glucose consumption by working muscles increases 5-8 times, glycogen is formed in the liver from fats and proteins.

Unlike proteins and fats, carbohydrates break down easily, so they are quickly mobilized by the body at high energy costs (muscle work, emotions of pain, fear, anger, etc.). The breakdown of carbohydrates keeps the body stable and is the main source of energy for the muscles. Carbohydrates are essential for the normal functioning of the nervous system. A decrease in blood sugar leads to a drop in body temperature, weakness and fatigue of muscles, and disorders of nervous activity.

In tissues, only a very small part of the glucose delivered by the blood is used with the release of energy. The main source of carbohydrate metabolism in tissues is glycogen, previously synthesized from glucose.

During the work of the muscles - the main consumers of carbohydrates - the glycogen reserves in them are used, and only after these reserves are completely used up, the direct use of glucose delivered to the muscles by the blood begins. This consumes glucose, formed from glycogen stores in the liver. After work, the muscles renew their supply of glycogen, synthesizing it from blood glucose, and the liver - due to absorbed monosaccharides in the digestive tract and the breakdown of proteins and fats.

For example, with an increase in blood glucose above 0.15-0.16% due to its abundant content in food, which is referred to as food hyperglycemia, it is excreted from the body with urine - glycosuria.

On the other hand, even with prolonged fasting, the level of glucose in the blood does not decrease, since glucose enters the blood from tissues during the breakdown of glycogen in them.

Brief description of the composition, structure and ecological role of carbohydrates

Carbohydrates are organic substances consisting of carbon, hydrogen and oxygen, having the general formula C n (H 2 O) m (for the vast majority of these substances).

The value of n is either equal to m (for monosaccharides), or greater than it (for other classes of carbohydrates). The above general formula does not correspond to deoxyribose.

Carbohydrates are divided into monosaccharides, di (oligo) saccharides and polysaccharides. Below is a brief description of the individual representatives of each class of carbohydrates.

Brief description of monosaccharides

Monosaccharides are carbohydrates whose general formula is C n (H 2 O) n (the exception is deoxyribose).

Classifications of monosaccharides

Monosaccharides are a rather extensive and complex group of compounds, so they have a complex classification according to various criteria:

1) according to the number of carbon contained in a monosaccharide molecule, tetroses, pentoses, hexoses, heptoses are distinguished; Pentoses and hexoses are of the greatest practical importance;

2) according to functional groups, monosaccharides are divided into ketoses and aldoses;

3) according to the number of atoms contained in the cyclic monosaccharide molecule, pyranoses (contain 6 atoms) and furanoses (contain 5 atoms) are distinguished;

4) based on the spatial arrangement of the "glucosidic" hydroxide (this hydroxide is obtained by attaching a hydrogen atom to the oxygen of the carbonyl group), monosaccharides are divided into alpha and beta forms. Let's take a look at some of the most important monosaccharides of greatest biological and ecological importance in nature.

Brief description of pentoses

Pentoses are monosaccharides, the molecule of which contains 5 carbon atoms. These substances can be both open-chain and cyclic, aldoses and ketoses, alpha and beta compounds. Among them, ribose and deoxyribose are of the most practical importance.

Ribose formula in general form C 5 H 10 O 5. Ribose is one of the substances from which ribonucleotides are synthesized, from which various ribonucleic acids (RNA) are subsequently obtained. Therefore, the furanose (5-membered) alpha form of ribose is of greatest importance (in formulas, RNA is depicted in the form of a regular pentagon).

The formula of deoxyribose in general form is C 5 H 10 O 4. Deoxyribose is one of the substances from which deoxyribonucleotides are synthesized in organisms; the latter are the starting materials for the synthesis of deoxyribonucleic acids (DNA). Therefore, the cyclic alpha form of deoxyribose, which lacks a hydroxide at the second carbon atom in the cycle, is of greatest importance.

The open-chain forms of ribose and deoxyribose are aldoses, that is, they contain 4 (3) hydroxide groups and one aldehyde group. With the complete breakdown of nucleic acids, ribose and deoxyribose are oxidized to carbon dioxide and water; This process is accompanied by the release of energy.

Brief description of hexoses

Hexoses are monosaccharides whose molecules contain six carbon atoms. The general formula of hexoses is C 6 (H 2 O) 6 or C 6 H 12 O 6. All varieties of hexoses are isomers corresponding to the above formula. Among hexoses, there are ketoses, and aldoses, and alpha and beta forms of molecules, open-chain and cyclic forms, pyranose and furanose cyclic forms of molecules. Of greatest importance in nature are glucose and fructose, which are briefly discussed below.

1. Glucose. Like any hexose, it has the general formula C 6 H 12 O 6 . It belongs to aldoses, that is, it contains an aldehyde functional group and 5 hydroxide groups (characteristic of alcohols), therefore, glucose is a polyhydric aldehyde alcohol (these groups are contained in an open-chain form, the aldehyde group is absent in the cyclic form, since it turns into a hydroxide a group called "glucosidic hydroxide"). The cyclic form can be either five-membered (furanose) or six-membered (pyranose). The most important in nature is the pyranose form of the glucose molecule. The cyclic pyranose and furanose forms can be either alpha or beta, depending on the location of the glucosidic hydroxide relative to other hydroxide groups in the molecule.

According to its physical properties, glucose is a white crystalline solid with a sweet taste (the intensity of this taste is similar to sucrose), highly soluble in water and capable of forming supersaturated solutions (“syrups”). Since the glucose molecule contains asymmetric carbon atoms (i.e., atoms connected to four different radicals), glucose solutions have optical activity, therefore, D-glucose and L-glucose are distinguished, which have different biological activity.

From a biological point of view, the ability of glucose to easily oxidize according to the scheme is most important:

С 6 Н 12 O 6 (glucose) → (intermediate stages) → 6СO 2 + 6Н 2 O.

Glucose is a biologically important compound, since it is used by the body through its oxidation as a universal nutrient and an easily accessible source of energy.

2. Fructose. This is ketosis, its general formula is C 6 H 12 O 6, that is, it is an isomer of glucose, it is characterized by open-chain and cyclic forms. The most important is beta-B-fructofuranose or beta-fructose for short. Sucrose is made from beta-fructose and alpha-glucose. Under certain conditions, fructose is able to turn into glucose during the isomerization reaction. Fructose is similar in physical properties to glucose, but sweeter than it.

Brief description of disaccharides

Disaccharides are products of the reaction of dicondensation of the same or different molecules of monosaccharides.

Disaccharides are one of the varieties of oligosaccharides (a small number of monosaccharide molecules (same or different) are involved in the formation of their molecules.

The most important representative of disaccharides is sucrose (beet or cane sugar). Sucrose is a product of the interaction of alpha-D-glucopyranose (alpha-glucose) and beta-D-fructofuranose (beta-fructose). Its general formula is C 12 H 22 O 11. Sucrose is one of the many isomers of disaccharides.

This is a white crystalline substance that exists in various states: coarse-grained ("sugar heads"), fine-crystalline (granulated sugar), amorphous (powdered sugar). It dissolves well in water, especially in hot water (compared to hot water, the solubility of sucrose in cold water is relatively low), so sucrose is able to form "supersaturated solutions" - syrups that can "candied", i.e. fine crystalline suspensions are formed. Concentrated solutions of sucrose are able to form special glassy systems - caramel, which is used by humans to obtain certain varieties of sweets. Sucrose is a sweet substance, but the intensity of the sweet taste is less than that of fructose.

The most important chemical property of sucrose is its ability to hydrolyze, in which alpha-glucose and beta-fructose are formed, which enter into carbohydrate metabolism reactions.

For humans, sucrose is one of the most important food products, as it is a source of glucose. However, excessive consumption of sucrose is harmful, because it leads to a violation of carbohydrate metabolism, which is accompanied by the appearance of diseases: diabetes, dental diseases, obesity.

General characteristics of polysaccharides

Polysaccharides are called natural polymers, which are products of the reaction of polycondensation of monosaccharides. As monomers for the formation of polysaccharides, pentoses, hexoses and other monosaccharides can be used. In practical terms, the hexose polycondensation products are most important. Polysaccharides are also known, the molecules of which contain nitrogen atoms, such as chitin.

Hexose-based polysaccharides have the general formula (C 6 H 10 O 5)n. They are insoluble in water, while some of them are able to form colloidal solutions. The most important of these polysaccharides are various varieties of vegetable and animal starches (the latter are called glycogens), as well as varieties of cellulose (fiber).

General characteristics of the properties and ecological role of starch

Starch is a polysaccharide that is a product of the polycondensation reaction of alpha-glucose (alpha-D-glucopyranose). By origin, vegetable and animal starches are distinguished. Animal starches are called glycogens. Although, in general, starch molecules have a common structure, the same composition, but the individual properties of starch obtained from different plants are different. So, potato starch is different from corn starch, etc. But all varieties of starch have common properties. These are solid, white, finely crystalline or amorphous substances, “brittle” to the touch, insoluble in water, but in hot water they are able to form colloidal solutions that retain their stability even when cooled. Starch forms both sols (for example, liquid jelly) and gels (for example, jelly prepared with a high starch content is a gelatinous mass that can be cut with a knife).

The ability of starch to form colloidal solutions is associated with the globularity of its molecules (the molecule is, as it were, rolled into a ball). Upon contact with warm or hot water, water molecules penetrate between the turns of starch molecules, the molecule volume increases and the density of the substance decreases, which leads to the transition of starch molecules to a mobile state characteristic of colloidal systems. The general formula of starch is: (C 6 H 10 O 5) n, the molecules of this substance have two varieties, one of which is called amylose (there are no side chains in this molecule), and the other is amylopectin (the molecules have side chains in which the connection occurs through 1 - 6 carbon atoms by an oxygen bridge).

The most important chemical property that determines the biological and ecological role of starch is its ability to undergo hydrolysis, ultimately forming either the disaccharide maltose or alpha-glucose (this is the final product of starch hydrolysis):

(C 6 H 10 O 5) n + nH 2 O → nC 6 H 12 O 6 (alpha-glucose).

The process takes place in organisms under the action of a whole group of enzymes. Due to this process, the body is enriched with glucose - the most important nutrient compound.

A qualitative reaction to starch is its interaction with iodine, in which a red-violet color occurs. This reaction is used to detect starch in various systems.

The biological and ecological role of starch is quite large. This is one of the most important storage compounds in plant organisms, for example, in plants of the cereal family. For animals, starch is the most important trophic substance.

Brief description of the properties and ecological and biological role of cellulose (fiber)

Cellulose (fiber) is a polysaccharide, which is a product of the polycondensation reaction of beta-glucose (beta-D-glucopyranose). Its general formula is (C 6 H 10 O 5) n. Unlike starch, cellulose molecules are strictly linear and have a fibrillar (“filamentous”) structure. The difference in the structures of starch and cellulose molecules explains the difference in their biological and ecological roles. Cellulose is neither a reserve nor a trophic substance, since it is not able to be digested by most organisms (the exception is some types of bacteria that can hydrolyze cellulose and assimilate beta-glucose). Cellulose is not capable of forming colloidal solutions, but it can form mechanically strong filamentous structures that provide protection for individual cell organelles and the mechanical strength of various plant tissues. Like starch, cellulose is hydrolyzed under certain conditions, and the end product of its hydrolysis is beta-glucose (beta-D-glucopyranose). In nature, the role of this process is relatively small (but it allows the biosphere to “assimilate” cellulose).

(C 6 H 10 O 5) n (fiber) + n (H 2 O) → n (C 6 H 12 O 6) (beta-glucose or beta-D-glucopyranose) (with incomplete hydrolysis of fiber, the formation of a soluble disaccharide is possible - cellobiose).

Under natural conditions, fiber (after the death of plants) undergoes decomposition, as a result of which the formation of various compounds is possible. Due to this process, humus (an organic component of the soil), various types of coal are formed (oil and coal are formed from the dead remains of various animal and plant organisms in the absence, i.e., under anaerobic conditions, the whole complex of organic substances is involved in their formation, including carbohydrates).

The ecological and biological role of fiber is that it is: a) protective; b) mechanical; c) a formative compound (for some bacteria it performs a trophic function). The dead remains of plant organisms are a substrate for some organisms - insects, fungi, various microorganisms.

Brief description of the ecological and biological role of carbohydrates

Summarizing the above material related to the characteristics of carbohydrates, we can draw the following conclusions about their ecological and biological role.

1. They perform a building function both in cells and in the body as a whole due to the fact that they are part of the structures that form cells and tissues (this is especially true for plants and fungi), for example, cell membranes, various membranes, etc. in addition, carbohydrates are involved in the formation of biologically necessary substances that form a number of structures, for example, in the formation of nucleic acids that form the basis of chromosomes; carbohydrates are part of complex proteins - glycoproteins, which are of particular importance in the formation of cellular structures and intercellular substance.

2. The most important function of carbohydrates is the trophic function, which consists in the fact that many of them are food products of heterotrophic organisms (glucose, fructose, starch, sucrose, maltose, lactose, etc.). These substances, in combination with other compounds, form food products used by humans (various cereals; fruits and seeds of individual plants, which include carbohydrates in their composition, are food for birds, and monosaccharides, entering into a cycle of various transformations, contribute to the formation of both their own carbohydrates, characteristic for a given organism, and other organo-biochemical compounds (fats, amino acids (but not their proteins), nucleic acids, etc.).

3. Carbohydrates are also characterized by an energy function, which consists in the fact that monosaccharides (in particular glucose) are easily oxidized in organisms (the end product of oxidation is CO 2 and H 2 O), while a large amount of energy is released, accompanied by the synthesis of ATP.

4. They also have a protective function, consisting in the fact that structures (and certain organelles in the cell) arise from carbohydrates that protect either the cell or the body as a whole from various damages, including mechanical ones (for example, chitinous covers of insects that form external skeleton, cell membranes of plants and many fungi, including cellulose, etc.).

5. An important role is played by the mechanical and shaping functions of carbohydrates, which are the ability of structures formed either by carbohydrates or in combination with other compounds to give the body a certain shape and make them mechanically strong; thus, the cell membranes of the mechanical tissue and vessels of the xylem create the frame (internal skeleton) of woody, shrubby and herbaceous plants, the external skeleton of insects is formed by chitin, etc.

Brief description of carbohydrate metabolism in a heterotrophic organism (on the example of a human body)

An important role in understanding metabolic processes is played by knowledge of the transformations that carbohydrates undergo in heterotrophic organisms. In the human body, this process is characterized by the following schematic description.

Carbohydrates in food enter the body through the mouth. Monosaccharides in the digestive system practically do not undergo transformations, disaccharides are hydrolyzed to monosaccharides, and polysaccharides undergo quite significant transformations (this applies to those polysaccharides that are consumed by the body, and carbohydrates that are not food substances, for example, cellulose, some pectins, are removed excreted in the feces).

In the oral cavity, food is crushed and homogenized (becomes more homogeneous than before entering it). Food is affected by saliva secreted by the salivary glands. It contains ptyalin and has an alkaline reaction of the environment, due to which the primary hydrolysis of polysaccharides begins, leading to the formation of oligosaccharides (carbohydrates with a small n value).

Part of the starch can even turn into disaccharides, which can be seen with prolonged chewing of bread (sour black bread becomes sweet).

Chewed food, richly treated with saliva and crushed by teeth, enters the stomach through the esophagus in the form of a food lump, where it is exposed to gastric juice with an acid reaction of the medium containing enzymes that act on proteins and nucleic acids. Almost nothing happens in the stomach with carbohydrates.

Then the food gruel enters the first section of the intestine (small intestine), beginning with the duodenum. It receives pancreatic juice (pancreatic secretion), which contains a complex of enzymes that promote the digestion of carbohydrates. Carbohydrates are converted into monosaccharides, which are water soluble and absorbable. Dietary carbohydrates are finally digested in the small intestine, and in the part where the villi are contained, they are absorbed into the bloodstream and enter the circulatory system.

With the blood flow, monosaccharides are carried to various tissues and cells of the body, but first all the blood passes through the liver (where it is cleared of harmful metabolic products). In the blood, monosaccharides are present mainly in the form of alpha-glucose (but other hexose isomers, such as fructose, are also possible).

If blood glucose is less than normal, then part of the glycogen contained in the liver is hydrolyzed to glucose. An excess of carbohydrates characterizes a serious human disease - diabetes.

From the blood, monosaccharides enter the cells, where most of them are spent on oxidation (in mitochondria), in which ATP is synthesized, which contains energy in a “convenient” form for the body. ATP is spent on various processes that require energy (the synthesis of substances needed by the body, the implementation of physiological and other processes).

Part of the carbohydrates in food is used to synthesize the carbohydrates of a given organism, which are required for the formation of cell structures, or compounds necessary for the formation of substances of other classes of compounds (this is how fats, nucleic acids, etc. can be obtained from carbohydrates). The ability of carbohydrates to turn into fats is one of the causes of obesity - a disease that entails a complex of other diseases.

Therefore, the consumption of excess carbohydrates is harmful to the human body, which must be taken into account when organizing a balanced diet.

In plant organisms that are autotrophs, carbohydrate metabolism is somewhat different. Carbohydrates (monosugar) are synthesized by the body itself from carbon dioxide and water using solar energy. Di-, oligo- and polysaccharides are synthesized from monosaccharides. Part of the monosaccharides is included in the synthesis of nucleic acids. Plant organisms use a certain amount of monosaccharides (glucose) in the processes of respiration for oxidation, in which (as in heterotrophic organisms) ATP is synthesized.

Plan:

1. Definition of the concept: carbohydrates. Classification.

2. Composition, physical and chemical properties of carbohydrates.

3. Distribution in nature. Receipt. Application.

Carbohydrates - organic compounds containing carbonyl and hydroxyl groups of atoms, having the general formula C n (H 2 O) m, (where n and m> 3).

Carbohydrates Substances of paramount biochemical importance are widely distributed in wildlife and play an important role in human life. The name carbohydrates arose on the basis of data from the analysis of the first known representatives of this group of compounds. The substances of this group consist of carbon, hydrogen and oxygen, and the ratio of the numbers of hydrogen and oxygen atoms in them is the same as in water, i.e. There is one oxygen atom for every 2 hydrogen atoms. In the last century they were considered as carbon hydrates. Hence the Russian name carbohydrates, proposed in 1844. K. Schmidt. The general formula for carbohydrates, according to what has been said, is C m H 2p O p. When taking “n” out of brackets, the formula C m (H 2 O) n is obtained, which very clearly reflects the name “carbohydrate”. The study of carbohydrates has shown that there are compounds that, according to all properties, must be attributed to the group of carbohydrates, although they have a composition that does not exactly correspond to the formula C m H 2p O p. Nevertheless, the old name "carbohydrates" has survived to this day, although along with with this name, a newer name, glycides, is sometimes used to refer to the group of substances under consideration.

Carbohydrates can be divided into three groups : 1) Monosaccharides - carbohydrates that can be hydrolyzed to form simpler carbohydrates. This group includes hexoses (glucose and fructose), as well as pentose (ribose). 2) Oligosaccharides - condensation products of several monosaccharides (for example, sucrose). 3) Polysaccharides - polymeric compounds containing a large number of monosaccharide molecules.

Monosaccharides. Monosaccharides are heterofunctional compounds. Their molecules simultaneously contain both carbonyl (aldehyde or ketone) and several hydroxyl groups, i.e. monosaccharides are polyhydroxycarbonyl compounds - polyhydroxyaldehydes and polyhydroxyketones. Depending on this, monosaccharides are divided into aldoses (the monosaccharide contains an aldehyde group) and ketoses (the keto group is contained). For example, glucose is an aldose and fructose is a ketose.

Receipt. Glucose is predominantly found in free form in nature. It is also a structural unit of many polysaccharides. Other monosaccharides in the free state are rare and are mainly known as components of oligo- and polysaccharides. In nature, glucose is obtained as a result of photosynthesis reaction: 6CO 2 + 6H 2 O ® C 6 H 12 O 6 (glucose) + 6O 2 For the first time, glucose was obtained in 1811 by the Russian chemist G.E. Kirchhoff during the hydrolysis of starch. Later, the synthesis of monosaccharides from formaldehyde in an alkaline medium was proposed by A.M. Butlerov