What type of carbohydrate is glucose? Glucose is the most important simple carbohydrate

The most important class organic compounds, found in nature. The best known are glucose, starch, cellulose, glycogen, heparin, etc., which play an important role in the life processes of humans and animals.

Carbohydrates are a group of natural substances belonging to polyoxycarbonyl compounds, as well as substances similar to them in structure.

In the nomenclature of carbohydrates, trivial names are widely used: ribose, fructose, lactose, galactose, glucose, etc.

Their classification is based on their ability to hydrolyze:

Monosaccharides (MS) Oligosaccharides (OS) Polysaccharides (PS)

(simple sugars) (low molecular weight) (high molecular weight)

not hydrolyzed hydrolyzed hydrolyzed

pentoses, hexoses sucrose cellulose

(aldoses, ketoses) maltose, lactose starch, glycogen

The most important hydrocarbons: from pentoses - ribose, deoxyribose, xylose;

from hexoses - glucose, fructose, galactose, mannose.

Monosaccharides (MS)

Isomerism

The presence of several asymmetric carbon atoms determines the existence large number optical isomers. These are enantiomers (mirror isomers, antipodes), diastereomers, and epimers. You are familiar with the concept of enantiomers and diastereomers.

Epimers are diastereomers that differ from each other in configuration only one asymmetric atom C. All isomers, except mirror ones, differ from each other in properties and have their own name:

Xylose Ribose

Whether an MS belongs to the D- or L-row is determined by the configuration of the latter (farthest from
gr.) chiral atom C by analogy with the standard - glyceraldehyde:

Natural sugars - D-sugars, L-sugars enter the body from the outside.

The newly formed hydroxyl is called hemiacetal or glycosidic and can be differently located in space relative to the ring, forming another asymmetric carbon atom in the cyclic form. If the hemiacetal hydroxyl is located on the same side as the hydroxyl that determines whether it belongs to the D- or L-series, then such an isomer is called an -isomer, and the other is called a -isomer. Stereoisomers that differ from each other in location only hemiacetal hydroxyl in space are called anomers. (-top, -bottom - follow our whim! For memorization.)

The process of formation of cyclic forms is called anomerization. The cyclic and open forms easily transform into each other and are in dynamic equilibrium. At room temperature, cyclic predominates; when heated, open predominates. The pyranose form is more typical for aldohexoses, while the furanose form is more typical for pentoses and fructoses. All this is reflected in the name, for example, -D-glucopyranose. In the crystalline state, the cyclic forms are fixed and the - and -isomers are stable and can be separated from each other. When dissolved, some of the molecules go into an open form, and from it all types of cyclic forms are formed. Since each shape has its own angle of rotation of the beam of polarized light, the angle of rotation will constantly change until dynamic equilibrium is established. The change in time of the angle of rotation of the plane of polarization of light of a freshly prepared carbohydrate solution is called mutarotation.

Currently, instead of the cyclic Colley-Tollens formulas, the promising Haworth formulas are more often used.

It is the cyclic form that is involved in the formation of di- and polysaccharides.

Chemical properties

The cyclic and open (aldehyde) forms are in equilibrium. Therefore, reactions characteristic of the aldehyde and cyclic forms are possible.

All monosaccharides interact with HCN, PC1 5, NH 2 OH, NH 2 –NH 2, NH 2 –NHC 6 H 5, are oxidized, reduced (H 2).

Depending on the nature of the oxidizing agent and the reaction of the medium, MS can form various oxidation products.

1. Under the action of weak oxidizing agents: Ag 2 O, NH 4 OH, t o or Cu(OH) 2, OH – , t o, the carbon-carbon chain is destroyed with the formation of hydroxy acids with a small number of C atoms, and the oxidizing agents themselves are reduced to Ag and Cu 2 O (Cu), respectively. R-tion finds application in biochemical analyzes for the quantitative determination of sugars in biological fluids.

Tollens test ("silver mirror" reaction):

Glucose Gluconic acid

Trommer test (copper mirror reaction). When glucose is oxidized with Cu(OH) 2, a red Cu 2 O precipitate forms.

With careful oxidation in an acidic aqueous environment, for example, with bromine water, compounds are formed due to the oxidation of the aldehyde group - aldonic acids:

When exposed to strong oxidizing agents (for example nitric acid) oxidation occurs at the first and sixth C atoms with the formation of glucaric acid:

Glucaric acid

When only the primary alcohol group (at the 6th C atom) is oxidized, if the aldehyde group is protected to form a glycoside, uronic acids are obtained. In the body, this process occurs easily under the influence of enzymes. Damage agents are capable of cyclo-oxo-tautomerism. They are important integral part acidic heteropolysaccharides, for example, heparin, hyaluronic acid.

Reactions with alcohol hydroxyls occur in both open and cyclic forms.

Monosaccharides interact with Me, Me(OH) 2, forming saccharates, with Cu(OH) 2, with CH 3 I to form ethers, with mineral and organic compounds, esters are formed, with NH 3 - amino sugars.

The most important are phosphorus esters of sugars and amino sugars. It is in the form of phosphorus esters that ribose and deoxyribose are included in NA; glucose and fructose compounds are involved in metabolism.

Fructose + 2H 3 PO 4 → 1,6-Disphosphate of fructose.

Amino sugars are formed quite easily in the body through the process of ammonolysis. Most often, at the second C atom:

Amino sugars are a component of heteropolysaccharides.

R-tions for hemiacetal hydroxyl

These districts are characteristic of the cyclic form. When monosaccharides are exposed to alcohol in the presence of gaseous HC1, the H atom of the hemiacetal hydroxyl is replaced by R to form a special type of ether - a glycoside. Glycoside solutions do not mutate. Depending on the size of the oxide ring, glycosides are divided into: pyranosides and furanosides, both - and -forms.

The formation of glycosides serves as evidence of the existence of cyclic forms of monosaccharides.

The transformation of a monosaccharide into a glycoside is a complex process that occurs through a series of successive processes. Due to tautomerism and the reversibility of the reaction of glycoside formation in the solution, in the general case, tautomeric forms of the original monosaccharide and, accordingly, 4 diastereomeric glycosides -  and -anomers of furanosides and pyranosides can be in equilibrium.

Glycosides can also be formed by reaction with phenols or NH-containing aliphatic and heterocyclic amines.

A glycoside molecule can formally be represented as consisting of two parts: carbohydrate and aglycone. Monosaccharides themselves can also act as hydroxyl-containing aglycones. Glycosides formed with OH-containing aglycones are called O-glycosides, with NH-containing compounds (for example, amines) called N-glycosides.

Glycosides are components of many medicinal plants. For example, cardiac glycosides isolated from digitalis. The antibiotic streptomycin is a glycoside, vanillin is a glycoside. All di- and polysaccharides are O-glycosides.

From a biological point of view, N-glycosides of ribose and deoxyribose are of particular importance, as products of compounds with nitrogenous purines

mi and pyrimidine bases. Their common name is nucleosides, because. together with H 3 PO 4 they are nucleic acids - DNA and RNA.

All glycosides, including nucleosides, are easily hydrolyzed in an acidic environment to form the starting products.

Glycosides are not capable of cyclo-oxo-tautomerism and exhibit reactions characteristic of alcohols.

IV. Specific areas

Action of diluted. alkali solutions

Epimers: glucose, fructose and mannose easily convert into each other, forming equilibrium systems. This process is called epimerization.

Action conc. acid solutions

Conc. HC1 and H 2 SO 4 solutions cause dehydration of monosaccharides: furfural is formed from pentoses, and 5-hydroxymethylfurfural is formed from fructose.

3. Fermentation

This is the breakdown of monosaccharides under the action of microbial enzymes, leading to the formation various products. Depending on the final product there are:

a) alcoholic fermentation

b) lactic acid

c) oil

Literature

1. Tyukavkina S. 377 – 406.

Oligosaccharides

These are carbohydrates containing 2-10 monosaccharide residues per molecule. The most important are disaccharides, that is, saccharides containing two monosaccharide residues. These include sucrose, maltose, lactose and cellobiose. When hydrolyzed, two monosaccharides are formed. Sucrose – unreduced

a disaccharide, the rest are reducing disaccharides. All disaccharides are glycosides and contain a-D-glucose.

The sucrose molecule consists of a-D-glucose and b-D-fructose:

In the formation of sucrose, both monosaccharides participate with their hemiacetal hydroxyls. Therefore, the cyclic form will be fixed and the oxo form (open) will not form. This sugar has the properties of a polyhydric alcohol and a glycoside. There are no reducing properties: the Trommer test and the Tollens reaction are negative. Like monosaccharides, sucrose reacts with Me (active), forms ethers and esters, and gives a high-quality reaction with Cu(OH) 2 - blue color:

Sucrose, as a glycoside, is easily hydrolyzed into sour environment with the formation of a-D-glucose and b-D-fructose. In this case, the angle of rotation of the polarized light changes. Sucrose has a right rotation (+66.5 0), the resulting fructose has a left rotation (-92 0), glucose has a right rotation (+52.5 0). The difference is -40 0.

This phenomenon is called inversion Sahara. A mixture of glucose and fructose - invert sugar. Natural invert sugar is honey.

The sweetness of sucrose is taken as 1, then fructose has a sweetness of 1.73, glucose - 0.74, sorbitol - 0.6, mannitol - 0.4.

Specific reactions

Sucrose after hydrolysis gives a positive Selivanov reaction, since hydrolysis produces fructose.

The Trommer test and the Tollens reaction are negative, since in alkaline environment sucrose is not hydrolyzed.

Sucrose is used in medicine for the preparation of powders, tablets, syrups, mixtures, etc.

The most important representatives of reducing disaccharides are maltose, lactose and cellobiose.

In solution, maltose exists in the form of cyclic and open forms (3 forms) due to mutarotation:

Chemical properties

Maltose is an aldehyde alcohol glycoside.

I. Reactions open form. Maltose gives all reactions at the aldehyde group with HCN, NH 2 OH, NH 2 –NH 2, reduction, oxidation.

Trommer's test and Tollens' reaction are positive:

Carbohydrates that give positive test Trommer are called restorative.

II. Reactions according to – OH gr. similar reactions for sucrose.

III. Maltose is hydrolyzed in an acidic environment to form 2 glucose molecules.

Lactose exists in solution in three forms: two cyclic and one open. Lactose is a reducing disaccharide and has all

properties characteristic of maltose. Lactose is found in human milk and can inhibit the growth of bacteria.

Polysaccharides

These are high molecular weight carbohydrates containing hundreds and even thousands of monosaccharide residues.

Among the polysaccharides, cellulose, starch and glycogen are widely known. They are built from the same monosaccharide - D-glucose. General formula (C 6 H 10 O 5)n.

Cellulose (fiber) is not only the most common polysaccharide, but also an organic substance in nature. Wood is approximately 50% cellulose, while cotton and flax are almost pure cellulose.

In cellulose, D-glucopyranose residues are linked together by b–(1®4) – glycosidic bonds:

The chain, built from thousands of D-glucose residues, has a linear structure. Linear chains are anchored by H-bonds between monosaccharide units within the same chain. H-bonds also arise between the parallel polysaccharide chains, which impart rigidity to the entire structure. Hence the high mechanical strength of cellulose.

From a chemical point of view, cellulose is a polyhydric alcohol containing three hydroxyl groups in each monosaccharide unit, and is capable of forming ethers and esters with the participation of these groups:

Either all or part of the hydroxyl groups of a polysaccharide fragment, where R is an alkyl or an organic or neoranic acid residue (in esters), can be converted into ester groups. Cellulose does not exhibit reducing properties.

Cellulose ethers - methylcellulose R=CH 3 and sodium carboxymethylcellulose R=CH 2 COONa - form viscous water solutions or gels and are used in pharmacy as thickeners, emulsifiers and stabilizers for ointments and emulsions. Carboxymethylcellulose R=CH 2 COOH and diethylaminoethylcellulose (abbreviated DEAE-cellulose) R=CH 2 CH 2 N (C 2 H 5) 2 have the ability to be ion exchangers and are used in biochemical research.

Acetic ether (triacetate) is used in the production of film and electrical insulating film. Acetate fiber is also produced from this polyester. Other artificial fibers are also obtained from cellulose: viscose and copper-ammonia.

Cellulose ethers containing nitrogen are widely used. Cellulose trinitrate is an explosive substance used in the production of gunpowder. A mixture of cellulose mono- and dinitrates is used in the production of celluloid, varnishes, and explosives.

By hydrolysis of cellulose in industry, glucose is produced, the fermentation of which produces ethyl alcohol. Other applications of cellulose: construction material, production of paper, cardboard.

Starch is another common plant polysaccharide, consisting of two fractions: amylopectin (the main component is 80-90%) and amylose. Amylose, like cellulose, is built from (1®4) - linked D-glucopyranose residues.

However, unlike cellulose, the glycosidic bond in amylose has an α-configuration, as a result of which the polysaccharide chain acquires a different spatial structure, reminiscent of a helix.

A

Glycosidic bonds

Amylose chain fragment

Amylopectin has a branched structure. In the main chain, D-glucopyranose residues are linked by an a-(1®4) glycosidic bond, and at branching sites by an a-(1®6) bond:

Amylopectin +I 2 ® violet coloring

In the body, starch undergoes hydrolysis:

Salivary amylase Gastric juice

Starch Dextrins large

Pancreatic juice amylase Intestinal maltase

Small dextrins Maltose α-D-glucose

a–D-Glucose is absorbed by the intestinal villi, enters the bloodstream and is used as a source of energy. Excess glucose is polymerized into glycogen and stored in the liver as a reserve.

The problem of obesity arises because the amount of glycogen in tissues is limited. After the synthesis of 50-60 g of glycogen per 1 kg of tissue, fat begins to be produced from glucose.

Glycogen (animal starch) has a similar structure to amylopectin, but its branching is greater than that of amylopectin.

Heteropolysaccharides are carbohydrates, the hydrolysis of which produces molecules of various monosaccharides and their derivatives. The latter include heparin, hyaluronic acid, chondroitinsulfuric acid. They contain amino sugars, uronic acids and residues of sulfuric and acetic acids.

Connective tissue is distributed throughout the body (skin, cartilage, tendons, joint fluid, cornea, walls of large blood vessels, bones) and determines the strength and elasticity of organs, the elasticity of their connections, and resistance to infection. Connective tissue polysaccharides are associated with proteins.

Connective tissue polysaccharides are sometimes called acidic mucopolysaccharides, because. they contain uronic acids, residues of sulfuric and acetic acids.

Functions of carbohydrates: 1) energy; 2) construction; 3) hereditary; 4) protective; 5) maintaining constant osmotic pressure and blood clotting; 6) medications and components for them.

Energy function. The human body's needs are satisfied by carbohydrates. During normal work activity, a person’s energy costs are covered by carbohydrates by 55-60%, fats by 20-25%, proteins by 15-20%.

The calorie content of carbohydrates, that is, the energy released during their dissimilation with the formation of CO 2 and H 2 O, is 16-17 kJ/g. The source of glucose is glycogen and starch from food. Glucose is an essential component of blood (3.3–3.5 mmol/l of whole blood).

Nerve cells are especially sensitive to the supply of glucose. With a lack of glucose, convulsions and loss of consciousness occur. The constant concentration of glucose depends on two hormones: adrenaline (adrenal hormone), which regulates the breakdown of glucose, and insulin (pancreatic hormone), which regulates the synthesis of glycogen from glucose. When insulin decreases, glucose levels increase approximately 2 times, blood pressure increases, a large number of “acetone bodies” are formed, and blood pH changes. This is observed in diabetes mellitus.

Test questions for the topic: “Carbohydrates”

What compounds are called monosaccharides.

Classification of monosaccharides.

Optical isomerism. Which chiral carbon atom is used to assign D- and L-isomers.

What is mutarotation.

What compounds are classified as disaccharides?

Which disaccharides are called reducing and which non-reducing. Explain why?

What carbohydrates are called polysaccharides.

List the functions of carbohydrates in the body.

Exercises:

Write the enantiomers of glucose, galactose and mannose using Fischer projection formulas. Indicate diastereomers and epimers. What forms of monosaccharides are found in the body?

Write the cyclic forms of D-glucopyranose.

Write the reactions of glucose according to the aldehyde group.

Write the “silver and copper mirror” reactions for glucose.

Write the reactions for glucose according to OH groups.

Write the fermentation reactions of glucose.

Write the reactions for the formation of maltose and lactose. What disaccharides are they?

Write a scheme for the formation of a non-reducing disaccharide.

Write the components contained in starch.

10. Write the formulas for cellulose and glycogen

Date___________ Class_______________
Subject: Glucose, sucrose - the most important representatives carbohydrates. Starch and cellulose are natural polymers.
Lesson objectives: consider the most important representatives of carbohydrates and natural polymers.

Progress

CARBOHYDRATES

Glucose C 6 H 12 O 6 – the most important of all monosaccharides, since it is a structural unit of most food di- and polysaccharides. During the metabolic process, they are broken down into individual molecules of monosaccharides, which, in the course of multi-stage chemical reactions transform into other substances and eventually oxidize to carbon dioxide and water - are used as “fuel” for cells. Glucose is a necessary component of metabolismcarbohydrates . If its level in the blood decreases or high concentration and the inability to use, as happens in diabetes, drowsiness occurs, and loss of consciousness may occur (hypoglycemic coma). It is found in fruits and berries and is necessary for the supply of energy and the formation of glycogen in the liver (a reserve carbohydrate for humans and animals).

There is especially a lot of it in grape juice, which is why glucose is sometimes called grape sugar. Honey mainly consists of a mixture of glucose and fructose.

Glucose is valuable nutritious product. In the body, it undergoes complex biochemical transformations, as a result of which carbon dioxide and water are formed, and energy is released according to the final equation:

C 6 H 12 O 6 +6O 2 → 6H 2 O+6CO 2 + 2800 kJ

Since glucose is easily absorbed by the body, it is used in medicine as a strengthening agent. remedy in cases of cardiac weakness and shock, it is included in blood replacement and anti-shock fluids. Glucose is widely used in confectionery(production of marmalade, caramel, gingerbread, etc.), in the textile industry as a reducing agent, as a starting product in the production of ascorbic acid, for the synthesis of a number of sugar derivatives, etc. Great importance have glucose fermentation processes. So, for example, when sauerkraut, cucumbers, and milk are pickled, lactic acid fermentation of glucose occurs, as well as when ensiling feed. If the mass subjected to ensiling is not sufficiently compacted, then butyric acid fermentation occurs under the influence of penetrated air and the feed becomes unsuitable for use. In practice, alcoholic fermentation of glucose is also used, for example in the production of beer.

Fructose C 6 H 12 O 6 is one of the most commoncarbohydrates fruits, found in honey. 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 sourcecarbohydrates for diabetic patients.

Sucrose WITH 12 N 22 ABOUT 11 , formed by molecules of glucose and fructose. The sucrose content in sugar is 99.5%. Sugar is often called an “empty calorie carrier” because sugar is purecarbohydrate and does not contain others nutrients, such as, for example, vitamins, mineral salts. Sucrose is found in sugar cane and sugar beets, as well as in sweets.

Starch and cellulose

Starch (WITH 6 N 10 ABOUT 5 ) n - a natural polymer, it accumulates in the form of grains, mainly in the cells of seeds, bulbs, tubers, as well as in leaves and stems. Starch is a white powder, insoluble in cold water. IN hot water it swells and forms a paste.
Starch is most often obtained from potatoes. To do this, the potatoes are crushed, washed with water and pumped into large vessels where settling occurs. The resulting starch is washed again with water, settled and dried in a stream of warm air.

Starch is the main part essential products food: flour (75 - 80%), potatoes (25%), sago, etc. Energy value about 16.8 kJ/g. It is a valuable nutritious product. To facilitate its absorption, starchy foods are exposed to high temperature, that is, potatoes are boiled, bread is baked. Under these conditions, partial hydrolysis of starch occurs and dextrins, soluble in water, are formed. Dextrins in digestive tract undergo further hydrolysis to glucose, which is absorbed by the body. Excess glucose is converted into glycogen (animal starch). The composition of glycogen is the same as that of starch - (C 6 H 10 O 5 ) n, but its molecules are more branched. The liver contains especially a lot of glycogen (up to 10%). In the body, glycogen is a reserve substance that is converted into glucose as it is consumed in cells.
In industry, starch is converted into molasses and glucose by hydrolysis. To do this, it is heated with dilute sulfuric acid, the excess of which is then neutralized with chalk.

(WITH 6 N 10 ABOUT 5 ) n + n H 2 O - H 2 SO 4, t ˚ C → n C 6 H 12 O 6

The resulting precipitate of calcium sulfate is filtered off, the solution is evaporated and glucose is isolated. If starch hydrolysis is not completed, a mixture of dextrins and glucose is formed - molasses, which is used in the confectionery industry. Dextrins obtained from starch are used as glue to thicken paints when applying designs to fabric. Starch is used for starching linen. Under a hot iron, starch is partially hydrolyzed and converted into dextrins. The latter form a dense film on the fabric, which adds shine to the fabric and protects it from contamination. Starch and its derivatives are used in the production of paper, textiles, foundries and other industries, and in the pharmaceutical industry.

Cellulose or fiber(WITH 6 N 10 ABOUT 5 ) n , one of the most common natural polymers; home component cell walls of plants, which determines the mechanical strength and elasticity of plant tissues. Thus, the cellulose content in the hairs of cotton seeds is 97-98%, in the stems of bast plants (flax, ramie, jute) 75-90%, in wood 40-50%, reeds, cereals, sunflowers 30-40%. Found in the body of some lower invertebrates.

COURSE WORK

Carbohydrates and their properties . Glucose

Introduction

AIDS, diabetes, bronchial asthma, cancer is an incomplete list of diseases for which no alternative drugs, helping to completely heal them. The challenge for healthcare is to find drugs to cure these diseases.

Pharmaceutical chemistry is a science that studies production methods, physical and chemical properties, and quality control methods. medicinal substances, influence individual features the structure of molecules of medicinal substances on the nature of their effect on the body, changes that occur during their storage.

Solving the problems facing pharmaceutical chemistry will help identify new properties of existing ones. medicines and open new ones.

1. Carbohydrates

Carbohydrates are a large group of polyhydroxycarbonyl compounds that are part of all living organisms. They are especially widespread in the plant world: 80% of the dry mass of plants is carbohydrates; Carbohydrates also include many derivatives obtained by chemical modification of these compounds by oxidation, reduction, or introduction of various substituents.

Carbohydrates are involved in the metabolism and energy in the human and animal body. As the main component of food, carbohydrates supply most of the energy needed for life (more than half of a person's energy comes from carbohydrates). Some carbohydrates are part of nucleic acids that carry out protein biosynthesis and the transmission of hereditary characteristics.

Carbohydrates include glucose, fructose, sugar (sucrose), starch, cellulose (fiber), etc. Some of them are staple foods, others (cellulose) are used to produce paper, plastics, fibers, etc.

The term "carbohydrates" arose because the first famous representatives carbohydrates in composition corresponded to the formula CmH2nOn (carbon + water); Subsequently, natural carbohydrates with a different elemental composition were discovered.

1.1 Classification and distribution

Carbohydrates are usually divided into monosaccharides, oligosaccharides and polysaccharides.

The most common and widespread monosaccharides in nature include D-glucose, D-galactose, D-mannose, D-fructose, D-xylose, L-arabinose and D-ribose carbohydrates. Of the representatives of other classes of monosaccharides, the following are often found:

1) deoxysugars, in the molecules of which one or more OH groups are replaced by H atoms (for example, L-rhamnose, L-fucose, 2-deoxy-D-ribose);

2) amino sugars, where one or more OH groups are replaced by amino groups (for example, 2-amino-2-deoxy-D-glucose, or D-glucosamine);

3) polyhydric alcohols (polyols, alditols) formed during the reduction of the carbonyl group of monosaccharides (D-sorbitol from D-glucose, D-mannitol from D-mannose);

4) uronic acids - aldoses in which the CH2OH group is oxidized to carboxyl (for example, D-glucuronic acid);

5) branched sugars containing a nonlinear chain of carbon atoms (apiose, or 3-C-hydroxymethyl-D-glycero-tetrose);

6) higher sugars with a chain length of more than six C atoms (for example, D-sedohep-tulose and sialic acids.

With the exception of D-glucose and D-fructose, free monosaccharides are rare in nature. Usually they are part of a variety of glycosides, oligo- and polysaccharides, and may. obtained from them after acid hydrolysis. Numerous methods have been developed chemical synthesis rare monosaccharides based on more accessible ones.

Oligosaccharides contain from 2 to 10-20 monosaccharide residues linked by glycosidic bonds. The most common disaccharides that perform the function spare B-B: sucrose in plants, trehalose in insects and fungi, lactose in mammalian milk. Numerous glycosides of oligosaccharides are known, which include various physiological active substances some saponins (in plants), many. antibiotics (in fungi and bacteria), glycolipids.

Polysaccharides are high-molecular compounds, linear or branched molecules of which are built from monosaccharide residues linked by glycosidic bonds. Polysaccharides may also contain non-carbohydrate substituents. In turn, chains of higher oligosaccharides and polysaccharides can join polypeptide chains to form glycoproteins.

A special group consists of biopolymers, in the molecules of which the residues of polyols, glycosyl polyols, nucleosides or mono- and oligosaccharides are connected not by glycosidic, but by phosphodiester bonds. This group includes teichoic acids of bacteria, components of the cell walls of some yeasts, as well as nucleic acids based on a poly-D-ribose phosphate (RNA) or poly-2-deoxy-D-ribose phosphate (DNA) chain.

Physicochemical characteristics. The abundance of polar functional groups in monosaccharide molecules leads to the fact that these substances are easily soluble in water and insoluble in low-polar organic solvents. The ability for tautomeric transformations usually makes it difficult for mono- and oligosaccharides to crystallize, but if such transformations are impossible (for example, as in glycosides and non-reducing oligosaccharides such as sucrose), then the substances crystallize easily. Many glycosides with low-polar aglycones (saponins) exhibit surfactant properties.

Polysaccharides are hydrophilic polymers, many of them form highly viscous aqueous solutions, and in some cases strong gels.

Some polysaccharides form highly ordered supramolecular structures that prevent the hydration of individual molecules; such polysaccharides (chitin, cellulose) are insoluble in water.

Biological role. The functions of carbohydrates in living organisms are extremely diverse. In plants, monosaccharides are the primary products of photosynthesis and serve as starting compounds for the biosynthesis of glycosides and polysaccharides, as well as others. classes B-B(amino acids, fat K-T, phenols, etc.). These transformations are carried out by enzymes, the substrates for which are, as a rule, energy-rich sugar derivatives, mainly nucleoside diphosphate sugars.

Carbohydrates are stored in plants (in the form of starch), animals, bacteria and fungi (in the form of glycogen), where they serve as an energy reserve. The source of energy is the breakdown of glucose formed from these polysaccharides. Various metabolites are transported in the form of glycosides in plants and animals. Polysaccharides and more complex carbohydrate-containing polymers perform supporting functions in living organisms. Rigid cell wall higher plants is a complex complex of cellulose, hemicelluloses and pectins. Reinforcing polymer in cell wall peptidoglycans (mureins) serve as bacteria, and chitin is used in the cell wall of fungi and the outer integument of arthropods. In the animal body, proteoglycans perform supporting functions. connective tissues. These substances are involved in providing specific physical and chemical properties tissues such as bones, cartilage, tendons, skin. Being hydrophilic polyanions, these polysaccharides also help maintain water balance and selective ion permeability of cells.

Particularly responsible role complex carbohydrates in the formation of cell surfaces and membranes and giving them specific properties. Thus, glycolipids are the most important components of membranes nerve cells and membranes of erythrocytes, and lipopolysaccharides - outer shell gram-negative bacteria. Cell surface carbohydrates often determine the specificity of immunological reactions (blood group substances, bacterial antigens) and the interaction of cells with viruses. Carbohydrate structures also take part in other highly specific phenomena of cellular interaction, such as fertilization, cell recognition during tissue differentiation, rejection of foreign tissues, etc.

Carbohydrates constitute the main part of the human diet, and therefore are widely used in the food and confectionery industries (starch, sucrose, etc.). Besides, in food technology structured substances of a polysaccharide nature are used that do not have nutritional value in themselves - gelling agents, thickeners, stabilizers of suspensions and emulsions (alginates, pectins, plant galactomannans, etc.).

The transformations of monosaccharides during alcoholic fermentation underlie the processes of ethanol production, brewing, and baking; Other types of fermentation make it possible to obtain glycerin, lactic, citric, gluconic acids and many other substances from sugars using biotechnological methods.

Glucose ascorbic acid, carbohydrate-containing antibiotics, heparin are widely used in medicine. Cellulose serves as the basis for the production of viscose fiber, paper, some plastics, BB, etc. Sucrose and polysaccharides are considered as a promising renewable raw material that can replace oil in the future.

2. Glucose

Colorless crystals or white fine crystalline powder, odorless, sweet taste. Soluble in water (1:15) and difficultly soluble in alcohol.

Solutions are sterilized at 100° for 60 minutes or at 119-121° for 5-7 minutes. To stabilize, add 0.1 N. solution of hydrochloric acid and sodium chloride; pH of solutions is 3.0-4.0.

For medical purposes, isotonic (4.5-5%) and hypertonic (10-40%) solutions are used.

An isotonic solution is used to replenish the body with fluid, but at the same time it is a source of valuable nutritional material that is easily absorbed by the body. When glucose is burned in tissues, a significant amount of energy is released, which is used to carry out body functions.

When injected into a vein hypertonic solutions The osmotic pressure of the blood increases, the flow of fluid from tissues into the blood increases, metabolic processes increase, the antitoxic function of the liver improves, the contractile activity of the heart muscle increases, blood vessels dilate, and diuresis increases. Glucose solutions are widely used in medical practice with hypoglycemia, infectious diseases, liver diseases (hepatitis, liver dystrophy and atrophy), cardiac decompensation, pulmonary edema, hemorrhagic diathesis, with toxic infections, various intoxications (poisoning with drugs, hydrocyanic acid and its salts, carbon monoxide, aniline, arsenic hydrogen, phosgene and other substances) and with various other pathological conditions.

They are part of the cells and tissues of all plant and animal organisms and, by mass, make up the bulk of organic matter on Earth. Carbohydrates account for about 80% of the dry matter in plants and about 20% in animals. Plants synthesize carbohydrates from inorganic compounds - carbon dioxide and water (CO 2 and H 2 O) during the process of photosynthesis:

6CO 2 + 6H 2 O light, chlorophyll→ C6H12O6 + 6O2

Carbohydrates have general formula C n (H 2 O) m, which is where the name of these natural compounds comes from. Carbohydrates are divided into: monosaccharides (the most important representatives are glucose and fructose); disaccharides (sucrose); polysaccharides (the most important representatives are starch and cellulose).

Fructose C6H12O6 is one of the most common carbohydrates fruits, found in honey. 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 source carbohydrates for diabetic patients.

WITH acharose C 12 H 22 O 11, formed by molecules of glucose and fructose . The sucrose content in sugar is 99.5%. Sugar is often called an “empty calorie carrier” because sugar is pure carbohydrate and does not contain other nutrients, such as vitamins, mineral salts. Sucrose is found in sugar cane and sugar beets, as well as in sweets.

Collection sugar reed. Fresco inPalace of Cortez in Cuernavaca.

Starch and cellulose

Starch (C 6 H 10 O 5)n- a natural polymer, it accumulates in the form of grains, mainly in the cells of seeds, bulbs, tubers, as well as in leaves and stems. Starch is a white powder, insoluble in cold water. In hot water it swells and forms a paste.
Starch is most often obtained from potatoes. To do this, the potatoes are crushed, washed with water and pumped into large vessels where settling occurs. The resulting starch is washed again with water, settled and dried in a stream of warm air.

Starch is the main part of the most important food products: flour (75 - 80%), potatoes (25%), sago, etc. Energy value is about 16.8 kJ/g. It is a valuable nutritious product. To facilitate its absorption, starch-containing foods are exposed to high temperatures, that is, potatoes are boiled, bread is baked. Under these conditions, partial hydrolysis of starch occurs and dextrins, soluble in water, are formed. Dextrins in the digestive tract undergo further hydrolysis to glucose, which is absorbed by the body. Excess glucose is converted into glycogen (animal starch). The composition of glycogen is the same as that of starch - (C 6 H 10 O 5) n, but its molecules are more branched. The liver contains especially a lot of glycogen (up to 10%). In the body, glycogen is a reserve substance that is converted into glucose as it is consumed in cells.
In industry, starch is converted into molasses and glucose by hydrolysis. To do this, it is heated with dilute sulfuric acid, the excess of which is then neutralized with chalk.

(C 6 H 10 O 5)n + n H 2 O- H 2 SO 4, t ˚ C → n C 6 H 12 O 6

The resulting precipitate of calcium sulfate is filtered off, the solution is evaporated and glucose is isolated. If starch hydrolysis is not completed, a mixture of dextrins and glucose is formed - molasses, which is used in the confectionery industry. Dextrins obtained from starch are used as glue to thicken paints when applying designs to fabric. Starch is used for starching linen. Under a hot iron, starch is partially hydrolyzed and converted into dextrins. The latter form a dense film on the fabric, which adds shine to the fabric and protects it from contamination. Starch and its derivatives are used in the production of paper, textiles, foundries and other industries, and in the pharmaceutical industry.

Starch detection

Celluloseor fiber (C 6 H 10 O 5) n, one of the most common natural polymers; the main component of plant cell walls, which determines the mechanical strength and elasticity of plant tissues. Thus, the cellulose content in the hairs of cotton seeds is 97-98%, in the stems of bast plants (flax, ramie, jute) 75-90%, in wood 40-50%, reeds, cereals, sunflowers 30-40%. Found in the body of some lower invertebrates.

Cellulose has been used by humans since very ancient times. At first, wood was used as a fuel and building material; then cotton, flax and other fibers began to be used as textile raw materials. The first industrial methods of chemical wood processing arose in connection with the development of the paper industry.
Paper is a thin layer of fiber fibers, compressed and glued to create mechanical strength, a smooth surface, and to prevent ink from bleeding. Initially, to make paper, plant materials were used, from which it was possible to obtain the necessary fibers purely mechanically, rice stalks (the so-called rice paper), cotton, and worn-out fabrics were also used. However, as book printing developed, the listed sources of raw materials became insufficient to satisfy the growing demand for paper. Especially a lot of paper is consumed for printing newspapers, and the issue of quality (whiteness, strength, durability) for newsprint paper does not matter. Knowing that wood consists of approximately 50% fiber, they began to add ground wood to the paper pulp. Such paper is fragile and quickly turns yellow (especially in the light).
To improve the quality of wood additives to paper pulp, various methods of chemical processing of wood have been proposed, making it possible to obtain more or less pure cellulose from it, freed from accompanying substances - lignin, resins and others. Several methods have been proposed for the isolation of cellulose, of which we will consider the sulfite method. According to the sulfite method, crushed wood is “cooked” under pressure with calcium hydrosulfite. In this case, the accompanying substances dissolve, and the cellulose freed from impurities is separated by filtration. The waste contains fermentable monosaccharides; they are used as raw material for the production of ethyl alcohol (the so-called hydrolytic alcohol). Cellulose is used to produce viscose, acetate, copper-ammonium fibers.

Tasks for consolidation

№1.

No. 2. When sucrose reacts with water, a mixture of glucose and sucrose is formed.

Solve the problem:
Calculate the mass of a sucrose solution (mass fraction of sucrose 20%), which was subjected to hydrolysis (reaction with water), if 7.2 g of glucose was released.

No. 3. Fill the table