Role in the nature of disaccharides. Chemical properties of disaccharides

20. Reducing disaccharides (maltose, lactose): structure, biochemical transformations (oxidation, reduction).

Reducing disaccharides. In these disaccharides, one of the monosaccharide residues participates in the formation of a glycosidic bond due to the hydroxyl group, most often at C-4 or C-6, less often at C-3. The disaccharide contains a free hemiacetal hydroxyl group, as a result of which the ability to open the ring is retained. The reducing properties of such disaccharides and the mutarotation of their freshly prepared solutions are due to the possibility of cyclo-oxo-tautomerism. Representatives of reducing disaccharides are maltose, cellobiose, and lactose.

maltose (trivial name: malt sugar)" - a product of enzymatic hydrolysis starch.

In this disaccharide, the monosaccharide residues are linked by a glycoside-glycose bond (a-1,4-linkage).

Due to the presence of a hemiacetal function in the maltose molecule, the a-anomer is in equilibrium with the p-anomer - p-maltose, 4-0-(a-D-glucopyranosyl)-p-0-glucopyranose. If it is subjected to acid hydrolysis, 2 mol of 0-(+)-glucose are obtained.

In contrast to sucrose, maltose is a reducing glycoside because it has a hemiacetal moiety in its structure. Maltose reacts with Benedict-Fehling's reagent and phenylhydrazine.

Maltose is a reducing sugar because it has an unsubstituted hemiacetal hydroxyl group. When maltose is boiled with dilute acid and under the action of the enzyme maltase is hydrolyzed (two molecules of glucose C6H12O6 are formed).

Maltose contains a free glycosidic hydroxyl near the C-1 carbon atom, and therefore has reducing properties characteristic of reducing mono- and disaccharides. In solutions, maltose can exist in two forms - cyclic and aldehyde, which are in dynamic equilibrium. When maltose is hydrolyzed by the enzyme maltase, two molecules of alpha-D-glucose are formed. When the aldehyde group of maltose is oxidized, maltobionic acid is formed.

Other examples of disaccharides include lactose (milk sugar) is a disaccharide containing a p-D-galactopyranose residue (in fixed (3-form) and D-glucose and is present in the milk of almost all mammals:

Hydrolysis of sucrose in the presence of mineral acids (H 2 SO 4, HCl, H 2 CO 3):

Oxidation of maltose (a reducing disaccharide), such as the “silver mirror” reaction:

21. Non-reducing disaccharides (sucrose): structure, inversion, application.

Sucrose is a disaccharide consisting of D-glucose and D-fructose residues linked by a glycosidic-glycosidic bond (a-1,-2 bond).

Sucrose is a non-reducing disaccharide (see Oligosaccharides), a widespread reserve substance in plants, formed during the process of photosynthesis and stored in leaves, stems, roots, flowers or fruits. When heated Above the melting temperature, decomposition and coloring of the melt occurs (caramelization). Sucrose does not reduce Fehling's reagent, it is quite resistant to alkalis, but, being a ketofuranoside, it is extremely easily (~ 500 times faster than trehalose or maltose) cleaved (hydrolyzed) into D-glucose and D-fructose. Hydrolysis of sucrose is accompanied by a change in the sign of the beat. rotation of the solution and therefore called inversion.

A similar hydrolysis occurs under the action of a-glucosidase (maltase) or b-fructofuranosidase (invertase). Sucrose is easily fermented by yeast. Being weak (K approx. 10-13), sucrose forms complexes (sugarates) with hydroxides of alkali and alkali earth metals, which regenerate sucrose under the influence of CO2.

Biosynthesis of sucrose occurs in the vast majority of photosynthetic eukaryotes, mainly. the mass of which consists of plants (with the exception of representatives of red, brown, as well as diatoms and certain other unicellular algae); its key stage is lending. uridine diphosphate glucose and 6-phosphate-D-fructose. Animals are not capable of biosynthesis of sucrose.

Sucrose inversion. Acid hydrolysis of (+) sucrose or the action of invertase produces equal amounts of D(+) glucose and D(-) fructose. Hydrolysis is accompanied by a change in the sign of the specific angle of rotation [α] from positive to negative, therefore the process is called inversion, and the mixture of D(+) glucose and D(-) fructose is called invert sugar.

Sucrose is obtained industrially. scales from sugar cane juice Saccharum officinarum or sugar beet Beta vulgaris; these two plants provide approx. 90% of the world's sucrose production (in a ratio of approx. 2:1), exceeding 50 million tons/year. Chem. the synthesis of sucrose is very complex and economical. doesn't matter.

Sucrose is used as food. product (sugar) directly or as part of confectionery products, and in high concentrations as a preservative; sucrose also serves as a substrate in industry. fermentation processes for producing ethanol, butanol, glycerin, citric and levulinic acid, dextran; also used in the preparation of lek. Wed; Certain sucrose esters with higher fatty acids are used as nonionic detergents.

For qualities. To detect sucrose, you can use blue staining with an alkaline solution of diazouracil, which, however, also produces higher oligosaccharides containing a sucrose fragment in the molecule - raffinose, gentianose, stachyose.

Disaccharides (from other Greek δύο - two and σάκχαρον - sugar)- organic compounds, one of the main groups of carbohydrates; are a special case of oligosaccharides.

Examples of disaccharides

• Lactose - consists of glucose and galactose residues.

• Sucrose - consists of glucose and fructose residues.

• Maltose - consists of two glucose residues.

Physical properties

Disaccharides are solid, crystalline substances, slightly white to brownish in color, highly soluble in water and in 45-48% alcohol, poorly soluble in 96% alcohol, and have optical activity; sweet to taste.

Chemical properties

• During hydrolysis, disaccharides are broken down into their constituent monosaccharides by breaking the glycosidic bonds between them. This reaction is the reverse of the process of formation of disaccharides from monosaccharides.
• When disaccharides condense, polysaccharide molecules are formed.

According to their chemical properties, disaccharides can be divided into two groups:

1. restorative;
2. non-restorative.

The first group includes: lactose, maltose, cellobiose. To the second: sucrose, trehalose.

Reducing (reducing) disaccharides

In these disaccharides, one of the monosaccharide residues participates in the formation of a glycosidic bond due to the hydroxyl group, most often at C-4 or C-6, less often at C-3. The disaccharide contains a free hemiacetal hydroxyl group, as a result of which the ability to open the ring is retained. The possibility of carrying out cyclo-oxo-tautometry (ring-chain) is due to the reducing properties of such disaccharides and mutarotation of their freshly prepared solutions.

Lactose

Lactose (from Latin lac - milk) C12H22O11 is a carbohydrate of the disaccharide group, found in milk and dairy products. The lactose molecule consists of residues of β-glucose and β-galactose molecules, which are connected to each other by a β(1→4)-glycosidic bond. Aqueous solutions of lactose mutate. Reacts with fehling liquid only after boiling for 15 minutes and Tollens reagent, reacts with phenylhydrazine, forming osazone. Lactose differs from other disaccharides in that it is not hygroscopic - it does not dampen. This property is of great practical importance in pharmacy: if you need to prepare any powder with sugar containing an easily hydrolyzed drug, then take milk sugar; if you take other sugar, it will quickly become damp and the easily hydrolyzed medicinal substance will quickly decompose. The importance of lactose is very high, as it is an essential nutrient, especially for growing human and mammalian bodies.

Maltose

Maltose (from Latin maltum - malt) -C12H22O11 - a disaccharide consisting of two glucose residues; contained in large quantities in sprouted grains (malt) of barley, rye and other grains; also found in tomatoes, pollen and nectar of a number of plants. Maltose is a reducing sugar, reduces Fehling's fluid, gives hydrazone and osazone and can be oxidized to monobasic maltobionic acid, which upon hydrolysis gives α-D-glucose and D-gluconic acid. Maltose was synthesized by the action of maltase (a yeast enzyme) on concentrated glucose solutions. It is characterized by the phenomenon of mutarotation, which strongly rotates the plane of polarization to the left. Maltose is less sweet than sucrose, for example, but it is more than 2 times sweeter than lactose.

Cellobiose

Cellobiose 4-(β-glucosido)-glucose is a disaccharide consisting of two glucose residues connected by a β-glycosidic bond; basic structural unit of cellulose. Higher animals are not able to digest cellulose, since they do not have the enzyme that decomposes it. However, snails, caterpillars and worms containing the enzymes cellobiase and cellulase are able to break down (and thereby utilize) plant debris containing cellobiose. Cellobiose, like lactose, has a 1→4 β-glycosidic bond and is a reducing disaccharide, but unlike lactose, upon complete hydrolysis it gives only β-D-glucose.

Non-reducing (non-reducing) disaccharides

Non-reducing disaccharides do not have an OH group at any anomeric center, as a result of which they do not react with fehling liquid and Tollens' reagent.

Sucrose

Trehalose

Being in nature

Disaccharides are widely distributed in animal and plant organisms. They are found in a free state (as products of biosynthesis or partial hydrolysis of polysaccharides), as well as structural components of glycosides and other compounds. Many disaccharides are obtained from natural sources, for example, for sucrose, the main sources are either sugar beets or sugar cane.

Biological role

• Energy - disaccharides (sucrose, maltose) serve as sources of glucose for the human body, sucrose is also the most important source of carbohydrates (it makes up 99.4% of all carbohydrates received by the body), lactose is used for dietary baby food.
• Structural - cellobiose has important for plant life, as it is part of cellulose.

Notes

1. XuMuK.ru - Disaccharides - Large Soviet Encyclopedia. Retrieved April 20, 2013. Archived April 28, 2013.
2. A. A. Petrov, H. V. Balyan, A. T. Troshchenko - Organic chemistry. Ed. A. A. Petrova. Ed. 3rd, rev. and additional Textbook for universities. M.: “Higher. school", 1973. 623 p. with ill.
3. N. A. Tyukavkina, Yu. I. Baukov. Bioorganic chemistry. - 2nd ed., revised. and additional - M.: Medicine, 1991. - 528 p. - ( Educational literature for students of medical institutes). -ISBN 5-225-00863-1
4. Polyudek-Fabini R., Beirich T. -Organic analysis - Translation from German. - L.: Chemistry, 1981. - 624 p.
5. Organic chemistry course. Stepanenko B.N. Textbook for honey. Inst. Ed. 2nd, revised and additional M., " graduate School", 1974. 440 pp. ill.
6. Sorochinskaya E.I. - Bioorganic chemistry. Poly- and heterofunctional compounds. Biopolymers and their structural components. St. Petersburg: St. Petersburg State University Publishing House, 1998. - 148 p.

Literature

Carbohydrates are important components of nutrition. Thanks to their breakdown, the human body receives about 57% of energy. The daily intake of carbohydrates is 500 g. All carbohydrates are classified into simple and complex. The group of simple carbohydrates includes monosaccharides and disaccharides.

The importance of monosaccharides for humans

Monosaccharides include easily digestible and highly soluble organic compounds that have a sweet taste. Important monosaccharides for humans are:

• glucose;
• fructose;
• galactose.

In the human body, 80% of monosaccharides are glucose, which is considered an irreplaceable source of energy. Fruit juices and berries are rich in glucose.

It regulates metabolic processes and activates the work of:

• brain cells;
• red blood cells;
• muscle cells.

To nervous system a person is fully functioning, the blood glucose level should be 3.3-5.5 mmol/l. Glucose is also involved in the synthesis of glycogen, nucleic acids, amino acids, lipids and enzymes.

Berries, fruits and bee honey are rich in fructose. This monosaccharide:

• nourishes brain cells;
• participates in glycogen synthesis;
• regulates blood sugar levels;
• activates muscle function.

Up to 80% of fructose is retained in the human liver and converted into glycogen. Fructose is absorbed slowly in the intestines and does not change blood sugar levels. This property of fructose is important for the nutrition of people who suffer from diabetic diseases.

Galactose is not contained in products, as it is a product of the breakdown of the milk carbohydrate - lactose. In the human liver, galactose is broken down into glucose.

Disaccharides include the following organic substances:

• sucrose;
• lactose;
• maltose.

These compounds are easily digestible sugars that are inferior to monosaccharides in solubility and sweetness.

Cane juice, melons, fruits, and vegetables are rich in sucrose. Refined sugar contains 99.75% sucrose. In the body, the disaccharide, which is contained in cane and fresh beet juice, quickly breaks down into monosaccharides. The functions of sucrose in the human body are identical to those of glucose.

Lactose is the main carbohydrate in dairy products. In the human gastrointestinal tract, this disaccharide is broken down by enzymes into galactose and glucose.

Maltose is an intermediate between glycogen and starch. Maltose is converted into glucose in the body. A large percentage of maltose is found in natural honey, malt extract and beer.

• low fiber content;
• high glycemic index;
• the presence of “empty” calories, which are transformed into fat deposits.

Nutritionists advise eating foods with simple carbohydrates after power loads. Simple carbohydrates will quickly restore the necessary level of muscle glycogen and replenish lost energy. It is most rational after physical activity eat dishes that include rice and banana.

1. Sugar. This product contains quickly digestible carbohydrates and is characterized by high energy value. Sugar has no biological significance for humans, and its excessive consumption leads to caries and the development of obesity.
   
2. Confectionery. Cakes, eclairs, cookies, waffles and other confectionery products contain simple carbohydrates, which charge the human body with energy and also improve his mood. Systematic consumption of confectionery products provokes the development of diabetes, gastrointestinal diseases and obesity.

   Product name	GI	Proteins (g)	Fat (g)	Carbohydrates (g)	Calories (kcal)
   Halva	70	11,6	29,7	54	516,2
   Cracker	70	7,4	9,4	73,1	407
   Waffles	75	3,2	2,8	81,1	342,1
   Sherbet	70	7,3	14,7	66,2	417
   Biscuit	70	5,9	0,8	56,3	258
   Donuts	85	6,4	22,8	43,1	403
   Marshmallow	65	0,8	0,1	79,8	326
   Jam	70	0,4	0,3	68,2	254

3. Potato. Raw potatoes contain B vitamins, carotene, magnesium, calcium, iron, and folic acid. Potatoes are also rich in starch, which is poorly digestible and has a high calorie content. Heat-treated potatoes are not dietary dish and contains “empty” calories.
   
4. Rice. This product is used in dietary nutrition, as it contains no cholesterol and is a good source of carbohydrates. Nutritionists do not advise consuming large quantities of purified White rice. Its excess in daily menu human leads to the development of organ diseases circulatory system and diabetes mellitus. It is best to use brown or unpolished rice for cooking.
   
5. Cornflakes. Corn flakes contain a large percentage of carbohydrates, as well as preservatives that “clog” our body with harmful compounds. Regular consumption of corn flakes in combination with sugar syrup, honey or yogurt increases a person's body weight and leads to obesity.
   
6. Chocolate. This product is not only tasty treat, but also natural medicine. With its help, you can increase the number of blood cells, as well as prevent the development of senile dementia in old age. Nutritionists advise consuming no more than 25 g of chocolate per day.
   
7. Fruits and berries. These products are a natural source of easily digestible simple carbohydrates. They contain vitamins and minerals that are valuable and essential for the human body.
   

   Product name	GI	Proteins (g)	Fat (g)	Carbohydrates (g)	Calories (kcal)
   A pineapple	65	0,4	0,2	11,5	49
   Bananas	60	1,5	0,1	21	89
   Dates	146	2	0,5	72,3	306
   Raisin	65	1,8	-	66	271
   Watermelon	72	0,7	0,2	8,8	40
   Melon	60	0,6	-	9,1	39
   Persimmon	55	0,5	0,3	13,5	55
   Mango	55	0,5	-	13,2	67

8. Natural honey. Honey contains glucose and fructose. These simple carbohydrates provide the human body with powerful energy. Honey is completely absorbed in the body. It is not recommended for use by people who are prone to allergies.
   
9. Carbonated drinks. Soda contains sugar, flavorings and acids. Regular consumption of such drinks leads to obesity, diabetes, destruction of tooth enamel and the development of cancer.
   

Excessive intake of simple carbohydrates enhances the process of fat formation and leads to the following disorders:

• increased cholesterol;
• an increase in the number of putrefactive microorganisms in the intestines;
• development of flatulence.

Excess simple carbohydrates increase the risk of obesity and diabetes.

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Disaccharides (disaccharides, oligosaccharides) are a group of carbohydrates whose molecules consist of two simple sugars united into one molecule by a glycosidic bond of different configurations. The generalized formula of disaccharides can be represented as C12H22O11.

Depending on the structure of the molecules and their chemical properties, a distinction is made between reducing (glycoside-glycosides) and non-reducing disaccharides (glycoside-glycosides). Reducing disaccharides include lactose, maltose and cellobiose, and non-reducing disaccharides include sucrose and trehalose.

Chemical properties

Disaccharides are crystalline solids. Crystals of different substances are colored from white to brown. They dissolve well in water and alcohols and have a sweet taste.

During the hydrolysis reaction, the glycosidic bonds are broken, causing the disaccharides to break down into two simple sugars. In the reverse process of condensation, hydrolysis, several molecules of disaccharides fuse into complex carbohydrates - polysaccharides.

Lactose - milk sugar

The term “lactose” is translated from Latin as “milk sugar”. This carbohydrate is named so because it is found in large quantities in dairy products. Lactose is a polymer consisting of molecules of two monosaccharides - glucose and galactose. Unlike other disaccharides, lactose is not hygroscopic. This carbohydrate is obtained from whey.

Range of applications

Lactose is widely used in the pharmaceutical industry. Due to the lack of hygroscopicity, it is used for the manufacture of easily hydrolyzed sugar-based drugs. Other carbohydrates, which are hygroscopic, quickly become damp and the active medicinal substance in them quickly disintegrates.

Milk sugar is used in biological pharmaceutical laboratories in the preparation of nutrient media for growing different cultures bacteria and fungi, for example in the production of penicillin.

When lactose is isomerized in pharmaceuticals, lactulose is obtained. Lactulose is a biological probiotic that normalizes intestinal motility during constipation, dysbacteriosis and other digestive problems.

Beneficial features

Milk sugar is the most important nutrient and plastic substance, vital for harmonious development the growing organism of mammals, including the human child. Lactose is a nutrient medium for the development of lactic acid bacteria in the intestines, which prevents putrefactive processes in it.

From beneficial properties lactose can be distinguished by the fact that, with high energy content, it is not used for the formation of fat and does not increase cholesterol levels in the blood.

Possible harm

Lactose does not harm the human body. The only contraindication to consuming foods containing milk sugar is lactose intolerance, which occurs in people with a deficiency of the lactase enzyme, which breaks down milk sugar into simple carbohydrates. Lactose intolerance is the reason why people, often adults, do not digest dairy products. This pathology manifests itself in the form of symptoms such as:

• nausea and vomiting;
• diarrhea;
• bloating;
• colic;
• itching and rashes on the skin;
• allergic rhinitis;
• swelling.

Lactose intolerance is most often physiological, and is associated with age-related lactose deficiency.

Maltose - malt sugar

Maltose, which consists of two glucose units, is a disaccharide produced by grains to build the tissues of their embryos. Maltose is found in smaller amounts in the pollen and nectar of flowering plants and tomatoes. Malt sugar is also produced by some bacterial cells.

In animals and humans, maltose is formed by the breakdown of polysaccharides - starch and glycogen - using the enzyme maltase.

Main biological role maltose is to provide the body with energy material.

Possible harm

Maltose exhibits harmful properties only in those people who have a genetic deficiency of maltase. As a result, under-oxidized products accumulate in the human intestines when consuming foods containing maltose, starch or glycogen, causing severe diarrhea. Excluding these foods from the diet or taking enzyme preparations with maltase helps to level out the manifestations of maltose intolerance.

Sucrose - cane sugar

Sugar, which is present in our daily diet, both in pure form and as part of various dishes, this is sucrose. It consists of glucose and fructose molecule residues.

In nature, sucrose is found in a variety of fruits: fruits, berries, vegetables, as well as in sugar cane, from where it was first mined. The process of breaking down sucrose begins in the mouth and ends in the intestines. Under the influence of alpha-glucosidase, cane sugar is broken down into glucose and fructose, which are quickly absorbed into the blood.

Beneficial features

The benefits of sucrose are obvious. As a very common disaccharide in nature, sucrose serves as a source of energy for the body. Saturating the blood with glucose and fructose, cane sugar:

• ensures normal functioning of the brain - the main consumer of energy;
• is a source of energy for muscle contraction;
• increases the body's performance;
• stimulates the synthesis of serotonin, thereby improving mood, being an antidepressant factor;
• participates in the formation of strategic (and not only) fat reserves;
• takes an active part in carbohydrate metabolism;
• supports the detoxification function of the liver.

The beneficial functions of sucrose appear only when consumed in limited quantities. It is considered optimal to consume 30-50 g of cane sugar in dishes, drinks or pure form.

Harm if abused

Excess daily norm consumption is fraught with manifestation harmful properties sucrose:

• endocrine disorders (diabetes mellitus, obesity);
• destruction of tooth enamel and pathologies of the musculoskeletal system as a result of impaired mineral metabolism;
• sagging skin, brittle nails and hair;
• deterioration of the skin condition (rash, acne formation);
• immunosuppression (effective immunosuppressant);
• suppression of enzyme activity;
• increased acidity of gastric juice;
• impaired renal function;
• hypercholesterolemia and triglyceridemia;
• acceleration of age-related changes.

Since B vitamins are actively involved in the absorption of sucrose breakdown products (glucose, fructose), excessive consumption of sweet foods can lead to a deficiency of these vitamins. A long-term lack of B vitamins is dangerous due to persistent disturbances in the functioning of the heart and blood vessels, and pathologies of neuropsychic activity.

In children, a passion for sweets leads to an increase in their activity up to the development of hyperactive syndrome, neuroses, and irritability.

Cellobiose disaccharide

Cellobiose is a disaccharide consisting of two glucose molecules. It is produced by plants and some bacterial cells. Cellobiose has no biological value for humans: this substance is not broken down in the human body, but is a ballast compound. In plants, cellobiose performs a structural function, as it is part of the cellulose molecule.

Trehalose - mushroom sugar

Trehalose consists of residues of two glucose molecules. Contained in higher fungi (hence its second name), algae, lichens, some worms and insects. It is believed that the accumulation of trehalose is one of the conditions for increased resistance of cells to desiccation. It is not absorbed by the human body, but its large intake into the blood can cause intoxication.

Disaccharides are widely distributed in nature - in the tissues and cells of plants, fungi, animals, and bacteria. They are part of the structure of complex molecular complexes and are also found in a free state. Some of them (lactose, sucrose) are an energy substrate for living organisms, others (cellobiose) perform a structural function.

One of the varieties organic compounds, necessary for the full functioning of the human body, are carbohydrates.

They are divided into several types according to their structure - monosaccharides, disaccharides and polysaccharides. You need to figure out why they are needed and what their chemical and physical properties are.

Classification of carbohydrates

Carbohydrates are compounds that contain carbon, hydrogen and oxygen. Most often they are of natural origin, although some are created industrially. Their role in the life of living organisms is enormous.

Their main functions are the following:

1. Energy. These compounds are the main source of energy. Most of organs can fully function using the energy obtained from the oxidation of glucose.
2. Structural. Carbohydrates are necessary for the formation of almost all cells in the body. Fiber plays the role of supporting material, and complex carbohydrates are found in bones and cartilage tissue. One of the components of cell membranes is hyaluronic acid. Also, carbohydrate compounds are required in the process of enzyme production.
3. Protective. During the functioning of the body, the work of glands is carried out, secreting secretory fluids necessary to protect internal organs from pathogenic influences. A significant portion of these liquids are carbohydrates.
4. Regulatory. This function is manifested in the effect on the human body of glucose (maintains homeostasis, controls osmotic pressure) and fiber (affects gastrointestinal peristalsis).
5. Special Features. They are characteristic certain species carbohydrates. These special functions include: participation in the process of transmission of nerve impulses, formation different groups blood, etc.

Based on the fact that the functions of carbohydrates are quite diverse, it can be assumed that these compounds should differ in their structure and characteristics.

This is true, and their main classification includes such varieties as:

1. Monosaccharides. They are considered the simplest. Other types of carbohydrates enter the process of hydrolysis and break down into smaller components. Monosaccharides do not have this ability; they are the final product.
2. Disaccharides. In some classifications they are classified as oligosaccharides. They contain two monosaccharide molecules. It is into them that the disaccharide is divided during hydrolysis.
3. Oligosaccharides. This compound contains from 2 to 10 molecules of monosaccharides.
4. Polysaccharides. These compounds are the largest variety. They contain more than 10 molecules of monosaccharides.

Each type of carbohydrate has its own characteristics. We need to look at them to understand how each of them affects the human body and what its benefits are.

Monosaccharides

These compounds are the simplest form of carbohydrates. They contain one molecule, so during hydrolysis they are not divided into small blocks. When monosaccharides combine, disaccharides, oligosaccharides and polysaccharides are formed.

They are distinguished by their solid state of aggregation and sweet taste. They have the ability to dissolve in water. They can also dissolve in alcohols (the reaction is weaker than with water). Monosaccharides almost do not react to mixing with esters.

Natural monosaccharides are most often mentioned. Some of them are consumed by people in food. These include glucose, fructose and galactose.

• chocolate;
• fruits;
• some types of wine;
• syrups, etc.

The main function of carbohydrates of this type is energy. This is not to say that the body cannot do without them, but they have properties that are important for the full functioning of the body, for example, participation in metabolic processes.

The body absorbs monosaccharides faster than anything that happens in the gastrointestinal tract. Process of assimilation complex carbohydrates, unlike simple connections, is not so simple. First, complex compounds must be separated into monosaccharides, only after which they are absorbed.

Glucose

This is one of the common types of monosaccharides. It represents white crystalline substance, which is formed naturally– during photosynthesis or hydrolysis. The formula of the compound is C6H12O6. The substance is highly soluble in water and has a sweet taste.

Glucose provides muscle and brain tissue cells with energy. Once ingested, the substance is absorbed, enters the bloodstream and spreads throughout the body. There it oxidizes and releases energy. This is the main source of energy for the brain.

When there is a lack of glucose in the body, hypoglycemia develops, which primarily affects the functioning of brain structures. However, its excessive content in the blood is also dangerous, since it leads to the development of diabetes mellitus. Also when consumed large quantity glucose levels, body weight begins to increase.

Fructose

It is a monosaccharide and is very similar to glucose. It has a slower rate of absorption. This is because fructose must first be converted into glucose in order to be absorbed.

Therefore, this compound is considered harmless for diabetics, since its consumption does not lead to a sharp change in the amount of sugar in the blood. However, with such a diagnosis, caution is still necessary.

Fructose has the ability to quickly convert into fatty acids, which causes the development of obesity. This compound also reduces insulin sensitivity, which causes type 2 diabetes.

This substance can be obtained from berries and fruits, and also from honey. Usually it is there in combination with glucose. The connection is also inherent White color. The taste is sweet, and this feature is more intense than in the case of glucose.

Other connections

There are other monosaccharide compounds. They can be natural or semi-artificial.

Galactose is a natural one. It is also contained in food products, but is not found in its pure form. Galactose is the result of the hydrolysis of lactose. Its main source is milk.

Other naturally occurring monosaccharides are ribose, deoxyribose and mannose.

There are also varieties of such carbohydrates, for the production of which industrial technologies are used.

These substances are also found in food and enter the human body:

• rhamnose;
• erythrulose;
• ribulose;
• D-xylose;
• L-allose;
• D-sorbose, etc.

Each of these connections has its own characteristics and functions.

Disaccharides and their uses

The next type of carbohydrate compounds are disaccharides. They are considered complex substances. As a result of hydrolysis, two molecules of monosaccharides are formed from them.

This type of carbohydrate has the following features:

• hardness;
• solubility in water;
• poor solubility in concentrated alcohols;
• sweet taste;
• color - from white to brown.

The main chemical properties of disaccharides are the reactions of hydrolysis (glycosidic bonds are broken and monosaccharides are formed) and condensation (polysaccharides are formed).

There are 2 types of such connections:

1. Restorative. Their peculiarity is the presence of a free hemiacetal hydroxyl group. Due to this, such substances have restorative properties. This group of carbohydrates includes cellobiose, maltose and lactose.
2. Non-restorative. These compounds cannot be reduced because they lack a hemiacetal hydroxyl group. The most well-known substances of this type are sucrose and trehalose.

These compounds are widely distributed in nature. They can occur both in free form and as part of other compounds. Disaccharides are a source of energy because they produce glucose when hydrolyzed.

Lactose is very important for children, as it is the main component of baby food. Another function of carbohydrates of this type is structural, since they are part of cellulose, which is necessary for the formation of plant cells.

Characteristics and features of polysaccharides

Another type of carbohydrates are polysaccharides. This is the most complex type of connection. They consist of a large number of monosaccharides (their main component is glucose). Polysaccharides are not absorbed in the gastrointestinal tract; they are first broken down.

The features of these substances are:

• insolubility (or weak solubility) in water;
• yellowish color (or no color);
• they have no smell;
• almost all of them are tasteless (some have a sweetish taste).

The chemical properties of these substances include hydrolysis, which is carried out under the influence of catalysts. The result of the reaction is the decomposition of the compound into structural elements– monosaccharides.

Another property is the formation of derivatives. Polysaccharides can react with acids.

The products formed during these processes are very diverse. These are acetates, sulfates, esters, phosphates, etc.

Examples of polysaccharides:

• starch;
• cellulose;
• glycogen;
• chitin.

Educational video material about the functions and classification of carbohydrates:

These substances are important for the full functioning of the body as a whole and individual cells. They supply the body with energy, participate in the formation of cells, and protect internal organs from damage and adverse effects. They also play the role of reserve substances that animals and plants need in case of difficult periods.

An example of the most common disaccharides in nature (oligosaccharides) is sucrose(beet or cane sugar).

Oligosaccharides are condensation products of two or more monosaccharide molecules.

Disaccharides - these are carbohydrates that, when heated with water in the presence of mineral acids or under the influence of enzymes, undergo hydrolysis, splitting into two molecules of monosaccharides.

Physical properties and occurrence in nature

1. It is colorless crystals with a sweet taste and is highly soluble in water.

2. The melting point of sucrose is 160 °C.

3. When molten sucrose hardens, an amorphous transparent mass is formed - caramel.

4. Contained in many plants: in the sap of birch, maple, carrots, melon, as well as in sugar beets and sugar cane.

Structure and chemical properties

1. The molecular formula of sucrose is C 12 H 22 O 11

2. Sucrose has a more complex structure than glucose. The sucrose molecule consists of glucose and fructose residues connected to each other through the interaction of hemiacetal hydroxyls (1→2)-glycosidic bond:

3. The presence of hydroxyl groups in the sucrose molecule is easily confirmed by reaction with metal hydroxides.

If a solution of sucrose is added to copper (II) hydroxide, a bright blue solution of copper sucrose is formed (a qualitative reaction of polyhydric alcohols).

Video experiment “Proof of the presence of hydroxyl groups in sucrose”

4. There is no aldehyde group in sucrose: when heated with an ammonia solution of silver (I) oxide, it does not give a “silver mirror”; when heated with copper (II) hydroxide, it does not form red copper (I) oxide.

5. Sucrose, unlike glucose, is not an aldehyde. Sucrose, when in solution, does not enter into the “silver mirror” reaction, since it is not able to transform into an open form containing an aldehyde group. Such disaccharides are not capable of oxidation (i.e., being reducing agents) and are called non-restorative sugars.

Video experiment “Lack of reducing ability of sucrose”

6. Sucrose is the most important of the disaccharides.

7. It is obtained from sugar beets (it contains up to 28% sucrose from dry matter) or from sugar cane.

Reaction of sucrose with water.

An important chemical property of sucrose is its ability to undergo hydrolysis (when heated in the presence of hydrogen ions). In this case, from one sucrose molecule a glucose molecule and a fructose molecule are formed:

C 12 H 22 O 11 + H 2 O t , H 2 SO 4 → C 6 H 12 O 6 + C 6 H 12 O 6

Video experiment “Acid hydrolysis of sucrose”

Among the isomers of sucrose with the molecular formula C 12 H 22 O 11, maltose and lactose can be distinguished.

During hydrolysis, various disaccharides are broken down into their constituent monosaccharides by breaking the bonds between them ( glycosidic bonds):

Thus, the hydrolysis reaction of disaccharides is the reverse of the process of their formation from monosaccharides.

Application of sucrose

· Food product;

· In the confectionery industry;

· Obtaining artificial honey

Carbohydrates formed by residues of two monosaccharides. Disaccharides common in animal and plant organisms are sucrose, lactose, maltose, trehalose... Big encyclopedic Dictionary

DISACCHARIDES, a type of sugar (which includes table sugar), formed by the condensation of two MONOSACHARIDES with the removal of water. Cane sugar (sucrose) is a disaccharide that, when HYDROLYZED in the presence of acid, gives... ... Scientific and technical encyclopedic dictionary

DISACCHARIDES- (sugar-like polyoses, bioses), carbohydrates that are broken down during hydrolysis (inversion) to form 2 molecules of monoses from 1 molecule D. D. are soluble in water, giving true solutions; most crystallize well and have a sweet taste. Leftovers... ... Great Medical Encyclopedia

Bioses, oligosaccharides, molecules are built from two monosaccharide residues linked by a glycosidic bond. In non-reducing D. (sucrose, trehalose), both glycosidic hydroxyls are involved in the formation of bonds between monosaccharides, in ... ... Biological encyclopedic dictionary

BIOSES are oligosaccharides, the molecules of which are built from two monosaccharide residues linked by a glycosidic bond. In non-reducing D. (sucrose, trehalose), both glycosidic hydroxyls are involved in the formation of bonds between monosaccharides, in ... ... Dictionary of microbiology

Carbohydrates formed by residues of two monosaccharides. The following disaccharides are common in animal and plant organisms: sucrose, lactose, maltose, trehalose. * * * DISACCHARIDES DISACCHARIDES, carbohydrates formed by residues of two monosaccharides. IN… … encyclopedic Dictionary

- (gr. di(s) twice + sakchar sugar + eidos species) a class of organic compounds, carbohydrates, the molecules of which consist of two monosaccharide residues; The most important representatives of disaccharides are sucrose and lactose. New dictionary foreign words. by EdwART,… … Dictionary of foreign words of the Russian language

- (syn. bios) complex sugars, consisting of two monosaccharide residues; are the main sources of carbohydrates in human and animal nutrition (lactose, sucrose, etc.) ... Large medical dictionary

Bioses, carbohydrates, the molecules of which consist of two monosaccharide residues (See Monosaccharides). All D. are constructed according to the type of glycosides (See Glycosides). In this case, the hydrogen atom of the glycosidic hydroxyl of one monosaccharide molecule is replaced... ... Great Soviet Encyclopedia

Same as saccharobioses, see Carbon hydrates... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

Books

• , . The collective monograph offered to the reader summarizes the scientific achievements of the last decade in the field of carbohydrate chemistry. For the first time, the structural features,...
• Scientific foundations of chemical technology of carbohydrates, Zakharov A.G.. The collective monograph offered to the reader summarizes the scientific achievements of the last decade in the field of carbohydrate chemistry. For the first time, the structural features,...

One of the types of organic compounds necessary for the full functioning of the human body are carbohydrates.

They are divided into several types according to their structure - monosaccharides, disaccharides and polysaccharides. You need to figure out why they are needed and what their chemical and physical properties are.

Carbohydrates are compounds that contain carbon, hydrogen and oxygen. Most often they are of natural origin, although some are created industrially. Their role in the life of living organisms is enormous.

Their main functions are the following:

1. Energy. These compounds are the main source of energy. Most organs can function fully using the energy obtained from the oxidation of glucose.
2. Structural. Carbohydrates are necessary for the formation of almost all cells in the body. Fiber plays the role of supporting material, and complex carbohydrates are found in bones and cartilage tissue. One of the components of cell membranes is hyaluronic acid. Also, carbohydrate compounds are required in the process of enzyme production.
3. Protective. During the functioning of the body, the work of glands is carried out, secreting secretory fluids necessary to protect internal organs from pathogenic influences. A significant portion of these liquids are carbohydrates.
4. Regulatory. This function is manifested in the effect on the human body of glucose (maintains homeostasis, controls osmotic pressure) and fiber (affects gastrointestinal peristalsis).
5. Special Features. They are characteristic of certain types of carbohydrates. Such special functions include: participation in the process of transmitting nerve impulses, the formation of different blood groups, etc.

Based on the fact that the functions of carbohydrates are quite diverse, it can be assumed that these compounds should differ in their structure and characteristics.

This is true, and their main classification includes such varieties as:

1. . They are considered the simplest. Other types of carbohydrates enter the process of hydrolysis and break down into smaller components. Monosaccharides do not have this ability; they are the final product.
2. Disaccharides. In some classifications they are classified as oligosaccharides. They contain two monosaccharide molecules. It is into them that the disaccharide is divided during hydrolysis.
3. Oligosaccharides. This compound contains from 2 to 10 molecules of monosaccharides.
4. Polysaccharides. These compounds are the largest variety. They contain more than 10 molecules of monosaccharides.

Each type of carbohydrate has its own characteristics. We need to look at them to understand how each of them affects the human body and what its benefits are.

These compounds are the simplest form of carbohydrates. They contain one molecule, so during hydrolysis they are not divided into small blocks. When monosaccharides combine, disaccharides, oligosaccharides and polysaccharides are formed.

They are distinguished by their solid state of aggregation and sweet taste. They have the ability to dissolve in water. They can also dissolve in alcohols (the reaction is weaker than with water). Monosaccharides almost do not react to mixing with esters.

Natural monosaccharides are most often mentioned. Some of them are consumed by people in food. These include glucose, fructose and galactose.

• chocolate;
• fruits;
• some types of wine;
• syrups, etc.

The main function of carbohydrates of this type is energy. This is not to say that the body cannot do without them, but they have properties that are important for the full functioning of the body, for example, participation in metabolic processes.

The body absorbs monosaccharides faster than anything that happens in the gastrointestinal tract. The process of assimilation of complex carbohydrates, unlike simple compounds, is not so simple. First, complex compounds must be separated into monosaccharides, only after which they are absorbed.

This is one of the common types of monosaccharides. It is a white crystalline substance that is formed naturally - during photosynthesis or hydrolysis. The formula of the compound is C6H12O6. The substance is highly soluble in water and has a sweet taste.

Glucose provides muscle and brain tissue cells with energy. Once ingested, the substance is absorbed, enters the bloodstream and spreads throughout the body. There it oxidizes and releases energy. This is the main source of energy for the brain.

When there is a lack of glucose in the body, hypoglycemia develops, which primarily affects the functioning of brain structures. However, its excessive content in the blood is also dangerous, since it leads to the development of diabetes mellitus. Also, when consuming large amounts of glucose, body weight begins to increase.

Fructose

It is a monosaccharide and is very similar to glucose. It has a slower rate of absorption. This is because fructose must first be converted into glucose in order to be absorbed.

Therefore, this compound is considered harmless for diabetics, since its consumption does not lead to a sharp change in the amount of sugar in the blood. However, with such a diagnosis, caution is still necessary.

Fructose has the ability to quickly convert into fatty acids, which causes the development of obesity. This compound also reduces insulin sensitivity, which causes type 2 diabetes.

This substance can be obtained from berries and fruits, and also from honey. Usually it is there in combination with glucose. The compound is also white in color. The taste is sweet, and this feature is more intense than in the case of glucose.

Other connections

There are other monosaccharide compounds. They can be natural or semi-artificial.

Galactose is a natural one. It is also found in food products, but is not found in its pure form. Galactose is the result of the hydrolysis of lactose. Its main source is milk.

Other naturally occurring monosaccharides are ribose, deoxyribose and mannose.

There are also varieties of such carbohydrates, for the production of which industrial technologies are used.

These substances are also found in food and enter the human body:

• rhamnose;
• erythrulose;
• ribulose;
• D-xylose;
• L-allose;
• D-sorbose, etc.

Each of these connections has its own characteristics and functions.

Disaccharides and their uses

The next type of carbohydrate compounds are disaccharides. They are considered complex substances. As a result of hydrolysis, two molecules of monosaccharides are formed from them.

This type of carbohydrate has the following features:

• hardness;
• solubility in water;
• poor solubility in concentrated alcohols;
• sweet taste;
• color - from white to brown.

The main chemical properties of disaccharides are the reactions of hydrolysis (glycosidic bonds are broken and monosaccharides are formed) and condensation (polysaccharides are formed).

There are 2 types of such connections:

1. Restorative. Their peculiarity is the presence of a free hemiacetal hydroxyl group. Due to this, such substances have restorative properties. This group of carbohydrates includes cellobiose, maltose and lactose.
2. Non-restorative. These compounds cannot be reduced because they lack a hemiacetal hydroxyl group. The most well-known substances of this type are sucrose and trehalose.

These compounds are widely distributed in nature. They can occur both in free form and as part of other compounds. Disaccharides are a source of energy because they produce glucose when hydrolyzed.

Lactose is very important for children, as it is the main component of baby food. Another function of carbohydrates of this type is structural, since they are part of cellulose, which is necessary for the formation of plant cells.

Characteristics and features of polysaccharides

Another type of carbohydrates are polysaccharides. This is the most complex type of connection. They consist of a large number of monosaccharides (their main component is glucose). Polysaccharides are not absorbed in the gastrointestinal tract; they are first broken down.

The features of these substances are:

• insolubility (or weak solubility) in water;
• yellowish color (or no color);
• they have no smell;
• almost all of them are tasteless (some have a sweetish taste).

The chemical properties of these substances include hydrolysis, which is carried out under the influence of catalysts. The result of the reaction is the decomposition of the compound into structural elements - monosaccharides.

Another property is the formation of derivatives. Polysaccharides can react with acids.

The products formed during these processes are very diverse. These are acetates, sulfates, esters, phosphates, etc.

Examples of polysaccharides:

• starch;
• cellulose;
• glycogen;
• chitin.

Educational video material about the functions and classification of carbohydrates:

These substances are important for the full functioning of the body as a whole and individual cells. They supply the body with energy, participate in the formation of cells, and protect internal organs from damage and adverse effects. They also play the role of reserve substances that animals and plants need in case of difficult periods.