Carbohydrates are made up of glucose. Glucose is the most important simple carbohydrate

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.

Carbohydrates are compounds that contain carbon, hydrogen and oxygen. Most often they have 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 in bones and cartilage tissue There are complex carbohydrates. 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 effects. A significant portion of these liquids are carbohydrates.
4. Regulatory. This function manifests itself in its influence on human body glucose (maintains homeostasis, controls osmotic pressure) and fiber (affects gastrointestinal peristalsis).
5. Special Features. They are characteristic certain species carbohydrates. To such special functions include: participation in the transfer process 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. . 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 hardness 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 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 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 contained in food products, but not found in 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 (breaking of glycosidic bonds and formation of monosaccharides) 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 baby food. Another function of carbohydrates of this type is structural, since they are part of cellulose, which is needed for the formation 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.

Remember: qualitative reaction to glycerol (§ 32).

The concept of carbohydrates and their classification

In nature great importance have carbohydrates (saccharides) - organic compounds with the general formula Cn(H2O)m (m, n > 3).. The name of this class of compounds comes from their property of decomposing into carbon and water when heated or under the influence of concentrated sulfate acid, which is also shown in their general formula(Fig. 36.1).

Rice. 36.1. Under the influence of concentrated sulfate acid, carbohydrates are decomposed into carbon and water

Carbohydrates are divided into simple (monosaccharides) and complex (disaccharides and polysaccharides) (Scheme 6). They differ fundamentally in that complex carbohydrates under certain conditions, they hydrolyze to simple ones (decompose), but simple ones cannot be hydrolyzed. Disaccharide molecules consist of two, and polysaccharides consist of a large number of monosaccharide molecule residues.

Scheme 6. Classification of carbohydrates

Glucose C 6 H 12 O 6 is the most common carbohydrate in living nature; it is one of the products of the photosynthesis process, as a result of which plants accumulate energy from the Sun.

Glucose is a colorless, odorless crystalline substance, density - 1.54 g/cm3, melting point - 146 °C. When heated above this temperature, the substance decomposes before reaching the boiling point. Glucose tastes sweet, but one and a half times less sweet than sucrose. It is highly soluble in water: 32 g of glucose dissolves in 100 g of water at 0 °C, and 82 g at 25 °C; it is poorly soluble in organic solvents. Its solutions do not conduct electricity(glucose is a non-electrolyte).

The glucose molecule contains several -OH groups, like glycerol, therefore, like it, it can interact with freshly precipitated cuprum(P) hydroxide (Fig. 36.2, a and b):

When heated, glucose decomposes, like all carbohydrates, into carbon and water:

Glucose is one of the main metabolic products in living organisms. In nature, it is formed in the green parts of plants during the process of photosynthesis, which occurs with the absorption of sunlight:

The reverse reaction is also possible:

This equation can describe the overall process as a result of which all animals receive energy for their life activities: glucose enters our body along with food, we inhale oxygen with our lungs, and we exhale the reaction product - carbon dioxide. This equation also describes the process of combustion and explosion of glucose. It is quite difficult to ignite glucose; it burns only in the presence of a catalyst, and explodes when crushed very strongly (see § 20).

In plants, glucose is converted into complex carbohydrates - starch and cellulose:

Rice. 36.2. Qualitative reaction to glucose: a — freshly precipitated cuprum(I) hydroxide; b - in the presence of glucose, the precipitate disappears, a dark blue compound is formed

It is much more difficult to synthesize glucose using organic chemistry methods. This synthesis was first realized by Emil Fischer.

WITH plant foods carbohydrates enter the body of animals, where they are the main source of energy. So, from 1 g of carbohydrates the body receives about 17 kJ (4 kcal). If this energy is not completely consumed, the body stores it “in reserve”, directing it to the synthesis of fats.

Glucose was first isolated from grapes, which is why it is also called grape sugar. In its pure form, glucose is found in sweet berries and fruits: it determines the sweetness of some parts of plants (berries, fruits, root vegetables, etc.). Together with fructose, it is contained in honey.

The glucose content in human blood is about 0.1%; deviation of this indicator from the norm indicates a disease diabetes mellitus. Blood glucose levels (often referred to simply as “blood sugar”) are monitored using a clinical blood test. This analysis can be done at home using a special device - a glucometer (Fig. 36.4).

German organic chemist, winner of the Nobel Prize in Chemistry in 1902. Higher education received from the universities of Bonn and Strasbourg. At the age of 22, after defending his dissertation, he became a teacher at the University of Strasbourg. Fischer was the first to determine the structure of some organic substances: caffeine, purine, uric acid, glucose and fructose. He discovered methods for their synthesis. He established the features of reactions involving enzymes and proposed a classification of proteins. For research and synthesis of saccharides and purine derivatives received Nobel Prize. In his honor, the German Chemical Society established the Emil Fischer Medal.

In industry, glucose is produced by hydrolysis of starch or cellulose. But pure glucose has no wide application. This glucose is used in various biological and biochemical research. In medicine, it is used to conduct a glucose tolerance test, a study that allows diagnosing diabetes mellitus. For some diseases, a glucose solution is administered to a person intravenously. IN Food Industry It is rarely used as a sweetener: it is more expensive and less sweet than sugar.

Glucose is characterized by a fermentation reaction. Under the influence of lactic acid bacteria, lactic acid is formed from glucose:

This reaction occurs when milk sours and is the basis for the production of various lactic acid products - curdled milk, yoghurt, cheese, sour cream, etc. Lactic acid fermentation occurs during sauerkraut and other vegetables, prevents the development of putrefactive bacteria and promotes long-term storage products. This process can also occur in oral cavity, which causes dental caries.

Sucrose

The most important among the disaccharides is sucrose C 12 H 22 O 1r This is the chemical name for ordinary sugar obtained from sugar beets or sugar cane.

Sucrose is a colorless, odorless crystalline substance, density - 1.59 g/cm3, melting point - 186 °C. Sucrose tastes sweet (one and a half times sweeter than glucose). It dissolves very well in water: 179 g of sucrose dissolves in 100 g of water at 0 °C, and 487 g at 100 °C.

Like glucose, sucrose decomposes when heated:

This reaction occurs when making caramel and baking pastries and cakes; thanks to it, a sweet caramelized crust with a specific taste of burnt sugar is formed (Fig. 36.5).

Like most organic substances, sucrose can burn to form carbon dioxide and water:

But if you just try to set fire to sugar, it will not ignite: for this you need a catalyst - Lithium salts. Heavily crushed sugar can not only burn, but its suspension in the air can explode, as discussed in § 20.

Rice. 36.5. The melting of sucrose is accompanied by a color change and the appearance of a specific caramel odor.

Sucrose is called a disaccharide because the sucrose molecule consists of the residues of two monosaccharide molecules - glucose and fructose - connected to each other.

During the hydrolysis of sucrose into acidic environment or under the action of enzymes the bond between these residues is broken and molecules of glucose and fructose are formed:

This transformation occurs in the bodies of bees: while collecting nectar from flowers, they consume sucrose, which is then hydrolyzed. Therefore honey is a mixture equal quantities glucose and fructose, of course, with admixtures of other substances (Fig. 36.6).

IN large quantities sucrose is found in only three plants: sugar beets and sugar cane, used for industrial sugar production, as well as in sugar maple (from it

get maple syrup). To attract insects, sucrose small quantity found in the nectar of flowers, as well as in fruits and berries.

In Ukraine, the sugar industry is one of the oldest and most important branches of the food industry, the products of which are valuable product export. The outstanding Ukrainian scientist N.A. Bunge made a significant contribution to the development of the sugar industry in Ukraine.

Outstanding Ukrainian chemist, professor at Kyiv University. Born in Warsaw. He graduated from Kiev University, where he taught technical chemistry from 1870. The main scientific achievements relate to technical chemistry, in particular winemaking, sugar production. Improved the technology for producing sugar from sugar beets. Researched the technology of formation of sugar crystals, conditions of formation, composition and transformation of beet jelly. He organized a technical school for sugar production and published 33 volumes of the “Yearbook of the Beet Sugar Industry.” He was one of the organizers of gas and electric lighting, as well as water supply in Kyiv.

Today in Ukraine there are about 100 sugar factories with a total maximum capacity of about 7 million tons per year. These enterprises can produce sugar from both beets (local raw material) and cane (usually exported from Cuba). The largest plant is the Lokhvitsky Sugar Refinery (Poltava region) with a daily capacity of 9,300 tons of sugar. IN last years Ukraine produces about 2 million tons of sugar annually, part of which is exported.

Brown sugar is regular cane sugar that has been removed from impurities during the manufacturing process. Interestingly, there are fewer technological processes in its production (there is no final purification), it is cheaper to produce, but is much more expensive to sell than regular white sugar.

The words “sucrose” and “sugar” come from the ancient Indian word “sarkar”, which means the pieces of crystalline substance formed when sugarcane juice is condensed.

Carbohydrates are a source of energy in the body: the combustion of 1 g of carbohydrates produces 3.75 kcal. They are part of cells and tissues, enzymes, some hormones, blood clotting factors, etc.
Carbohydrates are divided into monosaccharides (glucose and fructose), disaccharides (sucrose and lactose) and polysaccharides (starch, fiber, pectin, glycogen). Glucose and fructose are absorbed the fastest - they are found in fruits, berries, and honey.
The main sources of sucrose are sugar, confectionery, beets, carrots, etc.
Lactose is found in dairy products.
In the intestine, sucrose is broken down into glucose and fructose by enzymes, and lactose into glucose and galactose.
The highest starch content is in cereals, pasta, bread, potatoes, and legumes. In the intestines it is slowly digested and broken down into glucose.
Fiber is almost not absorbed, but participates in the formation feces, improves motor function intestines and prevents the development of constipation, increases the removal of cholesterol from the body, and improves the secretion of bile. Fiber is found in vegetables, fruits, berries, legumes, cereals (oatmeal, buckwheat), wholemeal bread.
Pectin has adsorbing properties and is therefore used in the treatment of diarrhea and for the prevention chronic intoxications, prescribed to persons in contact with salts heavy metals. Vegetables, fruits and berries are rich in pectin.
The muscles and liver contain about 1.5 kg of glycogen, which is a reserve of carbohydrates in the body. With carbohydrate deficiency, these reserves are quickly consumed, and subsequently carbohydrates in the body are synthesized from proteins and fats, which contributes to the accumulation of under-oxidized metabolic products in the blood and the development of acidosis.
The need for carbohydrates is determined by the nature of the work performed and is 300-500 g per day, of which 20-30% are easily digestible (sugar, jam, honey, syrup, etc.). In the diet of older people, the amount of carbohydrates should not exceed 250-300 g per day, of which 15-20% are easily digestible. In case of obesity and other diseases, carbohydrates in the diet are limited, but their limitation should occur gradually so that the body can adapt to new metabolic conditions. You should start with 200-250 g per day for 7-10 days, then increase this amount to 100 g.

Lack of carbohydrates in the diet for a long time or their sharp restriction disrupts their synthesis from proteins and fats, which contributes to a decrease in blood sugar, a decrease in mental and physical performance, the appearance of weakness, drowsiness, dizziness, headache, hunger, trembling hands. These phenomena disappear after eating sugar or other sweet foods.

An excess of carbohydrates in the diet, especially easily digestible ones, is also harmful to the body. It promotes the development of atherosclerosis, cardiac -vascular diseases, diabetes, obesity, dental caries.
The role of carbohydrates in the life of the human body
The main function of carbohydrates is to provide energy for all processes in the body. Cells are able to obtain energy from carbohydrates, as during their oxidation, i.e. "combustion" and under anaerobic conditions (without oxygen). Muscle pain after hard work is the result of the action of lactic acid on the cells, which is formed during the anaerobic breakdown of carbohydrates, when to ensure work muscle cells there is not enough oxygen supplied with the blood.

Often, a sharp restriction of carbohydrates in the diet leads to significant metabolic disorders. It especially suffers from this protein metabolism. In case of carbohydrate deficiency, proteins are used for other purposes: they become a source of energy and participants in some important chemical reactions. This leads to increased formation of nitrogenous substances and, as a consequence, to increased load on kidneys, disorders salt metabolism and other harmful consequences to health. With a sufficient supply of carbohydrates from food, proteins are used mainly for plastic metabolism, and not for energy production. Thus, carbohydrates are necessary for the rational use of proteins. They are also capable of stimulating the oxidation of metabolic intermediates fatty acids.

This, however, does not exhaust the role of carbohydrates. They are integral part molecules of some amino acids, participate in the construction of enzymes, the formation of nucleic acids, are precursors for the formation of fats, immunoglobulins, which play an important role in the immune system, and glycoproteins - complexes of carbohydrates and proteins that are the most important components of cell membranes. Hyaluronic acids and other mucopolysaccharides form a protective layer between all the cells that make up the body.

When there is a deficiency of carbohydrates in food, the body uses not only proteins, but also fats to synthesize energy. With increased breakdown of fats, disturbances may occur metabolic processes, associated with the accelerated formation of ketones (acetone, known to everyone, belongs to this class of substances) and their accumulation in the body. Overeducation ketones with increased oxidation of fats and partially proteins can lead to “acidification” internal environment body and poisoning of brain tissue up to the development of acidotic coma with loss of consciousness.

Carbohydrates according to their chemical structure can be divided into simple (mono- and disaccharides) and complex (polysaccharides). Simple carbohydrates consist of molecules closed in a ring with five (pentoses) or six (hexoses) carbon atoms. For each carbon atom in such a molecule there are two hydrogen atoms and one oxygen atom. This is where they come from common name(coal + water). The end product of carbohydrate metabolism is water and carbon dioxide. Monosaccharides vary in their properties (and names) depending on how many carbon atoms are in the molecule, how it is folded into a ring, and how the corners of the resulting pentagon or hexagon are bent.

When two monosaccharide molecules combine, disaccharides are formed; polysaccharides consist of straight or branched chains of monosaccharide molecules of varying lengths. A molecule of animal carbohydrates, glycogen, can contain up to 1 million monosaccharides.

Experts World Organization health (WHO, 2002) proposed a simplified classification of carbohydrates:
Classification groups Carbohydrates
Sugars (1-2 monomers):
Monosaccharides
Disaccharides
glucose, fructose, galactose
sucrose, lactose
Oligosaccharides (3-9 monomers): maltodextrins
Polysaccharides (more than 9 monomers):
starch
non-starch polysaccharides
amylose, amylopectin
cellulose, pectin

Glucose is the most important simple carbohydrate
The most important of all monosaccharides is glucose, since it is the structural unit (building block) for the construction of most food di- and polysaccharides. Mono-, di- and polysaccharides come to us with food. Monosaccharides are absorbed in the intestine. During their movement through the gastrointestinal tract, polysaccharides are broken down into individual monosaccharide molecules and absorbed into the bloodstream. small intestine. With blood portal vein Most of the glucose (about half) from the intestine enters the liver, the rest of the glucose is transported through the general bloodstream to other tissues. The concentration of glucose in the blood is normally maintained at a constant level and amounts to 3.33-5.55 µmol/l, which corresponds to 80-100 mg in 100 ml of blood. The transport of glucose into cells is regulated in many tissues by the pancreatic hormone - insulin. In the cell, through multi-step chemical reactions, glucose is converted into other substances, which are ultimately oxidized to carbon dioxide and water, releasing energy that the body uses to support life. If your blood glucose level decreases or high concentration and the inability to use, as happens in diabetes, drowsiness occurs, and loss of consciousness may occur (hypoglycemic coma).

Without the presence of insulin, glucose will not enter the cell and will not be used as fuel. In this case, fats are usually used as fuel (this is typical for people with diabetes). The rate at which glucose enters the tissues of the brain and liver does not depend on insulin and is determined only by its concentration in the blood. These tissues are called insulin-independent.

Fructose is a tasty carbohydrate
It is one of the most common fruit carbohydrates. 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 of carbohydrates for diabetics. Some of the fructose enters the liver cells, which convert it into a more versatile “fuel” - glucose, so fructose can also increase blood sugar levels, although to a much lesser extent than others simple sugars. Fructose is easier to convert into fat than glucose. The main advantage of fructose is that it is 2.5 times sweeter than glucose and 1.7 times sweeter than sucrose. Its use instead of sugar allows you to reduce your overall carbohydrate intake.

Galactose - milk carbohydrate
Not found in free form in products. It forms a disaccharide with glucose - lactose (milk sugar) - the main carbohydrate of milk and dairy products.

Lactose
Splits into gastrointestinal tract to glucose and galactose under the action of the enzyme lactase. A deficiency of this enzyme leads to milk intolerance in some people. Deficiency of this enzyme occurs in approximately 40% of the adult population. Undigested lactose is a good nutrient for intestinal microflora. It is possible excessive gas formation, stomach "swells". IN fermented milk products Most lactose is fermented to lactic acid, so people with lactase intolerance can tolerate fermented milk products without unpleasant consequences. In addition, lactic acid bacteria in fermented milk products suppress the activity of intestinal microflora and reduce the adverse effects of lactose.

Sucrose is an "empty" carbohydrate
The disaccharide formed by glucose and fructose molecules is sucrose. The sucrose content in sugar is 95%. Sugar is quickly 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 called a “carrier of empty calories”, since sugar is a pure carbohydrate, it does not contain other nutrients, such as, for example, vitamins, mineral salts. When two glucose molecules combine, maltose is formed - malt sugar. It contains honey, malt, beer, molasses and bakery and confectionery products made with the addition of molasses.

All polysaccharides present in human food, with rare exceptions, are polymers of glucose. The main means of deposition (accumulation) of carbohydrates in plants is a polysaccharide - starch. In animals, this is glycogen.

Starch is a common carbohydrate
The main digestible polysaccharide. It accounts for up to 80% of carbohydrates consumed in food. The source of starch is herbal products, mainly cereals: cereals, flour, bread, and potatoes. Cereals contain the most starch: from 60% in buckwheat (kernel) to 70% in rice. In cereals, the least amount of starch is found in oats and its processed products: oatmeal, oatmeal"Hercules" - 49%. Pasta contains from 62% to 68% starch, bread made from rye flour, depending on the type - from 33% to 49%, wheat bread and other products made from wheat flour - from 35% to 51% starch, flour - from 56% (rye) to 68% (premium wheat). There is a lot of starch in legume products- from 40% in lentils to 44% in peas. For this reason, dry peas, beans, lentils, and chickpeas are classified as legumes. Standing apart are soybeans, which contain only 3.5% starch, and soybean flour (10.0-15.5%). Because of high content starch in potatoes (15-18%) in dietetics it is classified not as a vegetable, where the main carbohydrates are represented by mono- and disaccharides, but as a starchy product along with cereals and legumes.

The main difference between polysaccharides is that when starch is digested in the gastrointestinal tract, enzymatic breakdown and formation of monosaccharides occur, the main of which is glucose. The breakdown of starch begins in the oral cavity with the participation of saliva, which partially breaks down molecular bonds, forming molecules smaller than starch - dextrins. And then the digestion process occurs gradually throughout the entire gastrointestinal tract. The glycogen molecule contains up to 1 million glucose residues, therefore, a significant amount of energy is spent on synthesis. The need to convert glucose into glycogen is due to the fact that the accumulation of a significant amount of glucose in the cell would lead to an increase in osmotic pressure, since glucose is a highly soluble substance. On the contrary, glycogen is contained in the cell in the form of granules and is slightly soluble. The breakdown of glycogen - glycogenolysis - occurs between meals. Glycogen is a convenient form of carbohydrate storage, which has an actively branched structure, which allows you to quickly and efficiently break down glycogen into glucose and quickly use it as an energy source.

Glycogen - reserve carbohydrate
The main form of carbohydrate storage in animals. Glycogen is stored mainly in the liver (up to 6% of the liver mass) and in the muscles, where its content rarely exceeds 1%. The carbohydrate reserves in the body of a normal adult (weighing 70 kg) after a meal are about 327 g:
liver glycogen 4.0% = 72 g (liver weight 1800 g);
muscle glycogen 0.7% = 245 g (muscle mass 35 kg);
extracellular glucose 0.1% = 10 g (total volume of extracellular fluid 10 l).

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 concentrations glucose in the blood, especially between meals. 12-18 hours after eating, the glycogen supply in the liver is almost completely depleted. The content of muscle glycogen decreases noticeably only after prolonged and strenuous exercise. physical work.

Dietary fiber - complex carbohydrate
This is a complex of carbohydrates: fiber (cellulose), hemicellulose, pectins, gums (gum), mucus, and also non-carbohydrate lignin. Thus, dietary fiber is a large group of substances of various chemical natures, the source of which is plant products. Some authors classify amino sugars from fungi and crustaceans as dietary fiber, such as chitin and chitosan.

There is a lot of dietary fiber in bran, wholemeal flour and bread made from it, cereals with shells, legumes, and nuts. There is less dietary fiber in most vegetables, fruits and berries, and especially in fine flour bread, pasta, and peeled cereals (rice, semolina and etc.)

Carbohydrates are the main source of energy for the body, and the body takes about 60% of this energy in the form of carbohydrates, and the rest in the form of proteins and fats. At the same time, carbohydrates are found mainly in foods plant origin. But still what are carbohydrates.

Carbohydrates in food products are divided into simple carbohydrates, This:

• monosaccharides (fructose, glucose, galactose),
• disaccharides (lactose, sucrose).

In addition, they include complex carbohydrates, and these are polysaccharides, including glycogen, starch, fiber and pectin.

Simple carbohydrates Easily soluble in water, they are absorbed quite quickly. They are easily recognized by their distinct sweet taste and are classified as sugars.

Carbohydrate glucose

The most common monosaccharide is glucose. It is part of many fruits and berries, but it is also produced in the body as a consequence of the breakdown of food starch and disaccharides. Glucose is best used in the body for the formation of glycogen; it feeds brain tissue and working muscles, it maintains the desired level of sugar in the blood and creates a reserve of liver glycogen. , as a source of energy.

Benefits of fructose

Fructose has the same properties as glucose, but it is absorbed somewhat more slowly in the intestines, and when it enters the blood, it leaves the bloodstream relatively quickly. Fructose in a noticeable amount (up to 80%) is retained in the liver and does not oversaturate the blood with sugar. In the liver, fructose is more easily converted into glycogen, which can be compared to glucose. than sucrose and it is sweeter. This property is used to reduce its amount when the desired order of sweetness of products is achieved, which allows reducing overall sugar consumption. This is important when prescribing reduced calorie diets. Fructose is mainly found in fruits, berries and sweet vegetables.

A large food source of glucose and fructose is honey, containing 36.2% glucose and 37.1% fructose. All the sugar in watermelons is fructose, it contains 8%. In pome fruits, there is also fructose, but in stone fruits, which include peaches, apricots, and plums, there is glucose.

Simple carbohydrates galactose and sucrose

Galactose is the result of the breakdown of lactose - main carbohydrate of milk and it is not found in free form in food products.

Of the disaccharides in human food, sucrose is mainly present, which breaks down during hydrolysis into glucose and fructose.

Sucrose- This is a very important product obtained from cane and beet sugar. Granulated sugar contains sucrose up to 99.75%. Natural suppliers of sucrose are melons, as well as some vegetables and fruits. Once in the body, sucrose easily breaks down into monosaccharides. However, this happens when we consume raw beet or cane juice. Regular sugar is much more difficult to digest.

Milk sugar - lactose

Milk sugar - lactose - is the main carbohydrate in dairy products. Its very large in the early childhood, while milk is . If the enzyme that breaks down lactose into glucose and galactose is reduced or absent, milk intolerance occurs in the gastrointestinal tract.

Complex carbohydrates- polysaccharides, have a complicated molecular structure and poor solubility in water. These are glycogen, starch, pectin and fiber.

Carbohydrate Maltose

Malt sugar - Maltose is an intermediate substance that occurs during the breakdown of starch and glycogen in the gastrointestinal tract. In its free form, it can be determined in honey, beer, malt, molasses and sprouted grains.

The most important supplier of carbohydrates is starch. The starch of raw plants progressively breaks down into digestive tract human body, and decay begins in the mouth. The saliva in the mouth begins to convert it into maltose. That is why chewing thoroughly food and its processing with saliva are very important.

You should always use products that contain natural glucose, fructose and sucrose. The most sugar is found in vegetables, fruits and dried fruits, but in addition, it is also found in sprouted grains.