Carbohydrates are classified according to the size of their molecules into 3 groups:

Monosaccharides– contain 1 carbohydrate molecule (aldose or ketose).

Trioses (glyceraldehyde, dihydroxyacetone).

Tetroses (erythrose).

Pentoses (ribose and deoxyribose).

Hexoses (glucose, fructose, galactose).

Oligosaccharides- contain 2-10 monosaccharides.

Disaccharides (sucrose, maltose, lactose).

Trisaccharides, etc.

Polysaccharides- contain more than 10 monosaccharides.

Homopolysaccharides - contain the same monosaccharides (starch, fiber, cellulose consist only of glucose).

Heteropolysaccharides - contain monosaccharides different types, their vapor-derived and non-carbohydrate components (heparin, hyaluronic acid, chondroitin sulfates).

Scheme No. 1. K classification of carbohydrates.

Carbohydrates Monosaccharides Oligosaccharides Polysaccharides

1. Trioses 1. Disaccharides 1. Homopolysaccharides

2. Tetroses 2. Trisaccharides 2. Heteropolysaccharides

3. Pentoses 3. Tetrasaccharides

4. Hexoses

3. 4. Properties of carbohydrates.

Carbohydrates are solid, crystalline white substances that almost all taste sweet.

Almost all carbohydrates are highly soluble in water, and true solutions are formed. The solubility of carbohydrates depends on mass (the greater the mass, the less soluble the substance, for example, sucrose and starch) and structure (the more branched the structure of the carbohydrate, the worse the solubility in water, for example, starch and fiber).

Monosaccharides can be found in two stereoisomeric forms: L-shape (leavus - left) and D-shape (dexter - right). These forms have the same chemical properties, but differ in the location of the hydroxide groups relative to the axis of the molecule and optical activity, i.e. rotate the plane of polarized light that passes through their solution through a certain angle. Moreover, the plane of polarized light rotates by one amount, but in opposite directions. Let's consider the formation of stereoisomers using the example of glyceraldehyde:

Sno sno

BUT-S-N N-S- HE

CH2OH CH2OH

L – shape D – shape

When producing monosaccharides in laboratory conditions, stereoisomers are formed in a 1:1 ratio; in the body, synthesis occurs under the action of enzymes that strictly distinguish between the L-form and the D-form. Since only D-sugars undergo synthesis and breakdown in the body, L-stereoisomers gradually disappeared in evolution (the definition of sugars in biological fluids using a polarimeter).

Monosaccharides in aqueous solutions can interconvert, this property is called mutation.

HO-CH2 O=C-H

S O NO-S-N

N N N N-S-OH

S S NO-S-N

BUT HE N HE BUT-S-N

C CH2-OH

Alpha form Open form of hexose

N N HE

BUT HE N N

Betta form.

In aqueous solutions, monomers consisting of 5 or more atoms can be found in cyclic (ring) alpha or beta forms and open (open) forms, and their ratio is 1:1. Oligo- and polysaccharides consist of monomers in cyclic form. In the cyclic form, carbohydrates are stable and moloactive, and in the open form they are highly reactive.

Monosaccharides can be reduced to alcohols.

IN open form can interact with proteins, lipids, and nucleotides without the participation of enzymes. These reactions are called glycation. The clinic uses a study of the level of glycosylated hemoglobin or fructosamine to diagnose diabetes mellitus.

Monosaccharides can form esters. Of greatest importance is the property of carbohydrates to form esters with phosphoric acid, because in order to be included in the metabolism, the carbohydrate must become a phosphorus ester, for example, glucose is converted into glucose-1-phosphate or glucose-6-phosphate before oxidation.

Aldolases have the ability to reduce metals from their oxides to an oxide or free state in an alkaline environment. This property is used in laboratory practice to detect aldoloses (glucose) in biological fluids. Most often used Trommer's reaction in which aldolose reduces copper oxide to oxide, and itself is oxidized to gluconic acid (1 carbon atom is oxidized).

CuSO4 + NaOH Cu(OH)2 + Na2SO4

Blue

C5H11COH + 2Cu(OH)2 C5H11COOH + H2O + 2CuOH

Brick red color

Monosaccharides can be oxidized to acids not only in the Trommer reaction. For example, when the 6th carbon atom of glucose is oxidized, glucuronic acid is formed in the body, which combines with toxic and poorly soluble substances, neutralizes them and makes them soluble, in which form these substances are excreted from the body in the urine.

Monosaccharides can combine with each other and form polymers. The connection that arises in this case is called glycosidic, it is formed by the OH group of the first carbon atom of one monosaccharide and the OH group of the fourth (1,4-glycosidic bond) or sixth carbon atom (1,6-glycosidic bond) of another monosaccharide. In addition, an alpha glycosidic bond (between two alpha forms of a carbohydrate) or a beta glycosidic bond (between the alpha and beta forms of a carbohydrate) can be formed.

Oligo- and polysaccharides can undergo hydrolysis to form monomers. The reaction occurs at the site of the glycosidic bond, and this process is accelerated in an acidic environment. Enzymes in the human body can distinguish between alpha and beta glycosidic bonds, so starch (has alpha glycosidic bonds) is digested in the intestines, but fiber (has beta glycosidic bonds) is not.

Mono- and oligosaccharides can undergo fermentation: alcoholic, lactic acid, citric acid, butyric acid.

Functions of soluble carbohydrates: transport, protective, signaling, energy.

Monosaccharides: glucose– the main source of energy for cellular respiration. Fructose – component flower nectar and fruit juices. Ribose and deoxyribose– structural elements of nucleotides, which are monomers of RNA and DNA.

Disaccharides: sucrose(glucose + fructose) is the main product of photosynthesis transported in plants. Lactose(glucose + galactose) – is part of the milk of mammals. Maltose(glucose + glucose) is a source of energy in germinating seeds.

Slide 8

Polymeric carbohydrates:

starch, glycogen, cellulose, chitin. They are not soluble in water.

Functions of polymeric carbohydrates: structural, storage, energy, protective.

Starch consists of branched spiral molecules that form reserve substances in plant tissues.

Cellulose- a polymer formed by glucose residues consisting of several straight parallel chains connected by hydrogen bonds. This structure prevents the penetration of water and ensures the stability of the cellulose membranes of plant cells.

Chitin consists of amino derivatives of glucose. The main structural element of the integument of arthropods and the cell walls of fungi.

Glycogen– reserve substance animal cell. Glycogen is even more branched than starch and is highly soluble in water.

Lipids– esters of fatty acids and glycerol. Insoluble in water, but soluble in non-polar solvents. Present in all cells. Lipids are made up of hydrogen, oxygen and carbon atoms. Types of lipids: fats, waxes, phospholipids.

Slide 9

Functions of lipids:

Storage– fats are stored in the tissues of vertebrate animals.

Energy– half of the energy consumed by the cells of vertebrates at rest is formed as a result of fat oxidation. Fats are also used as a source of water. The energy effect from the breakdown of 1 g of fat is 39 kJ, which is twice as much as the energy effect from the breakdown of 1 g of glucose or protein.

Protective – subcutaneous fat The new layer protects the body from mechanical damage.

Structural – phospholipids are part of cell membranes.

Thermal insulation– subcutaneous fat helps retain heat.

Electrical insulating– myelin secreted by Schwann cells (they form membranes nerve fibers), isolates some neurons, which speeds up transmission many times nerve impulses.

Nutritious– some lipid-like substances promote the growth muscle mass, maintaining body tone.

Lubricating– waxes cover the skin, wool, feathers and protect them from water. The leaves of many plants are covered with a waxy coating; wax is used in the construction of honeycombs.

Hormonal– adrenal hormone – cortisone and sex hormones are of lipid nature.

Slide 10

Proteins, their structure and functions

Proteins are biological heteropolymers whose monomers are amino acids. Proteins are synthesized in living organisms and perform certain functions in them.

Proteins contain atoms of carbon, oxygen, hydrogen, nitrogen and sometimes sulfur.

The monomers of proteins are amino acids - substances containing unchangeable parts - the amino group NH 2 and the carboxyl group COOH and a changeable part - the radical. It is the radicals that make amino acids different from each other.

Amino acids have the properties of an acid and a base (they are amphoteric), so they can combine with each other. Their number in one molecule can reach several hundred. Alternation of different amino acids in different sequence allows you to obtain a huge number of proteins with different structures and functions.

Proteins contain 20 types of different amino acids, some of which animals cannot synthesize. They get them from plants that can synthesize all the amino acids. It is to amino acids that proteins are broken down in the digestive tracts of animals. From these amino acids entering the body's cells, its new proteins are built.

Slide 11

Structure of a protein molecule.

The structure of a protein molecule is understood as its amino acid composition, the sequence of monomers and the degree of twisting of the molecule, which must fit into various departments and cell organelles, and not alone, but together with a huge amount other molecules.

The sequence of amino acids in a protein molecule forms its primary structure. It depends on the sequence of nucleotides in the section of the DNA molecule (gene) encoding the protein. Adjacent amino acids are linked by peptide bonds that occur between the carbon of the carboxyl group of one amino acid and the nitrogen of the amino group of another amino acid.

A long protein molecule folds and first takes on the appearance of a spiral. This is how the secondary structure of the protein molecule arises. Between CO and NH - groups of amino acid residues, adjacent turns of the helix, hydrogen bonds arise that hold the chain together.

A protein molecule of complex configuration in the form of a globule (ball) acquires a tertiary structure. The strength of this structure is provided by hydrophobic, hydrogen, ionic and disulfide S-S bonds.

Some proteins have a quaternary structure, formed by several polypeptide chains (tertiary structures). The quaternary structure is also held together by weak non-covalent bonds - ionic, hydrogen, hydrophobic. However, the strength of these bonds is low and the structure can be easily damaged. When heated or treated with certain chemicals the protein undergoes denaturation and loses its biological activity. Disruption of quaternary, tertiary and secondary structures is reversible. The destruction of the primary structure is irreversible.

In any cell there are hundreds of protein molecules that perform various functions. In addition, proteins have species specificity. This means that each species of organism has proteins not found in other species. This creates serious difficulties when transplanting organs and tissues from one person to another, when grafting one type of plant onto another, etc.

Slide 12

Functions of proteins.

Catalytic (enzymatic) – proteins speed up everything biochemical processes walking in a cage: splitting nutrients in the digestive tract, participate in matrix synthesis reactions. Each enzyme speeds up one and only one reaction (both forward and reverse). The rate of enzymatic reactions depends on the temperature of the medium, its pH level, as well as on the concentrations of the reacting substances and the concentration of the enzyme.

Transport– proteins provide active transport of ions through cell membranes, oxygen transport and carbon dioxide, transport of fatty acids.

Protective– antibodies provide immune protection body; fibrinogen and fibrin protect the body from blood loss.

Structural- one of the main functions of proteins. Proteins are part of cell membranes; the protein keratin forms hair and nails; proteins collagen and elastin – cartilage and tendons.

Contractive– provided by contractile proteins – actin and myosin.

Signal– protein molecules can receive signals and serve as their carriers in the body (hormones). It should be remembered that not all hormones are proteins.

Energy- at long fasting Proteins can be used as an additional source of energy after carbohydrates and fats have been used up.

Slide13

Nucleic acids

Nucleic acids were discovered in 1868 by the Swiss scientist F. Miescher. In organisms, there are several types of nucleic acids that are found in various cell organelles - the nucleus, mitochondria, plastids. Nucleic acids include DNA, i-RNA, t-RNA, r-RNA.

Deoxyribonucleic acid (DNA)– a linear polymer in the form of a double helix formed by a pair of antiparallel complementary (corresponding to each other in configuration) chains. The spatial structure of the DNA molecule was modeled by American scientists James Watson and Francis Crick in 1953.

The monomers of DNA are nucleotides . Each DNA nucleotide consists of a purine (A - adenine or G - guanine) or pyrimidine (T - thymine or C - cytosine) nitrogenous base, five carbon sugar– deoxyribose and phosphate group.

The nucleotides in a DNA molecule face each other with nitrogenous bases and are united in pairs in accordance with the rules of complementarity: thymine is located opposite adenine, and cytosine is located opposite guanine. The A – T pair is connected by two hydrogen bonds, and the G – C pair is connected by three. During the replication (doubling) of a DNA molecule, hydrogen bonds are broken and the chains separate, and a new DNA chain is synthesized on each of them. The backbone of DNA chains is formed by sugar phosphate residues.

The sequence of nucleotides in a DNA molecule determines its specificity, as well as the specificity of the body proteins that are encoded by this sequence. These sequences are individual for each type of organism and for individual individuals.

Example: the DNA nucleotide sequence is given: CGA – TTA – CAA.

On messenger RNA (i-RNA), the chain HCU - AAU - GUU will be synthesized, resulting in a chain of amino acids: alanine - asparagine - valine.

When nucleotides in one of the triplets are replaced or rearranged, this triplet will encode a different amino acid, and therefore the protein encoded by this gene will change.

Slide 14

Changes in the composition of nucleotides or their sequence are called mutation.

Slide 15

Ribonucleic acid (RNA)– a linear polymer consisting of a single chain of nucleotides. In RNA, the thymine nucleotide is replaced by uracil (U). Each RNA nucleotide contains a five-carbon sugar - ribose, one of four nitrogenous bases and a phosphoric acid residue.

Types of RNA.

Matrix, or informational, RNA. It is synthesized in the nucleus with the participation of the enzyme RNA polymerase. Complementary to the region of DNA where synthesis occurs. Its function is to remove information from DNA and transfer it to the place of protein synthesis - to ribosomes. Makes up 5% of the cell's RNA. Ribosomal RNA– synthesized in the nucleolus and is part of the ribosomes. Makes up 85% of the cell's RNA.

Transfer RNA(more than 40 species). Transports amino acids to the site of protein synthesis. It has the shape of a clover leaf and consists of 70-90 nucleotides.

Slide 16

Adenosine triphosphoric acid - ATP. ATP is a nucleotide consisting of a nitrogenous base - adenine, the carbohydrate ribose and three phosphoric acid residues, in two of which it is stored large number energy. When one phosphoric acid residue is eliminated, 40 kJ/mol of energy is released. Compare this figure with the figure indicating the amount of energy released by 1 g of glucose or fat. The ability to store such an amount of energy makes ATP its universal source. ATP synthesis occurs mainly in mitochondria.

Slide 17

II. Metabolism: energy and plastic exchange, their relationship. Enzymes, their chemical nature, role in metabolism. Stages energy metabolism. Fermentation and respiration. Photosynthesis, its significance, cosmic role. Phases of photosynthesis. Light and dark reactions of photosynthesis, their relationship. Chemosynthesis. The role of chemosynthetic bacteria on Earth

The general formula is Cn (H2O)n: carbohydrates contain only three chemical elements.

Table. Comparison of carbohydrate classes.

Water-soluble carbohydrates.

Monosaccharides:
glucose– the main source of energy for cellular respiration;
fructose– an integral part of flower nectar and fruit juices;
ribose and deoxyribose– structural elements of nucleotides, which are monomers of RNA and DNA.

Disaccharides:
sucrose(glucose + fructose) – the main product of photosynthesis transported in plants;
lactose(glucose + galactose) – part of mammalian milk;
maltose(glucose + glucose) is a source of energy in germinating seeds.

Functions of soluble carbohydrates :

• transport,
• protective,
• signal,
• energy.

Insoluble carbohydrates

polymer :
starch,
glycogen,
cellulose,
chitin.

Functions of polymeric carbohydrates :

• structural,
• storing,
• energy,
• protective.

Starch consists of branched spiral molecules that form reserve substances in plant tissues.

Cellulose - a polymer formed by glucose residues consisting of several straight parallel chains connected by hydrogen bonds. This structure prevents the penetration of water and ensures the stability of the cellulose membranes of plant cells.

Chitin consists of amino derivatives of glucose. The main structural element of the integument of arthropods and the cell walls of fungi.

Glycogen - reserve substance of an animal cell.

Table. The most common carbohydrates.

Table. Main functions of carbohydrates.

Lipids.

Lipids– esters of fatty acids and glycerol. Insoluble in water, but soluble in non-polar solvents. Present in all cells. Lipids are made up of hydrogen, oxygen and carbon atoms.

Functions of lipids :

Storage – fats are stored in the tissues of vertebrate animals.
Energy – half of the energy consumed by the cells of vertebrates at rest is formed as a result of fat oxidation. Fats are also used as a source of water. The energy effect from the breakdown of 1 g of fat is 39 kJ, which is twice as much as the energy effect from the breakdown of 1 g of glucose or protein.
Protective – the subcutaneous fat layer protects the body from mechanical damage.
Structural – phospholipids are part of cell membranes.
Thermal insulation – subcutaneous fat helps retain heat.
Electrical insulating – myelin, secreted by Schwann cells (form the sheaths of nerve fibers), insulates some neurons, which greatly accelerates the transmission of nerve impulses.
Nutritious – some lipid-like substances help build muscle mass and maintain body tone.
Lubricating – waxes cover the skin, wool, feathers and protect them from water. The leaves of many plants are covered with a waxy coating; wax is used in the construction of honeycombs.
Hormonal – adrenal hormone – cortisone and sex hormones are of lipid nature.

Table. Basic functions of lipids.

THEMATIC TASKS

Part A

A1. A polysaccharide monomer can be:
1) amino acid
2) glucose
3) nucleotide
4) cellulose

A2. In animal cells, storage carbohydrate is:
1) cellulose
2) starch
3) chitin
4) glycogen

A3. The most energy will be released during splitting:
1) 10 g protein
2) 10 g glucose
3) 10 g fat
4) 10 g amino acid

A4. Which function do lipids do not perform?
1) energy
2)catalytic
3) insulating
4) storing

A5. Lipids can be dissolved in:
1) water
2) solution table salt
3) hydrochloric acid
4) acetone

Part B

B1. Select structural features of carbohydrates
1) consist of amino acid residues
2) consist of glucose residues
3) consist of hydrogen, carbon and oxygen atoms
4) some molecules have a branched structure
5) consist of fatty acid and glycerol residues
6) consist of nucleotides

B2. Select the functions that carbohydrates perform in the body
1) catalytic
2) transport
3) signal
4) construction
5) protective
6) energy

VZ. Select the functions that lipids perform in the cell
1) structural
2) energy
3) storage
4) enzymatic
5) signal
6) transport

B4. Match the group chemical compounds with their role in the cell:

Part C

C1. Why does the body not accumulate glucose, but rather starch and glycogen?

Carbohydrates provide the body with energy and play important role in regulation of activities gastrointestinal tract. Carbohydrates are divided into two groups depending on their solubility: soluble And insoluble carbohydrates.

Monosaccharides may have alpha or beta configuration. Carbohydrates consisting of α-monosaccharides, easily digested by enzymes digestive tract animals and belong to soluble carbohydrates.

Carbohydrates consisting of β-monosaccharides, are resistant to the action of endogenous digestive enzymes and are classified as insoluble carbohydrates. However, in some animal species, microorganisms in the digestive tract produce the enzyme cellulase, which breaks down insoluble carbohydrates into CO 2, flammable gases and volatile fatty acids.

Volatile fatty acids (VFA) are the most important energy source for herbivores. In non-herbivorous animals such as dogs, microbial digestive processes are limited, so insoluble carbohydrates are not an option for them. energy value. They reduce the energy nutritional value of the diet.

Therefore, feeds containing high level insoluble carbohydrates, should not be used for dogs with high energy needs (growth, late stages pregnancy, lactation, stress, work). At the same time, such feeds are successfully used to reduce and control excess body weight in animals prone to obesity.

Alpha bonds in all carbohydrates, with the exception of disaccharides, are broken down by digestive enzyme — amylase. This enzyme is secreted by the pancreas and in some animal species small quantity also secreted by the salivary glands.

Disaccharides (maltose, sucrose, lactose) are broken down into monosaccharides using special enzymes - disaccharidases, such as: maltase, isomaltase, sucrase And lactase. These enzymes are contained in the villi of the brush border. epithelial cells intestines. If the brush border structure is damaged or these cells lack these enzymes, then animals are unable to metabolize disaccharides.

With this pathology, disaccharides remain in the intestine and are used by bacteria, stimulating their reproduction and increasing the osmolarity of the intestinal contents, which leads to the release of water into the intestinal lumen and diarrhea (diarrhea). Feeds containing disaccharides, such as milk containing lactose, lead to increased diarrhea if used to feed sick animals.

Soluble carbohydrates are easily accessible source energy and are contained in fairly high proportions in many diets, with the exception of those that consist almost entirely of meat, fish or animal tissue. When there is an excess content of soluble carbohydrates in the diet, some of the carbohydrates are stored in the body in the form of glycogen or adipose tissue for later use. Therefore, excess carbohydrates in the diet predisposes animals to obesity.

In the absence of carbohydrates in the diet of animals, the concentration of glucose in their blood does not decrease and there is no energy deficiency, since body proteins and glycerol can be used to form glucose, and fat and proteins are used as energy substances.

The digestibility of glucose, sucrose, lactose, dextrin and starch mixed with animal tissues with a properly formulated diet can reach 94%. However, the digestibility of soluble carbohydrates in industrial feed of average quality does not exceed 85%.

Although dogs are able to partially digest the raw starch contained in cereals, its digestibility increases significantly with heat treatment carried out during the preparation of food using a certain technology.

Insoluble carbohydrates, under common name “dietary fiber” or “fiber”, include cellulose, hemicellulose, pectin, gums, mucilage And lignin(being a structural element of plants).

Different fractions of dietary fiber differ significantly in their physical and chemical properties. Adding them to food is useful for many diseases, as well as for diarrhea and constipation. Their positive effect is associated with the ability of fibers to retain water and influence the composition of the microflora of the large intestine. Dietary fiber helps to irritate the receptors of the large intestine and stimulate the act of defecation, and also contribute to the formation of more voluminous and soft stool.

Dietary fiber may also influence lipid and carbohydrate metabolism. Pectin and gums can inhibit lipid absorption, thereby increasing the release of cholesterol and bile acids, and reducing the concentration of lipids in the blood, while cellulose has a very weak effect on the concentration of cholesterol in the blood serum.

Dietary fiber can have a major impact on blood glucose and insulin levels, which has important in animals with diabetes.

A decrease in the concentration of insulin and glucose in the blood occurs as a result of decreased absorption of glucose in the intestine, slower gastric emptying and changes in the level of secretion of gastrointestinal peptides.

Dietary fiber also affects the absorption of other nutrients. Thus, the higher the fiber content in the diet, the lower the absorption of proteins and energy. Effect of different dietary fibers on absorption minerals not the same. For example, pectin reduces the absorption of certain minerals, but cellulose does not affect this process. Therefore, a diet with high content pectins without appropriate mineral supplements can lead to a lack of microelements in the body of animals.

If there is too much fiber in the diet, dogs may experience energy deficiency.

Sources

1. "SMALL ANIMAL CLINICAL NUTRITION" L.D. Lewis, M. L. Morris (JR), M. S. Hand, MARK MORRIS ASSOCIATES TOPEKA, KANSAS 1987 (Translation from English and editing by Doctor of Biological Sciences A. S. Erokhin)
2. Feeding dogs. Directory. S.N. Khokhrin, “VSV-Sphinx”, 1996
3. Absolutely everything about your dog, composition. V.N.Zubko M.: Arnadia, 1996

Carbohydrate metabolism

Carbohydrates- an extensive group of organic compounds that are part of all living organisms.

The term “carbohydrates” arose because the first known representatives of carbohydrates in composition corresponded to the chemical formula C m H 2n O n (carbon + water). Subsequently, natural carbohydrates with a different elemental composition were discovered, but the previous name was retained.

Carbohydrates are divided into two groups depending on their solubility: soluble and insoluble.

Soluble carbohydrates, or Sahara, usually have a sweet taste and a crystalline structure. This:

• beet or cane sugar, orsucrose(Greek sakchar, from Sanskrit. sarkara- gravel, sand, granulated sugar);
• grape sugar, orglucose(Greek glykys- sweet);
• fruit sugar, orfructose(lat. fructus- fruit);
• milk sugar, orlactose(lat. lac, genus. case lactis- milk) etc.

Insoluble carbohydrates, or polysaccharides, do not have a sweet taste and crystalline structure. For example:

• starch;
• cellulose(lat. cellula- cell);
• glycogen(Greek glykys- sweet and genes- giving birth).

Functions of carbohydrates

1. Energy. Carbohydrates ( Sahara, starch, glycogen) is the main source of energy in the cell. When 1 g of carbohydrates is broken down into final metabolic products, 17.6 kJ of energy is released (the same as when 1 g of protein is broken down).

2. Storage (backup). The reserve carbohydrate in humans and other animals isglycogen, which is synthesized and accumulated in liver cells. The storage carbohydrate of plants is carbohydratestarch.

3. Structural (construction). From cellulosewhat the cell walls of plants are made of. Enzymes in the human digestive tract are not able to break down cellulose, so it does not have nutritional value as a source of energy, however, cellulose fibers have a beneficial effect on intestinal function. Some animals (termites, ruminants) contain special symbiotic protozoa in their intestines that decompose strong cellulose molecules into glucose molecules. That is why termites are able to feed on wood, hares on bark, and ruminants on hay, branches, and straw.

Carbohydrates are also part of nucleic acids and form the intercellular substance of connective tissue (in animals).

4. Protective. They interact in the liver with many toxic compounds, converting them into harmless and easily soluble substances.

Carbohydrates in human food. Carbohydrates provide the body with energy and play an important role in regulating the gastrointestinal tract. The main sources of carbohydrates are bread, potatoes, pasta, cereals, fruits, and sweets. Sugar is a pure carbohydrate. Honey, depending on its origin, contains 70 - 80% sugar.

All carbohydrates are divided into easily- And difficult to digest, and also indigestible.

Easily digestible carbohydrates- sugars - found in all sweet foods and drinks (sugar, honey, sweets, juices, fruits). They contribute rapid recovery strength, however, it is necessary to consume easily digestible carbohydrates with caution, since their excessive amounts lead to obesity and the development of diabetes.

Hard-to-digest carbohydrates- This is mainly starch. The optimal source of hard-to-digest, but most useful carbohydrates is cereals, potatoes, bread and pasta. They slowly and evenly deliver glucose into the blood and promote accumulation in the liver glycogen, which is the main reserve of carbohydrates in the human body. In addition, whole grain cereals and flakes contain a lot of dietary fiber, which absorbs toxins well and helps move food through the digestive canal. That is why wheat, buckwheat, corn and oatmeal very helpful.

Indigestible carbohydrates, the so-called dietary fiber (dietary fiber, cellulose), is found in vegetables and grains, especially in cabbage and bran. Indigestible carbohydrates are not destroyed by digestive juices and pass through the human intestines unchanged. Although they do not provide the body with energy, they must be contained in food, as they contribute to normal operation intestines and have a positive effect on the composition of the intestinal microflora.

Recommended daily norm carbohydrate consumption- the most unstable quantity. It depends on the level physical activity, gender, age, food traditions, etc. The approximate norm is the consumption of 300 - 350 g of carbohydrates per day.

When there is an excess amount of carbohydrates in the diet, some of them are stored in the body in the form of glycogen and adipose tissue for later use. Therefore, an excess of carbohydrates in the diet contributes to obesity.