§ 1. CLASSIFICATION AND FUNCTIONS OF CARBOHYDRATES

Even in ancient times, mankind got acquainted with carbohydrates and learned how to use them in their daily lives. Cotton, flax, wood, starch, honey, cane sugar are just some of the carbohydrates that played an important role in the development of civilization. Carbohydrates are among the most common organic compounds in nature. They are integral components of the cells of any organism, including bacteria, plants and animals. In plants, carbohydrates account for 80 - 90% of dry weight, in animals - about 2% of body weight. Their synthesis from carbon dioxide and water is carried out by green plants using the energy of sunlight ( photosynthesis ). The total stoichiometric equation for this process is:

Glucose and other simple carbohydrates are then converted into more complex carbohydrates such as starch and cellulose. Plants use these carbohydrates to release energy through the process of respiration. This process is essentially the reverse of the process of photosynthesis:

Interesting to know! Green plants and bacteria in the process of photosynthesis annually absorb approximately 200 billion tons of carbon dioxide from the atmosphere. In this case, about 130 billion tons of oxygen are released into the atmosphere and 50 billion tons of organic carbon compounds, mainly carbohydrates, are synthesized.

Animals are unable to synthesize carbohydrates from carbon dioxide and water. By consuming carbohydrates with food, animals spend the energy accumulated in them to maintain vital processes. Our foods are high in carbohydrates, such as baked goods, potatoes, cereals, etc.

The name "carbohydrates" is historical. The first representatives of these substances were described by the summary formula C m H 2 n O n or C m (H 2 O) n . Another name for carbohydrates is Sahara - due to the sweet taste of the simplest carbohydrates. According to their chemical structure, carbohydrates are a complex and diverse group of compounds. Among them, there are both fairly simple compounds with a molecular weight of about 200, and giant polymers, the molecular weight of which reaches several million. Along with carbon, hydrogen, and oxygen atoms, carbohydrates can contain atoms of phosphorus, nitrogen, sulfur, and, rarely, other elements.

Classification of carbohydrates

All known carbohydrates can be divided into two large groups - simple carbohydrates and complex carbohydrates. A separate group consists of carbohydrate-containing mixed polymers, for example, glycoproteins- a complex with a protein molecule, glycolipids - complex with lipid, etc.

Simple carbohydrates (monosaccharides, or monoses) are polyhydroxycarbonyl compounds that are not capable of forming simpler carbohydrate molecules upon hydrolysis. If monosaccharides contain an aldehyde group, then they belong to the class of aldoses (aldehyde alcohols), if ketone - to the class of ketoses (keto alcohols). Depending on the number of carbon atoms in a monosaccharide molecule, trioses (C 3), tetroses (C 4), pentoses (C 5), hexoses (C 6), etc. are distinguished:

The most common in nature are pentoses and hexoses.

Complex carbohydrates ( polysaccharides, or polioses) are polymers built from monosaccharide residues. They hydrolyze to form simple carbohydrates. Depending on the degree of polymerization, they are divided into low molecular weight ( oligosaccharides, the degree of polymerization of which, as a rule, is less than 10) and macromolecular. Oligosaccharides are sugar-like carbohydrates that are soluble in water and have a sweet taste. According to their ability to reduce metal ions (Cu 2+, Ag +), they are divided into regenerating and non-reducing. Polysaccharides, depending on the composition, can also be divided into two groups: homopolysaccharides and heteropolysaccharides. Homopolysaccharides are built from monosaccharide residues of the same type, and heteropolysaccharides are built from residues of different monosaccharides.

What has been said with examples of the most common representatives of each group of carbohydrates can be represented as the following diagram:

Functions of carbohydrates

The biological functions of polysaccharides are very diverse.

Energy and storage function

Carbohydrates contain the main amount of calories consumed by a person with food. Starch is the main carbohydrate in food. It is found in bakery products, potatoes, as part of cereals. The human diet also contains glycogen (in the liver and meat), sucrose (as additives to various dishes), fructose (in fruits and honey), lactose (in milk). Polysaccharides, before being absorbed by the body, must be hydrolyzed by digestive enzymes to monosaccharides. Only in this form they are absorbed into the blood. With the blood flow, monosaccharides enter the organs and tissues, where they are used to synthesize their own carbohydrates or other substances, or undergo splitting in order to extract energy from them.

The energy released from the breakdown of glucose is stored in the form of ATP. There are two processes of glucose breakdown: anaerobic (in the absence of oxygen) and aerobic (in the presence of oxygen). Lactic acid is formed as a result of the anaerobic process

which, during heavy physical exertion, accumulates in the muscles and causes pain.

As a result of the aerobic process, glucose is oxidized to carbon monoxide (IV) and water:

As a result of aerobic breakdown of glucose, much more energy is released than as a result of anaerobic breakdown. In general, the oxidation of 1 g of carbohydrates releases 16.9 kJ of energy.

Glucose can undergo alcoholic fermentation. This process is carried out by yeast under anaerobic conditions:

Alcoholic fermentation is widely used in industry for the production of wines and ethyl alcohol.

Man learned to use not only alcoholic fermentation, but also found the use of lactic acid fermentation, for example, to obtain lactic acid products and pickle vegetables.

In humans and animals there are no enzymes capable of hydrolyzing cellulose; nevertheless, cellulose is the main food component for many animals, in particular for ruminants. The stomach of these animals contains large quantities of bacteria and protozoa that produce the enzyme cellulase catalyzes the hydrolysis of cellulose to glucose. The latter can undergo further transformations, as a result of which butyric, acetic, propionic acids are formed, which can be absorbed into the blood of ruminants.

Carbohydrates also perform a reserve function. So, starch, sucrose, glucose in plants and glycogen in animals they are the energy reserve of their cells.

Structural, supporting and protective functions

Cellulose in plants and chitin in invertebrates and fungi, they perform supporting and protective functions. Polysaccharides form a capsule in microorganisms, thereby strengthening the membrane. Lipopolysaccharides of bacteria and glycoproteins of the surface of animal cells provide selectivity of intercellular interaction and immunological reactions of the body. Ribose is the building block of RNA, while deoxyribose is the building block of DNA.

Performs a protective function heparin. This carbohydrate, being an inhibitor of blood clotting, prevents the formation of blood clots. It is found in the blood and connective tissue of mammals. Cell walls of bacteria, formed by polysaccharides, fastened with short amino acid chains, protect bacterial cells from adverse effects. Carbohydrates are involved in crustaceans and insects in the construction of the external skeleton, which performs a protective function.

Regulatory function

Fiber enhances intestinal motility, thereby improving digestion.

An interesting possibility is the use of carbohydrates as a source of liquid fuel - ethanol. Since ancient times, wood has been used for heating homes and cooking. In modern society, this type of fuel is being replaced by other types - oil and coal, which are cheaper and more convenient to use. However, vegetable raw materials, despite some inconveniences in use, unlike oil and coal, are a renewable source of energy. But its use in internal combustion engines is difficult. For these purposes, it is preferable to use liquid fuel or gas. From low-grade wood, straw or other plant materials containing cellulose or starch, you can get liquid fuel - ethyl alcohol. To do this, you must first hydrolyze cellulose or starch and get glucose:

and then subject the resulting glucose to alcoholic fermentation and obtain ethyl alcohol. Once refined, it can be used as a fuel in internal combustion engines. It should be noted that in Brazil, for this purpose, annually billions of liters of alcohol are obtained from sugar cane, sorghum and cassava and used in internal combustion engines.

In this material, we will fully understand such information as:

• What are carbohydrates?
• What are the “right” carbohydrate sources and how to include them in your diet?
• What is the glycemic index?
• How is the breakdown of carbohydrates?
• Do they really turn into body fat after processing?

Starting with theory

Carbohydrates (also called saccharides) are organic compounds of natural origin, which are mostly found in the plant world. They are formed in plants during photosynthesis and are found in almost any plant food. Carbohydrates include carbon, oxygen and hydrogen. Carbohydrates enter the human body mainly with food (found in cereals, fruits, vegetables, legumes and other products), and are also produced from certain acids and fats.

Carbohydrates are not only the main source of human energy, but also perform a number of other functions:

Of course, if we consider carbohydrates solely from the point of view of building muscle mass, then they act as an affordable source of energy. In general, in the body, the energy reserve is contained in fat depots (about 80%), in protein - 18%, and carbohydrates account for only 2%.

Important: Carbohydrates accumulate in the human body in combination with water (1g of carbohydrates requires 4g of water). But fat deposits do not need water, so it is easier to accumulate them, and then use them as a backup energy source.

All carbohydrates can be divided into two types (see image): simple (monosaccharides and disaccharides) and complex (oligosaccharides, polysaccharides, fiber).

Monosaccharides (simple carbohydrates)

They contain one sugar group, for example: glucose, fructore, galactose. And now about each in more detail.

Glucose- is the main "fuel" of the human body and supplies energy to the brain. It also takes part in the formation of glycogen, and for the normal functioning of red blood cells, about 40 g of glucose per day is needed. Together with food, a person consumes about 18g, and the daily dose is 140g (necessary for the proper functioning of the central nervous system).

A natural question arises, where does the body then draw the necessary amount of glucose for its work? About everything in order. In the human body, everything is thought out to the smallest detail, and glucose reserves are stored in the form of glycogen compounds. And as soon as the body requires "refueling", some of the molecules are split and used.

The level of glucose in the blood is a relatively constant value and is regulated by a special hormone (insulin). As soon as a person consumes a lot of carbohydrates, and the glucose level rises sharply, insulin takes over, which lowers the amount to the required level. And you don’t have to worry about the portion of carbohydrates eaten, exactly as much as the body requires (due to the work of insulin) will enter the bloodstream.

Foods rich in glucose are:

• Grapes - 7.8%;
• Cherries and sweet cherries - 5.5%;
• Raspberry - 3.9%;
• Pumpkin - 2.6%;
• Carrot - 2.5%.

Important: the sweetness of glucose reaches 74 units, and sucrose - 100 units.

Fructose is a naturally occurring sugar found in fruits and vegetables. But it is important to remember that consuming large amounts of fructose is not only not beneficial, but also harmful. Huge portions of fructose enter the intestines and cause increased secretion of insulin. And if now you are not engaged in active physical activity, then all glucose is stored in the form of body fat. The main sources of fructose are foods such as:

• Grapes and apples;
• Melons and pears;

Fructose is much sweeter than glucose (2.5 times), but despite this, it does not destroy teeth and does not cause caries. Galactose is not found in free form almost anywhere, but most often it is a component of milk sugar, called lactose.

Disaccharides (simple carbohydrates)

The composition of disaccharides always includes simple sugars (in the amount of 2 molecules) and one molecule of glucose (sucrose, maltose, lactose). Let's look at each of them in more detail.

Sucrose is made up of fructose and glucose molecules. Most often, it is found in everyday life in the form of ordinary sugar, which we use during cooking and simply put in tea. So it is this sugar that is deposited in the layer of subcutaneous fat, so you should not get carried away with the amount consumed, even in tea. The main sources of sucrose are sugar and beets, plums and jam, ice cream and honey.

Maltose is a compound of 2 glucose molecules, which are found in large quantities in such products as: beer, young, honey, molasses, any confectionery. Lactose, on the other hand, is mainly found in dairy products, and is broken down in the intestines and converted into galactose and glucose. Most lactose is found in milk, cottage cheese, kefir.

So we figured out the simple carbohydrates, it's time to move on to complex ones.

Complex carbohydrates

All complex carbohydrates can be divided into two categories:

• Those that are digested (starch);
• Those that are not digested (fiber).

Starch is the main source of carbohydrates that underlies the food pyramid. Most of it is found in cereals, legumes and potatoes. The main sources of starch are buckwheat, oatmeal, pearl barley, as well as lentils and peas.

Important: Use baked potatoes in your diet, which are high in potassium and other minerals. This is especially important because starch molecules swell during cooking and reduce the useful value of the product. That is, at first the product may contain 70%, and after cooking it may not remain 20%.

Fiber plays a very important role in the functioning of the human body. With its help, the work of the intestines and the entire gastrointestinal tract as a whole is normalized. It also creates the necessary nutrient medium for the development of important microorganisms in the intestine. The body practically does not digest fiber, but provides a feeling of rapid satiety. Vegetables, fruits and wholemeal bread (which are high in fiber) are used to prevent obesity (because they quickly make you feel full).

Now let's move on to other processes associated with carbohydrates.

How the body stores carbohydrates

The reserves of carbohydrates in the human body are located in the muscles (2/3 of the total is located), and the rest is in the liver. The total supply is enough for only 12-18 hours. And if you do not replenish the reserves, then the body begins to experience a shortage, and synthesizes the substances it needs from proteins and intermediate metabolic products. As a result, glycogen stores in the liver can be significantly depleted, which will cause the deposition of fats in its cells.

By mistake, many people who lose weight for a more “effective” result significantly cut the amount of carbohydrates consumed, hoping that the body will use up fat stores. In fact, proteins go first, and only then fat deposits. It is important to remember that a large amount of carbohydrates will lead to rapid weight gain only if they are ingested in large portions (and they must also be quickly absorbed).

Carbohydrate metabolism

The metabolism of carbohydrates depends on how much glucose is in the circulatory system and is divided into three types of processes:

• Glycolysis - glucose is broken down, as well as other sugars, after which the required amount of energy is produced;
• Glycogenesis - glycogen and glucose are synthesized;
• Glyconeogenesis - in the process of splitting glycerol, amino acids and lactic acid in the liver and kidneys, the necessary glucose is formed.

In the early morning (after waking up), blood glucose reserves drop sharply for a simple reason - the lack of nourishment in the form of fruits, vegetables and other foods that contain glucose. The body is also fed by its own forces, 75% of which is carried out in the process of glycolysis, and 25% falls on gluconeogenesis. That is, it turns out that the morning time is considered optimal in order to use the available fat reserves as an energy source. And add to this light cardio loads, you can get rid of a few extra pounds.

Now we finally move on to the practical part of the question, namely: what carbohydrates are good for athletes, as well as in what optimal amounts they should be consumed.

Carbohydrates and bodybuilding: who, what, how much

A few words about the glycemic index

When it comes to carbohydrates, one cannot fail to mention such a term as "glycemic index" - that is, the rate at which carbohydrates are absorbed. It is an indicator of the speed with which a particular product is able to increase the amount of glucose in the blood. The highest glycemic index is 100 and refers to glucose itself. The body, after consuming food with a high glycemic index, begins to store calories and deposits fat deposits under the skin. So all foods with high GI are faithful companions in order to rapidly gain extra pounds.

Products with a low GI index are a source of carbohydrates, which for a long time, constantly and evenly feeds the body and ensures a systematic intake of glucose into the blood. With their help, you can adjust the body as correctly as possible for a long-term feeling of satiety, as well as prepare the body for active physical exertion in the gym. There are even special tables for foods that list the glycemic index (see image).

The body's need for carbohydrates and the right sources

So the moment has come when we will figure out how many carbohydrates you need to consume in grams. It is logical to assume that bodybuilding is a very energy-consuming process. Therefore, if you want the quality of training not to suffer, you need to provide your body with a sufficient amount of “slow” carbohydrates (about 60-65%).

• duration of training;
• load intensity;
• metabolic rate in the body.

It is important to remember that you do not need to go below the bar of 100g per day, and also have 25-30g in reserve, which fall on fiber.

Remember that an ordinary person consumes about 250-300g of carbohydrates per day. For those who work out in the gym with weights, the daily rate increases and reaches 450-550g. But they still need to be used correctly, and at the right time (in the morning). Why do you need to do it this way? The scheme is simple: in the first half of the day (after sleep), the body accumulates carbohydrates in order to “feed” their body with them (which is necessary for muscle glycogen). The remaining time (after 12 hours) carbohydrates are quietly deposited in the form of fat. So stick to the rule: more in the morning, less in the evening. After training, it is important to adhere to the rules of the protein-carbohydrate window.

Important: protein-carbohydrate window - a short period of time during which the human body becomes able to absorb an increased amount of nutrients (used to restore energy and muscles).

It has already become clear that the body needs to constantly receive nourishment in the form of “correct” carbohydrates. And to understand the quantitative values, consider the table below.

The concept of “correct” carbohydrates includes those substances that have a high biological value (amount of carbohydrates / 100 g of product) and a low glycemic index. These include products such as:

• Baked or boiled potatoes in their skins;
• Various cereals (oatmeal, barley, buckwheat, wheat);
• Bakery products from wholemeal flour and with bran;
• Pasta (from durum wheat);
• Fruits that are low in fructose and glucose (grapefruits, apples, pomelo);
• Vegetables are fibrous and starchy (turnips and carrots, pumpkins and zucchini).

These are the foods that should be included in your diet.

The ideal time to consume carbohydrates

The most appropriate time to consume a dose of carbohydrates is:

• Time after morning sleep;
• Before training;
• After training;
• During a workout.

Moreover, each of the periods is important and among them there is no more or less suitable one. Also in the morning, in addition to healthy and slow carbohydrates, you can eat something sweet (a small amount of fast carbohydrates).

Before you go to training (2-3 hours), you need to feed the body with carbohydrates with an average glycemic index. For example, eat pasta or corn/rice porridge. This will provide the necessary supply of energy for the muscles and brain.

During classes in the gym, you can use intermediate nutrition, that is, drink drinks containing carbohydrates (every 20 minutes, 200 ml). This will have a double benefit:

• Replenishment of fluid reserves in the body;
• Replenishment of muscle glycogen depot.

After training, it is best to take a rich protein-carbohydrate shake, and after 1-1.5 hours after the end of the training, eat a heavy meal. Buckwheat or barley porridge or potatoes are best suited for this.

Now is the time to talk about the role carbohydrates play in the muscle building process.

Do carbs help build muscle?

It is generally accepted that only proteins are the building material for muscles and only they need to be consumed in order to build muscle mass. In fact, this is not entirely true. What's more, carbs not only help with muscle building, they can help with weight loss. But all this is possible only if they are consumed correctly.

Important: in order for the body to have 0.5 kg of muscle, you need to burn 2500 calories. Naturally, proteins cannot provide such an amount, so carbohydrates come to the rescue. They provide the body with the necessary energy and protect proteins from destruction, allowing them to act as building blocks for muscles. Also, carbohydrates contribute to the rapid burning of fat. This is due to the fact that a sufficient amount of carbohydrates contributes to the consumption of fat cells, which are constantly burned during exercise.

It must also be remembered that, depending on the level of training of the athlete, his muscles can store a larger supply of glycogen. To build muscle mass, you need to take 7g of carbohydrates for every kilogram of body. Do not forget that if you began to take more carbohydrates, then the intensity of the load must also be increased.

In order for you to fully understand all the characteristics of nutrients and understand what and how much you need to consume (depending on age, physical activity and gender), carefully study the table below.

• Group 1 - predominantly mental / sedentary work.
• Group 2 - service sector / active sedentary work.
• Group 3 - work of medium severity - locksmiths, machine operators.
• Group 4 - hard work - builders, oilmen, metallurgists.
• Group 5 - very hard work - miners, steelworkers, loaders, athletes during the competitive period.

And now the results

To ensure that the effectiveness of training is always on top, and you have a lot of strength and energy for this, it is important to adhere to certain rules:

• The diet for 65-70% should consist of carbohydrates, and they must be “correct” with a low glycemic index;
• Before training, you need to consume foods with average GI indicators, after training - with low GI;
• Breakfast should be as dense as possible, and in the morning you need to eat most of the daily dose of carbohydrates;
• When buying products, check the glycemic index table and choose those that have medium and low GI values;
• If you want to eat foods with high GI values ​​(honey, jam, sugar), it is better to do this in the morning;
• Include more cereals in your diet and eat them regularly;
• Remember, carbohydrates are protein assistants in the process of building muscle mass, so if there is no tangible result for a long time, then you need to review your diet and the amount of carbohydrates consumed;
• Eat non-sweet fruits and fiber;
• Remember wholemeal bread, as well as baked potatoes in their skins;
• Constantly replenish your stock of knowledge about health and bodybuilding.

If you follow these simple rules, then your energy will noticeably increase, and the effectiveness of training will increase.

Instead of a conclusion

As a result, I would like to say that you need to approach training meaningfully and with knowledge of the matter. That is, you need to remember not only what exercises, how to do them and how many approaches. But also pay attention to nutrition, remember about proteins, fats, carbohydrates and water. After all, it is the combination of proper training and high-quality nutrition that will allow you to quickly achieve your goal - a beautiful athletic body. Products should be not just a set, but a means to achieve the desired result. So think not only in the hall, but also during meals.

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General characteristics, structure and properties of carbohydrates.

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

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

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

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

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

Functions of carbohydrates:

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

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

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

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

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

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

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

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

Monosaccharides

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

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

Chemical properties of monosaccharides :

• Oxidation to mono-, dicarboxylic and glycuronic acids;

• Recovery to alcohols;

• Esters formation;

• The formation of glycosides;

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

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

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

Tetroses: erythrosis - actively involved in metabolic processes.

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

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

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

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

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

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

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

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

Monosaccharides can have an amino group .

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

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

Amino sugars are the most important constituent glycosaminoglycans.

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

Oligosaccharides

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

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

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

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

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

Polysaccharides

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

Polysaccharides are divided into homo- and gete roposaccharides.

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

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

Amylopectin - a branched polymer consisting of both straight chains (bond 1,4) and branched chains, which are formed due to bonds between the first carbon atom of one glucose molecule and the sixth carbon atom of another with the help of an oxygen bridge (bond 1,6).

Representatives of homopolysaccharides are starch, fiber and glycogen.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Brief description of monosaccharides

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

Classifications of monosaccharides

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

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

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

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

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

Brief description of pentoses

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

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

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

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

Brief description of hexoses

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

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

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

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

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

Glucose is a biologically important compound, as it is used by the body through its oxidation as a universal nutrient and a readily available source of energy.

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

Brief description of disaccharides

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

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

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

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

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

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

General characteristics of polysaccharides

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

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

General characteristics of the properties and ecological role of starch

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

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

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

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

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

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

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

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

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

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

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

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

Brief description of the ecological and biological role of carbohydrates

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Carbohydrates in food.

Carbohydrates are the main and easily accessible source of energy for the human body. All carbohydrates are complex molecules consisting of carbon (C), hydrogen (H) and oxygen (O), the name comes from the words "coal" and "water".

Of the main sources of energy known to us, three can be distinguished:

Carbohydrates (up to 2% of reserves)
- fats (up to 80% of reserves)
- proteins (up to 18% of stocks )

Carbohydrates are the fastest fuel, which is primarily used for energy production, but their reserves are very small (on average 2% of the total). their accumulation requires a lot of water (to retain 1g of carbohydrates, 4g of water is needed), and water is not required for the deposition of fats.

The main stores of carbohydrates are stored in the body in the form of glycogen (a complex carbohydrate). Most of its mass is contained in the muscles (about 70%), the rest in the liver (30%).
You can find out all other functions of carbohydrates as well as their chemical structure

Carbohydrates in foods are classified as follows.

Types of carbohydrates.

Carbohydrates, in a simple classification, are divided into two main classes: simple and complex. Simple, in turn, consist of monosaccharides and oligosaccharides, complex of polysaccharides and fibrous.

Simple carbohydrates.

Monosaccharides

Glucose("grape sugar", dextrose).
Glucose- the most important of all monosaccharides, since it is the structural unit of most dietary di- and polysaccharides. In the human body, glucose is the main and most versatile source of energy for metabolic processes. All cells of the animal body have the ability to absorb glucose. At the same time, not all cells of the body, but only some of their types, have the ability to use other energy sources - for example, free fatty acids and glycerol, fructose or lactic acid. In the process of metabolism, they are broken down into individual molecules of monosaccharides, which, in the course of multi-stage chemical reactions, are converted into other substances and ultimately oxidized to carbon dioxide and water - used as "fuel" for cells. Glucose is an essential component of metabolism carbohydrates. With a decrease in its level in the blood or a high concentration and the inability to use, as happens with diabetes, drowsiness occurs, loss of consciousness (hypoglycemic coma) may occur.
Glucose "in its pure form", as a monosaccharide, is found in vegetables and fruits. Especially rich in glucose are grapes - 7.8%, cherries, cherries - 5.5%, raspberries - 3.9%, strawberries - 2.7%, plums - 2.5%, watermelon - 2.4%. Of the vegetables, most glucose is found in pumpkin - 2.6%, in white cabbage - 2.6%, in carrots - 2.5%.
Glucose is less sweet than the most famous disaccharide, sucrose. If we take the sweetness of sucrose as 100 units, then the sweetness of glucose will be 74 units.

Fructose(fruit sugar).
Fructose is one of the most common carbohydrates fruits. Unlike glucose, it can pass from the blood into tissue cells without the participation of insulin (a hormone that lowers blood glucose levels). For this reason, fructose is recommended as the safest source. carbohydrates for diabetic patients. Part of the fructose enters the liver cells, which turn it into a more universal "fuel" - glucose, so fructose is also able to increase blood sugar, although to a much lesser extent than other simple sugars. Fructose is more easily converted 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 can reduce overall intake carbohydrates.
The main sources of fructose in food are grapes - 7.7%, apples - 5.5%, pears - 5.2%, cherries, sweet cherries - 4.5%, watermelons - 4.3%, black currants - 4.2% , raspberries - 3.9%, strawberries - 2.4%, melons - 2.0%. In vegetables, the fructose content is low - from 0.1% in beets to 1.6% in white cabbage. Fructose is found in honey - about 3.7%. Fructose, which has a much higher sweetness than sucrose, has been well proven to not cause tooth decay, which is promoted by sugar consumption.

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

Oligosaccharides

sucrose(table sugar).
sucrose is a disaccharide (carbohydrate consisting of two components) formed by glucose and fructose molecules. The most common type of sucrose is - sugar. The content of sucrose in sugar is 99.5%, in fact, sugar is pure sucrose.
Sugar is rapidly broken down in the gastrointestinal tract, glucose and fructose are absorbed into the blood and serve as a source of energy and the most important precursor of glycogen and fats. It is often referred to as the "empty calorie carrier" since sugar is pure carbohydrate and does not contain other nutrients, such as, for example, vitamins, mineral salts. Of the vegetable products, the most sucrose is found in beets - 8.6%, peaches - 6.0%, melons - 5.9%, plums - 4.8%, tangerines - 4.5%. In vegetables, except for beets, a significant content of sucrose is noted in carrots - 3.5%. In other vegetables, the sucrose content ranges from 0.4 to 0.7%. In addition to sugar itself, the main sources of sucrose in food are jam, honey, confectionery, sweet drinks, ice cream.

Lactose(milk sugar).
Lactose broken down in the gastrointestinal tract to glucose and galactose by the action of the enzyme lactase. Deficiency of this enzyme in some people leads to milk intolerance. Undigested lactose serves as a good nutrient for the intestinal microflora. At the same time, abundant gas formation is possible, the stomach “swells”. In fermented milk products, most of the lactose is fermented to lactic acid, so people with lactase deficiency can tolerate fermented milk products without unpleasant consequences. In addition, lactic acid bacteria in fermented milk products inhibit the activity of the intestinal microflora and reduce the adverse effects of lactose.
Galactose, formed during the breakdown of lactose, is converted into glucose in the liver. With a congenital hereditary deficiency or absence of an enzyme that converts galactose into glucose, a serious disease develops - galactosemia , which leads to mental retardation.
The lactose content in cow's milk is 4.7%, in cottage cheese - from 1.8% to 2.8%, in sour cream - from 2.6 to 3.1%, in kefir - from 3.8 to 5.1% , in yoghurts - about 3%.

Maltose(malt sugar).
Formed when two glucose molecules combine. Contained in such products as: malt, honey, beer, molasses, bakery and confectionery products made with the addition of molasses.

Athletes should avoid taking glucose in its pure form and foods rich in simple sugars in large quantities, as they trigger the process of fat formation.

Complex carbohydrates.

Complex carbohydrates consist mainly of repeating units of glucose compounds. (glucose polymers)

Polysaccharides

Plant polysaccharides (starch).
Starch- the main of the digested polysaccharides, it is a complex chain consisting of glucose. It accounts for up to 80% of carbohydrates consumed with food. Starch is a complex or "slow" carbohydrate, so it is the preferred source of energy for both weight gain and weight loss. In the gastrointestinal tract, starch is amenable to hydrolysis (decomposition of a substance under the action of water) is broken down into dextrins (starch fragments), and as a result, into glucose and is already absorbed by the body in this form.
The source of starch is vegetable products, mainly cereals: cereals, flour, bread, and potatoes. Cereals contain the most starch: from 60% in buckwheat (kernel) to 70% in rice. Of the cereals, the least starch is found in oatmeal and its processed products: oatmeal, oatmeal "Hercules" - 49%. Pasta contains from 62 to 68% starch, rye flour bread, depending on the variety, from 33% to 49%, wheat bread and other products made from wheat flour - from 35 to 51% starch, flour - from 56 (rye) to 68% (wheat premium). There is also a lot of starch in legumes - from 40% in lentils to 44% in peas. And also it can be noted not a small content of starch in potatoes (15-18%).

Animal polysaccharides (glycogen).
Glycogen-consists of highly branched chains of glucose molecules. After a meal, a large amount of glucose begins to enter the bloodstream and the human body stores excess glucose in the form of glycogen. When blood glucose levels begin to drop (for example, during exercise), the body breaks down glycogen with the help of enzymes, as a result of which glucose levels remain normal and organs (including muscles during exercise) get enough of it for energy production. Glycogen is deposited mainly in the liver and muscles. It is found in small amounts in animal products (2-10% in the liver, 0.3-1% in muscle tissue). The total supply of glycogen is 100-120 g. In bodybuilding, only the glycogen that is contained in muscle tissue matters.

fibrous

dietary fiber (indigestible, fibrous)
Dietary fiber or dietary fiber refers to nutrients that, like water and mineral salts, do not provide the body with energy, but play a huge role in its life. Dietary fiber found primarily in plant-based foods that are low or very low in sugar. It is usually combined with other nutrients.

Types of fiber.

Cellulose and Hemicellulose
Cellulose present in whole wheat flour, bran, cabbage, baby peas, green and waxy beans, broccoli, Brussels sprouts, cucumber skins, peppers, apples, carrots.
Hemicellulose found in bran, cereals, unrefined grains, beets, Brussels sprouts, mustard green shoots.
Cellulose and hemicellulose absorb water, facilitating the activity of the colon. In essence, they "volume" the waste and move it through the large intestine faster. This not only prevents constipation, but also protects against diverticulosis, spasmodic colitis, hemorrhoids, colon cancer and varicose veins.

lignin
This type of fiber is found in cereals used for breakfast, in bran, stale vegetables (when vegetables are stored, the lignin content in them increases and they are less digestible), as well as in eggplant, green beans, strawberries, peas, and radishes.
Lignin reduces the digestibility of other fibers. In addition, it binds to bile acids, helping to lower cholesterol levels and speeding up the passage of food through the intestines.

Gum and Pectin
Comedy found in oatmeal and other oat products, in dried beans.
Pectin present in apples, citrus fruits, carrots, cauliflower and cabbage, dried peas, green beans, potatoes, strawberries, strawberries, fruit drinks.
Gum and pectin affect absorption processes in the stomach and small intestine. By binding to bile acids, they reduce fat absorption and lower cholesterol levels. They delay gastric emptying and, by enveloping the intestines, slow down the absorption of sugar after a meal, which is useful for diabetics, as it reduces the required dose of insulin.

Knowing the types of carbohydrates, and their functions, the following question arises -

What carbohydrates and how much to eat?

In most products, carbohydrates are the main component, therefore, there should not be any problems with obtaining them from food, therefore, carbohydrates make up the bulk of the daily diet of most people.
Carbohydrates that enter our body with food have three metabolic pathways:

1) Glycogenesis(The complex carbohydrate food that enters our gastrointestinal tract is broken down into glucose, and then stored in the form of complex carbohydrates - glycogen in muscle and liver cells, and is used as a backup source of nutrition when the concentration of glucose in the blood is low)
2) Gluconeogenesis(the process of formation in the liver and cortical substance of the kidneys (about 10%) - glucose, from amino acids, lactic acid, glycerol)
3) Glycolysis(breakdown of glucose and other carbohydrates with energy release)

The metabolism of carbohydrates is mainly determined by the presence of glucose in the bloodstream, this important and versatile source of energy in the body. The presence of glucose in the blood depends on the last meal and the nutritional composition of the food. That is, if you recently had breakfast, then the concentration of glucose in the blood will be high, if you refrain from eating for a long time, it will be low. Less glucose - less energy in the body, this is obvious, which is why there is a breakdown on an empty stomach. At a time when the glucose content in the bloodstream is low, and this is very well observed in the morning hours, after a long sleep, during which you did not maintain the level of available glucose in the blood with portions of carbohydrate food, the body is replenished in a state of starvation with the help of glycolysis - 75%, and 25% with the help of gluconeogenesis, that is, the breakdown of complex stored carbohydrates, as well as amino acids, glycerol and lactic acid.
Also, pancreatic hormone plays an important role in regulating the concentration of glucose in the blood. insulin. Insulin is a transport hormone that carries excess glucose to muscle cells and other tissues of the body, thereby regulating the maximum level of glucose in the blood. In overweight people who do not follow their diet, insulin converts excess carbohydrates from food into fat into the body, this is mainly characteristic of fast carbohydrates.
To choose the right carbohydrates from the whole variety of food, such a concept is used as - glycemic index.

Glycemic index is the rate of absorption of carbohydrates from food into the bloodstream and the insulin response of the pancreas. It shows the effect of foods on blood sugar levels. This index is measured on a scale from 0 to 100, it depends on the types of products, different carbohydrates are digested differently, some quickly, and accordingly they will have a high glycemic index, some slowly, the standard for rapid absorption is pure glucose, it has a glycemic index equals 100.

The GI of a product depends on several factors:

- Type of carbohydrates (simple carbohydrates have a high GI, complex carbohydrates have a low GI)
- The amount of fiber (the more it is in food, the lower the GI)
- The way food is processed (for example, GI increases during heat treatment)
- The content of fats and proteins (the more of them in food, the lower the GI)

There are many different tables that determine the glycemic index of foods, here is one of them:

The food glycemic index table allows you to make the right decisions when choosing which foods to include in your daily diet and which ones to consciously exclude.
The principle is simple: the higher the glycemic index, the less often you include such foods in your diet. Conversely, the lower the glycemic index, the more often you eat these foods.

However, fast carbohydrates are also useful to us in such important meals as:

- in the morning (after a long sleep, the concentration of glucose in the blood is very low, and it must be replenished as quickly as possible in order to prevent the body from obtaining the necessary energy for life with the help of amino acids, by destroying muscle fibers)
- and after training (when energy expenditure for intense physical labor significantly reduces the concentration of glucose in the blood, after training it is ideal to take carbohydrates faster to replenish them as quickly as possible and prevent catabolism)

How much to eat carbohydrates?

In bodybuilding and fitness, carbohydrates should make up at least 50% of all nutrients (of course, we are not talking about “drying” or losing weight).
There are plenty of reasons to load yourself with a lot of carbohydrates, especially when it comes to whole, unprocessed foods. However, first of all, you must understand that there is a certain limit to the ability of the body to accumulate them. Imagine a gas tank: it can only hold a certain number of liters of gasoline. If you try to pour more into it, the excess will inevitably spill. Once carbohydrate stores have been converted into the required amount of glycogen, the liver begins to process their excess into fat, which is then stored under the skin and in other parts of the body.
The amount of muscle glycogen you can store depends on how much muscle you have. Just as some gas tanks are larger than others, muscles differ from person to person. The more muscular you are, the more glycogen your body can store.
To make sure you're getting the right amount of carbs—no more than you should—calculate your daily carbohydrate intake using the following formula. To build muscle mass per day you should take -

7g of carbohydrates per kilogram of body weight (multiply your weight in kilograms by 7).

By raising your carbohydrate intake to the required level, you must add additional strength training. Plentiful amounts of carbohydrates during bodybuilding will provide you with more energy, allowing you to work out harder and longer and achieve better results.
You can calculate your daily diet by studying this article in more detail.