The main source of energy for the body. What is the only source of energy for the human body and why

chemical work

+ Q 2

Electrical work

+ Q 2

active transport

+ Q 2

Scheme 1. Energy sources in the body, the results of the complete oxidation of nutrients and the types of heat released in the body.

It should be added that the amount of nutrients released during oxidation does not depend on the number of intermediate reactions, but depends on the initial and final state of the chemical system. This provision was first formulated by Hess (Hess' law).

You will consider these processes in more detail at lectures and classes that will be conducted with you by teachers of the Department of Biochemistry.

Energy value of food substances.

The energy value of nutrients is estimated using special devices - oxicalorimeters. It has been established that with the complete oxidation of 1 g of carbohydrates, 4.1 kcal is released (1 kcal = 4187 J.), 1 g of fat - 9.45 kcal, 1 g of protein - 5.65 kcal. It should be added that part of the nutrients entering the body is not absorbed. For example, on average, about 2% of carbohydrates, 5% of fats and up to 8% of proteins are not digested. In addition, not all nutrients in the body are broken down into final products - carbon dioxide (carbon dioxide) and water. For example, part of the products of incomplete breakdown of proteins in the form of urea is excreted in the urine.

In view of the foregoing, it can be noted that the real energy value of nutrients is somewhat lower than that established under experimental conditions. The real energy value of 1 g of carbohydrates is 4.0 kcal, 1 g of fat - 9.0 kcal, 1 g of protein - 4.0 kcal.

Basic concepts and definitions of the physiology of metabolism and energy.

The integral (general) characteristic of the energy metabolism of the human body is the total energy expenditure or gross energy expenditure.

Gross energy expenditure organism- the total energy expenditure of the body during the day in the conditions of its normal (natural) existence. Gross energy expenditure includes three components: basal metabolism, the specific dynamic action of food, and work gain. Gross energy expenditure is estimated in kJ/kg/day or kcal/kg/day (1 kJ=0.239 kcal).

BX.

The study of basal metabolism began with the work of Bidder and Schmidt, scientists of the University of Tartu (Bidder and Schmidt, 1852).

BX- the minimum level of energy expenditure necessary to maintain the vital activity of the body.

The concept of basal metabolism as the minimum level of energy expenditure of the body also imposes a number of requirements on the conditions under which this indicator should be evaluated.

Conditions under which basal metabolism should be assessed:

a state of complete physical and mental rest (preferably in a prone position);

ambient comfort temperature (18-20 degrees Celsius);

10 to 12 hours after the last meal to avoid the increase in energy metabolism associated with the meal.

Factors affecting basal metabolism.

Basal metabolism depends on age, height, body weight and gender.

Influence age for the main exchange.

The highest basic exchange in terms of 1 kg. Body weight in newborns (50-54 kcal / kg / day), the lowest in the elderly (after 70 years, the main metabolism averages 30 kcal / kg / day). The basal metabolism reaches a constant level by the time of puberty by the age of 12-14 and remains stable until the age of 30-35 (about 40 kcal / kg / day).

Influence height and weight body for basal metabolism.

There is an almost linear, direct relationship between body weight and basal metabolism - the greater the body weight, the greater the level of basal metabolism. However, this dependence is not absolute. With an increase in body weight due to muscle tissue, this dependence is almost linear, however, if an increase in body weight is associated with an increase in the amount of adipose tissue, this dependence becomes non-linear.

Since body weight, ceteris paribus, depends on growth (the greater the growth, the greater the body weight), there is a direct relationship between growth and basal metabolism - the greater the growth, the greater the basal metabolism.

Given the fact that height and body weight affect the total body area, M. Rubner formulated the law according to which the basal metabolism depends on the body area: the larger the body area, the greater the basal metabolism. However, this law practically ceases to work in conditions when the ambient temperature is equal to the body temperature. In addition, uneven hairiness of the skin significantly changes the heat exchange between the body and the environment, and therefore Rubner's law also has limitations under these conditions.

Influence gender to the basal level.

In men, the basal metabolic rate is 5-6% higher than in women. This is due to the different ratio of adipose and muscle tissue per 1 kg of body weight, as well as different levels of metabolism due to differences in the chemical structure of sex hormones and their physiological effects.

Specific dynamic action of food.

The term specific dynamic action of food was first introduced into scientific use by M. Rubner in 1902.

The specific dynamic effect of food is an increase in the energy metabolism of the human body associated with food intake. The specific dynamic effect of food is the energy expenditure of the body on the mechanisms of utilization of the food taken. The indicated effect in changing the energy metabolism is noted from the moment of preparation for a meal, during a meal and lasts 10-12 hours after a meal. The maximum increase in energy metabolism after a meal is noted after 3-3.5 hours. Special studies have shown that from 6 to 10% of its energy value is spent on the utilization of food.

Working increase.

The working increase is the third component of the body's gross energy expenditure. The working increase is part of the energy expenditure of the body for muscle activity in the environment. During heavy physical work, the energy expenditure of the body can increase by 2 times compared to the level of basal metabolism.

Methods for studying energy metabolism in humans.

To study energy metabolism in humans, a number of methods have been developed under the common name - calorimetry.

The next class of basic chemical compounds in our body is carbohydrates. Carbohydrates are well known to all of us in the form of ordinary food sugar (chemically, it is sucrose) or starch.
Carbohydrates are divided into simple and complex. Of the simple carbohydrates (monosaccharides), the most important for humans are glucose, fructose and galactose.
Complex carbohydrates are oligosaccharides(disaccharides: sucrose, lactose, etc.) and non-sugar-like carbohydrates - polysaccharides(starch, glycogen, fiber, etc.).
Monosaccharides and polysaccharides differ in their physiological effect on the body. The use of an excess of easily digestible mono- and disaccharides in the diet contributes to a rapid increase in blood sugar levels, which can be negative for patients with diabetes mellitus (DM) and obesity.
Polysaccharides are much more slowly broken down in the small intestine. Therefore, the increase in the concentration of sugar in the blood occurs gradually. In this regard, the consumption of foods rich in starch (bread, cereals, potatoes, pasta) is more beneficial.
Together with starch, vitamins, minerals, and indigestible dietary fiber enter the body. The latter include fiber and pectin.
Cellulose(cellulose) has a beneficial regulatory effect on the functioning of the intestines, biliary tract, prevents stagnation of food in the gastrointestinal tract, promotes the excretion of cholesterol. Fiber-rich foods include cabbage, beets, beans, rye flour, etc.
pectin substances are part of the pulp of fruits, leaves, green parts of the stems. They are able to adsorb various toxins (including heavy metals). Many pectins are found in marmalade, marmalade, jams, marshmallows, but most of these substances are found in pumpkin pulp, which is also rich in carotene (a precursor of vitamin A).
Most carbohydrates for the human body are a rapidly digestible source of energy. However, carbohydrates are not absolutely essential nutrients. Some of them, such as the most important fuel for our cells - glucose, can be synthesized quite easily from other chemical compounds, in particular amino acids or lipids.
However, the role of carbohydrates should not be underestimated. The fact is that they are not only able, quickly burning in the body, to provide it with a sufficient amount of energy, but also to be stored in reserve in the form glycogen- a substance very similar to the well-known vegetable starch. Our main stores of glycogen are concentrated in the liver or muscles. If the body's energy needs grow, for example, with significant physical exertion, then glycogen stores are easily mobilized, glycogen turns into glucose, and that is already used by the cells and tissues of our body as an energy carrier.

The danger of simple carbohydrates!

Scientists from the universities of Jerusalem (Israel) and Yale (USA) came to such conclusions after conducting a series of experiments.

Grasshoppers of the species Melanoplus femurrubrum were placed in two cages, one of which also included the spiders Pisaurina mira, their natural enemies. The task was only to scare the grasshoppers in order to track their reaction to predators, so the spiders were provided with "muzzles" by gluing their mandibles. Grasshoppers experienced severe stress, as a result, the metabolism in their bodies greatly increased and a "brutal" appetite appeared - by analogy with people who eat a lot of sweets when they are worried. Grasshoppers absorbed a large amount of carbohydrates in a short time, the hydrocarbon of which was perfectly absorbed by the body.

In addition, "overeating" grasshoppers, as it turned out, after death can harm the ecosystem. Scientists discovered this by placing the remains of their bodies in soil samples where the humus process took place. Soil microbial activity dropped 62% in the lab and 19% in the field, the study said.

To test the results of the experiment, the scientists created a "real-time" chemical model, replacing the skeletons of real grasshoppers with organic "chrysalis" consisting, like natural prototypes, of carbohydrates, proteins and chitin in different proportions. The results of the experiments showed that the greater the percentage of nitrogen (contained in proteins) in the remains of grasshoppers, the better the processes of decomposition of organic matter were in the soils.

Carbohydrates Organic

Carbohydrates

Organic compounds make up an average of 20-30% of the cell mass of a living organism. These include biological polymers: proteins, nucleic acids, carbohydrates, as well as fats and a number of small hormone molecules, pigments, ATP, etc. Different types of cells include an unequal amount of organic compounds. Complex carbohydrates-polysaccharides predominate in plant cells, while in animals there are more proteins and fats. Nevertheless, each of the groups of organic substances in any type of cells performs similar functions: it provides energy, is a building material.

1. A BRIEF SUMMARY OF CARBOHYDRATES

Carbohydrates are organic compounds consisting of one or more molecules of simple sugars. The molar mass of carbohydrates ranges from 100 to 1,000,000 Da (Dalton mass, approximately equal to the mass of one hydrogen atom). Their general formula is usually written as Cn(H2O)n (where n is at least three). For the first time in 1844, this term was introduced by the domestic scientist K. Schmid (1822-1894).

The name "carbohydrates" arose on the basis of the analysis of the first known representatives of this group of compounds. It turned out that these substances consist of carbon, hydrogen and oxygen, and the ratio of the number of hydrogen and oxygen atoms in them is the same as in water: two hydrogen atoms - one oxygen atom. Thus, they were considered as a combination of carbon and water. In the future, many carbohydrates that did not meet this condition became known, but the name "carbohydrates" still remains generally accepted. In an animal cell, carbohydrates are found in an amount not exceeding 2-5%. Plant cells are the richest in carbohydrates, where their content in some cases reaches 90% of the dry mass (for example, in potato tubers, seeds).

2. CLASSIFICATION OF CARBOHYDRATES

There are three groups of carbohydrates: monosaccharides, or simple sugars (glucose, fructose); oligosaccharides - compounds consisting of 2-10 consecutively connected molecules of simple sugars (sucrose, maltose); polysaccharides containing more than 10 sugar molecules (starch, cellulose).

3. STRUCTURAL AND FUNCTIONAL FEATURES OF THE ORGANIZATION OF MONO- AND DISACCHARIDES: STRUCTURE; FINDING IN NATURE; RECEIVING. CHARACTERISTICS OF INDIVIDUAL REPRESENTATIVES

Monosaccharides are ketone or aldehyde derivatives of polyhydric alcohols. The carbon, hydrogen and oxygen atoms that make up their composition are in a ratio of 1:2:1. The general formula for simple sugars is (CH2O)n. Depending on the length of the carbon skeleton (the number of carbon atoms), they are divided into: triose-C3, tetrose-C4, pentose-C5, hexose-C6, etc. In addition, sugars are divided into:

Aldoses containing an aldehyde group are C=O. These include | | H glucose:

H H H H H
CH2OH - C - C - C - C - C
| | | | \\
OH OH OH OH OH

Ketose containing a ketone group - C-. To them, for example, || refers to fructose.

In solutions, all sugars, starting with pentoses, have a cyclic form; in the linear form, only trioses and tetroses are present. When the cyclic form is formed, the oxygen atom of the aldehyde group is covalently bonded to the penultimate carbon atom of the chain, resulting in the formation of hemiacetals (in the case of aldoses) and hemiketals (in the case of ketoses).

CHARACTERISTICS OF MONOSACCHARIDES, INDIVIDUAL REPRESENTATIVES

Of the tetroses, erythrosis is the most important in metabolic processes. This sugar is one of the intermediate products of photosynthesis. Pentoses are found in natural conditions mainly as constituents of molecules of more complex substances, such as complex polysaccharides called pentosans, as well as vegetable gums. Pentoses in a significant amount (10-15%) are found in wood and straw. In nature, arabinose is predominantly found. It is found in cherry glue, beets and gum arabic, from where it is obtained. Ribose and deoxyribose are widely represented in the animal and plant world; these are sugars that make up the monomers of nucleic acids RNA and DNA. Ribose is obtained by epimerization of arabinose.

Xylose is formed by the hydrolysis of the polysaccharide xylosan contained in straw, bran, wood, and sunflower husks. The products of various types of xylose fermentation are lactic, acetic, citric, succinic and other acids. Xylose is poorly absorbed by the human body. Hydrolysates containing xylose are used to grow some types of yeast, they are used as a protein source for feeding farm animals. When xylose is reduced, xylitol alcohol is obtained, it is used as a sugar substitute for diabetics. Xylitol is widely used as a moisture stabilizer and plasticizer (in the paper industry, perfumery, cellophane production). It is one of the main components in the production of a number of surfactants, varnishes, adhesives.

Of the hexoses, glucose, fructose, and galactose are the most widely distributed; their general formula is C6H12O6.

Glucose (grape sugar, dextrose) is found in the juice of grapes and other sweet fruits, and in small quantities in animals and humans. Glucose is part of the most important disaccharides - cane and grape sugars. High molecular weight polysaccharides, i.e. starch, glycogen (animal starch) and cellulose, are entirely built from the remains of glucose molecules connected to each other in various ways. Glucose is the primary source of energy for cells.

Human blood contains 0.1-0.12% glucose, a decrease in the indicator causes a violation of the vital activity of nerve and muscle cells, sometimes accompanied by convulsions or fainting. The level of glucose in the blood is regulated by a complex mechanism of the nervous system and endocrine glands. One of the massive severe endocrine diseases - diabetes mellitus - is associated with hypofunction of the islet zones of the pancreas. It is accompanied by a significant decrease in the permeability of the membrane of muscle and fat cells for glucose, which leads to an increase in the glucose content in the blood, as well as in the urine.

Glucose for medical purposes is obtained by purification - recrystallization - technical glucose from aqueous or water-alcohol solutions. Glucose is used in textile production and in some other industries as a reducing agent. In medicine, pure glucose is used in the form of solutions for injection into the blood for a number of diseases and in the form of tablets. Vitamin C is obtained from it.

Galactose, together with glucose, is part of some glycosides and polysaccharides. The remains of galactose molecules are part of the most complex biopolymers - gangliosides, or glycosphingolipids. They are found in the nerve nodes (ganglia) of humans and animals and are also found in the brain tissue, in the spleen in erythrocytes. Galactose is obtained mainly by the hydrolysis of milk sugar.

Fructose (fruit sugar) in a free state is found in fruits, honey. Included in many complex sugars, such as cane sugar, from which it can be obtained by hydrolysis. Forms a complex structured high-molecular polysaccharide inulin, contained in some plants. Fructose is also obtained from inulin. Fructose is a valuable food sugar; it is 1.5 times sweeter than sucrose and 3 times sweeter than glucose. It is well absorbed by the body. When fructose is reduced, sorbitol and mannitol are formed. Sorbitol is used as a sugar substitute in the diet of diabetics; in addition, it is used for the production of ascorbic acid (vitamin C). When oxidized, fructose gives tartaric and oxalic acid.

Disaccharides are typical sugar-like polysaccharides. These are solids, or non-crystallizing syrups, highly soluble in water. Both amorphous and crystalline disaccharides usually melt over a range of temperatures and usually decompose. Disaccharides are formed by a condensation reaction between two monosaccharides, usually hexoses. The bond between two monosaccharides is called a glycosidic bond. It is usually formed between the first and fourth carbon atoms of neighboring monosaccharide units (1,4-glycosidic bond). This process can be repeated countless times, resulting in the formation of giant polysaccharide molecules. Once the monosaccharide units are linked together, they are called residues. Thus, maltose consists of two glucose residues.

The most common disaccharides are maltose (glucose + glucose), lactose (glucose + galactose), and sucrose (glucose + fructose).

INDIVIDUAL REPRESENTATIVES OF DISACCHARIDES

Maltose (malt sugar) has the formula C12H22O11. The name arose in connection with the method of obtaining maltose: it is obtained from starch when exposed to malt (Latin maltum - malt). As a result of hydrolysis, maltose is split into two molecules of glucose:

С12Н22О11 + Н2О = 2С6Н12О6

Malt sugar is an intermediate product in the hydrolysis of starch, it is widely distributed in plant and animal organisms. Malt sugar is much less sweet than cane sugar (by 0.6 times at the same concentrations).

Lactose (milk sugar). The name of this disaccharide arose in connection with its preparation from milk (from Latin lactum - milk). Upon hydrolysis, lactose is broken down into glucose and galactose:

Lactose is obtained from milk: in cow's milk it contains 4-5.5%, in women's milk - 5.5-8.4%. Lactose differs from other sugars in the absence of hygroscopicity: it does not become damp. Milk sugar is used as a pharmaceutical preparation and food for infants. Lactose is 4 or 5 times less sweet than sucrose.

Sucrose (cane or beet sugar). The name arose in connection with its production either from sugar beet or sugar cane. Cane sugar has been known for many centuries BC. Only in the middle of the XVIII century. this disaccharide was discovered in sugar beet and only at the beginning of the 19th century. it was obtained in a production environment. Sucrose is very common in the plant kingdom. Leaves and seeds always contain a small amount of sucrose. It is also found in fruits (apricots, peaches, pears, pineapples). There is a lot of it in maple and palm juices, corn. This is the most famous and widely used sugar. When hydrolyzed, glucose and fructose are formed from it:

С12Н22О11 + Н2О = С6Н12О6 + С6Н12О6

A mixture of equal amounts of glucose and fructose, resulting from the inversion of cane sugar (due to the change in the process of hydrolysis of the right rotation of the solution to the left), is called invert sugar (inversion of rotation). Natural invert sugar is honey, which consists mainly of glucose and fructose.

Sucrose is obtained in large quantities. Sugar beet contains 16-20% sucrose, sugar cane - 14-26%. The washed beets are crushed and sucrose is repeatedly extracted in apparatuses with water having a temperature of about 80 degrees. The resulting liquid, containing, in addition to sucrose, a large number of various impurities, is treated with lime. Lime precipitates a number of organic acids in the form of calcium salts, as well as proteins and some other substances. Part of the lime forms cold-water-soluble calcium saccharates with cane sugar, which are destroyed by treatment with carbon dioxide.

The precipitate of calcium carbonate is separated by filtration, the filtrate after further purification is evaporated in vacuum until a mushy mass is obtained. The separated crystals of sucrose are separated using centrifuges. This is how raw granulated sugar is obtained, which has a yellowish color, a brown mother liquor, a non-crystallizing syrup (beet molasses, or molasses). Sugar is cleaned (refined) and the finished product is obtained.

4. BIOLOGICAL ROLE OF BIOPOLYMERS - POLYSACCHARIDES

Polysaccharides are high-molecular (up to 1,000,000 Da) polymeric compounds consisting of a large number of monomers - sugars, their general formula is Cx (H2O) y. The most common monomer of polysaccharides is glucose, mannose, galactose, and other sugars are found. Polysaccharides are divided into:
- homopolysaccharides, consisting of monosaccharide molecules of the same type (for example, starch and cellulose consist only of glucose);
- heteropolysaccharides, which may contain several different sugars (heparin) as monomers.

If only 1,4= glycosidic bonds are present in the polysaccharide, we will get a linear, unbranched polymer (cellulose); if both 1,4= and 1,6= bonds are present, the polymer will be branched (glycogen). Among the most important polysaccharides are: cellulose, starch, glycogen, chitin.

Cellulose, or fiber (from Latin cellula - cell), is the main component of the cell wall of plant cells. It is a linear polysaccharide composed of glucose linked by 1,4= bonds. Fiber makes up 50 to 70% of wood. Cotton is almost pure fiber. Flax and hemp fibers are composed primarily of fiber. The purest examples of fiber are refined cotton wool and filter paper.

Starch is a branched polysaccharide of plant origin, consisting of glucose. In the polysaccharide, glucose residues are linked by 1,4= and 1,6= glycosidic bonds. When they are broken down, plants receive glucose, which is necessary in the course of their life. Starch is formed during photosynthesis in green leaves in the form of grains. These grains are especially easy to detect under a microscope using a lime reaction with iodine: starch grains turn blue or blue-black.

By the accumulation of starch grains, one can judge the intensity of photosynthesis. The starch in the leaves is broken down into monosaccharides or oligosaccharides and transferred to other plant parts, such as potato tubers or cereal grains. Here again there is a deposition of starch in the form of grains. The highest starch content in the following crops:

Rice (grain) - 62-82%;
- corn (grain) - 65-75%;
- wheat (grain) - 57-75%;
- potatoes (tubers) - 12-24%.

In the textile industry, starch is used to make paint thickeners. It is used in the match, paper, printing industry, in bookbinding. In medicine and pharmacology, starch is used to prepare powders, pastes (thick ointments), and is also necessary in the production of tablets. By subjecting starch to acid hydrolysis, glucose can be obtained in the form of a pure crystalline preparation or in the form of molasses - a colored non-crystallizing syrup.

The production of modified starches subjected to special processing or containing additives that improve their properties has been established. Modified starches are widely used in various industries.

Glycogen is a polysaccharide of animal origin, more branched than starch, consisting of glucose. It plays an extremely important role in animal organisms as a reserve polysaccharide: all life processes, primarily muscle work, are accompanied by the breakdown of glycogen, which releases the energy concentrated in it. In body tissues, lactic acid can be formed from glycogen as a result of a series of complex transformations.

Glycogen is found in all animal tissues. It is especially abundant in the liver (up to 20%) and muscles (up to 4%). It is also present in some lower plants, yeasts and fungi, and can be isolated by treating animal tissues with 5-10% trichloroacetic acid, followed by precipitation of the extracted glycogen with alcohol. With iodine, glycogen solutions give a wine-red to reddish-brown color, depending on the origin of the glycogen, the type of animal, and other conditions. The iodine color disappears on boiling and reappears on cooling.

Chitin in its structure and function is very close to cellulose - it is also a structural polysaccharide. Chitin is found in some fungi, where it plays a supporting role in the cell walls due to its fibrous structure, as well as in some groups of animals (especially arthropods) as an important component of their external skeleton. The structure of chitin is similar to that of cellulose; its long parallel chains are also bundled.

5. CHEMICAL PROPERTIES OF CARBOHYDRATES

All monosaccharides and some disaccharides, including maltose and lactose, belong to the group of reducing (restoring) sugars. Sucrose is a non-reducing sugar. The reducing ability of sugars in aldoses depends on the activity of the aldehyde group, while in ketoses it depends on the activity of both the keto group and the primary alcohol groups. In non-reducing sugars, these groups cannot enter into any reactions, because here they participate in the formation of a glycosidic bond. Two common reactions to reducing sugars, the Benedict reaction and the Fehling reaction, are based on the ability of these sugars to reduce the divalent copper ion to the monovalent one. Both reactions use an alkaline solution of copper(2) sulfate (CuSO4) which is reduced to insoluble copper(1) oxide (Cu2O). Ionic equation: Cu2+ + e = Cu+ gives a blue solution, a brick-red precipitate. All polysaccharides are non-reducing.

CONCLUSION

The main role of carbohydrates is related to their energy function. During their enzymatic cleavage and oxidation, energy is released, which is used by the cell. Polysaccharides play mainly the role of reserve products and easily mobilized energy sources (for example, starch and glycogen), and are also used as building materials (cellulose and chitin).

Polysaccharides are convenient as reserve substances for a number of reasons: being insoluble in water, they do not have either an osmotic or chemical effect on the cell, which is very important for long-term storage in a living cell: the solid, dehydrated state of polysaccharides increases the useful mass of reserve products due to their savings. At the same time, the probability of consumption of these products by pathogenic bacteria, fungi and other microorganisms, which, as you know, cannot swallow food, but absorb nutrients from the entire surface of the body, is significantly reduced. If necessary, storage polysaccharides can easily be converted into simple sugars by hydrolysis. In addition, combining with lipids and proteins, carbohydrates form glycolipids and glycoproteins-two.

There are several reasons why we should pay special attention to nutrition. First, all the cells and tissues of our body are formed from the food we eat. Secondly, food is a source of energy necessary for the functioning of the body. Thirdly, food is the main part of the environment with which we interact. Lastly, food was created to be enjoyed, to be an integral part of the joy of life, and our senses allow us to appreciate the quality, taste and very texture of the food we eat.

Today we invite you to talk about the energy nutrients found in our food. These include carbohydrates, fats and proteins. Generally speaking, we consider carbohydrates as a direct source of energy, proteins as the building blocks of our entire body, and fats as energy stores.

In vegetables and fruits, the main nutrients are carbohydrates. Garden and garden products contain simple (glucose, fructose, sucrose) and complex (starch, pectins, fiber) carbohydrates. In vegetables, carbohydrates are represented by starch, with the exception of beets and carrots, where sugars predominate. Fruit contains mostly sugars.

Starch is the most important carbohydrate in plants. It consists of a large number of glucose molecules. Potatoes are rich in starch. It is slightly less in legumes and late varieties of apples. In apples, for example, during their ripening, the amount of starch increases, and decreases during storage. This is due to the fact that when ripening during storage, the starch in the product turns into sugar. There is a lot of it in green bananas, and in mature ones it is 10 times less, as it turns into sugar. Starch is needed by the body mainly to satisfy its need for sugar. In the digestive tract, under the influence of enzymes and acids, starch is broken down into glucose molecules, which are then used for the needs of the body.

Fructose is found in many fruits and vegetables. The richer the fruits are, the sweeter they are. A direct dependence of a person's endurance and performance on the content of this substance in the muscles and liver has been proven. With low human mobility, nervous stress, putrefactive processes in the intestines, obesity, fructose is the most favorable of other carbohydrates.

Glucose is found in free form in fruits. It is part of starch, fiber, sucrose and other carbohydrates. Glucose, which our body uses for energy, is a high quality fuel. Circulating with the blood stream, glucose fills the constant need of body cells. It is most quickly and easily used by the body for the formation of glycogen, the nutrition of brain tissues, and the work of muscles, including the heart.

Sucrose is found in large quantities in sugar beet and sugar cane. Regardless of the raw material sources, sugar is almost pure sucrose. Its content in granulated sugar is 99.75%, and in refined sugar - 99.9%.

Digestion is not required for the absorption of simple carbohydrates (glucose, fructose and galactose). Table sugar and maltose are digested into simple sugars in minutes. In order to supply the blood with this rapidly digestible energy, our diet requires very little sugar. In the event of a glut, the pancreas is forced to work overtime, producing excess insulin to convert excess sugar into fat. At any given time, our bodies can only handle a limited amount of simple sugars properly.

Excess sugar stalls the human car, just as a full carburetor stalls a car engine, this is just one of the dangers of sugar abuse. There are other harmful effects as well. They are:

• depletion of vitamin B1 reserves;
• dental disease, since sugar creates an ideal environment for tooth-destroying microorganisms;
• suppression of the immune system due to the fact that sugar inhibits the ability of white blood cells to kill germs;
• increased amount of fat in the blood (from the conversion of glucose into triglyceride);
• stimulation of hypoglycemia and possible onset of diabetes;
• gastric irritation that occurs when the stomach contains more than 10% sugar (concentrated sugar solution is a strong mucosal irritant);
• constipation (sugar-rich foods are usually low in fiber);
• increase in blood cholesterol levels.

We can avoid these complications if we replace refined sugar with fruits in our diet (one ripe banana contains six teaspoons of sugar), and make complex carbohydrates found in wheat, rice, potatoes, legumes and other foods that contain starch.

Most complex carbohydrates are digested over several hours and release simple sugars gradually. This allows the pancreas, liver, adrenal gland, kidneys and other organs to use this energy properly. Moreover, due to the high fiber content of carbohydrate-containing foods, we usually do not overeat on such a diet.

Another advantage of complex carbohydrates is that they contain the minerals needed for proper absorption of other nutrients. Refined sugar has no minerals, no vitamins, and no fiber content.

The ideal diet should include, if at all, a minimum amount of sugar (honey, sucrose, maltose, sweet syrups), and instead an abundance of complex carbohydrates, which are rich in potatoes, cereals, bread and other products from wholemeal flour. Complex carbohydrates should make up the bulk of your daily caloric intake.

“And God said, Behold, I have given you every herb yielding seed, which is in all the earth, and every tree bearing fruit of a tree yielding seed, this shall be food for you” (Genesis 1:29).

Prepared by A. Konakova

Energy sources for the human body are proteins, fats, carbohydrates, which make up 90% of the dry weight of all nutrition and supply 100% of energy. All three nutrients provide energy (measured in calories), but the amount of energy in 1 gram of the substance is different:

• 4 kilocalories per gram of carbohydrates or proteins;
• 9 kilocalories per gram of fat.

A gram of fat has 2 times more energy for the body than a gram of carbohydrates and proteins.

These nutrients also differ in how quickly they deliver energy. Carbohydrates are delivered faster and fats are slower.

Proteins, fats, carbohydrates are digested in the intestine, where they are broken down into basic units:

• carbohydrates in sugar
• proteins in amino acids
• fats in fatty acids and glycerol.

The body uses these basic units to create the substances it needs to perform basic life functions (including other carbohydrates, proteins, fats).

Types of carbohydrates

Depending on the size of the carbohydrate molecules, they can be simple or complex.

• Simple Carbohydrates: Various types of sugars, such as glucose and sucrose (table sugar), are simple carbohydrates. These are small molecules, so they are quickly absorbed by the body and are a quick source of energy. They quickly increase blood glucose (blood sugar levels). Fruits, dairy products, honey, and maple syrup are high in simple carbohydrates, which provide the sweet taste in most candies and cakes.
• Complex Carbohydrates: These carbohydrates are made up of long strings of simple carbohydrates. Because complex carbohydrates are large molecules, they must be broken down into simple molecules before they can be absorbed. Thus, they tend to provide energy to the body more slowly than simple ones, but still faster than protein or fat. This is because they are digested more slowly than simple carbohydrates and are less likely to be converted to fat. They also raise blood sugar levels at a slower rate and at lower levels than regular ones, but for a longer time. Complex carbohydrates include starches and proteins found in wheat products (bread and pasta), other grains (rye and corn), beans, and root vegetables (potatoes).

Carbohydrates can be:

• refined
• unrefined

refined– processed , fiber and bran, as well as many of the vitamins and minerals they contain, are removed. Thus, the metabolism processes these carbohydrates quickly and provides little nutrition, although they contain about the same number of calories. Refined foods are often fortified, meaning vitamins and minerals are artificially added to increase nutritional value. A diet high in simple or refined carbohydrates tends to increase the risk of obesity and diabetes.

unrefined carbohydrates from plant foods. They contain carbohydrates in the form of starch and fiber. These are foods such as potatoes, whole grains, vegetables, fruits.

If people consume more carbohydrates than they need, the body stores some of these carbohydrates in the cells (as glycogen) and converts the rest into fat. Glycogen is a complex carbohydrate to convert into energy and is stored in the liver and muscles. Muscles use glycogen for energy during periods of intense exercise. The amount of carbohydrates stored as glycogen can provide calories per day. Several other body tissues store complex carbohydrates that cannot be used as an energy source for the body.

Glycemic index of carbohydrates

The glycemic index of carbohydrates represents how quickly their consumption raises blood sugar levels. The range of values ​​is from 1 (slowest absorption) to 100 (fast, pure glucose index). However, how quickly levels actually rise depends on the foods ingested.

The glycemic index is generally lower for complex carbohydrates than for simple carbohydrates, but there are exceptions. For example, fructose (sugar in fruits) has little effect on blood sugar levels.

The glycemic index is influenced by processing technology and food composition:

• processing: processed, chopped or finely ground foods tend to have a high glycemic index
• type of starch: different types of starch are absorbed differently. Potato starch is digested and relatively quickly absorbed into the blood. Barley is digested and absorbed much more slowly.
• fiber content: The more fiber a food has, the harder it is to digest. As a result, sugar is more slowly absorbed into the blood.
• fruit ripeness: ripe fruit, more sugar in it and the higher its glycemic index
• fat or acid content: contains more fat or acid food, slowly digested and slowly its sugars are absorbed into the blood
• Cooking: How food is prepared can affect how quickly it is absorbed into the bloodstream. Generally, cooking or chopping food increases its glycemic index as it is easier to digest and absorb after the cooking process.
• other factors : The body's nutritional processes vary from person to person, how quickly carbohydrates are affected by conversion to sugar and absorption. How well the food is chewed and how quickly it is swallowed is important.

Glycemic index of some foods

The glycemic index is an important parameter, because carbohydrates increase blood sugar, if quickly (with a high glycemic index) then insulin levels increase. An increase in insulin can lead to low blood sugar (hypoglycemia) and hunger, which tends to consume excess calories and gain weight.

Carbohydrates with a low glycemic index do not increase insulin levels much. As a result, people feel full longer after eating. Consumption of low glycemic carbohydrates also leads to healthier cholesterol levels and reduces the risk of obesity and diabetes in people with diabetes, the risk of complications due to diabetes.

Despite the link between low glycemic index foods and improved health, using the index to select foods does not automatically lead to healthy eating.

For example, the high glycemic index of potato chips and some candies are not a healthy choice, but some high glycemic foods contain valuable vitamins and minerals.

Thus, the glycemic index should only be used as a general guide to food selection.

Glycemic load of foods

The glycemic index measures how quickly carbohydrates in food are absorbed into the blood. It does not include the amount of carbohydrates in food, which are important.

Glycemic load, a relatively new term, includes the glycemic index and the amount of carbohydrates in a food.

Foods such as carrots, bananas, watermelon, or wholemeal bread may have a high glycemic index but are relatively low in carbohydrates and thus have a low glycemic load of foods. These foods have little effect on blood sugar levels.

Proteins in products

Proteins are made up of a structure called amino acids and form complex formations. Because proteins are complex molecules, it takes longer for the body to absorb them. As a result, they are a much slower and longer source of energy for the human body than carbohydrates.

There are 20 amino acids. The human body synthesizes some of the components in the body, but it cannot synthesize 9 amino acids - called essential amino acids. They must be included in the diet. Everyone needs 8 of these amino acids: isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Babies also need the 9th amino acid, histidine.

The percentage of protein that the body can use to synthesize essential amino acids varies. The body can use 100% of the protein in an egg and a high percentage from milk and meat proteins, but can use slightly less than half the protein from most vegetables and grains.

The body of any mammal needs protein to maintain and replace tissue growth. Protein is not usually used as an energy source for the human body. However, if the body is not getting enough calories from other nutrients or stored body fat, protein is used for energy. If there is more protein than needed, the body converts the protein and stores its components as fat.

The living body contains a large amount of protein. Protein, the main building block in the body and is the main component of most cells. For example, muscles, connective tissue and skin are all built from protein.

Adults should eat about 60 grams of protein per day (1.5 grams per kilogram of body weight, or 10-15% of total calories).

Adults who are trying to build muscle need a little more. Children also need more protein as they grow.

Fats

Fats are complex molecules made up of fatty acids and glycerol. The body needs fats for growth and as a source of energy for the body. Fat is also used for the synthesis of hormones and other substances necessary for the functioning of the body (for example, prostaglandins).

Fats are a slow source of energy, but the most energy efficient type of food. Each gram of fat provides the body with about 9 calories, more than twice as much as supplied proteins or carbohydrates. Fats are an efficient form of energy and the body stores excess energy as fat. The body stores excess fat in the abdomen (omental fat) and under the skin (subcutaneous fat) to be used when more energy is needed. The body can also remove excess fat from blood vessels and organs, where it can block the flow of blood, and from damaged organs, often causing serious problems.

Fatty acid

When the body needs fatty acids, it can make (synthesize) some of them. Some acids, called essential fatty acids, cannot be synthesized and must be consumed in the diet.

Essential fatty acids make up about 7% of the fat consumed in a normal diet and about 3% of total calories (about 8 grams). They include linoleic and linolenic acids, which are present in some vegetable oils. Eicosapentaenoic and docosahexaenoic acids, which are essential fatty acids for brain development, can be synthesized from linoleic acid. However, they are also present in some marine fish products, which are a more efficient source.

Where is fat located?

Linoleic and arachidonic acids are both omega-6 fatty acids.

Linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid are omega-3 fatty acids.

A diet rich in omega-3 fatty acids may reduce the risk of atherosclerosis (including coronary artery disease). Lake trout and some deep sea fish are high in omega-3 fatty acids.

You need to consume enough omega-6 fatty acids

Types of fats

There are different types of fats

• monounsaturated
• polyunsaturated
• rich

Eating saturated fat increases cholesterol levels and the risk of atherosclerosis. Products derived from animals usually contain saturated fats, which tend to be solid at room temperature. Fats derived from plants usually contain monounsaturated or polyunsaturated fatty acids, which are usually liquid at room temperature. The exceptions are palm and coconut oil. They contain more saturated fats than other vegetable oils.

Trans fats (trans fatty acids) are another category of fat. They are artificial and are formed by the addition of hydrogen atoms (hydrogenation) of monounsaturated or polyunsaturated fatty acids. Fats can be fully or partially hydrogenated (saturated with water atoms). The main nutritional source of trans fats is partially hydrogenated vegetable oils in commercially prepared foods. Consumption of trans fats can negatively affect cholesterol levels in the body and may contribute to the risk of atherosclerosis.

Fats in the diet

• fat must be limited and make up less than 30% of total daily calories (or less than 90 grams per day)
• Saturated fat should be limited to 10%.

When fat intake is reduced to 10% or less of total daily calories, cholesterol levels drop dramatically.

Carbohydrates, proteins and fats are the main sources of energy necessary for human life and their quality is important for health.

The primary source of energy for living organisms is the energy of sunlight. Phototrophs - plants and photosynthetic microorganisms - directly use light energy for the synthesis of complex organic substances (fats, proteins, carbohydrates, etc.), which are secondary sources of energy. Heterotrophs, which include animals, use the chemical energy released during the oxidation of organic substances synthesized by plants.

Bioenergetic processes can be divided into processes of production and accumulation of energy and processes in which useful work is performed due to the stored energy (Fig. 1.1). Photosynthesis is the main bioenergy process on Earth. This is a complex multi-stage system of photophysical, photochemical and dark biochemical processes in which the energy of sunlight is transformed into chemical or electrochemical forms of energy. In the first case, this is the energy contained in complex organic molecules, and in the second, the energy of the proton gradient on the membranes, which is also converted into a chemical form. In photosynthetic organisms, quanta of sunlight are absorbed by chlorophyll molecules and transfer their electrons to an excited state with increased energy. It is due to the energy of excited electrons in chlorophyll molecules that the photosynthetic system of phototrophs from simple molecules of carbon dioxide and water synthesizes glucose and other organic molecules (amino acids, fatty acids, nucleotides, etc.), from which carbohydrates, proteins, fats are subsequently built in the body and nucleic acids. The product of these reactions is also molecular oxygen.

The overall equation of the main reactions of photosynthesis:

6 CO 2 + 6 H 2 O C 6 H 12 O 6 (glucose) + 6 O 2,

where hn - photon energy.

The global role of photosynthesis is exceptionally great. The power of solar radiation is about 10 26 W. About 2 10 17 W reach the Earth's surface from it, and of this value, approximately 4 10 13 W is used by photosynthetic organisms for the synthesis of organic substances (Samoilov, 2004). This energy sustains life on Earth. Due to it, about 7,510 10 tons of biomass are synthesized per year (in terms of carbon). At the same time, about 4 10 10 tons of carbon is fixed by phytoplankton in the ocean and 3.510 10 tons by plants and photosynthetic microorganisms on land.

Mankind consumes the products of photosynthesis in the form of food, eating organic substances primarily produced by plants or secondarily produced by animals that eat plants, and in the form of fuel, which is 90% used by previously stored photosynthesis products - oil and coal (the rest of the energy is provided by nuclear and hydroelectric power plants). ).

The extraction of energy accumulated by phototrophic organisms and its subsequent use is carried out in the processes of nutrition and respiration. When passing through the digestive tract, food is crushed, cells are destroyed and biopolymers (proteins, nucleic acids, fats and carbohydrates) are broken down into low molecular weight monomers (amino acids, nucleotides, fatty acids and sugars), which are absorbed into the blood in the intestine and transported throughout the body. From them, cells extract hydrogen atoms carrying high-energy electrons, the energy of which can be partially stored in the form of adenosine triphosphate (ATP) molecules. ATP is a universal source of energy, used as a battery, where and when useful work is needed.