Features of metabolism in different organisms. Metabolism and energy, its age-related features

Proper metabolism and energy provide the vital activity of the human body. But people are prone to various diseases. Why this happens, and what does metabolism have to do with diseases, you will learn from this article.

What you need to know about metabolism

What is metabolism? This is the activity of the body, as a result of which tissues, organs and organ systems receive the necessary nutrients (fats, carbohydrates and proteins) and remove the decay products of the body (salts, unnecessary chemical compounds). If these processes work well in the body, a person does not have health problems, and, conversely, various diseases develop with metabolic disorders.

Why does the body need nutrients? In the human body, there is a continuous, intensive synthesis, that is, complex chemical compounds are formed from simpler ones in organs, tissues and at the cellular level. At the same time, the second process is uninterrupted - the process of decomposition and oxidation of organic compounds that are no longer needed by the body and are removed from it. This complex metabolic process ensures the vital activity, formation and growth of new cells, and nutrients are the building material of all organs and systems as a whole.

Nutrients are not only needed to build tissues and organs, but also for the intensive, well-established work of all systems - the cardiovascular, respiratory, endocrine, genitourinary systems and the gastrointestinal tract. This is the energy that enters the human body during the oxidation and decomposition of organic compounds in the metabolic process. Therefore, nutrients are a significant source of energy necessary for the smooth functioning of the whole organism.

Speaking of types nutrients, then proteins, namely their enzymes, are the main material for the structure and growth of organs. Fats and carbohydrates are designed to produce and cover energy costs. All types of nutrients, including minerals and vitamins, must be supplied to the body in a certain daily amount. Lack of vitamins or a norm that exceeds the allowable one leads to disorders in the work of the whole organism and provokes various diseases. Therefore, the role of metabolism is certainly significant for the body in every sense of the word.

When metabolism is disturbed and slowed down, there is often a problem excess weight. Many people ask: "Is it possible to speed up the metabolic process?". Of course, but it takes a lot of effort to achieve the desired result. So, dreaming of having an ideal weight and, many women resort to grueling workouts and sports exercises. Of course, physical activity can build muscle mass by destroying body fat, but here you need an integrated approach to losing weight, including a balanced diet. Regular consumption of green tea helps to speed up metabolism, which has been proven by well-known nutritionists.

Many people want to change their weight in extraordinary ways. Some even start smoking because they believe that smoking promotes fat burning. Indeed, the body spends fat reserves to restore the body from tobacco poisons. In this case, you need to think about whether it is worth sacrificing the health of the whole organism for the sake of the disappearance of a few kilograms.

Often, hereditary diseases provoke weight gain and a slowdown in the metabolic process. So, obesity is observed in patients with diabetes mellitus, due to disruption of the thyroid gland. In most cases, these diseases are passed down through the genes to children. Therefore, the most optimal diet option is prescribed by an endocrinologist.

Age-related features of metabolism

The nutritional requirements of a child's body are much higher than those of an adult. Therefore, there is an intensive metabolism, where the processes of anabolism (synthesis) and catabolism (decay) are much faster than in the body of an adult. Since there is an intensive growth of cells and the development of a young organism, protein as a building material is needed two or even more times than an adult. So if child under 4 years old a daily rate of 30 ... 50g is required, then a 7-year-old needs up to 80g of protein per day. Protein enzymes in the human body do not accumulate like fats. If you increase the daily dose of proteins, it threatens with digestive disorders.

Together with fats, hormones and vitamins necessary for life enter the body. They are divided into 2 main groups: those that are broken down with the help of fats and those that need only water. The younger the child, the more percentage of fat is needed for its development. Thus, an infant with mother's milk receives approximately 90%, the body of an older child absorbs 80%. The digestibility of fats directly depends on the amount of carbohydrates, the deficiency of which leads to various undesirable changes in digestion, an increase in acidity in the body. It is a sufficient daily intake of fat that helps to strengthen the immune system.

Carbohydrates are needed by the children's body in large quantities. With age, the need of a growing organism for them also increases. Exceeding the norm of carbohydrates raises blood sugar in a child only for a few hours after ingestion of carbohydrates, then the level is normalized. Therefore, the risk of getting sick with diabetes is practically excluded, in adults, the opposite is true.

The metabolism of older people changes significantly, as it is associated with hormonal changes in the body. 2 main stages of metabolism slow down: the processes of synthesis and decomposition of compounds. So, people over 60 need to limit the intake of proteins with food. Therefore, meat consumption should be limited, but not completely. Since the elderly are prone to frequent constipation and intestinal problems, it is useful for them to take sour-milk products, raw vegetables and fruits. It is better to use fats at a minimum, it is better - vegetable. Carbohydrates should also not be carried away (meaning sweets, but sweet fruits are allowed).

Improper nutrition, age-related changes, aging of organs, tissues and cells makes it difficult and slows down the metabolism in the body. Therefore, older people should eat moderately and lead an active lifestyle.

Introduction

1. Muscle mass and strength at different ages

2. Age-related features of metabolism

3. Age dynamics of basal metabolism

4. Biochemical substantiation of the methodology of physical culture and sports with children and adolescents.

5. Biochemical substantiation of the methodology of physical culture lessons with the elderly.

References

Introduction

The method of physical exercises with people of different ages is characterized by a number of distinctive features. These differences are based on the characteristics of a growing, mature and aging organism. Be especially careful when doing physical education with children and the elderly. This is due to the greatest vulnerability of a growing and aging organism to various kinds of influences, including physical exercises.

There are the following age periods:

1. Children's age - from birth to the onset of puberty (12-13 years).

2. Adolescence (puberty) - from 12-13 to 16 years for girls and from 13-14 to 17-18 years for boys.

3. Adolescence - from 16 to 25 years for women and from 17 to 26 years for men.

4. Adult age - from 25 to 40 years for women and from 26 to 45 years for men. The period of relative stabilization of morphological and metabolic processes.

5. Mature age - from 40 to 55 years for women and from 45 to 60 years for men. 6. Old age - from 55 to 75 years for women and from 60 to 75 years for men.

7. Senile age - over 75 years for women and men. The general involution of the organism begins to develop.

The growth period is characterized by non-intensive, protein and nucleic acid synthesis. There is an increase in the percentage of muscle tissue to body weight. Intensive synthesis of proteins and nucleic acids requires significant energy costs. The child is also characterized by increased motor activity and significant heat loss (the ratio of body surface to weight in children is higher than in adults). It also requires a significant amount of energy. A growing organism is characterized by reduced anaerobic capacity. This is due to the relatively low content of creatine phosphate and glycogen, limited buffering capabilities of the body, and less resistance to anaerobic metabolic products.

An aging organism is characterized by a general decrease in the intensity of metabolic processes, a significant decrease in plastic metabolism. The process of protein breakdown begins to prevail over their synthesis, which leads to a decrease in the content of total protein and its fractions in cells and body fluids. Many nerve, muscle and other cells atrophy, the content and activity of protein-enzymes, the content of blood hemoglobin and muscle myoglobin decrease. The content of mobile energy sources decreases, the buffering capacity and resistance of enzymes to changes in the pH of the internal environment decrease.

By old age, the content of salts in the bone tissue increases, which reduces their elasticity and increases fragility. The elasticity and strength of the ligaments decreases, the blood supply to the muscles and other organs and tissues deteriorates. All this makes it dangerous for health to perform intense exercises of a high-speed and high-speed-strength nature: sprinting, various jumps, exercises with heavy weights, etc. By old age, there is a decrease in the functions of the endocrine glands, including those providing "the body's readiness for work" - increased activity of energy metabolism enzymes, supply of working muscles with energy substrates, etc.

The task of physical exercise in old age is to slow down the development of age-related changes and maintain working capacity.

The elderly should have a comprehensive effect on the body, moderate intensity of work and sufficient time for rest.

MASS AND STRENGTH OF MUSCLES AT DIFFERENT AGES

mechanism of muscle contraction.

Skeletal muscles have properties such as excitability, conductivity, and contractility. The excitation and contraction of the muscle is caused by nerve impulses coming from the nerve centers. Nerve impulses arriving at the contact area of ​​the nerve and muscle lead to the release of the mediator acetylcholine, which causes an action potential. Under the influence of the action potential, calcium is released, which triggers the entire system of muscle contraction. In the presence of Ca ions, under the influence of the active enzyme myosin, the breakdown of adenosine triphosphate (ATP), which is the main source of energy during muscle contraction, begins. When this energy is transferred to the myofibrils, the protein filaments begin to move relative to each other, as a result of which the length of the myofibrils changes - the muscles contract. Muscles act on bone levers, set them in motion. Each movement involves several muscles. Muscles that act in one direction are called synergists, those that act in different directions are called antagonists.

Mass and strength of muscles in different age periods

The strength of the muscles depends on the features of their attachment to the bones. The bones, together with the muscles attached to them, are a kind of levers, and the muscle can develop the greater force, the farther from the fulcrum of the lever and closer to the point of application of gravity, it is attached. In humans, muscle strength is 5-10 kg. per 1 cm of the physiological diameter of the muscle.

In early childhood, the muscles of the trunk develop much faster than the muscles of the upper and lower limbs. By one year, the muscles of the upper limb are more developed than the muscles of the lower limb. By the age of 4-5, the muscles of the shoulder and forearm overtake the muscles of the hand in development. The acceleration of the development of the muscles of the hand occurs at the age of 6-7, when the child is accustomed to work and writing. The development of the flexor muscles begins to outstrip the development of the extensor muscles. The flexors have more mass than the extensors.

Muscle mass increases intensively when the child begins to walk, and by the age of 2-3 years it is approximately 23% of body weight, then it rises to 27% by the age of 8 years. In adolescents 15 years old, it is 32.6% of body weight. The fastest muscle mass increases at the age of 15 to 17-18 years and is 44.2%.

An increase in muscle mass is achieved both by their lengthening and by an increase in their thickness, mainly due to the diameter of the muscle fibers. By 3-4 years, the diameter of the muscles increases by 2-2.5 times. With age, the number of myofibrils sharply increases. By the age of 7, compared with a newborn, it increases by 15-20 times. In the period from 7 to 14 years, the growth of muscle tissue occurs both due to structural transformations of the muscle fiber, and in connection with a significant increase in tendons.

An increase in muscle mass and structural transformations (extensibility, elasticity) of muscle fibers lead to an increase in muscle strength with age. At preschool age, muscle strength is negligible. After 4-5 years, the strength of individual muscle groups increases. Muscle strength increases most intensively during adolescence. In boys, the increase in strength begins at 13-14 years old, in girls - from 10-12 years old. At the age of 13-14, gender differences in muscle strength appear, the indicators of the relative muscle strength of girls are significantly inferior to the corresponding indicators of boys.

At the age of 18, the growth of strength slows down and ends by the age of 25-26.

The strength of the muscles that carry out the extension of the body reaches a maximum at 16 years of age. The maximum strength of the extensor and flexor of the upper and lower extremities is observed at 20-30 years of age.

In old people, the average skeletal muscle mass decreases to 25-30% of body weight.

Calculation of the maximum force per 1 kg. body weight allows you to evaluate the perfection of nervous regulation, chemistry and muscle structure. It is noted that at the age of 4-5 to 6-7 years, the increase in maximum strength is almost not accompanied by changes in its relative index. The reason for this growth is the imperfection of nervous regulation and the functional immaturity of motor neurons, which do not allow effective mobilization of the muscle mass increased by this age. In the future, after the age of 6-7 to 9-11 years for muscles, the increase in relative strength becomes especially noticeable. At this time, there are rapid rates of improvement in the nervous regulation of voluntary muscle activity, as well as changes in the biochemical and histological structure of muscles. This position is confirmed by the fact that in the age period from 4 to 30 years, muscle mass increases by 8 times, and muscle strength by 9-14 times.

AGE CHARACTERISTICS OF METABOLISM

1. Protein metabolism in a developing organism.

Growth processes, quantified by weight gain and positive nitrogen balance, are one side of development. Its second side is the differentiation of cells and tissues, the biochemical basis of which is the synthesis of enzymatic, structural and functional proteins.

Proteins are synthesized from amino acids that come from the organs of the digestive system. Moreover, these amino acids are divided into essential and non-essential. If essential amino acids (leucine, methionine and tryptophan, etc.) are not supplied with food, then protein synthesis in the body is disturbed. The intake of essential amino acids for a growing organism is especially important, for example, the lack of lysine in food leads to growth retardation, depletion of the muscular system, and a lack of valine - balance disorders in a child.

In the absence of non-essential amino acids in food, they can be synthesized from essential ones (tyrosine can be synthesized from phenylalanine).

Finally, proteins containing all the necessary set of amino acids that ensure normal synthesis processes are biologically complete proteins. The biological value of the same protein for different people is different depending on the state of the body, diet, age.

The ability to retain nitrogen in children is subject to significant individual fluctuations and persists throughout the entire period of progressive growth.

As a rule, adults do not have the ability to retain food nitrogen, their metabolism is in a state of nitrogen balance. This indicates that the potential for protein synthesis persists for a long time - for example, under the influence of physical activity, an increase in muscle mass occurs (positive nitrogen balance).

During periods of stable and regressive development, upon reaching maximum weight and cessation of growth, the main role begins to be played by self-renewal processes that occur throughout life and which, with old age, fade much more slowly than other types of synthesis.

Age-related changes affect not only protein, but also fat and carbohydrate metabolism.

2. Age dynamics of fat and carbohydrate metabolism.

The physiological role of lipids - fats, phosphatides and sterols in the body is that they are part of cellular structures (plastic metabolism), and are also used as rich sources of energy (energy metabolism). Carbohydrates in the body are the energy material.

With age, fat and carbohydrate metabolism changes. In the processes of growth and differentiation, fats play an essential role. Fat-like substances are especially important, primarily because they are necessary for the morphological and functional maturation of the nervous system, for the formation of all types of cell membranes. That is why the need for them in childhood is great. With a lack of carbohydrates in food, fat depots in children are quickly depleted. The intensity of synthesis largely depends on the nature of nutrition.

The phases of stable and regressive development are characterized by a kind of reorientation of anabolic processes: switching of anabolism from protein synthesis to fat synthesis, which is one of the characteristic features of age-related changes in metabolism during aging.

The age-related reorientation of anabolism towards the accumulation of fat in a number of organs is based on a decrease in the ability of tissues to oxidize fat, as a result of which, with a constant and even reduced rate of synthesis of fatty acids, the body is enriched with fats (for example, the development of obesity was observed even with 1-2 meals a day). It is also undoubted that in the reorientation of synthesis processes, in addition to nutritional factors and nervous regulation, a change in the hormonal spectrum is of great importance, in particular changes in the rate of formation of somatotropic hormone, thyroid hormones, insulin, and steroid hormones.

Rebuilds with age and carbohydrate metabolism. In children, the metabolism of carbohydrates occurs with greater intensity, which is explained by a high level of metabolism. In childhood, carbohydrates perform not only an energy, but also a plastic function, forming cell membranes, connective tissue substances. Carbohydrates are involved in the oxidation of the products of protein and fat metabolism, thereby helping to maintain the acid-base balance in the body.

Carbohydrates are absorbed by the children's body better than adults. One of the significant indicators of age-related changes in carbohydrate metabolism is a sharp increase in old age in the time to eliminate hyperglycemia caused by the introduction of glucose during sugar load tests.

3. Water-salt exchange.

The transformation of substances in the body takes place in an aquatic environment, together with mineral substances, water takes part in the construction of cells and serves as a reagent in cellular chemical reactions. The concentration of mineral salts dissolved in water determines the magnitude of the osmotic pressure of blood and tissue fluid, thus being of great importance for absorption and excretion. changes in the amount of water in the body and shifts in the salt composition of the body fluid and tissue structures entail a violation of the stability of colloids, which may result in irreversible damage and death of individual cells and then the body as a whole. That is why maintaining a constant amount of water and mineral composition is a necessary condition for normal life.

In the phase of progressive growth, water is involved in the processes of creating body weight. It is known, for example, that out of a daily weight gain of 25 g, water accounts for 18, protein - 3, fat - 3 and mineral salts - 1 g. The younger the body, the greater the daily need for water. In the first six months of life, a child's need for water reaches 110-125 g per 1 kg of weight, by 2 years it decreases to 115-136 g, at 6 years old - 90-100 g, 18 years old - 40-50 g. Children are able to quickly lose and also quickly deposit water.

The general pattern of individual evolution is the reduction of water in all tissues. With age, there is a redistribution of water in the tissues - the volume of water in the intercellular spaces increases and the volume of intracellular water decreases.

The balance of many mineral salts depends on age. In youth, the content of most inorganic salts is less than in adults. Of particular importance is the exchange of calcium and phosphorus. The increased requirements for the intake of these elements in children under one year old are explained by the increased formation of bone tissue. But these elements are no less important in old age. Therefore, the elderly need to introduce foods containing these elements (milk, dairy products) into the diet in order to avoid the consumption of these elements from bone tissue. And the content of sodium chloride, on the contrary, should be reduced in the diet due to the weakening of the production of mineralocorticoids in the adrenal glands with age.

4. Age dynamics of basal metabolism

The basic metabolism is understood as the minimum level of metabolism and energy expenditure for the body under strictly constant conditions: 14-16 hours before a meal, in the supine position in a state of muscle rest at a temperature of 8-20 C. In a middle-aged person, the basic metabolism is 4187 J per 1 kg of mass in 1 hour. On average, this is 7-7.6 MJ per day. At the same time, for each person, the basal metabolic rate is relatively constant.

The basal metabolism in children is more intense than in adults, since they have a relatively large body surface per unit mass, and the processes of dissimilation, not assimilation, are predominant. The energy costs of growth are greater the younger the child. So the energy expenditure associated with growth at the age of 3 months is 36%, at the age of 6 months. - 26%, 9 months - 21% of the total energy value of food.

In extreme old age (phase of regressive development) there is a decrease in body weight, as well as a decrease in the linear dimensions of the human body, the main metabolism drops to low values. Moreover, the degree of decrease in basal metabolism at this age correlates, according to various researchers, with how old people show signs of decrepitude and lost.

In ontogenesis, not only the average value of energy metabolism varies, but the possibilities of increasing this level under conditions of intense, for example, muscular activity also change significantly.

An increase in skeletal muscle tone with insufficient activity of the vagus nerve center during the first year of life contributes to an increase in energy metabolism. The role of age-related restructuring of the activity of skeletal muscles in the dynamics of energy metabolism is especially clearly distinguished in the study of gas exchange in people of different ages at rest and during physical activity. For progressive growth, an increase in metabolism at rest is characterized by a decrease in the level of basal metabolism and an improvement in energy adaptation to muscle activity. During the period of the stable phase, a high exchange of functional rest is maintained and the exchange during work increases significantly, reaching a stable, minimum level of basal metabolism. And in the regressive phase, the difference between the exchange of functional rest and the main exchange continuously decreases, the rest time lengthens.

Many researchers believe that the decrease in the energy metabolism of the whole organism during ontogenesis is primarily due to quantitative and qualitative changes in metabolism in the tissues themselves, the magnitude of which is judged by the ratio between the main mechanisms of energy release - anaerobic and aerobic. This allows us to find out the potential capabilities of tissues to generate and use the energy of macroergic bonds.

As a result of mastering this chapter, the student should: know

• stages of metabolism and energy: anabolism and catabolism;
• characteristics of general and basal metabolism;
• specific dynamic action of food;
• ways to assess the energy consumption of the body;
• age-related features of metabolism; be able to
• explain the importance of metabolism for the human body;
• to connect age-related features of metabolism with energy consumption in different age periods;

own

Knowledge about the participation of nutrients in metabolism.

Characteristics of metabolism in the body

metabolism, or metabolism(from Greek. metabole- transformation) is a set of chemical and physical transformations that occur in a living organism and ensure its vital activity in conjunction with the external environment. In the metabolism and energy metabolism, two opposite interrelated processes are distinguished: anabolism, which underlies assimilation, and catabolism, which is based on dissimilation.

Anabolism(from Greek. anabole- rise) - a set of processes for the synthesis of tissue and cellular structures, as well as compounds necessary for the life of the body. Anabolism ensures the growth, development and renewal of biological structures, the accumulation of an energy substrate. Energy is stored in the form of high-energy phosphate compounds (macroergs) such as ATP.

Catabolism(from Greek. catabole- dropping down) - a set of processes of disintegration of tissue and cellular structures and splitting of complex compounds for energy and plastic support of life processes. During catabolism, chemical energy is released, which is used by the body to maintain the structure and function of the cell, as well as to provide specific cellular activity: muscle contraction, secretion of glands, etc. The end products of catabolism - water, carbon dioxide, ammonia, urea, uric acid, etc. - are removed from the body.

Thus, catabolic processes supply energy and raw materials for anabolism. Anabolic processes are necessary for the construction and restoration of structures and cells, the formation of tissues in the process of growth, for the synthesis of hormones, enzymes and other compounds necessary for the life of the body. For catabolism reactions, they supply macromolecules to be cleaved. The processes of anabolism and catabolism are interconnected and are in the body in a state dynamic balance. The state of equilibrium or non-equilibrium ratio of anabolism and catabolism depends on age, health status, physical or mental load. In children, the predominance of anabolic processes over catabolic characterizes the processes of growth and accumulation of tissue mass. The most intensive increase in body weight is observed in the first three months of life - 30 g / day. By the year it decreases to 10 g/day, in subsequent years the decrease continues. The energy cost of growth is also highest in the first three months and is about 140 kcal/day or 36% of the energy value of food. From three years to puberty, it decreases to 30 kcal / day, and then increases again - up to 110 kcal / day. Anabolic processes are more intense in adults during the recovery period after illness. The predominance of catabolic processes is typical for people who are old or exhausted by a severe long-term illness. As a rule, this is due to the gradual destruction of tissue structures and the release of energy.

The essence of metabolism is the intake of various nutrients from the external environment into the body, the assimilation and use of them as sources of energy and material for building the structures of the body and the release of metabolic products formed in the process of vital activity into the external environment. In this regard, allocate four main components of the exchange function.

• extraction of energy from the environment in the form of chemical energy of organic substances;
• the transformation of nutrients from poverty into simpler substances, from which macromolecules are formed that make up the components of cells;
• assembly of proteins, nucleic acids and other cellular components from these substances;
• synthesis and destruction of molecules necessary to perform various specific functions of the body.

Metabolism in the body occurs in several stages. First stage - the transformation of nutrients in the digestive tract. Here, the complex substances of the diet are broken down into simpler ones - glucose, amino acids and fatty acids that can be absorbed into the blood or lymph. When nutrients are broken down in the gastrointestinal tract, energy is released, which is called primary heat. It is used by the body to maintain temperature homeostasis.

Second phase the transformation of substances takes place inside the cells of the body. This is the so-called intracellular, or intermediate, exchange. Inside the cell, the products of the first stage of metabolism - glucose, fatty acids, glycerol, amino acids - are oxidized and phosphorylated. These processes are accompanied by the release of energy, most of which is stored in the macroergic bonds of ATP. The reaction products provide the cell with building blocks for the synthesis of various molecular components. Numerous enzymes play a decisive role in this. With their participation, complex chemical reactions of oxidation and reduction, phosphorylation, transamination, etc. are carried out inside the cell. Metabolism in the cell is possible only with the integration of all complex biochemical transformations of proteins, fats and carbohydrates with the participation of their common energy sources (ATP) and due to the existence common precursors or common intermediates. The total energy supply of the cell is formed due to the reaction of biological oxidation.

Biological oxidation is either aerobic or anaerobic. Aerobic(from lat. aeg - air) processes require the presence of oxygen, are carried out in mitochondria and are accompanied by the accumulation of a large amount of energy that covers the main energy expenditure of the body. Anaerobic processes proceed without the participation of oxygen, mainly in the cytoplasm and are accompanied by the accumulation of a small amount of energy in the form of ATP, which is used to meet the limited short-term needs of the cell. So, for the muscle tissue of an adult, aerobic processes are characteristic, while anaerobic processes predominate in the energy metabolism of the fetus and children of the first days of life.

With the complete oxidation of 1 M glucose or amino acids, 25.5 M ATP is formed, and with the complete oxidation of fats, 91.8 M ATP. The energy stored in ATP is used by the body to perform useful work and is converted into secondary heat. Thus, the energy released during the oxidation of nutrients in the cell is ultimately converted into thermal energy. As a result of aerobic oxidation, nutrient products are converted into CO 2 and H 2 0, which are harmless to the body.

However, a direct combination of oxygen with oxidizable substances without the participation of enzymes, which is called free radical oxidation, can also occur in the cell. In this case, highly toxic free radicals and peroxides are formed. They damage cell membranes and destroy structural proteins. This type of oxidation is prevented by eating vitamins E, A, C, etc., as well as trace elements (Se, etc.), which convert free radicals into stable molecules and prevent the formation of toxic peroxides. This ensures the normal course of biological oxidation in the cell.

final stage metabolism - excretion of decay products with urine and excretions of sweat and sebaceous glands.

Plastic and energy exchanges act in the body as a whole, but the role of various nutrients in their implementation is not the same. In an adult, the breakdown products of fats and carbohydrates are mainly used to provide energy processes, and proteins are used to build and restore cell structures. In children, due to the intensive growth and development of the body, carbohydrates are involved in plastic processes. Biological oxidation serves as a source not only of energy-rich phosphates, but also of carbon compounds used in the biosynthesis of amino acids, carbohydrates, lipids and other cell components. This explains the significantly higher intensity of energy metabolism in children.

All the energy of chemical bonds of nutrients entering the body eventually turns into heat (primary and secondary heat), therefore, by the amount of heat generated, one can judge the amount of energy costs for vital activity.

To assess the energy consumption of the body, methods of direct and indirect calorimetry are used, with the help of which it is possible to determine the amount of heat released by the human body. Direct calorimetry is based on the measurement of the amount of heat that the body releases into the environment (for example, per hour or per day). For this purpose, a person is placed in a special chamber - calorimeter(Fig. 12.1). The walls of the calorimeter are washed by water, the heating temperature of which is used to judge the amount of energy released. Direct calorimetry provides a high accuracy in assessing the body's energy consumption, but due to its bulkiness and complexity, this method is used only for special purposes.

To determine the energy consumption of a person, a simpler and more affordable method is often used. indirect calorimet-

Rice. 12.1.

The calorimeter is used for research conducted on humans. The total energy released consists of: 1) heat generated, measured by the rise in temperature of the water flowing in the chamber coil; 2) the latent heat of vaporization, measured by the amount of water vapor extracted from the ambient air by the first H 2 0 absorber; 3) work aimed at objects outside the chamber. Consumption of 0 2 is measured by its amount, which must be added so that its content in the chamber remains constant

rii - according to gas exchange. Considering that the total amount of energy released by the body is the result of the breakdown of proteins, fats and carbohydrates, and also knowing the amount of energy released during the breakdown of each of these substances (their energy value), and the amount of decayed substances over a certain period of time, we can calculate the amount released energy. To determine which substances have been oxidized in the body (proteins, fats or carbohydrates), calculate respiratory coefficient(DC), which is understood as the ratio of the volume of carbon dioxide released to the volume of oxygen absorbed. The respiratory coefficient is different in the oxidation of proteins, fats and carbohydrates. In the presence of information about the volumes of oxygen absorbed and exhaled carbon dioxide, the method of indirect calorimetry is called "total gas analysis". For its implementation, equipment is needed that allows you to determine the amount of carbon dioxide. In classical bioenergetics, for this purpose, a Douglas bag, a gas clock, and a Holden gas analyzer are used, in which carbon dioxide and oxygen absorbers exist. The method allows to estimate the percentage of 0 2 and CO 2 in the air sample under study. According to the measurement data, the volume of absorbed oxygen and exhaled carbon dioxide is calculated.

Let us analyze the essence of this method using the example of glucose oxidation. The total formula for the breakdown of carbohydrates is expressed by the equation

For fats, DC is 0.7. During the oxidation of protein and mixed food, the DC value takes on an intermediate value: between 1 and 0.7.

The subject takes the mouthpiece of the Douglas bag into his mouth (Fig. 12.2), his nose is closed with a clamp, and all the air exhaled over a certain period of time is collected in a rubber bag.

The volume of exhaled air is determined using a gas watch. An air sample is taken from the bag and the content of oxygen and carbon dioxide is determined in it. The content of gases in the inhaled air is known. The percentage difference is used to calculate the amount of oxygen consumed, carbon dioxide released and DC:

Knowing the value of the DC, they find the caloric equivalent of oxygen (KEO2) (Table 12.1), i.e. the amount of heat generated in the body when consuming 1 liter of oxygen.

Rice. 12.2.

By multiplying the value of KE0 2 by the number of liters of 0 2 consumed, the exchange value is obtained for the period of time during which gas exchange was determined.

It determines the daily value of the exchange.

Currently, there are automatic gas analyzers that allow you to simultaneously determine the volume of consumed 0 2 and the volume of exhaled CO 2. However, most of the available medical devices make it possible to determine only the volume of absorbed 0 2, therefore, the method is widely used in practice. indirect calorimetry, or incomplete gas analysis. In this case, only the volume of absorbed 0 2 is determined, so the calculation of DC is impossible. It is conditionally accepted that carbohydrates, proteins, fats are oxidized in the body. It is believed that DC in this case is equal to 0.85. It corresponds to KE0 2, equal to 4.862 kcal / l. Further calculations are carried out as in the case of full gas analysis.

Table 12.1

The value of DC and EC0 2 during the oxidation of various nutrients in the body

IN CHILDHOOD

I.S. Grieg VolGMU

CHILD DEVELOPMENT PERIODS

Intrauterine (antenatal) period.

The neonatal period (neonatal period).

The period of infancy.

Early childhood.

Preschool age.

Junior school age.

Senior school age (puberty).

In the process of growth of the child's body, not only quantitative, but also qualitative changes in metabolism and energy occur.

Each age period

corresponds to a certain ratio

plastic and energy processes.

Anabolism processes in children dominate over catabolism.

General characteristics of metabolic processes in childhood

The prevalence of anabolic processes requires a greater supply of plastic material and energy.

Children have a positive nitrogen balance,

positive balance of mineral substances (at 1 year of life). In the process of growth, the child is becoming and maturing

metabolic processes. The expression of this is the lability of metabolism, the instability of homeostasis.

The growth and development of the child is subject to the genetic program, which is supplemented by regulatory influences of the neuroendocrine system.

Critical periods of development. homeoresis

Critical periods of development separate

periods of ontogeny(during fetal development - the 1st and last trimesters of pregnancy, the perinatal period - the transition to extrauterine existence, infancy, early childhood, preschool and pubertal periods), when

qualitative restructuring of metabolism or the intensity of metabolic processes changes.

Critical periods are characterized by high sensitivity to environmental factors.

homeoresis

Homeoresis - the ability to stabilize growth rates and return to a given genetic development program if it was temporarily stopped by illness or prolonged starvation of the child.

Homeoresis - maintaining the constancy of the developing system, in contrast to the homeostasis of an adult organism.

Homeoresis is a manifestation of gene regulation of growth and anabolic orientation of metabolic processes in the child's body.

The peculiarity of the metabolism of different age groups of children

Many indicators that are considered physiological in one age period are pathological in

another period of growth.

Each period of a child's life is characterized by a certain direction of chemical

transformations in its organs and tissues, i.e.

the originality of metabolism is formed, inherent in the specific age of the child.

The predominance of anabolic processes

(synthesis of protein, glycogen, fatty acids, triacylglycerols, etc.). The focus of metabolic processes is to provide the fetus with energy reserves (glycogen, TAG).

In the last 3 months of intrauterine life - fat deposition in the body of the fetus in the amount of 600 - 700 g.

Formation of the placenta (system mother -

placenta - fetus). Functions of the placenta: protective, transport, barrier, deposition, endocrine, etc.

Biochemical characteristics of the intrauterine period of development. Fetal metabolism

Formation of the fetoplacental endocrine system , which includes the mother's body, the placenta, which becomes the VHF, and the fetus.

Hormones of the placenta

1. Chorionic gonadotropin , close in action

pituitary luteinizing hormone, maintains the existence of the corpus luteum.

2. Progesterone.

3. Estrogens (mostly estriol). Synthesis

estriol is carried in a single system fetus - placenta. The level of estrogen in the urine reflects the condition of the fetus. A decrease in their excretion indicates severe pathology or even death of the fetus.

4. Placental lactogens(placental growth hormone)

possesses the biological properties of prolactin and growth hormone.

Biochemical characteristics of the intrauterine period of development. Fetal metabolism

The peculiarity of the fetal metabolism - strengthening

anaerobic breakdown of glucose, an increase in metabolic acidosis.

Formation of brown adipose tissue

performing the function of thermoregulation.

Transient states of the neonatal period - physiological azotemia, physiological jaundice, physiological proteinuria, etc.

The processes of metabolism and energy are especially intense during the growth and development of children and adolescents, which is one of the characteristic features of a growing organism. At this stage of ontogenesis, plastic processes significantly predominate over destruction processes, and only in an adult person a dynamic balance is established between these processes of metabolism and energy. Thus, in childhood, the processes of growth and development or assimilation predominate, in old age - the processes of dissimilation. This pattern can be violated as a result of various diseases and other extreme environmental factors.

Protein metabolism. The absence of any of the essential amino acids in food causes serious disturbances in the vital activity of the organism, especially when it is growing. Protein starvation leads to a delay, and then to a complete cessation of growth and physical development.

For a growing organism, protein requirements are much higher than for an adult. In the first year of postnatal development, a child should receive more than 4 g of protein per 1 kg of body weight, at 2-3 years old - 4 g, at 3-5 years old - 3.8 g, etc.

Metabolism of fats and carbohydrates. The needs of children and adolescents in fats have their own age characteristics. So, up to 1.5 years there is no need for vegetable fats, and the total need is 50 g per day, from 2 to 10 years the need for fats increases 80 g per day, and for vegetable fats - up to 15 g, during puberty the need for fat in boys is 110 g per day, and in girls - 90 g, and the need for vegetable fats in both sexes is the same - 20 g per day.

The carbohydrate requirements of children and adolescents are much less, especially in the first years of life. So, up to 1 year the need for carbohydrates is 110 g per day, from 1.5 to 2 years - 190 g, at 5-6 years old - 250 g, at 11-13 years old - 380 g and in young men - 420 g, and for girls - 370 g. In the children's body, there is a more complete and rapid absorption of carbohydrates and greater resistance to excess sugar in the blood.

Water-salt exchange. The water content in the child's body is much higher, especially in the early stages of development. The total water requirement of children and adolescents increases as the body grows. If a one-year-old child needs about 800 ml of water per day, then at 4 years old - 1000 ml, at 7-10 years old - 1350 ml, and at 11-14 years old - 1500 ml.

mineral exchange. The needs of an adult and a child for minerals differ significantly, a lack of minerals in a child's food more quickly leads to various metabolic disorders and, accordingly, to a violation of the growth and development of the body. By the end of puberty, the need for trace elements decreases slightly.

Vitamins. They are required for our body in negligible amounts, but their absence leads the body to death, and a lack of nutrition or a violation of their absorption processes leads to the development of various diseases called hypovitaminosis.

About 30 vitamins are known that affect various aspects of metabolism, both individual cells and the whole organism. This is due to the fact that many vitamins are an integral part of enzymes. Consequently, the lack of vitamins causes the cessation of enzyme synthesis and, accordingly, metabolic disorders.

A person receives vitamins from food of plant and animal origin. For normal life, a person needs 16-18 out of 30 vitamins. A growing organism is highly sensitive to a lack of vitamins in food. The most common hypovitaminosis among children is a disease called rickets. It develops with a lack of vitamin D in baby food and is accompanied by a violation of the formation of the skeleton. Rickets occurs in children under 5 years of age.

It should also be noted that the intake of an excess amount of vitamins into the body can cause serious impairment of its functional activity and even lead to the development of diseases called hypervitaminosis. Therefore, vitamin preparations should not be abused and included in the diet only on the advice of a doctor.

Energy exchange. Metabolism in the body is closely related to the conversion of energy. One of the most important indicators of the intensity of metabolic processes in the body is the value of basal metabolism, which depends on age, sex and weight.

On average, the basal metabolic rate in men is 7140-7560 kJ per day, and in women 6430-6800 kJ. The intensity of metabolic reactions in children in terms of 1 kg of body weight or 1 m 2 of its surface is much higher than in adults, although the absolute values ​​are smaller. So, in boys of 8 years, the value of the main metabolism in terms of 1 m 2 of surface is 6190 kJ, and in girls - 5110 kJ. Further, with age, the value of the basal metabolism decreases and in boys of 15 years old it is 4800 kJ, in girls it is 4480 kJ.

Knowing the body's energy costs, it is possible to compose an optimal diet so that the amount of energy supplied with food fully covers the body's energy costs. For children and adolescents, the composition of food is especially important, since the child's body needs a certain amount of proteins, fats, carbohydrates, mineral salts, water and vitamins for normal development and growth.

7. Thermoregulation, its age-related features

thermoregulation (Greek thermē heat and Latin regulare to order)- a set of physiological processes in the human body aimed at maintaining a constant body temperature (normally 36.0-37.0 0 С).

Body temperature depends on heat production and heat loss.

Heat production, i.e., the production of heat in the body, depends on the intensity of metabolism. Heat transfer from the surface of the body to the external environment is carried out in several ways: by changing the intensity of blood circulation, perspiration, heat release with exhaled air, as well as with urine and feces. In children, especially infants, heat transfer is increased due to abundant blood supply to the skin, the thinness of the skin itself, and the immaturity of the thermoregulation center (when an adult organism cools due to a decrease in ambient temperature, the vessels of its skin narrow reflexively, which allows you to save heat).

Normally, thermoregulation is carried out reflexively. The thermoregulatory center is located in the hypothalamus.

If the process of heat production prevails over the process of heat transfer, the body overheats, up to heat stroke. If the process of heat transfer prevails over heat production, hypothermia of the body occurs.

Violation of thermoregulation is observed with fever accompanying inflammatory and infectious diseases, circulatory disorders, alcohol consumption, etc.

In newborns and infants, thermoregulation is not completely formed (heat transfer prevails over heat production).

Isothermia - the equalization of the body temperature of a child with an adult organism during ontogenesis - develops gradually, only by the 5th year of life. The maturation of the thermoregulation system in postnatal ontogenesis is closely related to the maturation of the mechanisms of neuroendocrine regulation and the implementation of the standing posture, with the maturation of skeletal muscles. By the time of birth, thermoregulatory mechanisms, even in premature babies, can already be included in the work: increased heat generation of predominantly non-shivering origin, vascular reactions, sweating, behavioral reactions. Due to the fact that the mechanisms of thermoregulation function in a child from the moment of birth, his hardening must begin as early as possible.

Questions for self-examination:

1. What is metabolism and what processes does it include?

2. List the functions of proteins.

3. What are essential amino acids?