Mineral metabolism (salt metabolism) is a set of processes of absorption, distribution, transformation and release of inorganic salts that take place in the body.

The main part of inorganic salts are chlorides, sulfates and carbonates, sodium, and magnesium. Mineral metabolism plays the role of a regulator of a number of physicochemical processes in the body, for example, in maintaining a constant osmotic pressure of body fluids, stabilizing the pH of blood and tissues, regulating cell membranes, etc. Ions of some salts serve as activators and inhibitors (see). Absorption of inorganic substances occurs mainly in the small intestine; they are carried to various organs by blood and lymph. The main depot of calcium and magnesium is bone tissue, sodium and potassium - skin, most salts -. The excretion of inorganic salts from the body occurs through the intestines and skin. Violation of mineral metabolism, for example, due to a lack of certain salts in food, leads to the emergence of severe pathological phenomena in the body.

See also Trace elements, Mineral substances, Metabolism and energy.

Mineral metabolism is a set of processes of absorption, distribution, transformation and excretion of inorganic compounds from the body. The main part of these compounds in humans is made up of chloride, sulfate, phosphate and carbonate salts of potassium, sodium, calcium and magnesium. In adults (weighing about 70 kg), the total amount of ash in the body is approximately 3 kg, of which calcium accounts for 39%, phosphorus - 22%, sulfur - 4%, chlorine - 3%, potassium - 5%, sodium - 2 % and magnesium - 0.7%. The relatively high content of calcium and phosphorus in ash is explained by the fact that these elements in the form of various salts of calcium phosphate constitute the predominant part of the bone skeleton. The content of the above elements in whole blood is (in mg%): sodium - 175, potassium - 210, calcium - 5, magnesium - 4.3, chlorine - 280, inorganic phosphorus - 3.5, inorganic sulfur - 1; in the blood serum of adults, the corresponding values ​​are: sodium - 335 ± 10, potassium - 20 ± 2, calcium - 10 ± 0.3, magnesium - 2.4 ± 0.7, chlorine - 365 ± 15, inorganic phosphorus - 3 , 7 ± 0.8, inorganic sulfur - 1.3 ± 0.5. In addition to the above elements, which are usually designated as macronutrients, almost all other chemical elements can be found in the human body, but they are found in dense tissues and blood only in very small amounts (fractions of mg%) and only a small part of them are true bioelements. that is, the elements necessary for the normal implementation of the vital processes of the organism. The elements designated as trace elements (see) include iron, copper, zinc, manganese, cobalt, molybdenum, iodine and fluorine. As for others (mercury, arsenic, aluminum, nickel, titanium), there is still no data that would indicate that they have any physiological significance. Part of trace elements enters the body with the inhaled air.

Unlike the exchange of organic compounds, mineral metabolism has no energy value and its plastic value (with the exception of the role of calcium, phosphorus and magnesium in the formation of the skeletal system) is very limited. Despite this, mineral starvation of animals, that is, a lack of one or many true bioelements in food, quickly causes the emergence of severe pathological phenomena, and then the death of animals. This is due to the fact that inorganic compounds of tissues and body fluids play an important role as bioregulators of the basic metabolic processes in the body. So, for example, sodium, potassium and chlorine ions are the main regulators of the osmotic pressure of blood, cerebrospinal fluid, lymph, extra- and intracellular tissue fluids, and any violation in their normal ratios causes significant changes in the distribution of water between dense tissues and body fluids. The pH of tissues and blood and the possibility of its change in one direction or another in various pathological conditions largely depend on the ratio of the total amount of inorganic cations and anions. Equally important is the fact that ions of calcium, potassium, sodium, manganese, magnesium, etc. are powerful activators, and in some cases inhibitors of many enzymes. A number of trace elements (copper, molybdenum, zinc) are part of the active center of a number of enzymes, and iron is an irreplaceable component of hemoglobins and cytochromes. Calcium and phosphorus are essential for ossification processes; in addition, inorganic phosphorus is the main source of the formation of adenosine triphosphoric acid (ATP) and many organic phosphorus compounds, which are the most important energy carriers, and inorganic sulfur is a source for the formation of a number of sulfur-containing organic compounds.

Thus, maintaining a constant concentration of inorganic compounds in organs and tissues is an indispensable condition for the normal exchange of organic compounds.

See also Metabolism and Energy.

The human body is a chemical factory with no vacations or downtime. On its invisible conveyors, in vats and retorts, one substance is constantly being transformed into another. First of all, we will consider the most important part of metabolism - the metabolism of minerals, including water. Then we will move on to the exchange of organic substances, their mutual transformations, we will study how organic substances are consumed and created in the body.

Metabolism includes certain types of metabolism. Any process is regulated under the influence of other systems - we will consider how these mechanisms work. Finally, the metabolism is determined by nutrition. What is the optimal proportion of protein, fat and carbohydrates in food? What is the desired diet? What are the consequences of malnutrition, what are the causes of bulimia and anorexia? Let's try to answer these and other questions.

Exchange of water and mineral salts. The importance of water for the body

1. Water is an irreplaceable basis for fluids circulating in a living organism: blood plasma, lymph, digestive juices, saliva.

2. It under normal conditions is up to 75 percent of body weight. The minimum water is in the teeth (only 10 percent), a little more in the bones (20-25 percent), and the maximum water is contained in the brain (up to 80 percent of its mass). Interestingly, adipose tissue contains less water than bones, liver, skeletal muscles, and the brain.

3. Half of the water enters our body with food, the other half - with drinks. A person needs 1.5-2 liters of water per day, especially in hot countries. Without water, a person can die within 2-3 days (whereas without food he can live for several weeks), the loss of even 20 percent of the liquid by the body is fatal.

4. With a shortage of water, it can be synthesized during the breakdown of fat - this water is called endogenous (from 1 gram of fat, 1.1 grams of water is obtained).

5. Excess water is harmful, as is lack. With "overcrowding" the load on the heart and kidneys increases, and edema appears. The deficiency can cause high viscosity of blood and other fluids, slow down the metabolism.

6. Water is excreted in the urine (this is how most of it leaves), as well as through the intestines, during perspiration, during breathing.

The importance of some mineral salts

1. The body needs 10-15 grams of minerals per day.

2. The salts of calcium, sodium, iron, potassium, phosphorus, magnesium are of the greatest importance.

4. Calcium salts are responsible for blood clotting.

5. Sodium and potassium salts are required for the functioning of muscle and nerve cells.

6. Iron is an integral part of hemoglobin.

7. Table salt should be added to food in a reasonable amount, the greatest need for it is up to 10 grams per day.

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Metabolism and energy, the concept of intermediate exchange. Enzymes.

Metabolism (synonym: metabolism) - the totality of all chemical transformations in the body, ensuring its vital activity. There are two aspects of metabolism - assimilation, in the process of which the body synthesizes substances specific to it, and dissimilation, during which the splitting (oxidation) of organic substances and the release of the energy contained in them occurs.

Energy exchange. A person is characterized by the transformation of the chemical energy of oxidative processes into thermal and mechanical energy of the formation of the most complex organic molecules. Consuming food and oxygen, the body uses these substances to obtain energy, which then releases into the surrounding space in the form of heat or in the form of mechanical movements of objects or parts of its own body.

Enzymes (Latin fermentum - fermentation, fermentation) - complex proteins of animals and plant organisms that perform the functions of biological catalysts, accelerating chemical reactions and metabolism in cells.

Distinguish between general (external) metabolism, taking into account the intake of substances into the body and their excretion, and intermediate metabolism , which covers the transformation of these substances in the body.

Exchange of proteins, fats, carbohydrates, water, mineral salts.

From the tutorial:

Protein metabolism- a set of chemical transformations of proteins in the body, ending with their splitting to water, carbon dioxide, ammonia and the release of the energy contained in them. Proteins are used by the body to renew and

building new tissues, enzymes, are an energy source. When 1 g of protein is broken down, 4.1 kcal of energy is released.

Fat metabolism- a set of chemical transformations of fats in the body, ending with their splitting (to water and carbon dioxide) and the release of energy. Fats are used by the body to renew and build new tissues, enzymes, hormones, as well as to obtain the energy the body needs.

When 1 g of fat is broken down, 9.3 kcal of energy are released.

Mineral salt exchange- a set of processes of consumption, use of mineral salts in the body and their release into the environment. Mineral salts are used in the body to maintain osmotic pressure, acid-base balance (pH) of the blood, are part of enzymes, vitamins, hormones.

Metabolism of carbohydrates- a set of chemical transformations of carbohydrates in the body, ending with their breakdown and release of energy. Carbohydrates are the body's main energy source. When 1 g of carbohydrates are broken down, 4.1 kcal of energy are released.

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Protein metabolism. Proteins make up about 25% of the total body weight. This is the most difficult part of it. Proteins are polymeric compounds made up of amino acids. The protein set of each person is strictly unique and specific. In the body, food protein under the action of digestive juices is split into its simple components - peptides and amino acids, which are then absorbed in the intestine and enter the bloodstream. Of the 20 amino acids, only 8 are essential for humans. These include tryptophan, leucine, isoleucine, valine, threonine, lysine, methionine, and phenylalanine. A growing body also needs histidine.

The absence of any of the essential amino acids in food causes serious disruption of the vital functions of the organism, especially the growing one. Protein starvation leads to a delay, and then to a complete cessation of growth and physical development. The child becomes lethargic, there is a sharp weight loss, profuse edema, diarrhea, inflammation of the skin, anemia, a decrease in the body's resistance to infectious diseases, etc. This is due to the fact that protein is the main plastic material of the body, from which various cellular structures are formed. In addition, proteins are part of enzymes, hormones, nucleoproteins, form hemoglobin and blood antibodies.

If work is not associated with intense physical activity, the human body, on average, needs about 1.1-1.3 g of protein per 1 kg of body weight per day. With an increase in physical activity, the body's needs for protein also increase. For a growing body, the need for protein is much higher. In the first year of postnatal development, the 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. These organic substances have a simpler structure, they are composed of three chemical elements: carbon, oxygen and hydrogen. The same chemical composition of fats and carbohydrates enables the body to build fats from them with an excess of carbohydrates, and, conversely, if necessary, carbohydrates are easily formed from fats in the body.

The total amount of fat in the human body is on average about 10-20%, and carbohydrates - 1%. Most of the fat is found in adipose tissue and constitutes a reserve energy reserve. A smaller portion of fat is used to build new cell membrane structures and replace old ones. Some cells of the body are capable of storing fat in huge amounts, acting as thermal and mechanical isolation in the body.

In the diet of a healthy adult, fats should account for about 30% of the total calorie content of food, i.e. 80-100 g per day. Insufficient intake of these fatty acids in the human body leads to metabolic disorders and the development of atherosclerotic processes in the cardiovascular system.

The fat needs of children and adolescents 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 by 80 g per day, and in 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.

Carbohydrates in the body are broken down to glucose, fructose, galactose, etc. and then absorbed into the bloodstream. The glucose content in the blood of an adult is constant and equal to an average of 0.1%. With an increase in the amount of sugar in the blood to 0.11-0.12%, glucose comes from the blood to the liver and muscle tissues, where it is stored in the form of animal starch - glycogen. With a further increase in the blood sugar content to 0.17%, the kidneys are included in its excretion from the body, and sugar appears in the urine. This phenomenon is called glucosuria.

The body uses carbohydrates primarily as energy material. 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 boys - 420 g, and in girls - 370 g. In the child's body, there is a more complete and rapid assimilation of carbohydrates and greater resistance to excess sugar in the blood.

Salt exchange. With the exclusion of mineral substances from the diet of animals, severe disorders in the body and even death occur. The presence of mineral substances is associated with the phenomenon of excitability - one of the main properties of living things. The growth and development of bones, nerve elements, muscles depend on the content of minerals; they determine the reaction of the blood (pH), contribute to the normal functioning of the heart and nervous system, and are used for the formation of hemoglobin (iron), hydrochloric acid of gastric juice (chlorine).

Mineral salts create a certain osmotic pressure, which is so necessary for the vital activity of cells.

With a mixed diet, an adult receives all the minerals he needs in sufficient quantities. Only table salt is added to human food during its culinary processing. A growing child's body especially needs additional intake of many minerals.

The body constantly loses a certain amount of mineral salts in the composition of urine, sweat and feces. Therefore, mineral salts, like water, must constantly enter the body. The content of individual elements in the human body is not the same.

Water exchange. For the vital functions of the body, water plays a much greater role than other components of food. The fact is that water in the human body is at the same time a building material, a catalyst for all metabolic processes and a thermoregulator of the body. The total amount of water in the body depends on age, gender and weight. On average, a man's body contains over 60% of water, a woman's body - 50%.

The water content in the child's body is much higher, especially in the early stages of development. According to embryologists, the water content in the body of a 4-month-old fetus reaches 90%, and in a 7-month-old fetus - 84%. In the body of a newborn, the volume of water is from 70 to 80%. In postnatal ontogeny, the water content decreases rapidly. So, a child is 8 months old. the water content is 60%, for a 4.5-year-old child - 58%, for 13-year-old boys - 59%, and for girls of the same age - 56%. The higher water content in the body of children is obviously associated with a greater intensity of metabolic reactions associated with their rapid growth and 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.

Water in an adult it is 60%, and in a newborn - 75% of the body weight. It is the environment in which metabolic processes take place in cells, organs and tissues. The continuous flow of water into the body is one of the main conditions for maintaining its vital activity. About 70% of all water in the body is part of the protoplasm of cells, making up the so-called intracellular water. Extracellular water is part of tissue or interstitial fluid(about 25%) and blood plasma water(around 5%). The balance of water is made up of its consumption and excretion. With food, a person receives about 750 ml of water per day, in the form of drinks and pure water - about 630 ml. About 320 ml of water is formed during metabolism during the oxidation of proteins, carbohydrates and fats. With evaporation from the surface of the skin and alveoli of the lungs, about 800 ml of water are released per day. The same amount is necessary for the dissolution of osmotically active substances excreted by the kidney at the maximum osmolarity of urine. 100 ml of water is excreted in the faeces. Therefore, the minimum daily requirement is about 1,700 ml of water.

Water intake is regulated by its need, manifested by a feeling of thirst, which depends on the osmotic concentration of substances in liquids and their volume. This feeling arises when the hypothalamus drinking center is excited.

The body needs a constant supply of not only water, but also mineral salts (the regulation of water-salt metabolism is described in Chapter 8).

Mineral salts.Sodium(Na +) is the main cation of extracellular fluids. Its content in the extracellular environment is 6-12 times higher than the content in cells. Sodium in an amount of 3-6 g per day enters the body in the form of table salt and is absorbed mainly in the small intestine. The role of sodium in the body is manifold. It participates in maintaining the acid-base state, osmotic pressure of extracellular and intracellular fluids, takes part in the formation of an action potential, influences the activity of almost all body systems; great importance is attached to it in the development of a number of diseases. In particular, it is believed that sodium mediates the development of arterial hypertension due to both an increase in the volume of extracellular fluid and an increase in microvascular resistance. The balance of sodium in the body is mainly supported by the activity of the kidneys (see chapter 8).

The most important sources of sodium are table salt, canned meat, feta cheese, cheese, pickles, tomatoes, sauerkraut, and salted fish. With a lack of table salt, dehydration, loss of appetite, vomiting, muscle cramps occur; in case of an overdose - thirst, depression, vomiting. A constant excess of sodium increases blood pressure.

Potassium(K +) is the main cation of the intracellular fluid. Cells contain 98% potassium. Potassium is absorbed in the small and large intestines. Potassium is of particular importance due to its potential-forming role at the level of maintaining the resting membrane potential. Potassium also takes an active part in the regulation of the balance of the acid-base state of cells. It is a factor in maintaining osmotic pressure in cells. Regulation of its excretion is carried out mainly by the kidneys (see Ch. 8).

The richest in potassium are potatoes with peels, garlic, parsley, pumpkin, zucchini, dried apricots, apricots, raisins, prunes, bananas, apricots, legumes, meat, fish.

With a deficiency of potassium, there is a loss of appetite, arrhythmia, a decrease in blood pressure; in case of overdose - muscle weakness, heart rhythm disturbances and renal function.

Calcium(Ca 2+) has a high biological activity. It is the main structural component of the bones of the skeleton and teeth, which contains about 99% of the total Ca 2+. Children need a lot of calcium due to the intensive growth of bones. Calcium is absorbed mainly in the duodenum in the form of monobasic salts of phosphoric acid. Approximately 3/4 of calcium is excreted by the digestive tract, where endogenous calcium enters with the secretions of the digestive glands, and * / 4 - by the kidneys. The role of calcium in the life of the body is great. Calcium takes part in the generation of the action potential, in the initiation of muscle contraction, is a necessary component of the blood coagulation system, increases the reflex excitability of the spinal cord and has a sympathicotropic effect.

The main suppliers of calcium are milk and dairy products, cheese, liver, fish, egg yolk, raisins, cereals, and dates.

With a calcium deficiency, muscle cramps, pain, spasms, rigidity appear, in children - bone deformation, in adults - osteoporosis, in athletes - convulsions, tinnitus, hypotension. Overdose causes loss of appetite, weight loss, weakness, fever, and constipation. Regulation is carried out mainly by hormones - thyrocalcitonin, parathyroid hormone and vitamin Z) 3 (see Chapter 10).

Magnesium(Mg 2+) is contained in an ionized state in blood plasma, erythrocytes, in the composition of bone tissue in the form of phosphates and bicarbonates. Magnesium has an antispasmodic and vasodilatory effect, stimulates intestinal motility and increases bile secretion. It is part of many enzymes that release energy from glucose, stimulating the activity of enzymes, and has a calming effect on the heart and nervous system.

Magnesium is found in wholemeal bread, cereals (buckwheat, full-grain rice, oatmeal), chicken eggs, beans, peas, bananas, spinach. In milk and dairy products, magnesium is found in small quantities, but it is well absorbed.

With a magnesium deficiency, cramps, muscle pain, dizziness, apathy, depression are noted. A lack of magnesium increases the calcium content in the heart and skeletal muscles, which leads to irregular heart rhythms and other diseases. In case of an overdose, respiratory and central nervous system functions are inhibited.

Chlorine(SG) participates in the formation of gastric juice, enters the human body as part of table salt and, together with sodium and potassium, participates in the creation of membrane potential and conduction of nerve impulses, maintains acid-base balance, promotes the transport of carbon dioxide by erythrocytes. Chlorine is able to be deposited in the skin, retained in the body in case of excess intake.

Chlorine is mainly found in table salt, canned meat, cheese, feta cheese.

With a chlorine deficiency, sweating, diarrhea, insufficient secretion of gastric juice are noted, and edema develops. An increase in the chlorine content occurs with dehydration of the body and with impaired renal excretory function.

Phosphorus(P) is a vital substance that is part of the bone tissue and is the main part of the nuclei of the cells of the nervous system, especially the brain. He is actively involved in the metabolism of proteins, fats and carbohydrates; necessary for the formation of bones and teeth, the normal functioning of the nervous system and heart muscle; takes part in the synthesis of enzymes, proteins and nucleic acids (DNA and RNA). In body tissues and food, phosphorus is contained in the form of phosphoric acid and organic compounds (phosphates).

Phosphorus is found in animal products: milk, cottage cheese, cheese, liver, meat, eggs; in wheat bran, wholemeal bread, sprouted wheat; various cereals, potatoes, legumes, dried fruits, nuts, sunflower seeds, seafood and, especially, fish are rich in phosphorus.

Phosphorus deficiency is noted during prolonged starvation (the body consumes phosphorus contained in the tissues). Symptoms: weakness, further loss of appetite, bone pain, metabolic disorders in the myocardium. With an excess of phosphorus, a decrease in the level of calcium in the blood occurs, possibly a violation of the heart rhythm. Excess phosphorus can develop in formula-fed babies. Parathyroid hormone and thyrocalcitonin are involved in regulation (see Ch. 10).

Sulfur(S) is a part of proteins, cartilage tissue, hair, nails, participates in collagen synthesis. It is necessary for the neutralization in the liver of toxic substances coming from the large intestine as a result of putrefaction.

The most important source of sulfur is protein products: meat, fish, dairy products, eggs, legumes.

Daily requirement, deficit and overdose have not been reliably established. It is believed that the daily requirement is compensated by the usual diet.

Iron(Fe) is a major constituent of many body tissues and some enzymes. A significant amount of iron is found in erythrocytes, about 70% in hemoglobin. The main physiological significance of iron is participation in the process of hematopoiesis, transport of oxygen and carbon dioxide, and the provision of cellular respiration. Iron can be deposited in the body. Such "depots" for him are the spleen, liver and bone marrow.

Iron is especially needed for girls entering puberty and young children. Lack of iron in the body can lead to the development of anemia and suppression of the body's defenses. Iron is found in meat, liver (especially pork), heart, brain, egg yolk, porcini mushrooms, beans, peas, garlic, horseradish, beets, carrots, tomatoes, pumpkin, white cabbage, lettuce, spinach.

Iron deficiency reduces the activity of respiratory enzymes, which can lead to a disorder of tissue respiration, the development of iron deficiency anemia (anemia). Many trendy diets aimed at fast weight loss lead to iron deficiency. Excess iron can impair the function of the liver and digestive system.

Iodine(I -) participates in the formation of thyroxine - the thyroid hormone, helps to reduce blood cholesterol levels, increase the absorption of calcium and phosphorus by the body.

The largest amount of iodine is found in seaweed (seaweed), sea fish, eggs, meat, milk, vegetables (beets, carrots, lettuce, cabbage, potatoes, onions, celery, tomatoes), fruits (apples, plums, grapes). It must be remembered that during long-term storage of food iodine-containing products and their heat treatment, up to 60% of iodine is lost.

Lack of iodine in the body leads to hypothyroidism, enlargement of the thyroid gland (goiter), in childhood - to cretinism (stunted growth and decreased intelligence). Excess iodine leads to hyperthyroidism (toxic goiter). For prophylaxis, iodized salt is taken (see Ch. 10).

Copper(Cu) participates in the formation of a number of enzymes and hemoglobin, promotes the absorption of iron in the intestine, the release of energy from fats and carbohydrates; copper ions take part in oxidation reactions of substances in the body. The copper content in the human body is associated with gender, age, daily and seasonal temperature fluctuations, and inflammatory diseases.

Copper is found in meat, liver, seafood (squid, crabs, shrimps), in all vegetables, melons and legumes, nuts, cereals (oat, buckwheat, millet, etc.), mushrooms, fruits (apples, pears, apricots, plums), berries (wild strawberries, strawberries, cranberries, gooseberries, raspberries, etc.).

Lack of copper in diseases of scarlet fever, diphtheria, Botkin's disease, pulmonary tuberculosis complicates their course. Toxicosis is more common in pregnant women with a lack of copper. Lack of copper in food reduces the activity of oxidative enzymes and leads to various forms of anemia (anemia). Overdose of copper leads to poisoning.

Fluorine(F -) is found in small amounts in all tissues of the body, but its main role is participation in the formation of dentin, tooth enamel and bone tissue. The main source of fluoride is drinking water. Fluoride is found in sufficient quantities in food - fish, liver, lamb, nuts, oatmeal, tea and fruits. Vegetables rich in fluorine are salad, parsley, celery, potatoes, white cabbage, carrots, beets.

A sharp decrease in fluoride in drinking water leads to caries and tooth decay, the increased content has a depressing effect on the thyroid gland and leads to the development of fluorosis (spotted tooth damage).

Zinc(Zn 2+) participates in the synthesis of proteins, RNA, in the formation of most enzymes and hematopoiesis, is in the bone system, skin and hair, is an integral part of the male sex hormone - testosterone, promotes wound healing, increases immunity, takes part in the mechanism of cell division , normalizes carbohydrate metabolism. Chronic psycho-emotional stress, alcohol, tobacco smoking impair zinc absorption. A zinc deficiency in the diet can lead to infertility, anemia, skin diseases, slowing nail growth and hair loss, increased tumor growth, delayed puberty, and growth retardation during puberty.

With a lack of zinc, wounds heal poorly, there is a loss of appetite, taste and olfactory sensitivity weaken, ulcers appear in the mouth, on the tongue, and pustules form on the skin. In case of an overdose, the risk of poisoning increases. In large quantities, zinc has a carcinogenic effect, and therefore it is not recommended to store water and food in galvanized dishes.

Zinc is found in walnuts, seafood, meat, poultry, all vegetables, especially garlic and onions, legumes, cereals (especially oatmeal). The assimilability of zinc from animal products is over 40%, and plant - up to 10%.

The regulation of most microelements is practically not studied.

ChapterIV.13.

Mineral exchange

Mineral metabolism is a set of processes of absorption, distribution, assimilation and excretion of mineral substances that are in the body mainly in the form of inorganic compounds.

In total, over 70 elements of D.I.'s table are found in the body. Mendeleev, 47 of them are constantly present and are called biogenic. Mineral substances play an important role in maintaining acid-base balance, osmotic pressure, blood coagulation system, regulation of numerous enzyme systems, etc. are critical in creating and maintaining homeostasis.

By their quantitative content in the body, they are divided into macronutrients if there are more than 0.01% of body weight (K, Ca, Mg, Na, P, Cl) and trace elements ( Mn, Zn, Cr, Cu, Fe, Co, Al, Se). The main part of the body's mineral substances are chloride, phosphate and carbonate salts of sodium, calcium, potassium, magnesium. Salts in body fluids are partially or completely dissociated, therefore minerals are present in the form of ions - cations and anions.

Functions of minerals:

1) plastic (calcium, phosphorus, magnesium);

2) maintaining osmotic pressure (potassium, sodium, chlorine);

3) maintaining the buffering capacity of biological fluids (phosphorus, potassium, sodium);

4) maintaining the colloidal properties of tissues (all elements);

5) detoxification (iron as part of cytochrome P-450, sulfur as part of glutathione);

6) conduction of a nerve impulse (sodium, potassium);

7) participation in enzymatic catalysis as a cofactor or inhibitor;

8) participation in hormonal regulation (iodine, zinc and cobalt are part of hormones).

Intermediate and final metabolism of mineral substances

Mineral substances enter the body in free or bound form. Ions are absorbed already in the stomach, the bulk of minerals - in the intestine by active transport with the participation of carrier proteins. From the gastrointestinal tract, they enter the blood and lymph, where they bind to specific transport proteins. Mineral substances are released mainly in the form of salts and ions.

With urine: sodium, potassium, calcium, magnesium, chlorine, cobalt, iodine, bromine, fluorine.

With feces: iron, calcium, copper, zinc, manganese, molybdenum, and heavy metals.

Characteristics of individual elements

Sodium - the main cation of the extracellular department. It makes up 0.08% of body weight. Plays a major role in maintaining osmotic pressure. In the absence or limitation of sodium intake into the body, its excretion in the urine almost completely stops. It is absorbed in the upper part of the small intestine with the participation of carrier proteins and requires the consumption of ATP. The daily requirement varies depending on the body's drainage-salt supply. It is deposited in the skin and muscles. Intestinal sodium loss occurs with diarrhea.

1) participates in the emergence and maintenance of electrochemical potential on the plasma membranes of cells;

2) regulates the state of water-salt metabolism;

3) participates in the regulation of enzymes;

4) component K + - Na + of the pump.

Chlorine - the most important anion of the extracellular space. It is 0.06% of body weight. Most of it is found in gastric juice. Participates in maintaining osmotic balance. Activates amylase and peptidase. Absorbed in the upper intestines, excreted mainly in the urine. Chlorine and sodium concentrations usually vary in parallel.

Potassium - is 0.25% of body weight. The extracellular space contains only 2% of the total, and the rest is in cells, where it is associated with carbohydrate compounds. Absorbed throughout the entire gastrointestinal tract. Some of the potassium is deposited in the liver and skin, while the rest goes into the general bloodstream. The exchange proceeds very quickly in the muscles, intestines, kidneys and liver. In erythrocytes and nerve cells, a slower exchange of potassium. Plays a leading role in the origin and conduct of a nerve impulse. It is necessary for the synthesis of proteins (per 1 g of protein - 20 mg of potassium ions), ATP, glycogen, takes part in the formation of resting potential. It is excreted mainly in the urine and less in the feces.

Calcium - extracellular cation. It accounts for 1.9% of body weight. The content rises during growth or pregnancy. It functions as an integral part of supporting tissues or membranes, participates in the conduction of a nerve impulse and the initiation of muscle contraction, and is one of the factors of hemocoagulation. Ensures the integrity of membranes (affects permeability), since it promotes tight packing of membrane proteins. Calcium is limitedly involved in maintaining osmotic balance. Together with insulin, it activates the penetration of glucose into cells. Absorbed in the upper intestine. The degree of its assimilation depends on the pH of the medium (calcium salts are insoluble in an acidic medium). Fats and phosphates interfere with calcium absorption. For complete absorption from the intestines, the presence of an active form of vitamin D 3 is required

Most of the calcium is contained in bone tissue (99%) in the composition of microcrystals of carbonate apatite 3Ca 2 (PO 4) 2· CaCO 3 and hydroxylapatite 3Ca 2 (PO 4) 2· SaON. Total blood calcium includes three fractions: protein-bound, ionized and non-ionized (which is found in citrate, phosphate and sulfate).

Magnesium - is 0.05% of body weight. It contains 10 times more in cells than in extracellular fluid. There is a lot of magnesium in muscle and bone tissue, as well as in the nervous and hepatic tissues. Forms complexes with ATP, citrate, and a number of proteins.

1) is part of almost 300 enzymes;

2) complexes of magnesium with phospholipids reduce the fluidity of cell membranes;

3) participates in maintaining normal body temperature;

4) participates in the work of the neuromuscular apparatus.

Inorganic phosphorus - is found mainly in bone tissue. It accounts for 1% of body weight. In blood plasma at physiological pH, phosphorus is 80% bivalent and 20% monovalent phosphoric acid anion. Phosphorus is a part of coenzymes, nucleic acids, phosphoproteins, phospholipids. Together with calcium, phosphorus forms apatite - the basis of bone tissue.

Copper is a part of many enzymes and biologically active metalloproteins. Participates in the synthesis of collagen and elastin. Is a component cytochrome c electron transport chain.

Sulfur - is 0.08%. It enters the body in a bound form in the composition of AA and sulfate ions. It is part of bile acids and hormones. As part of glutathione participates in the biotransformation of poisons.

Iron is a part of iron-containing proteins and heme of hemoglobin, cytochromes, peroxidases.

Zinc - is a cofactor of a number of enzymes.

Cobalt is part of vitamin B 12.

Exchange of water and electrolytes

Water-electrolyte metabolism is a set of processes of intake, absorption, distribution and excretion of water and electrolytes from the body. It ensures the constancy of the ionic composition, acid-base balance and volume of fluids in the internal environment of the body. The leading role in it is played by water.

Functions of water:

1) internal environment of the body;

2) structural;

3) absorption and transport of substances;

4) participation in biochemical reactions (hydrolysis, dissociation, hydration, dehydration);

5) the final product of the exchange;

6) excretion of end metabolic products with the participation of the kidneys.

Water that is supplied by the alimentary (with food) route is called exogenous, and the water that is formed as a product of biochemical transformations is called endogenous.