What proteins do in the human body. Excess protein: how harmful it is

High molecular weight organic substances, consisting of combinations of amino acids of various amounts and composition, connected in a chain.

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Proteins are the building blocks of the body. What other functions do these substances perform, and why does a protein-free diet threaten with dangerous complications?

Proteins are a large group of organic substances that perform a number of important functions in the human body. It is they that promote tissue growth and assimilation of food, and their lack can lead to serious and irreversible metabolic disorders. Proteins, fats and carbohydrates form the basis of human nutrition, and without these substances our existence is impossible. But what exactly are proteins responsible for? What are they and how are they useful? What can blood protein tests tell you? The MedAboutMe portal understood all the questions.

The functions of proteins in the human body are varied. They are responsible for the rational use of nutrients, help muscles to contract, provide immune protection, and regulate hormone synthesis. The essence of proteins is that, along with DNA and RNA, they provide storage and transmission of information about the body and its functioning. It is from them that all important cell structures are composed, therefore, without proteins, life would be impossible.

Disorders of protein metabolism have serious consequences. A person loses weight, appetite worsens, performance decreases, digestive disorders appear, in particular, constipation or diarrhea is characteristic. In the event that protein synthesis is impaired, they accumulate in the body and can lead to severe intoxication. Congenital pathologies are especially dangerous, in particular, various fermentopathies - a lack of enzymes.

The essence of proteins for humans

Proteins are part of the structural elements of cells; without them, the growth and renewal of any tissue is impossible. The highest protein content is in muscles (50% of the total mass), 20% is in bones and cartilage, and 10% in skin.

To ensure the normal functioning of the body, a person needs to eat an average of 0.75-1 g of pure protein per 1 kg of weight per day. If the diet is not sufficiently enriched with these substances, a person develops protein starvation. Since proteins of different groups are responsible for a number of functions, including providing many vital metabolic processes, their deficiency is comparable to complete starvation. At first, the person shows symptoms of malnutrition:

• Weight loss.
• Deterioration of health, weakness.
• Loss of appetite.
• Stunted growth in children and retarded mental development.
• Hormonal disorders.

If the lack of protein is critical, even if you consume enough carbohydrates and fatty acids in the food, the person can die of starvation. Proteins are best absorbed from animal products - meat and poultry, fish and seafood, quail and chicken eggs, dairy and dairy products. And with sufficient nutrition, protein starvation develops extremely rarely. However, this danger can threaten vegetarians, so they need to be especially careful about the amount of protein in foods. You can compensate for the lack of animal food in the diet with the help of mushrooms, legumes, cereals and some types of vegetables. For more information, see the protein table at the end of the article.

One of the most important functions of proteins for humans is their participation in tissue formation. These substances are often called the main building blocks of the body. Protein is especially important for the formation of muscles, tendons and bones, hair and nails are made of it.

For the full growth of a child, the protein rate should be as follows:

• Newborns - 1.5-2 g / kg body weight.
• After 1 year - 36-87 g / day.

It is also believed that 60% of the protein children should get from food of animal origin. It is in this case that it will be enough for the normal growth and development of the body. The World Health Organization today does not recommend introducing complementary foods to children of the first half of the year who are breastfed. And continue feeding with breast milk or formula for at least 1 year. This approach, in particular, makes it possible to provide a child's diet with a sufficient protein content.

Protein foods are relevant for children during periods of active growth:

• Girls are 10-12 years old, on average up to 16 years old.
• Boys are 12-14 years old, on average up to 19 years old.

During this period, jumps in growth hormone somatotropin are observed in the body. And he, like many other hormones, is protein in structure. Inadequate nutrition at this age will inevitably lead to stunted growth, and it will be impossible to compensate for it later. The fact is that growth hormone affects the growth of tubular bones - it activates growth zones at their ends, which are completely closed by the age of 18-20 years.

Protein building function is important not only in childhood. Proteins help the body to renew itself and tissues to wear out less. Therefore, a deficiency of these nutrients in the diet of adults leads to premature aging, skin laxity, and deterioration of hair and nails. In addition, a lack of protein can affect the function of the heart muscle.

Protein composition

Proteins are complex high molecular weight compounds composed of amino acids. It is these components that are responsible for all the functions of proteins. Entering the body with food, complex chains of matter are split into components, and then the compounds necessary for vital activity are formed from them.

The main chemical component in proteins is nitrogen. It is he who is originally used by plants for the biosynthesis of proteins necessary for their growth and life. After that, animals that eat plant foods can break down these substances and form compounds suitable for their body from them. Man, as a representative of omnivores, can process both plant and animal proteins. At the same time, both types of substances should normally be present in the diet.

A protein molecule is a chain of amino acids connected in series by a peptide bond. Its length is not limited and can consist of 2 or more components. Protein molecules consisting of 2-40 amino acids are called peptides. These include such important substances:

• Hormones (oxytocin, growth hormone, prolactin, thyroid hormones, TSH and others).
• Neuropeptides that regulate the functioning of the central nervous system.
• Endorphins.
• Regulators of blood pressure and vascular tone.
• Digestion and appetite regulators.
• Natural pain relievers.

Therefore, receiving protein molecules of any structure with food, the body can transform them into chains of different lengths. Including create peptides necessary for life.

Protein structure

The amino acid chain of proteins can be quite long, sometimes over 300 elements. And with a large number of components, it begins to fold. There are 4 types of possible types of molecules:

• Primary protein structure.

This is exactly the first, original thread of amino acids. It is more typical for peptides.

• Secondary protein structure.

The chain is twisted in the form of a spiral or laid in a "snake", thus reducing its length. One protein molecule at different sites can be compressed in different ways. It is characteristic of collagen and keratin - structural proteins that provide tissue strength.

• Tertiary structure.

A chain of amino acids forms a three-dimensional globule with a nearly spherical shape. It is characteristic of some hormones, as well as enzymes and immunoglobulins.

• Quaternary protein structure.

Molecules form several globules at once. The most complex structure. The most striking example of a protein with such an organization is hemoglobin.

Each protein has its own structure, which is dictated by the sequence of amino acids and their bonds. In the event that connections are destroyed for some reason, the protein loses its ability to perform its functions. So, for example, it is a violation in the structure of hemoglobin that leads to the development of sickle cell anemia and the inability to transport oxygen to cells.

Amino acids in proteins

The main value of proteins is the amino acids of which they are composed. It is from them that the necessary proteins are synthesized in the human body, which provide metabolic processes. All proteins from food are broken down to constituent components. But the human body uses only 20 amino acids for the synthesis of substances it already needs.

Therefore, the value of food is usually assessed not only by the pure protein content, but also by the presence of different types of amino acids in the protein composition.

All amino acids necessary for humans are usually divided into nonessential and irreplaceable. The fact is that the body is able to synthesize some types of these organic compounds on its own. Their content in food is desirable, but if such amino acids are absent in products, this will not affect vital functions.

This type of substance includes the following amino acids of proteins:

• Arginine.

It is not synthesized in the child's body, therefore it must be present in the child's diet. Also, a lack of arginine is observed in the elderly and debilitated people. The amino acid is important for the health of joints, skin, muscle tissue, and strengthens the immune system.

• Asparagine.

It is necessary for the normal functioning of the nervous system, promotes the conduction of impulses through nerve cells.

• Aspartic acid.

Improves metabolism, participates in the synthesis of the ATP molecule - energy for cells.

• Alanin.

The amino acid contributes to a longer cell life, relieves intoxication.

• Cysteine.

Accelerates the recovery processes in the body.

• Glutamic acid (glutamate).

Participates in the breakdown of fats, which means it helps with weight loss. Important for mental development.

• Glycine.

Collagen protein consists of 30% of this amino acid.

• Tyrosine.

Regulates appetite, maintains blood pressure, participates in the synthesis of neurotransmitters.

• Glutamine.

Eliminates toxins from the liver, helps build muscle.

• Proline.

An important component in cartilage tissue.

• Serine.

Important for the normal functioning of the central nervous system and brain.

Essential amino acids

Essential amino acids in proteins are one of the key components of nutrition. If there are not enough of them in the diet, the body begins to use reserve reserves of substances, in particular, to use muscle tissue. Such processes are reflected not only in appearance, but also in health. A person may experience muscle pain, weakness, and one of the most dangerous consequences is damage to the heart muscle (myocardium) and the central nervous system. For people who play sports, the lack of these organic compounds in the diet leads to the inability to build sufficient muscle mass.

This class includes the following protein amino acids:

• Histidine.

It is necessary for the formation of leukocytes and erythrocytes, plays an important role in the prevention of allergic reactions and the development of autoimmune diseases. The amino acid is involved in the digestion process - under its action, gastric juice is produced.

• Leucine.

Promotes fat burning, along with insulin, regulates blood glucose, helps muscles to quickly recover.

• Methionine.

The amino acid is important for strengthening bones and muscle tissue. In addition, it plays an important role in the normalization of the immune system - it prevents allergic reactions.

• Lysine.

It is important for the synthesis of immunoglobulins, improves the supporting properties of the body, participates in the formation of hormones, in particular, growth hormone somatotropin.

• Isoleucine.

It helps to develop physical endurance and regenerate muscle tissue faster, therefore it is important for athletes.

• Threonine.

It is important for the growth and restoration of muscle tissue, regulates protein metabolism and prevents liver degeneration (fatty degeneration), the development of cirrhosis.

• Tryptophan.

An important component in the synthesis of the hormone serotonin.

• Valine.

Regulates blood glucose levels, prevents muscle tissue damage.

• Phenylalanine.

An important amino acid for the functioning of the central nervous system, improves memory and concentration. It is dangerous only for people with congenital fermentopathy - phenylketonuria, in which the amino acid cannot be used by the body. As a result, it builds up in the body and causes severe intoxication. Therefore, people with this disease, on the contrary, are advised to avoid foods containing this amino acid in proteins.

The synthesis of proteins in the cell takes place under the control of DNA and RNA - they are responsible for how the obtained amino acids will combine, as well as what proteins are now needed by the body.

The whole process of protein biosynthesis can be divided into several stages, each of which is important for the normal functioning of the body:

• Formation of peptides. Protein from food is broken down into peptides in the gastrointestinal tract. This happens with the help of the stomach enzyme pepsin and the pancreatic enzymes trypsin and chymotrypsin.
• Peptide fragments are cleaved to free amino acids. Protein molecules also pass this stage in the gastrointestinal tract.
• Amino acids are absorbed into the bloodstream.
• New protein compounds are formed from free amino acids.

Correct protein metabolism is a balance between protein breakdown and synthesis. To begin with, the body must have enough amino acids to build new compounds. Disorders at this stage can occur for two reasons: insufficient nutrition with a low protein content, inability to break down and assimilate proteins (for example, fermentopathy). Disrupted protein biosynthesis at this stage is manifested by the following symptoms:

• Delayed growth and development.
• Small muscle mass.
• Cardiovascular diseases.
• Poor appetite.
• Lethargy, apathy, fatigue.
• Poor condition of skin, hair, nails.

In the event that the biosynthesis of proteins is disrupted at the stage of building new compounds and removing excess, a person may suffer from protein poisoning. The following are typical signs of intoxication:

• Damage to the liver and kidneys.
• Disorders of the gastrointestinal tract.
• Influence on the central nervous system (up to serious lesions in congenital metabolic disorders).

The causes of protein metabolism disorders can be hereditary diseases, for example gout, as well as serious conditions, such as oncopathology, a consequence of radiation exposure, and so on. But in most cases, in an adult, the symptoms of a violation of protein biosynthesis indicate an unbalanced diet.

Protein classes and their functions

Scientists distinguish 7 main classes of proteins, each of which performs its own functions in the body.

• Structural components.

These substances form elastic fibers that provide strength and elasticity to fabrics. The most popular protein in this group is collagen. Most often it is remembered in the context of youthfulness and elasticity of the skin, as well as getting rid of wrinkles. However, the lack of collagen affects the condition of the cartilage and tendons in the body, because these proteins are the main component in their structure. Another commonly cited protein in this class is keratin, which makes up hair and nails.

• Transport proteins.

This class of proteins is responsible for the delivery of nutrients to cells. An example is hemoglobin, a protein found in red blood cells (erythrocytes) and is responsible for oxygen transport. Lack of hemoglobin leads to anemia, fatigue and cell destruction, because without oxygen they cannot exist. Lipoproteins are transferred from the liver to other organs, and the hormone insulin delivers glucose to the cells.

• Enzymes.

It is simply impossible to imagine metabolic processes in the body without this class of proteins. It is they who are involved in the breakdown and synthesis of nutrients coming from food. As a rule, enzymes are highly specialized proteins in the body, which means that each group is responsible for converting a certain type of substance. Deficiency of enzymes has a heavy effect on the state of health, because in this case, metabolism is disturbed.

• Proteins that provide movement (contractile).

They enable a cell or an organism to move, for example, human muscles are able to contract precisely thanks to proteins. The most popular type of substances in this class are myosins.

• Protective components.

Proteins that are responsible for immunity. In particular, we are talking about different classes of immunoglobulins (antibodies) that suppress the development of infections. Another type of substances in this class is fibrinogen and thrombin, which are responsible for blood clotting and protect the body from blood loss.

• Regulatory proteins.

This class of substances is responsible for the regulation of metabolism and even for the intensity of gene transcription. This class includes hormones - insulin (regulates blood sugar), growth hormone (responsible for bone growth) and others.

• Reserve (food) proteins.

The essence of this class of proteins is that they provide the egg and the embryo with a supply of nutrients. One of the most famous proteins in this class is casein (milk protein).

If the body uses up the reserves of carbohydrates and fats, or for some reason cannot break them down, protein molecules can be used as a source of energy. From 1 g of the substance, 17.6 kJ (4 kcal) is released.

The protein in the blood is checked using a biochemical test. One of the most important indicators is total protein, which reflects the amount of albumin and globulin proteins contained in the blood serum. The main functions of these proteins are:

• Immune response to infections and tissue damage.
• Transport of substances, including fatty acids, hormones and others.
• Participation in blood coagulation (to clarify the data, the patient can additionally be directed to a coagulogram, within which the amount of fibrinogen and prothrombin proteins is determined).

Biochemical analysis shows the content of albumin, C-reactive protein in blood serum, as well as decay products arising in the course of protein metabolism. All these indicators help to assess the general condition of the body, to identify diseases of the kidneys and liver, metabolic disorders of various etiologies, the consequences of thermal and chemical burns, organ necrosis and others. In addition, the data helps doctors suspect the presence of cancerous tumors.

Hemoglobin, one of the most important proteins in the blood, is detected in. This is the main indicator for the diagnosis of anemia, it can also indicate the presence of internal bleeding, an unbalanced diet with a lack of iron-containing foods, and impaired protein absorption.

Another analysis that assesses the protein content is a general urine test. Unlike blood, there may be no protein at all in the norm. The indicator makes it possible to identify violations of the functions of the kidneys and urinary tract, as well as tumor processes.

The norm of protein in the blood (biochemistry)

Total blood protein levels:

• Children of the first 3 years of life - 47-73 g / l.
• Preschoolers - 61-75 g / l.
• Schoolchildren - 52-76 g / l.
• From 18 years old and older - 64–83 g / l.

In the event that a low or high protein is found in the analysis results, this does not necessarily mean serious illness. The indicator strongly depends on the general condition of the body, the nutritional system and other things, therefore it is always evaluated in conjunction with other data. So, for example, an increased protein is fixed during the acute stage of an infectious disease, as soon as a person recovers, the indicator returns to normal without additional treatment.

Other important indicators of a biochemical blood test:

• Albumin is one of the most important whey proteins, which shows the condition of the kidneys and liver, and can confirm dehydration. The albumin protein norm for an adult is 35-52 g / l.
• C-reactive protein (CRP) is an element that responds quickly to tissue destruction. Therefore, it is important for assessing the condition after injuries, necrosis, burns. Protein norm: maximum 5 mg / l.
• Urea is the end product of the breakdown of proteins in the human body. It is excreted by the kidneys along with urine, therefore, increased indicators indicate a disruption in the work of these organs. Norm: 2.8-7.2 mmol / l.
• Bilirubin is a yellow pigment, a breakdown product of hemoglobin and other blood constituents. With its help, renal and hepatic dysfunction is diagnosed, it can also increase in severe conditions that cause a sharp breakdown of red blood cells (hemolytic anemia). Normal value: from 3 to 17 μmol / L.

Elevated serum protein (hyperproteinemia) is not always a sign of serious metabolic disorders. In particular, it is fixed under such temporary conditions:

• Diarrhea, vomiting, and other factors that cause dehydration.
• Infectious diseases (viruses, bacteria, fungal infections)
• Massive blood loss and various types of burns.
• Poisoning, general intoxication of the body.
• Allergic reactions.

At the same time, high levels of total protein in the blood can be a symptom of quite serious diseases. Among them:

• Liver diseases - cirrhosis, viral and non-viral hepatitis, liver failure.
• Kidney disease - nephritis, pyelonephritis, renal failure.
• Autoimmune diseases - lupus erythematosus, rheumatoid arthritis, scleroderma.
• Malignant tumors, including multiple myeloma.
• Diabetes insipidus.
• Intestinal obstruction.

Increased protein in urine

In a healthy person, protein in the urine is absent, but in 17% it can be detected in the analysis and at the same time not indicate any health problems. In addition, some factors increase its amount in absolutely any person. For example, mild proteinuria (albuminuria) is caused by:

• Intense physical activity (physiological proteinuria).
• Hypothermia.
• Stress and nervous tension.
• The recovery period after infectious diseases.
• Protein-rich foods (alimentary proteinuria).

The increased content of proteins in urine is also observed in children of the first days of life. For adults, the permissible norm of protein in morning urine is up to 0.03 g / l.

The main reason for persistently high rates is kidney disease. Very often, proteinuria is observed in pregnant women as a result of mechanical compression of the kidneys, as well as excessive stress on them.

Other causes of high protein include:

• Allergic reactions.
• Inflammation of the urinary tract.
• Inflammation of the kidneys.
• Swollen in the bladder and urinary tract.
• Chronic heart failure in the later stages.
• Diseases with severe fever.

Unlike fats and carbohydrates, protein in the human body does not accumulate, so a lack of protein in the diet quickly affects health. WHO notes that if the amount of protein in the daily diet is less than 35-40 g per day (the minimum requirement), different types of protein deficiency develop. Children especially often suffer from it, the most common diagnoses are:

• Alimentary dystrophy (nutritional insanity) - body weight is less than 60% of the required.

It develops, as a rule, in children of the first year of life, especially in those who are artificially fed and receive unbalanced mixtures. As a result, there is a general depletion of muscles, slow growth and weight gain, the disappearance of the subcutaneous fat layer, and mental retardation.

• Kwashiorkor - body weight 60-80% of the required.

More often observed in children 1-4 years old and adults with severe exhaustion. Typical symptoms of exhaustion: edema, distended abdomen, low body weight.

Mild to moderate protein deficiency can be observed in the following categories of people:

• Strict vegetarians (cheeses, milk, eggs are excluded from the diet).
• Children and adolescents with insufficient protein food.
• Pregnant women and women who are breastfeeding.
• People on strict diets. Mono diets are especially dangerous.
• People with alcoholism.

The lack of proteins may be associated not with the alimentary factor (nutritional disorders), but with diseases that contribute to the disruption of protein synthesis, their accelerated destruction. Among such diseases:

• Tuberculosis.
• Diseases of the esophagus, ulcerative colitis, chronic enterocolitis.
• Disorders of protein absorption in different parts of the gastrointestinal tract (for example, gastritis with low acidity).

Mild protein deficiency is manifested by the following symptoms:

• General weakness.
• Tremors in the limbs.
• Headache.
• Insomnia.
• Impaired coordination of movements.
• Nervousness, tearfulness.
• Pale skin, poorly healing wounds.
• Swelling.
• Bad hair, partial baldness.
• Tachycardia, arrhythmia and other problems in the work of the heart.

Excessive amounts of protein in the body also have a negative impact on health. Excess protein increases the burden on the liver, and its breakdown products can cause severe intoxication.

Protein poisoning can also be associated with nutritional factors. If the percentage of protein in the diet exceeds 50%, it is likely that the body will not be able to fully digest these substances. However, intoxication can also occur as a result of congenital and acquired diseases. In fermentopathies, specific classes of proteins are not able to break down and gradually accumulate in the blood in excessive amounts.

The increased protein content leads to the following disorders:

• Diseases and pathologies of the liver and kidneys.

Since these organs remove waste products and excess substances from the body, excessive amounts of protein increase the load on them. With prolonged poisoning, renal and hepatic failure can develop.

• Digestive disorders.

At the initial stage, the secretion of gastric juice may increase, and after that, on the contrary, it decreases - the absorption of food worsens.

• Effects on the central nervous system.

The increased protein affects the conduction of the nerves, in severe cases it can even cause paralysis. Also, excess protein causes conditions similar to neuroses.

• Bone damage (osteoporosis).

The body can only assimilate a certain amount of proteins, the excess is processed and excreted. In order to bind excess proteins, the body uses calcium. If there are too many of them, then the requirements for macronutrients increase significantly - the calcium contained in the bones begins to be used.

Proteins fats carbohydrates

Proteins, fats and form the basis of the human diet. Each of these substances perform their own important functions:

• The essence of proteins is the construction of cells, without which the growth and renewal of body tissues is impossible.
• Fats are stores of energy.
• Carbohydrates are the main source of energy, which is consumed immediately after entering the bloodstream.

The complete exclusion of at least one component has dire consequences and detrimental effects on health. However, when losing weight or, conversely, gaining weight, the ratio in the diet of proteins, fats and carbohydrates can be changed:

• For the normal functioning of the body, maintaining all systems in the usual mode, the following ratio is most suitable: proteins - 25-35%, fats - 25-35%, carbohydrates - up to 50%.
• In the event that you need to lose weight (reduce fat mass), the ratio of the components should be as follows: proteins - up to 50%, fats - 30%, carbohydrates - 20%.
• Weight gain (we are not talking about muscle building in athletes): proteins - 35%, fats - 15-25%, carbohydrates - up to 60%.

Increasing the amount of protein in the daily diet promotes the formation of muscle tissue, and it uses more energy even at rest. Therefore, building muscle contributes to weight loss as it increases the amount of calories you burn.

Protein diets are one of the most popular ways to lose weight. However, only the right ratio of protein, fat and carbohydrates will lead to the desired result. With an excess of proteins, the body suffers from intoxication, which as a result affects metabolic processes and, after the end of the diet, can provoke weight gain.

The amount of protein in the diet directly depends on the needs of a particular organism. The norms for a child during growth and an elderly person with low physical activity will differ significantly. On average, doctors recommend the following amount of protein:

• Children from birth to 3 years old - 1.1-2 g / kg per day.
• 4-13 years old - 0.95-1.5 g / kg per day.
• 14-18 years old - 0.85-1.2 g / kg per day.
• Adults with low and medium physical activity - 0.75-1 g / kg per day.
• Athletes - 1.5-2 g / kg per day.
• Pregnant and lactating women - 1.1-1.5 g / kg per day.
• Elderly people - 0.8 g / kg per day.

The rates may vary depending on the needs of the body and the state of health. For example, in case of liver and kidney diseases, the amount of protein can be reduced. But before a serious physical activity, a hike, competition and other things, on the contrary, increase the protein content in the menu.

It should be understood that the values ​​indicated are the amount of pure protein, not the protein product. For example, 100 grams of meat contains on average about 20 grams of pure protein. In addition, substances of animal and plant origin are assimilated in different ways by the human body. And if, for example, plant components are more effective for fats, then amino acids are better absorbed from animal protein. Therefore, in a child's diet, animal products should make up 60% of the total protein consumed, and for an adult - at least 30-40%.

Vegetarian diets, unless they are medicinal and are not specifically designed to reduce the amount of protein, must necessarily be carried out with a high content of plant-based protein products.

The human body receives proteins from two sources - plant and animal products. The content of pure proteins in specific species is shown in the protein table below.

When calculating the required volume, several more factors must be taken into account:

• Assimilation of protein foods.

Proteins in products of plant origin are assimilated only by 60%, in animals - by 80-90%.

• Heat treatment.

A protein molecule is capable of being destroyed or modified by temperature. A well-known example is the egg white, which, after heating, changes its structure, transparency, color. After cooking in animal products, some of the protein molecules are destroyed and cannot be absorbed by the body. For example, the amino acid lysine in meat and fish becomes less valuable. Legumes, on the other hand, are easier to digest after heating, since the trypsin inhibitor they contain becomes inactive.

• The content of other components in the product (proteins, fats and carbohydrates).

For example, animal food is always enriched with saturated fat, and excessive amounts of them negatively affect the health of blood vessels.

The main advantage of proteins in animal products is their composition - they contain all the essential amino acids for the human body. Therefore, the consumption of such dishes definitely makes the diet complete. Moreover, products of animal origin always contain fats in their composition, the consumption of which must be limited. All things considered, the best sources of animal protein are:

• Milk, cottage cheese (do not require heat treatment and are better absorbed).
• Yogurt and fermented milk products (additionally contain beneficial lactic acid bacteria).
• Fish, seafood (unlike meat, they contain unsaturated healthy fats).
• Low-fat meats and poultry (low fat content).
• Eggs (additionally enriched with vitamins A, B, PP, calcium, potassium, iron).

Foods that are better to exclude or minimize their number:

• Salo.
• Butter.
• Mutton.
• Fatty parts of pork.

Vegetable proteins

The composition of plant proteins differs from those described above in that it does not contain all essential amino acids. Therefore, if they are the main source of protein (for example, in vegans), the menu should be as varied as possible. It is unacceptable to use only one type of plant proteins.

Moreover, their composition significantly outperforms animal products - they are less high in calories, do not contain cholesterol and saturated fats, are rich in vitamins and microelements, they contain fiber that improves digestion. Therefore, proteins in plant-based foods are an important part of a healthy diet.

The best sources of plant-based protein include:

• Legumes - soybeans, lentils, beans, chickpeas, peas.
• Pumpkin seeds, sunflower seeds, flax seeds.
• Avocado.
• Nuts - almonds, walnuts, pistachios.
• Cereals - wheat, buckwheat, brown and brown rice.
• Dried fruits - prunes, dried apricots, dried figs.
• Vegetables - Brussels sprouts, broccoli, spinach, asparagus, beets (including young leaves), garlic, potatoes.
• Mushrooms.

Protein table

The protein table shows the pure protein content of different foods.

Protein table: foods with essential amino acids

Foods with protein composition containing high levels of essential amino acids:

The essence of proteins for the nutrition of athletes is the ability to build muscle mass, recover faster after training and increase the body's endurance. Protein diets are most often preferred by those involved in bodybuilding, but a higher amount of protein is recommended for any intense exercise.

Therefore, it is not surprising that the main component of sports nutrition is special protein supplements. Among the most popular in their composition are the following substances:

• Egg protein (best absorbed).
• Collagen protein (helps build and repair muscle tissue, ligaments, tendons).
• Whey protein (breaks down faster than others).
• Casein (long absorption time, so it is recommended to take it at night, but not before training).
• Milk Protein (a blend of whey proteins, casein, and carbohydrates).
• Soy protein (helps lower blood cholesterol, among other things).

Supplements should only be taken under medical supervision as they can lead to excess protein and dangerous toxicity. In addition, a sufficient amount of protein can be obtained from conventional products - 50% should come from animal proteins and 50% from plant proteins. Calculate portion sizes according to the norm of 1.5-2 g / kg per day.

1. Composition of protein molecules. Proteins are organic substances, the molecules of which include

carbon, hydrogen, oxygen and nitrogen, and sometimes sulfur and other chemical

elements.

2. Protein structure. Proteins are macromolecules composed of

from tens, hundreds of amino acids. Variety of amino acids (about 20 types),

included in the proteins.

3. Species specificity of proteins - the difference in proteins,

included in organisms belonging to different species, determined by the number

amino acids, their diversity, the sequence of compounds in molecules

squirrel. The specificity of proteins in different organisms of the same species is the reason

rejection of organs and tissues (tissue incompatibility) during their transplantation from

one person to another.

4. Protein structure - complex molecular configuration

proteins in space, supported by a variety of chemical bonds -

ionic, hydrogen, covalent. The natural state of protein. Denaturation -

violation of the structure of protein molecules under the influence of various factors -

heating, radiation, chemical action. Examples of denaturation:

changes in the properties of the protein when boiling eggs, the transition of the protein from a liquid state to

solid when building a spider's web.

5. The role of proteins in the body:

Catalytic. Proteins are catalysts that increase

the rate of chemical reactions in the cells of the body. Enzymes - biological

catalysts;

Structural. Proteins are elements of the plasma

membranes, as well as cartilage, bones, feathers, nails, hair, all tissues and organs;

Energy. The ability of protein molecules to

oxidation with the release of the energy necessary for the vital activity of the body;

Contractile. Actin and myosin are proteins included in

the composition of muscle fibers and ensuring their contraction due to the ability

molecules of these proteins to denaturation;

Motor. Movement of a number of unicellular organisms

organisms, as well as sperm with the help of cilia and flagella, in the composition

which includes proteins;

Transport. For example, hemoglobin is a protein entering

in the composition of erythrocytes and providing the transfer of oxygen and carbon dioxide;

Storing. The accumulation of proteins in the body as

reserve nutrients, such as eggs, milk, plant seeds;

Protective. Antibodies, fibrinogen, thrombin - proteins,

participating in the development of immunity and blood clotting;

Regulatory. Hormones are substances that provide

along with the nervous system, humoral regulation of body functions. The role of the hormone

insulin in the regulation of blood sugar.

2. The biological significance of the reproduction of organisms. Reproduction methods.

1. Reproduction and its meaning.

Reproduction - reproduction of similar organisms, which provides

the existence of species for many millennia, contributes to an increase

the number of individuals of the species, the continuity of life. Asexual, sexual and

vegetative reproduction of organisms.

2. Asexual reproduction is the most ancient method. V

one organism is asexually involved, while sex is most often involved

two individuals. In plants, asexual reproduction using spores - one

specialized cell. Reproduction by spores of algae, mosses, horsetails,

lycopods, ferns. The pouring out of spores from plants, their germination and development from

them new daughter organisms in favorable conditions. The death of a huge number

dispute falling into unfavorable conditions. Low probability of occurrence

new organisms from spores because they are low in nutrients and

the seedling absorbs them mainly from the environment.

3. Vegetative propagation - propagation of plants with

with the help of vegetative organs: aboveground or underground shoot, part of the root,

leaf, tuber, bulb. Participation in vegetative reproduction of one organism

or part of it. The similarity of the daughter plant with the mother, since it

continues the development of the maternal organism. Greater efficiency and

the spread of vegetative reproduction in nature, since the daughter organism

formed faster from the maternal part than from the spore. Examples of vegetative

reproduction: using rhizomes - lily of the valley, mint, wheatgrass, etc.; rooting

the lower branches touching the soil (layering) - currants, wild grapes; mustache

Strawberries; bulbs - tulip, daffodil, crocus. Using vegetative

reproduction when growing cultivated plants: potatoes are propagated by tubers,

bulbs - onions and garlic, layering - currants and gooseberries, root

offspring - cherry, plum, cuttings - fruit trees.

4. Sexual reproduction. The essence of sexual reproduction

in the formation of germ cells (gametes), the fusion of the male reproductive cell

(sperm) and female (egg) - fertilization and the development of a new

a daughter organism from a fertilized egg. Through fertilization, obtaining

a daughter organism with a more diverse set of chromosomes, hence, with more

various hereditary characteristics, as a result of which it may be

more adapted to the environment. Sexual reproduction in

sexual process in plants in the process of their evolution, the emergence of the most complex

forms in seed plants.

5. Seed propagation takes place with the help of seeds,

vegetative reproduction is also widespread). Sequence of stages

seed reproduction: pollination - the transfer of pollen on the stigma of the pistil, its

germination, appearance by dividing two sperm, their advancement into

ovule, then the fusion of one sperm with the egg, and the other with

secondary nucleus (in angiosperms). Formation from the ovule of the seed -

the embryo with a supply of nutrients, and from the walls of the ovary - the fetus. Seed -

the rudiment of a new plant, in favorable conditions it germinates and the first time

the seedling feeds on the nutrients of the seed and then its roots

begin to absorb water and minerals from the soil, and the leaves - carbon dioxide

gas from the air in sunlight. Independent life of a new plant.

Let's try to find out what value proteins have for the human body. Carbohydrates, proteins, mineral salts, fats, vitamins, which are part of food, are needed by a person for various internal processes.

Nutrients are a source of energy that covers all the costs of a living organism. Arguing about the importance of proteins in the body, we note that they are an excellent building material necessary for the growth and reproduction of new cells.

The basic elements include carbohydrates, fats, proteins. The importance of proteins, fats, carbohydrates for the human body is obvious. Once in the digestive tract, under the influence of enzymes, they undergo physical and chemical changes, break down into simpler chemical compounds, are absorbed into the intestines, and are absorbed by the body.

Discovery history

How were the proteins identified? The significance of these organic substances for the body was found out only after their chemical composition was determined. In 1838, the Dutch biochemist Gerard Mülder succeeded in discovering protein bodies and formulating a theory of protein. The researcher noted that a certain substance is present in animals and plants, it is the basis of life on the planet.

What are proteins, the significance for the body of which was revealed by Gerard Mülder? The word "protein" means "in first place" in Greek. These biopolymers account for about half of the dry weight of living organisms. For viruses, this figure is in the range of 45-95%.

Features of enzymes

What is the importance of proteins in the human body? They are called one of the main four organic substances of living matter. They differ significantly in biological functions. About a third of all proteins in the human body are concentrated in muscles, about 20% are distributed in tendons and bones, and only 10% are in the skin.

Considering the importance of proteins in the human body, we note that enzymes are the most important. Despite the fact that they are present in cells in trace amounts, these compounds control many chemical reactions that take place in a living organism:

• muscle activity;
• activity of the endocrine glands;
• brain functioning;
• oxidative interactions.

A small bacterium contains hundreds of enzymes.

Protein specificity

Analyzing the importance of proteins for living organisms, we note that proteins are an indispensable component of living cells. They may contain different chemical elements: hydrogen, oxygen, carbon, sulfur, nitrogen. Some protein molecules contain phosphorus. Amino acids are considered their main nitrogen-containing substances.

To understand the importance of proteins in the body, we note that the properties of macromolecules are determined by the composition and sequence of arrangement of amino acid residues.

Chemical composition

Peptide (amide) bonds are formed between them. In addition to polymeric long chains, residues of other organic compounds are found in proteins. On one ring of the amide bond there is an acylated or free group, the other is equipped with an amidated or free carboxyl moiety.

The portion of the chain that has an amino group is referred to as the M-terminus. A fragment with a carboxyl group is called the C-terminus of the peptide chain.

Hydrogen bonds are formed between the amide fragment of one peptide group and the NH-piece of the second substance.

Those groups that are included in the amino acid radical R are capable of interacting with each other, neighboring molecules, creating various complex structures.

Protein macromolecules contain one or more peptide chains, which are linked by chemical cross-links. Among the most common of these are disulfide bridges created by the amino acid residues of cysteine.

Protein structures

What structures do proteins have? The significance of this class of organic substances for the organism is explained by their ability to form several structures. The simplest structure is formed by linear insertion of amino acid fragments connected by amide (peptide) bonds. In the process of the formation of hydrogen bonds, twisting of the peptide chains in the spiral is observed. The process is accompanied by the formation of a large number of hydrogen bonds and ends with the formation of the most favorable energy configuration.

Such a complex structure was first discovered by the American physicist and chemist Pauling, who analyzed the main protein of wool and hair, keratin, on the basis of X-ray analysis.

He called the seen structure a-helix (a-structure).

One loop of it has 3.6-3.7 amino acid residues, the distance between which reaches 0.54 billionths of a meter.

Arguing about the importance of proteins for the vital activity of the organism, we note that the stability of such a spiral is explained by the hydrogen bonds formed inside the molecule. In the case of stretching the macrostructure, it transforms into a linear form.

The forces of electrostatic interaction (attraction and repulsion) prevent the formation of the correct structure. They appear between amino acid groups. Also, this process is influenced by pyrrolidine rings, forcing the peptide chain to bend in certain areas.

Then, the orientation of individual sections of the protein macromolecule in space occurs, accompanied by the formation of a strongly curved, spatial structure. It owes its stability to the interaction of radicals R with amino acids, accompanied by the formation of disulfide bridges, ion pairs, and hydrogen bonds. It is she who characterizes the basic biological and chemical properties of protein polymers.

Classification

Depending on the features of the spatial structure, it is customary to subdivide all proteins into two classes:

• fibrillar, acting as a structural material;
• globular, which include antibodies, enzymes, hormones.

Polypeptide chains have a spiral shape, fixed by hydrogen intramolecular bonds. In fibers of this class, peptide twisted chains are parallel to the axis, oriented towards each other. Their close location allows the formation of filamentous structures. This explains the high degree of asymmetry of these biopolymers.

Practically insoluble in water, forming high-viscosity solutions. These include proteins that are part of integumentary formations and tissues:

• myosin, a muscle protein;
• collagen, which forms the basis of the skin and sedimentary tissues;
• creatine contained in the horns, hair, feathers, wool.

The representative of this class is fibroin - a protein of natural silk. This syrupy liquid, which solidifies in air into an insoluble strong thread, is a structure that is formed using hydrogen intermolecular bonds. This is what determines the high mechanical strength of natural silk.

They differ in the curved shape of the peptide chains. Globules have an insignificant degree of asymmetry, are distinguished by high solubility in water, insignificant viscosity of the solutions formed. Among them are blood proteins:

• albumen;
• hemoglobin;
• globulin.

The division of proteins into globular and fibrillar is very arbitrary, since there are a huge number of macromolecules with an intermediate structure.

Property dependency

What is the reason for such a high value of protein in the human body? Briefly, it can be noted that the variety of physical and chemical properties of protein molecules is determined by the difference in the configurations of the polypeptide chains, the conditions for the formation of the spatial structure of the macromolecule, which will affect its main functions in the body. The number of amino acid residues included in macromolecules ranges from 51 (insulin) to 140 (myoglobin).

That is why the relative value ranges from several thousand to many millions.

With the help of the elementary composition, the empirical formula of the protein molecule - blood hemoglobin - was established. Hormones and enzymes are less complex. So, insulin has a molecular weight of 6,500, and the influenza virus has a molecular weight of 320,000,000.

Features of polypeptide molecules

It is customary to refer to them as substances of a protein nature, which contain amino acid residues united by peptide bonds. They have a lower relative molecular weight and degree of spatial organization than protein.

When dissolved in water, a molecular dispersed system is obtained, which is a solution of a high-molecular compound. Some of the compounds are isolated in the form of crystals: blood hemoglobin, chicken egg protein.

Proteins, fats, carbohydrates are of great importance for the body.

During the digestive process, polypeptides are digested to various amino acids. They are highly soluble in water, therefore they enter through the blood to all cells and tissues of the body.

In part, they are spent on the synthesis of proteins specific to each organism, the synthesis of hormones, enzymes, and other biologically significant substances. The remaining amino acids are energetic material.

Functions

The following functions of protein molecules are distinguished:

• catalytic (enzymes accelerate the course of hydrolysis);
• regulatory (hormones);
• protective (thrombin, antibodies);
• transport (ceruloplasmin, hemoglobin).

Protein metabolism takes a special place. The importance of protein metabolism in the body cannot be described in one sentence. They are the main components of animal feed, human food. Metabolism is based precisely on the continuous processes of their transformations, depends on the amino acids that make up their composition.

The importance of vitamins

Arguing about the importance of proteins, fats, carbohydrates for the body, let's talk about a group of compounds called vitamins.

Each of them has a specific function, indispensable for a living organism.

Vitamin E protects cells from the negative effects of free radicals. It slows down the aging process, improves the appearance of nails, hair, skin. This compound is a means of preventing blood clots in blood vessels.

Vitamin A controls growth in children and adolescents, it optimizes metabolic processes in the adult body, and maintains the normal state of the mucous membranes.

Vitamin B 12 affects the digestive processes, takes part in the metabolism. It significantly reduces the risk of anemia, contributes to the formation of endurance, is responsible for the tone of the body, and systematizes brain processes.

Vitamin D is a means of preventing rickets in children. It improves the absorption of calcium, has a positive effect on the state of the blood, stimulates cardiac activity, improves the functioning of the thyroid gland, and improves immunity.

Vitamin B6 optimizes the production of amino acids, assimilation of proteins. This substance stimulates the production of hemoglobin and red blood cells.

B1 stimulates metabolic processes in a living organism. This vitamin strengthens the nervous system, optimizes the activity of the cardiovascular system.

PP regulates the activity of the gastrointestinal tract, liver, pancreas. It is he who controls the production of gastric juice.

Vitamin H provides a normal level of beneficial microflora in the intestines, it has a positive effect on the condition of nails, hair, skin.

Ascorbic acid is an integral part of enzyme synthesis. It maintains the elasticity of cartilaginous and connective tissues, promotes the absorption of iron by the body.

Vitamin K is responsible for the development of bone tissue, blood clotting. Lack of any of these substances negatively affects the vital activity of the body, leads to a weakening of immunity, a decrease in human performance.

Lipids

Let's continue the conversation about the importance of proteins, fats, carbohydrates, vitamins for the body. The most "hated" part, according to the female representatives, are fats. But without these organic compounds, the body will not be able to fully function, the person will turn into a withered skeleton, devoid of strength.

Lipids are compounds that are composed of fatty acids and glycerol (polyhydric alcohol). They are a source of energy, accompany the process of assimilation of vitamins E, D, A.

It is with these organic compounds that a person receives essential fatty acids: linolenic, linoleic, arachidonic.

Without fats, the transmission of nerve impulses is impossible, since they are part of the cell membranes and affect their permeability.

For example, more than half of the brain is made up of fats that enter the body with food.

Scientists have come to the conclusion that an adult needs 3.5-4 liters of fat for full-fledged activity. Among its main functions, we note:

• body temperature control;
• accumulation of nutrients and energy;
• protection against mechanical damage;
• filtration of substances entering the body;
• the production of hormones that are responsible for the normal functioning of the body.

In addition, fats help to maintain external beauty, give the skin elasticity and natural shine.

It is customary to subdivide them by origin into animal and plant species. The first group includes: lard, sausages, fatty meat. During oxidation, they are partially converted into energy, the rest are accumulated under the skin. With an excess of such acids, a significant amount of cholesterol appears, and atherosclerosis develops. The body absorbs them slowly.

Vegetable fats contain significant amounts of unsaturated organic acids, which are quickly broken down in the body. For example, fatty acids Omega 3, Omega 6 are needed by a person for the full functioning of the cardiovascular system, preventing the production of cholesterol.

The value of fats for the body is comparable to proteins and carbohydrates. An adult should consume at least 100 grams of fat every day.

Conclusion

With the correct composition of the diet, you can count on the supply of the body with all the necessary components, without worrying about gaining excess weight.

Currently, many people are trying to monitor their health: physical activity, nutrition, skin condition. In order to be a successful, wealthy, in-demand person, it is important to control the amount of vitamins, proteins, fats, carbohydrates consumed by the body. All of these organic compounds perform important functions, so one cannot be replaced by others.

Protein (protein) is the main building material for the human body, since it is from proteins that cells are built. It is an organic compound that contains 22 amino acids, which are also essential for the construction of cells. Proteins are involved in many biological processes and perform many different functions. What does the lack of protein in the body lead to?

In the human body, protein reserves are practically absent, and the synthesis of new proteins is possible only from amino acids that come with food. The protein consumed by a person with food, entering the body, is broken down into amino acids during digestion, which are then easily absorbed into the bloodstream and absorbed by the body. Cells synthesize a protein from amino acids, which differs from the consumed protein and is characteristic only for the human body. The amino acids synthesized in our body are considered to be replaceable, and from which the proteins of our body are built are irreplaceable. They are not synthesized in our body and must be supplied with food. We can say that nonessential amino acids are more important for the cell than essential ones. Nutritional requirements for certain compounds indicate that dependence on an external source of amino acids may be more favorable for the survival of the organism than the independent synthesis of these compounds by the body.

Proteins are usually subdivided into plant and animal groups. Proteins of animal origin include chicken egg protein and whey protein. Chicken protein is easily digestible, it is the standard, since it is 100% albumin and yolk. Other proteins are evaluated in relation to chicken protein. Vegetable proteins include soy. Since the synthesis of new protein in the human body is ongoing, it is necessary to ensure a constant supply of protein to the body in the required amount.

Problems arising from a lack of protein.
The lack of protein in the body is caused by the lack of its required amount or the amount of amino acids necessary for protein synthesis. As a rule, a lack of protein is a regular occurrence in strict vegetarians, in people with strenuous physical activity due to imbalanced nutrition. Protein deficiency in the body has negative consequences for almost the entire body. Insufficient intake of protein with food leads to a slowdown in the growth and development of children, in adults - to disturbances in the activity of the endocrine glands, to changes in the liver, changes in hormonal levels, disturbances in the production of enzymes, as a result of which, a deterioration in the absorption of nutrients, many microelements, useful fats, vitamins. In addition, protein deficiency contributes to memory impairment, decreased performance, weakening of immunity due to a decrease in the level of antibody formation, and is also accompanied by vitamin deficiency. Inadequate protein intake leads to a weakening of the heart and respiratory system, loss of muscle mass.

The daily protein requirement of the female body should be based on 1.3 g multiplied by a kilogram of weight. For men, this coefficient increases to 1.5 g. When exercising or doing any kind of physical activity, the protein intake must be increased to 2.5 g multiplied by a kilogram. It is better if the consumed protein is easily digestible, that is, in the form of milk, soy proteins or specially prepared amino acid mixtures.

Excess protein in the body.
In addition to the lack of protein food, there may be an excess of it, which is also undesirable for the body. With a slight excess of protein in the diet compared to the norm, there will be no harm, but an excess of its consumption of 1.7 g per kilogram of weight in the absence of strong physical exertion leads to negative consequences. Excess protein is converted by the liver into glucose and nitrogenous compounds (urea), which must be removed from the body by the kidneys. In addition, compliance with the drinking regime is now becoming important. An excess of protein provokes an acidic reaction in the body, which leads to a loss of calcium. In addition, meat products, which contain a huge amount of protein, contain purines, some of which are metabolized in the joints, which can cause the development of gout. Cases of excess protein in the body are rare. As a rule, there is not enough of it in our diet. An excess of protein overloads the digestive system, contributes to a deterioration in appetite, increased excitability of the central nervous system, as well as endocrine glands. In addition, fatty deposits in the liver accumulate, the cardiovascular system, liver and kidneys suffer, and vitamin metabolism is disturbed.

You can estimate the sufficient or excess amount of protein in the diet by the nitrogen balance.
The human body systematically synthesizes new proteins and removes the end products of protein metabolism from it. Nitrogen is a part of proteins; when they decompose, nitrogen leaves their composition, being removed with urine. For optimal functioning of the body, a constant replenishment of the removed nitrogen is necessary. Nitrogen or protein balance is when the amount of nitrogen replenished with food matches the amount removed from the body.

To avoid a violation of protein metabolism, the following recommendations must be observed:

• It is forbidden to use semi-finished products and meat products of long-term storage (sausage, sausages, ham, wieners). Since there is little complete protein in semi-finished products and finished "meat" products, people who often consume these products most often experience protein starvation.
• Fatty meats and fish should be eaten in rare cases, since they contain a large percentage of fat, which interferes with the absorption of protein.
• Eat more poultry, eggs, lean beef. Vegetable proteins contained in peas, beans, nuts, buckwheat should be regularly included in the daily diet.
• The meat is best cooked on the grill or in the form of a kebab, as this method of cooking removes excess fat, which does not overload the gastrointestinal tract.
• Do not combine meat and fish with cereals, potatoes and bread; vegetable salad would be the best addition.
• Protein food should be consumed in the evening before 18.00 hours.
• High quality protein foods include milk, eggs and meat.
• Preferred protein foods: Egg white, low-fat cottage cheese, low-fat cheeses, low-fat fresh fish and seafood, young lamb, lean veal, chicken, turkey (skinless meat), soy milk, soy meat.
• The basic rule that must be followed when choosing a protein food is: choose foods that are low in fat and high in protein.

However, most of the common low-calorie diets (vegetable, fruit) limit protein intake. Such diets are not recommended to be carried out frequently, since protein starvation occurs, which leads to negative consequences in general.

On low-calorie diets, a slowdown in metabolic processes is manifested due to a decrease in the calorie content of the diet. This leads to a loss of muscle mass. Adequate protein in low-calorie diets accelerates metabolism during weight loss, and when combined with physical activity helps to increase muscle mass, which makes it easier to maintain weight after switching to a normal diet.

With a lack of protein in the body, physical activity will not bring any benefit, but only harm your health. Even if the kilograms go away, it won't be long. They come back with an "addition". Therefore, in any case, do not combine unbalanced low-calorie diets and intense physical activity.

Proteins are high molecular weight natural substances consisting of chains that are linked by a peptide bond. The most important function of these compounds is the regulation of chemical reactions in the body (enzymatic role). In addition, they perform protective, hormonal, structural, nutritional, energetic activities.

By their structure, proteins are divided into simple (proteins) and complex (proteids). The number of amino acid residues in the molecules is different: myoglobin - 140, insulin - 51, which explains the high molecular weight of the compound (Mr), which ranges from 10,000 to 3,000,000 daltons.

17% of the total weight of a person is made up of proteins: 10% falls on the skin, 20% on cartilage, bones, 50% on muscles. Despite the fact that the role of proteins and proteids has not yet been thoroughly studied, the functioning of the nervous system, the ability to grow, reproduce the body, the course of metabolic processes at the cellular level is directly related to the activity of amino acids.

Discovery history

The process of studying proteins dates back to the 18th century, when a group of scientists led by the French chemist Antoine François de Furcroix investigated albumin, fibrin, and gluten. As a result of these works, proteins were generalized and separated into a separate class.

In 1836, Mulder for the first time proposed a new model of the chemical structure of a protein, based on the theory of radicals. It remained generally accepted until the 1850s. The modern name for protein is proteins, the compound was given in 1838. And by the end of the 19th century, the German scientist A. Kossel made a sensational discovery: he came to the conclusion that amino acids are the main structural elements of the "building components". This theory was experimentally proved by the German chemist Emil Fischer at the beginning of the 20th century.

In 1926, the American scientist James Sumner discovered during research that the urease enzyme produced in the body belongs to proteins. This discovery revolutionized the world of science and led to the realization of how important proteins play in human life. In 1949, the English biochemist Fred Sanger experimentally deduced the amino acid sequence of the hormone insulin, thereby confirming the correctness of thinking that proteins are linear polymers of amino acids.

In the 1960s, for the first time, on the basis of X-ray diffraction, the spatial structures of proteins at the atomic level were obtained. At the same time, the study of this high-molecular-weight organic compound continues to this day.

The main structural units of proteins are amino acids, consisting of amino groups (NH2) and carboxyl residues (COOH). In some cases, "hydrogen nitrogen" radicals are associated with carbon ions, the number and location of which determines the specific characteristics of peptide substances. At the same time, the position of the carbon in relation to the amino group is emphasized in the name with a special "prefix": alpha, beta, gamma.

For proteins, alpha-amino acids act as structural units, since only they, with the lengthening of the polypeptide chain, give the protein fragments additional stability and strength. Compounds of this type occur naturally in two forms: L and D (except). At the same time, the elements of the first type are part of the proteins of living organisms produced by animals and plants, and the second - into the structures of peptides formed by nonribosomal synthesis in fungi and bacteria.

"Building material" for proteins binds to each other by a polypeptide bond, which is formed by combining one amino acid with the carboxyl of another amino acid. Short structures are usually called peptides or oligopeptides (molecular weight 3,400 - 10,000 daltons), and long ones, consisting of more than 50 amino acids, polypeptides. Most often, the composition of protein chains includes 100 - 400 amino acid residues, and sometimes 1000 - 1500. Proteins, due to intramolecular interactions, form specific spatial structures. They are called "protein conformations".

There are four levels of protein organization:

1. Primary - a linear sequence of amino acid residues connected by a strong polypeptide bond.
2. Secondary - the ordered organization of protein fragments in space in a spiral or folded conformation.
3. Tertiary is a method of spatial folding of a helical polypeptide chain by folding the secondary structure into a ball.
4. Quaternary - an assembly protein (oligomer), which is formed by the interaction of several polypeptide chains of the tertiary structure.

According to their structural form, proteins are divided into 3 groups:

• fibrillar;
• globular;
• membrane.

The first type of proteins are cross-linked filamentous molecules that form continuous fibers or layered structures. Considering that fibrillar proteins are characterized by high mechanical strength, they perform protective and structural functions in the body. Typical representatives of these proteins are hair keratins and tissue collagens.

Globular proteins consist of one or more polypeptide chains folded into a compact ellipsoidal structure. This type of protein includes enzymes, blood transport components, tissue proteins.

Membrane compounds are polypeptide structures that are embedded in the membrane of cell organelles. These substances act as receptors, passing the necessary molecules and specific signals through the surface.

Today, there is a huge variety of protein structures, determined by the number of amino acid residues included in them, the spatial structure and the sequence of their location.

However, for normal functioning of the body, only 20 alpha - amino acids of the L - series are required, 8 of which are not synthesized by the human body.

Physical and chemical properties

The spatial structure and amino acid composition of each protein determine its characteristic physicochemical properties.

Proteins are solids; when interacting with water, they form colloidal solutions. In aqueous emulsions, proteins are present in the form of charged particles, since the composition includes polar and ionic groups (–NH2, –SH, –COOH, –OH). In this case, the charge of a protein molecule depends on the ratio of carboxyl (–COOH), amine (NH) residues and the pH of the medium. It is interesting that in the structure of animal proteins there are more dicarboxylic amino acids (glutamic and), which determines their negative "potential" in aqueous solutions.

Some substances contain significant amounts of diamino acids (histidine, lysine, arginine), which is why they behave in liquids as cation proteins. In aqueous solutions, a substance is stable due to the mutual repulsion of particles with the same charges. However, a change in the pH of the medium entails a quantitative modification of the ionized groups in the protein.

In an acidic environment, the decomposition of carboxyl groups is suppressed, which leads to a decrease in the negative potential of the protein particle. In alkali, on the contrary, the ionization of amine residues slows down, as a result of which the positive charge of the protein decreases. At a certain pH, the so-called isoelectric point, alkaline dissociation is equivalent to acid dissociation, as a result of which protein particles aggregate and precipitate. For most peptides, this value is in a weakly acidic environment. However, there are structures with a sharp predominance of alkaline properties.

At the isoelectric point, proteins are unstable in solutions and, as a consequence, easily coagulate when heated. When acid or alkali is added to the precipitated protein, the molecules are recharged, after which the compound dissolves again. However, proteins retain their characteristic properties only at certain pH parameters. If somehow the bonds that hold the spatial structure of the protein are destroyed, then the ordered conformation of the substance is deformed, as a result of which the molecule takes the form of a random chaotic ball. This phenomenon is called denaturation.

The effect of chemical and physical factors leads to a change in the properties of the protein: high temperature, ultraviolet irradiation, vigorous shaking, combination with protein "precipitators". As a result of denaturation, the component loses its biological activity.

Proteins give color during hydrolysis reactions. When the peptide solution is combined with copper sulfate and alkali, a lilac color appears (biuret reaction), when proteins are heated in nitric acid, a yellow tint (xanthoprotein reaction), when interacting with a nitric acid solution of mercury, a raspberry color (Milon reaction). These studies are used to detect various types of protein structures.

Types of proteins, if possible, synthesis in the body

The importance of amino acids for the human body cannot be underestimated. They play the role of neurotransmitters, are needed for the proper functioning of the brain, supply energy to muscles, and control the adequacy of their functions with vitamins and minerals.

The main significance of the compound is to ensure the normal development and functioning of the body. Amino acids produce enzymes, hormones, hemoglobin, antibodies. The synthesis of proteins in living organisms is ongoing.

However, this process is suspended if the cells lack at least one essential amino acid. Disruption of protein formation leads to digestive disorders, growth retardation, psycho-emotional instability.

Most of the amino acids are synthesized in the human body in the liver. However, there are compounds that must be taken with food on a daily basis.

This determines the distribution of amino acids into the following categories:

• irreplaceable;
• semi-replaceable;
• interchangeable.

Each group of substances has specific functions. Let's consider them in detail.

Organic compounds of this group, the internal organs of a person are not able to produce on their own, but they are necessary to maintain the vital activity of the body.

Therefore, these amino acids have acquired the name "irreplaceable" and must be regularly supplied from the outside with food. Protein synthesis is impossible without this building material. As a result, a lack of at least one compound leads to metabolic disorders, a decrease in muscle mass, body weight and a stop in protein production.

The most important amino acids for the human body, in particular for athletes, and their importance.

1. ... It is a structural component of the branched chain protein (BCAA). It is a source of energy, participates in nitrogen metabolism, repairs damaged tissues, and regulates glycemic levels. Valine is essential for muscle metabolism and normal mental activity. It is used in medical practice in combination with leucine, isoleucine to treat the brain, liver, affected by drug, alcohol or drug intoxication of the body.
2. Leucine and Isoleucine. They lower blood glucose levels, protect muscle tissues, burn fat, serve as catalysts for the synthesis of growth hormone, regenerate skin and bones. Leucine, like valine, is involved in energy supply, which is especially important for maintaining the body's endurance during exhausting workouts. In addition, isoleucine is needed for the synthesis of hemoglobin.
3. Threonine. Prevents fatty degeneration of the liver, participates in protein and fat metabolism, the synthesis of collagen, elastane, the creation of bone tissue (enamel). The amino acid increases immunity, the body's susceptibility to ARVI diseases. Threonine is found in skeletal muscles, central nervous system, heart, supporting their work.
4. Methionine. Improves digestion, participates in the processing of fats, protects the body from the harmful effects of radiation, relieves signs of toxicosis during pregnancy, and is used to treat rheumatoid arthritis. The amino acid is involved in the production of taurine, cysteine, glutathione, which neutralize and remove toxic substances from the body. Methionine helps to reduce the level of histamine in cells in people with allergies.
5. Tryptophan. Stimulates the release of growth hormone, improves sleep, reduces the harmful effects of nicotine, stabilizes mood, and is used for the synthesis of serotonin. Tryptophan in the human body is able to convert to niacin.
6. Lysine. Participates in the production of albumins, enzymes, hormones, antibodies, tissue repair and collagen formation. This amino acid is a part of all proteins and is necessary for lowering serum triglycerides, normal bone formation, full absorption of calcium and thickening of the hair structure. Lysine has an antiviral effect, suppressing the development of acute respiratory infections and herpes. It increases muscle strength, supports nitrogen metabolism, improves short-term memory, erection, and female libido. Due to its positive properties, 2,6-diaminohexanoic acid protects a healthy heart, prevents the development of atherosclerosis, osteoporosis, genital herpes. Lysine in combination with proline prevents the formation of lipoproteins that cause blockage of arteries and lead to cardiovascular pathologies.
7. Phenylalanine. Suppresses appetite, reduces pain, improves mood, memory. In the human body, phenylalanine is able to transform into an amino acid - tyrosine, which is vital for the synthesis of neurotransmitters (dopamine and norepinephrine). Due to the compound's ability to cross the blood-brain barrier, it is often used to treat neurological diseases. In addition, the amino acid is used to combat white lesions of depigmentation on the skin (vitiligo), schizophrenia, and Parkinson's disease.

Lack of essential amino acids in the human body leads to:

• growth retardation;
• violation of the biosynthesis of cysteine, proteins, kidney function, thyroid gland, nervous system;
• dementia;
• decrease in body weight;
• phenylketonuria;
• decreased immunity and the level of hemoglobin in the blood;
• disorder of coordination of movements.

When playing sports, the deficiency of the above-described structural units reduces athletic performance, increasing the risk of injury.

Food Sources of Essential Amino Acids

The table is compiled based on data taken from the US Agricultural Library - USA National Nutrient Database.

Semi-replaceable

Compounds belonging to this category can be produced by the body only if they are partially supplied with food. At the same time, each type of semi-essential acids performs special functions that cannot be replaced.

Let's consider their types.

1. ... It is one of the most important amino acids in the human body. It accelerates the healing of damaged tissues, lowers cholesterol levels and is needed to maintain healthy skin, muscles, joints, and liver. Arginine increases the production of T-lymphocytes, which strengthen the immune system, and serves as a barrier preventing the introduction of pathogens. In addition, the compound promotes liver detoxification, lowers blood pressure, slows down the growth of tumors, resists the formation of blood clots, increases potency and increases blood circulation in blood vessels. The amino acid is involved in nitrogen metabolism, creatine synthesis and is indicated for people who want to lose weight and gain muscle mass. Interestingly, arginine is found in semen, connective tissue of the skin and hemoglobin. A deficiency of the compound in the human body is dangerous for the development of diabetes mellitus, infertility in men, delayed puberty, hypertension, immunodeficiency. Natural sources of arginine: chocolate, coconut, gelatin, meat, dairy products, walnuts, wheat, oats, peanuts, soybeans.
2. Histidine. It is a part of all tissues of the human body, enzymes. This amino acid is involved in the exchange of information between the central nervous system and peripheral regions. Histidine is necessary for normal digestion, since the formation of gastric juice is possible only with the participation of this structural unit. In addition, the substance prevents the occurrence of autoimmune, allergic reactions from the body. A deficiency of the component causes hearing loss, increases the risk of developing rheumatoid arthritis. Histidine is found in cereals (rice, wheat), dairy products, meat.
3. Tyrosine. Promotes the formation of neurotransmitters, reduces painful sensations of the premenstrual period, contributes to the normal functioning of the whole body, acts as a natural antidepressant. The amino acid reduces dependence on narcotic, caffeine drugs, helps control appetite and serves as a starting component for the production of dopamine, thyroxine, epinephrine. In protein synthesis, tyrosine partially replaces phenylalanine. In addition, it is needed for the synthesis of thyroid hormones. Amino acid deficiency slows down metabolic processes, lowers blood pressure, increases fatigue. Tyrosine is found in pumpkin seeds, almonds, oatmeal, peanuts, fish, avocado, soybeans.
4. Cystine. It is found in the main structural protein of hair, nail plates, skin, beta-keratin. The amino acid is best absorbed in the form of N-acetyl cysteine ​​and is used in the treatment of smoker's cough, septic shock, cancer, bronchitis. Cystine supports the tertiary structure of peptides, proteins, and also acts as a powerful antioxidant. It binds destructive free radicals, toxic metals, protects body cells from X-rays and radiation. The amino acid is part of somatostatin, insulin, immunoglobulin. Cystine can be obtained with the following foods: broccoli, onions, meat products, eggs, garlic, red pepper.

A distinctive feature of semi-essential amino acids is the ability to use them by the body for the production of proteins instead of methionine, phenylalanine.

Replaceable

The human body can produce organic compounds of this class on its own, covering the minimum needs of internal organs and systems. Essential amino acids are synthesized from metabolic products and assimilated nitrogen. To replenish the daily requirement, they must be taken daily in the composition of proteins with food.

Let's consider which substances belong to this category.

1. ... This type of amino acid is consumed as a source of energy, removes toxins from the liver, and accelerates the conversion of glucose. It prevents the breakdown of muscle tissue due to the course of the alanine cycle, presented in the following form: glucose - pyruvate - alanine - pyruvate - glucose. Thanks to these reactions, the building block of protein increases energy stores, prolonging the life of cells. Excess nitrogen during the alanine cycle is eliminated from the body in the urine. In addition, the substance stimulates the production of antibodies, ensures the metabolism of organic acids, sugars and raises the immune function. Sources of alanine: dairy products, avocados, meat, poultry, eggs, fish.
2. Glycine. Participates in the building of muscles, the production of hormones for the immune system, increases the level of creatine in the body, promotes the conversion of glucose into energy. Glycine is 30% part of collagen. Cellular synthesis is impossible without the participation of this compound. In fact, if tissues are damaged, without glycine, the human body will not be able to heal wounds. Sources of amino acids are: milk, beans, cheese, fish, meat.
3. Glutamine. After the conversion of an organic compound into glutamic acid, it crosses the blood-brain barrier and acts as fuel for the brain. The amino acid removes toxins from the liver, increases the level of GABA, maintains muscle tone, improves concentration and is involved in the production of lymphocytes. L-glutamine preparations are usually used in bodybuilding to prevent muscle tissue destruction by transporting nitrogen to organs, removing toxic ammonia and increasing glycogen stores. In addition, the substance is used to relieve symptoms of chronic fatigue, improve emotional background, treat rheumatoid arthritis, ulcers, alcoholism, impotence, scleroderma. The leaders in glutamine content are parsley and spinach.
4. Carnitine. Binds and removes fatty acids from the body. The amino acid enhances the action, C, reduces excess weight, reducing the burden on the heart. In the human body, carnitine is produced from glutamine and methionine in the liver and kidneys. It is of the following types: D and L. The greatest value for the body is L-carnitine, which increases the permeability of cell membranes for fatty acids. Thus, the amino acid increases the utilization of lipids, slows down the synthesis of triglyceride molecules in the subcutaneous fat depot. After taking carnitine, the oxidation of fats in the body increases, the process of loss of adipose tissue starts, which is accompanied by the release of energy stored in the form of ATP. L-carnitine enhances the creation of lecithin in the liver, lowers cholesterol levels, and prevents the appearance of atherosclerotic plaques. Despite the fact that this amino acid does not belong to the category of irreplaceable compounds, regular intake of the substance prevents the development of heart pathologies and allows you to achieve active longevity. Remember, carnitine levels fall with age, so older people should first of all add a dietary supplement to their daily diet. ... In addition, most of the substance is synthesized from vitamins C, methionine, iron, lysine. Lack of any of these compounds causes a deficiency of L-carnitine in the body. Natural sources of the amino acid: poultry, egg yolks, pumpkin, sesame seeds, lamb, cottage cheese, sour cream.
5. Aspargin. Needed for the synthesis of ammonia, the proper functioning of the nervous system. The amino acid is found in dairy products, asparagus, whey, eggs, fish, nuts, potatoes, and poultry.
6. Aspartic acid. Participates in the synthesis of arginine, lysine, isoleucine, the formation of a universal fuel for the body - adenosine triphosphate (ATP), which provides energy for intracellular processes. Aspartic acid stimulates the production of neurotransmitters, increases the concentration of nicotinamide adenine dinucleotide (NADH), which is necessary to maintain the functioning of the nervous system, the brain. This amino acid in the human body is synthesized independently, while its concentration in cells can be increased by including the following foods in the diet: sugar cane, milk, beef, poultry.
7. Glutamic acid. It is the most important excitatory neurotransmitter of the spinal cord, brain. The organic compound is involved in the movement of potassium across the blood-brain barrier into the cerebrospinal fluid and plays a fundamental role in triglyceride metabolism. The brain is able to use glutamate as fuel. The body's need for additional intake of amino acids increases with epilepsy, depression, early gray hair (up to 30 years), disorders of the nervous system. Natural sources of glutamic acid: walnuts, tomatoes, mushrooms, seafood, fish, yogurt, cheese, dried fruits.
8. Proline. Stimulates collagen synthesis, is necessary for the formation of cartilage tissue, accelerates the healing process. Sources of proline: eggs, milk, meat. Vegetarians are advised to take amino acid with dietary supplements.
9. Serine. Regulates the amount of cortisol in muscle tissue, creates antibodies, immunoglobulins, promotes the absorption of creatine, participates in the metabolism of fats, the synthesis of serotonin. Serine supports the normal functioning of the central nervous system and the brain. The main food sources of the amino acid: cauliflower, broccoli, nuts, eggs, milk, soybeans, kumis, beef, wheat, peanuts, poultry.

Thus, amino acids are involved in all vital functions in the human body. It is recommended that you consult with a specialist before purchasing nutritional supplements. Although it is considered safe to take amino acid preparations, it can exacerbate hidden health problems.

Today, the following types of protein are distinguished: egg, whey, vegetable, meat, fish.

Let's consider a description of each of them.

1. Egg. It is considered the benchmark among proteins, all other proteins are rated relative to it, since it has the highest digestibility. The yolk contains ovomucoid, ovomucin, lysocin, albumin, ovoglobulin, coalbumin, avidin, and the protein component is albumin. it is not recommended for people with digestive tract disorders to take it raw. This is due to the fact that they contain an inhibitor of the enzyme trypsin, which slows down the digestion of food, and the protein avidin, which adds vital vitamin H. The compound formed "at the exit" is not absorbed by the body and is excreted. Therefore, nutritionists insist on the use of egg white only after heat treatment, which releases the nutrient from the biotin-avidin complex and destroys the trypsin inhibitor. Advantages of this type of protein: it has an average absorption rate (9 grams per hour), high amino acid composition, helps to reduce body weight ... The disadvantages of chicken egg protein include their high cost.
2. Whey. Proteins in this category have the highest rate of degradation (10 - 12 grams per hour) among whole proteins. After ingestion of whey-based products, the level of pethides and amino acids in the blood increases sharply during the first hour. At the same time, the acid-forming function of the stomach does not change, which eliminates the likelihood of gas formation and disruption of the digestive process. The composition of human muscle tissue in terms of the content of essential amino acids (valine, leucine and isoleucine) is closest to the composition of whey proteins. This type of protein reduces cholesterol levels, increases the amount glutathione, has a low cost relative to other types of amino acids. The main drawback of whey protein is its rapid absorption, which makes it advisable to take it before or immediately after training. The main source of protein is sweet whey obtained during the production of rennet cheeses. There are concentrates, isolates, whey protein hydrolyzates, casein. The first of the obtained forms is not distinguished by high purity and contains fats, lactose, which stimulates gas formation. The protein level in it is 35-70%. For this reason, whey protein concentrate is the cheapest form of building material in sports nutrition circles. Isolate is a "cleaner" product, it contains 95% protein fractions. However, unscrupulous manufacturers sometimes cheat by providing a mixture of isolate, concentrate, hydrolyzate as whey protein. Therefore, you should carefully check the composition of the supplement, in which the isolate should act as the only component. Hydrolyzate is the most expensive type of whey protein, which is ready for immediate absorption and quickly penetrates into muscle tissue. Casein, when it enters the stomach, turns into a clot that takes a long time to split (4 - 6 grams per hour). Thanks to this property, protein is included in baby food formulas, since it enters the body stably and evenly, while an intense flow of amino acids leads to deviations in the development of the baby.
3. Vegetable. Despite the fact that the proteins in such products are deficient, in combination with each other they form a complete protein (the best combination is legumes + grains). Striking suppliers of plant-based building material are soy products, which fight osteoporosis, saturate the body with vitamins E, B, phosphorus, iron, potassium, zinc. neoplasms in the chest. It is indicated for people with dairy intolerances. For the production of supplements, soy isolate (contains 90% protein), soy concentrate (70%), soy flour (50%) are used. The rate of protein absorption is 4 grams per hour. The disadvantages of the amino acid include: estrogenic activity (due to this, the compound should not be taken by men in large doses, as this causes reproductive disorders), the presence of trypsin, which slows down digestion. Plants containing phytoestrogens (non-steroidal compounds) structurally similar to female sex hormones): flax, licorice, hops, red clover, alfalfa, red grapes. Vegetable proteins are also found in vegetables and fruits (cabbage, pomegranates, apples, carrots), cereals and legumes (rice, alfalfa, lentils pea protein is often used in sports nutrition. It is a highly purified isolate containing the highest amounts of the amino acid arginine (8.7% per gram of protein) relative to whey, soy, casein and egg material. In addition, pea protein is rich in glutamine, lysine. The amount of BCAAs in it reaches 18%. Interestingly, rice protein enhances the benefits of hypoallergenic pea protein and is used in the diets of raw foodists, athletes, and vegetarians.
4. Meat. The amount of protein in it reaches 85%, of which 35% are essential amino acids. Meat protein is characterized by zero fat content and has a high absorption rate.
5. Fish. This complex is recommended for use by an ordinary person. At the same time, it is extremely undesirable for athletes to use protein to cover the daily needs of athletes, since fish protein isolate is degraded into amino acids 3 times longer than casein.

Thus, to reduce weight, gain muscle mass, when working on relief, it is recommended to use complex proteins. They provide peak amino acid concentration immediately after consumption.

Obese athletes with a tendency to form fat should prefer the 50-80% slow protein relatively fast. Their main spectrum of action is aimed at long-term nutrition of the muscles.

Absorption of casein is slower than whey protein. Due to this, the concentration of amino acids in the blood increases gradually and is kept at a high level for 7 hours. Unlike casein, whey protein is absorbed much faster in the body, which creates the strongest release of the compound over a short period of time (half an hour). Therefore, it is recommended to take it to prevent muscle protein catabolism immediately before and immediately after training.

Egg white occupies an intermediate position. To saturate the blood immediately after exercise and maintain a high concentration of protein after strength exercises, its intake should be combined with whey isolate, the amino acid scor. This mixture of three proteins eliminates the disadvantages of each component, combines all the positive qualities.

Soy is the most compatible with whey protein.

Meaning for a person

The role that proteins play in living organisms is so great that it is almost impossible to consider each function, but we will briefly highlight the most important ones.

1. Protective (physical, chemical, immune). Proteins protect the body from the harmful effects of viruses, toxins, bacteria, microbes, triggering the mechanism of antibody synthesis. When protective proteins interact with foreign substances, the biological action of harmful cells is neutralized. In addition, proteins are involved in the clotting process of fibrinogen in the blood plasma, which contributes to the formation of a clot and clogging of the wound. Thanks to this, in the event of damage to the body, the protein protects the body from blood loss.
2. Catalytic, based on the fact that all so-called biological catalysts are proteins.
3. Transport. The main "carrier" of oxygen is hemoglobin, a blood protein. In addition, other types of amino acids in the process of reactions form compounds with vitamins, hormones, fats, ensuring their transport to the cells in need, internal organs, and tissues.
4. Nutritious. The so-called reserve proteins (casein, albumin) are sources of nutrition for the formation and growth of the fetus in the womb.
5. Hormonal. Most of the hormones in the human body (adrenaline, norepinephrine, thyroxine, glucagon, insulin, corticotropin, growth) are proteins.
6. Construction. Keratin is the main structural component of hair, collagen is of connective tissue, elastin is of the walls of blood vessels. Cytoskeleton proteins give shape to organelles, cells. Most of the structural proteins are filamentous.
7. Reducing. Actin and myosin (muscle proteins) are involved in the relaxation and contraction of muscle tissue. Proteins regulate translation, splicing, the intensity of gene transcription, as well as the process of cell movement through the cycle. Motor proteins are responsible for the movement of the body, the movement of cells at the molecular level (cilia, flagella, leukocytes), intracellular transport (kinesin, dynein).
8. Signal. This function is performed by cytokines, growth factors, hormone proteins. They transmit signals between organs, organisms, cells, tissues.
9. Receptor. One part of the protein receptor receives an irritating signal, the other reacts and promotes conformational changes. Thus, compounds catalyze a chemical reaction, bind intracellular intermediary molecules, and serve as ion channels.

In addition to the above functions, proteins regulate the pH level of the internal environment, act as a reserve source of energy, ensure the development, reproduction of the organism, and form the ability to think.

In combination with triglycerides, proteins are involved in the laying of cell membranes, with carbohydrates - in the production of secretions.

Protein synthesis is a complex process that occurs in the ribonucleoprotein particles of a cell (ribosomes). Proteins are transformed from amino acids and macromolecules "under the control" of information encoded in genes (in the cell nucleus). Moreover, each protein consists of enzyme residues, which are determined by the nucleotide sequence of the genome encoding the given "building material". Since DNA is concentrated in the cell nucleus, and protein synthesis "goes" in the cytoplasm, a special messenger called i-RNA transmits information from the biological memory code to the ribosomes.

Protein biosynthesis occurs in six stages.

1. Transfer of information from DNA to m-RNA (transcription). In prokaryotic cells, "rewriting" of the genome begins with the recognition by the RNA polymerase enzyme of a specific DNA nucleotide sequence.
2. Amino acid activation. Each "precursor" of a protein, using the energy of ATP, binds covalently to a transport RNA (t-RNA) molecule. In this case, t-RNA consists of sequentially connected nucleotides - anticodons, which determine the individual genetic code (triplet codon) of the activated amino acid.
3. Binding of proteins to ribosomes (initiation). An i-RNA molecule, containing information about a specific protein, combines with a small ribosome particle and an initiating amino acid attached to the corresponding t-RNA. In this case, the transport macromolecules mutually correspond to the m-RNA triplet, which signals the beginning of the protein chain.
4. Elongation of the polypeptide chain (elongation). The build-up of protein fragments occurs through the sequential addition of amino acids to the chain, transported to the ribosome using transport RNAs. At this stage, the final protein structure is formed.
5. Stopping the synthesis of the polypeptide chain (termination). The completion of protein construction is signaled by a special i-RNA triplet, after which the polypeptide is released from the ribosome.
6. Protein folding and processing. To adopt a characteristic structure, the polypeptide spontaneously folds, forming its characteristic spatial configuration. After synthesis on the ribosome, the protein undergoes chemical modification (processing) by enzymes, in particular, phosphorylation, hydroxylation, glycosylation, and tyrosinization.

Newly formed proteins contain at the end polypeptide "leaders", which serve as signals that direct substances to the "workplace".

The transformation of proteins is controlled by genes - operators, which, together with structural genes, form an enzymatic group called an operon. This system is controlled by genes-regulators with the help of a special substance, which they, if necessary, synthesize. The interaction of this substance with the "operator" leads to blocking of the controlling gene, and as a consequence, the termination of the operon. The signal to resume the work of the system is the reaction of the substance with the particles-inductors.

Daily rate

As you can see, the body's need for proteins depends on age, gender, physical condition, stress. Lack of protein in foods leads to disruption of the activity of internal organs.

Exchange in the human body

Protein metabolism is a set of processes reflecting the "activity" of proteins within the body: digestion, breakdown, assimilation in the digestive tract, as well as participation in the synthesis of new substances required for life support. Given that protein metabolism regulates, integrates and coordinates most of the chemical reactions, it is important to understand the main stages of "protein" transformations.

The liver plays a key role in the metabolism of peptides. If the "filtering" organ stops participating in this process, then, after 7 days, there will be a lethal outcome.

The sequence of metabolic processes.

1. Deamination of amino acids. This process is necessary to convert excess protein structures into and carbohydrates. In the course of enzymatic reactions, amino acids are modified into the corresponding keto acids, forming a decomposition by-product, ammonia. Deanimation of 90% of protein structures occurs in the liver, and in some cases in the kidneys. The exception is the branched-chain amino acids (valine, leucine, isoleucine), which are metabolized in the skeletal muscles.
2. Urea formation. Ammonia released during the deamination of amino acids is toxic to the human body. The neutralization of the toxic substance occurs in the liver under the influence of enzymes that convert it into uric acid. After that, the urea enters the kidneys, from where it is excreted along with the urine. The remainder of the molecule, which does not contain nitrogen, is modified into glucose, which releases energy when it decays.
3. Interconversions between nonessential amino acids. As a result of biochemical reactions in the liver (reductive amination, transamination of keto acids, amino acid transformations), the formation of nonessential and conditionally irreplaceable protein structures occurs, which compensate for their lack in the diet.
4. Plasma protein synthesis. Almost all blood proteins, with the exception of globulins, are formed in the liver. The most important of them, in quantitative terms, are albumins and blood coagulation factors.
   The process of digestion of proteins in the digestive tract occurs through the sequential action of proteolytic enzymes on them to impart the ability of decomposition products to be absorbed into the blood through the intestinal wall.

The breakdown of proteins begins in the stomach under the influence of gastric juice (pH 1.5 - 2), which contains the enzyme pepsin, which accelerates the hydrolysis of peptide bonds between amino acids. After that, digestion continues in the upper segments of the small intestine, duodenum and jejunum, where pancreatic and intestinal juice (pH 7.2 - 8.2), containing inactive precursors of enzymes (trypsinogen, procarboxypeptidase, chymotrypsinogen, proelastase), enters. Moreover, the intestinal mucosa produces the enzyme enteropeptidase, which activates these proteases. Proteolytic substances are also contained in the cells of the intestinal mucosa, as a result of which hydrolysis of small peptides occurs after final absorption.

As a result of these reactions, 95 - 97% of proteins are broken down into free amino acids, which are absorbed in the small intestine. With a lack or low activity of proteases, undigested protein enters the large intestine, where it undergoes decay processes.

Proteins are a class of high-molecular nitrogen-containing compounds, the functional and structural "basis" of human life. Considering that proteins are "responsible" for the construction of cells, tissues, organs, the synthesis of hemoglobin, enzymes, peptide hormones, the normal course of metabolic reactions, their lack in the diet leads to disruption of the functioning of all body systems.

Protein deficiency symptoms:

• hypotension and muscle dystrophy;
• decreased ability to work;
• a decrease in the thickness of the skin fold, especially over the triceps muscle of the shoulder;
• drastic weight loss;
• mental and physical fatigue;
• edema (latent and then obvious);
• chilliness;
• loss of skin turgor, as a result of which it becomes dry, flabby, lethargic, wrinkled;
• deterioration of the functional state of hair (loss, thinning, dryness);
• decreased appetite;
• poor wound healing;
• a constant feeling of hunger or thirst;
• impairment of cognitive functions (memory, attention);
• lack of weight gain (in children).

Remember, signs of a mild form of protein deficiency may be absent or hidden for a long time.

However, any phase of protein deficiency is accompanied by a weakening of cellular immunity and an increase in susceptibility to infections.

As a result, patients are more likely to suffer from respiratory diseases, pneumonia, gastroenteritis, pathologies of the genitourinary organs. With a prolonged shortage of nitrogenous compounds, a severe form of protein-energy deficiency develops, accompanied by a decrease in myocardial volume, atrophy of the subcutaneous tissue, and retraction of the intercostal spaces.

Consequences of severe protein deficiency:

• slowing down the heart rate;
• deterioration in the assimilation of protein and other substances, due to inadequate synthesis of enzymes;
• a decrease in the volume of the heart;
• anemia;
• violation of egg implantation;
• growth retardation (in newborns);
• functional disorders of the endocrine glands;
• hormonal disbalance;
• immunodeficiency states;
• exacerbation of inflammatory processes, due to a violation of the synthesis of protective factors (interferon and lysozyme);
• decrease in breathing intensity.

Lack of protein in the diet especially adversely affects the child's body: growth slows down, bone formation is impaired, mental development is delayed.

There are two forms of protein deficiency in children:

1. Insanity (dry protein deficiency). This disease is characterized by severe muscle and subcutaneous tissue atrophy (due to protein utilization), growth retardation, and weight loss. At the same time, swelling, obvious or latent, is absent in 95% of cases.
2. Kwashiorkor (isolated protein deficiency). At the initial stage, the child has apathy, irritability, lethargy. Then growth retardation, muscle hypotonia, fatty degeneration of the liver, and a decrease in tissue turgor are noted. Along with this, edema appears, masking a decrease in body weight, hyperpigmentation of the skin, peeling of certain parts of the body, and thinning of hair. Often, with kwashiorkor syndrome, vomiting, diarrhea, anorexia occur, and in severe cases, coma or stupor, which are often fatal.

Along with this, in children and adults, mixed forms of protein deficiency can develop.

Reasons for the development of protein deficiency

Possible reasons for the development of protein deficiency are:

• qualitative or quantitative nutritional imbalance (diet, fasting, protein-poor menu, poor diet);
• congenital disorders of amino acid metabolism;
• increased loss of protein in the urine;
• long-term shortage;
• violation of protein synthesis, due to chronic liver pathologies;
• alcoholism, drug addiction;
• severe burns, bleeding, infectious diseases;
• violation of protein absorption in the intestine.

Protein-energy deficiency is of two types: primary and secondary. The first disorder is due to inadequate intake of nutrients into the body, and the second is due to functional disorders or the intake of drugs that inhibit the synthesis of enzymes.

With a mild and moderate stage of protein deficiency (primary), it is important to eliminate the possible causes of the development of pathology. For this, the daily intake of proteins is increased (in proportion to the optimal body weight), and the intake of multivitamin complexes is prescribed. In the absence of teeth or loss of appetite, liquid nutritional mixtures are additionally used for tube feeding or self-feeding. If the "protein deficiency" is complicated by diarrhea, then it is preferable for patients to give yogurt formulations. In no case is it recommended to consume dairy products, due to the inability of the body to process lactose.

Severe forms of secondary failure require treatment in an inpatient setting, since laboratory testing is necessary to identify the disorder. To clarify the cause of the pathology, the level of a soluble interleukin-2 receptor in the blood or C-reactive protein is measured. At the same time, analyzes for the content of plasma albumin, skin antigens, the total number of lymphocytes and CD4 + T-lymphocytes will help to confirm the history and determine the degree of functional dysfunction.

The main priorities of treatment are adherence to a controlled diet, correction of water and electrolyte balance, elimination of infectious pathologies, and saturation of the body with nutrients. Given that a secondary lack of protein can prevent the cure of the disease that triggered its development, in some cases, parenteral or tube feeding with concentrated mixtures is prescribed. At the same time, vitamin therapy is used in dosages twice the daily requirement of a healthy person.

If the patient has anorexia or the cause of the dysfunction has not been identified, drugs that increase appetite are additionally used. To increase muscle mass, the use of anabolic steroids is permissible (under the supervision of a physician). The restoration of protein balance in adults occurs slowly, over 6 - 9 months. In children, the period of complete recovery takes 3 to 4 months.

Remember, for the prevention of protein deficiency, it is important to include protein products of plant and animal origin in the diet every day.

Overdose

Excessive intake of protein-rich foods has a negative impact on human health. Remember, an overdose of protein in the diet is just as dangerous a deficiency!

Typical symptoms of excess protein in the body:

• exacerbation of kidney and liver problems;
• deterioration in appetite, breathing;
• increased nervous irritability;
• profuse menstrual flow (in women);
• the difficulty of shedding excess weight;
• problems with the cardiovascular system;
• intensification of the processes of putrefaction in the intestines.

Determine the violation of protein metabolism using nitrogen balance. If the amount of nitrogen received and removed is the same value, it is considered that the person has a positive balance. Negative equilibrium indicates insufficient intake or poor absorption of protein, which leads to the burning of the body's own protein. This phenomenon underlies the development of depletion.

The slight excess of protein in the diet required to maintain a normal nitrogen balance does not pose any harm to human health. In this case, excess amino acids are used as an energy source. However, in the absence of physical activity, for most people, protein intake in an amount exceeding 1.7 grams per 1 kilogram of weight contributes to the conversion of excess protein into nitrogenous compounds (urea), glucose, which must be excreted by the kidneys. An excess amount of a building component contributes to the formation of an acidic reaction in the body, an increase in calcium loss. In addition, animal protein often contains purines, which can be deposited in the joints, which is a precursor to the development of gout.

An overdose of protein in the human body is extremely rare. Today, the usual diet of complete proteins (amino acids) is sorely lacking.

What are the pros and cons of animal and plant proteins?

The main advantage of animal protein sources is that they contain all essential amino acids necessary for the body, mainly in concentrated form. The disadvantages of such a protein are the intake of an excess amount of the building component, which is 2-3 times higher than the daily norm. In addition, products of animal origin often contain harmful components (hormones, antibiotics, fats,), which cause poisoning of the body with decay products, wash out "calcium" from the bones, create an extra load on the liver.

Vegetable proteins are well absorbed by the body. They do not contain harmful components that are "loaded" with animal proteins. However, vegetable proteins are not immune to their deficiencies. Most products (except for soy) are combined with fats (in seeds) and contain an incomplete set of essential amino acids.

What protein is the best absorbed in the human body?

1. Egg, the degree of absorption reaches 95 - 100%.
2. Dairy, cheese - 85 - 95%.
3. Meat, fish - 80 - 92%.
4. Soy - 60 - 80%.
5. Grain - 50 - 80%.
6. Bean - 40 - 60%.

This discrepancy is explained by the fact that the digestive tract organs do not produce the enzymes necessary for the breakdown of all types of protein.

1. Cover the body's daily requirement for organic compounds.
2. Ensure that different combinations of protein are supplied with food.
3. Do not overuse excessive amounts of protein for an extended period.
4. Avoid eating protein-rich foods at night.
5. Combine proteins of plant and animal origin. This will improve their absorption.
6. For athletes, it is recommended to drink a protein-rich protein shake before training to overcome high loads. After exercise, a gainer will help replenish the reserves of nutrients. The sports supplement raises the level of carbohydrates, amino acids in the body, stimulating the rapid recovery of muscle tissue.
7. 50% of the daily diet should be animal protein.
8. To remove the products of protein metabolism, much more water is required than for the breakdown and processing of other food components. To avoid dehydration of the body, you need to drink 2 liters of non-carbonated liquid per day. To maintain the water-salt balance, athletes are advised to consume 3 liters of water.

How much protein can you digest at a time?

Among the supporters of frequent eating, there is an opinion that no more than 30 grams of protein can be absorbed in one meal. It is believed that a larger volume is a burden on the digestive tract and it is not able to cope with the digestion of the product. However, this is nothing more than a myth.

The human body is able to overcome more than 200 grams of protein in one sitting. At the same time, a portion of the protein will go to participate in anabolic processes or SMP and will be stored as glycogen. The main thing to remember is that the more protein enters the body, the longer it will take to digest it, but the whole will be absorbed.

An excessive amount of proteins leads to an increase in the deposition of fat in the liver, increased excitability of the endocrine glands and the central nervous system, enhances the processes of putrefaction, and negatively affects the functioning of the kidneys.