Main article:Enzymes

The most well-known role of proteins in the body is the catalysis of various chemical reactions. Enzymes are a group of proteins with specific catalytic properties, that is, each enzyme catalyzes one or more similar reactions. Enzymes catalyze the reactions of splitting complex molecules (catabolism) and their synthesis (anabolism), as well as DNA replication and repair and RNA template synthesis. Several thousand enzymes are known; among them, such as, for example, pepsin break down proteins in the process of digestion. In the process of post-translational modification, some enzymes add or remove chemical groups on other proteins. About 4,000 protein-catalyzed reactions are known. The acceleration of the reaction as a result of enzymatic catalysis is sometimes enormous: for example, the reaction catalyzed by the enzyme orotate carboxylase proceeds 10 17 times faster than the non-catalyzed one (78 million years without the enzyme, 18 milliseconds with the participation of the enzyme). Molecules that attach to an enzyme and change as a result of the reaction are called substrates.

Although enzymes are usually composed of hundreds of amino acids, only most of of these interact with the substrate, and even fewer - an average of 3-4 amino acids, often located far from each other in the primary amino acid sequence - are directly involved in catalysis. The part of the enzyme that attaches the substrate and contains the catalytic amino acids is called the active site of the enzyme.

[edit] structural function

Main articles:Structural function of proteins , fibrillar proteins

Structural proteins of the cytoskeleton, like a kind of armature, give shape to cells and many organelles and are involved in changing the shape of cells. Most structural proteins are filamentous proteins: for example, actin and tubulin monomers are globular, soluble proteins, but after polymerization they form long filaments that make up the cytoskeleton that allows the cell to maintain its shape. Collagen and elastin are the main components of the intercellular substance of connective tissue (for example, cartilage), and hair, nails, bird feathers, and some shells are made up of another structural protein, keratin.

Mouse anti-cholera antibody linked to a carbohydrate antigen (top)

Protective function

Main article:Protective function of proteins

There are several types of protective functions of proteins:

1. Physical protection. Collagen takes part in it - a protein that forms the basis of the intercellular substance of connective tissues (including bones, cartilage, tendons and deep layers of the skin (dermis)); keratin, which forms the basis of horny shields, hair, feathers, horns, and other derivatives of the epidermis. Usually such proteins are considered as proteins with structural function. Examples of this group of proteins are fibrinogens and thrombins, which are involved in blood clotting.

2. Chemical protection. The binding of toxins to protein molecules can provide their detoxification. A particularly important role in human detoxification is played by liver enzymes that break down poisons or convert them into a soluble form, which contributes to their rapid elimination from the body.

3. Immune protection. Proteins that make up the blood and other biological fluids are involved in the body's defense response to both damage and attack by pathogens. Proteins of the complement system and antibodies (immunoglobulins) belong to the proteins of the second group; they neutralize bacteria, viruses, or foreign proteins. Antibodies, which are part of the adaptive immune system, attach to substances, antigens, foreign to the given organism, and thereby neutralize them, directing them to the places of destruction. Antibodies can be secreted into the intercellular space or become anchored in the membranes of specialized B-lymphocytes called plasma cells. While enzymes have a limited affinity for a substrate, since attachment to a substrate too strong can interfere with the catalyzed reaction, there is no limit to the persistence of antibody attachment to an antigen.

Regulatory function

Main articles:Activator (proteins) , Proteasome , Regulatory function of proteins

Many processes inside cells are regulated by protein molecules, which serve neither as a source of energy nor building material for the cell. These proteins regulate transcription, translation, splicing, as well as the activity of other proteins, etc. Proteins carry out the regulatory function either due to enzymatic activity (for example, protein kinase) or due to specific binding to other molecules, which usually affects the interaction of enzymes with these molecules. .

Thus, gene transcription is determined by the attachment of transcription factors - activator proteins and repressor proteins - to the regulatory sequences of genes. At the level of translation, the reading of many mRNAs is also regulated by the addition of protein factors, and the degradation of RNA and proteins is also carried out by specialized protein complexes. The most important role in the regulation of intracellular processes is played by protein kinases - enzymes that activate or inhibit the activity of other proteins by attaching phosphate groups to them.

Structure of myoglobin with α-helices highlighted

Signal function

Main articles:Protein signaling function , Hormones , Cytokines

The signaling function of proteins is the ability of proteins to serve as signaling substances, transmitting signals between cells, tissues, organs and different organisms. The signaling function is often combined with the regulatory function, since many intracellular regulatory proteins also carry out signal transduction.

The signal function is performed by hormone proteins, cytokines, growth factors, etc.

Hormones are carried in the blood. Most animal hormones are proteins or peptides. The binding of the hormone to the receptor is a signal that triggers a response in the cell. Hormones regulate the concentration of substances in the blood and cells, growth, reproduction and other processes. An example of such proteins is insulin, which regulates the concentration of glucose in the blood.

Cells interact with each other using signal proteins transmitted through the intercellular substance. Such proteins include, for example, cytokines and growth factors.

Cytokines are small peptide information molecules. They regulate interactions between cells, determine their survival, stimulate or suppress growth, differentiation, functional activity and apoptosis, ensure the coordination of actions of the immune, endocrine and nervous systems. An example of cytokines is tumor necrosis factor, which transmits inflammation signals between body cells.

transport function

Main article:Transport function of proteins

Soluble proteins involved in the transport of small molecules must have a high affinity (affinity) for the substrate when it is present in high concentration, and it is easy to release it in places of low substrate concentration. An example of transport proteins is hemoglobin, which carries oxygen from the lungs to other tissues and carbon dioxide from tissues to the lungs, as well as proteins homologous to it found in all kingdoms of living organisms.

Some membrane proteins are involved in the transport of small molecules through the cell membrane, changing its permeability. The lipid component of the membrane is waterproof (hydrophobic), which prevents the diffusion of polar or charged (ions) molecules. Membrane transport proteins are commonly classified into channel proteins and carrier proteins. Channel proteins contain internal water-filled pores that allow ions (via ion channels) or water molecules (via aquaporins) to move across the membrane. Many ion channels are specialized for the transport of only one ion; thus, potassium and sodium channels often distinguish between these similar ions and allow only one of them to pass through. Carrier proteins bind, like enzymes, every molecule or ion they carry and, unlike channels, can actively transport using the energy of ATP. The "powerhouse of the cell" - ATP synthase, which carries out the synthesis of ATP due to the proton gradient, can also be attributed to membrane transport proteins.

Like other biological macromolecules (polysaccharides, lipids and nucleic acids), proteins are essential components of all living organisms and play an important role in cell life. Proteins carry out metabolic processes. They are part of the intracellular structures - the organellicytoskeleton, secreted into the extracellular space, where they can act as a signal transmitted between cells, participate in the hydrolysis of food and the formation of an intercellular substance.

The classification of proteins according to their functions is rather arbitrary, since the same protein can perform several functions. A well-studied example of this multifunctionality is lysyl-tRNA synthetase - which not only adds a lysine-actRNA residue, but also regulates the transcription of several genes. Proteins perform many functions due to their enzymatic activity. So, enzymes are motor protein myosin, regulatory proteins protein kinases, transport protein sodium-potassium adenosine triphosphatase, etc.

catalytic function

The most well-known function of proteins in the body is to catalyze various chemical reactions. Enzymes are proteins that have specific catalytic properties, that is, each enzyme catalyzes one or more similar reactions. Enzymes catalyze reactions that break down complex molecules (catabolism) and synthesize them (anabolism), including DNA replication and repair and RNA template synthesis. By 2013, more than 5,000 enzymes had been described. The acceleration of the reaction as a result of enzymatic catalysis can be enormous. Molecules that attach to an enzyme and change as a result of the reaction are called substrates. The part of the enzyme molecule that provides substrate binding and catalysis is called the active site.

The International Union of Biochemistry and Molecular Biology in 1992 proposed the final version of the hierarchical nomenclature of enzymes based on the type of reactions they catalyze. According to this nomenclature, the names of enzymes must always end in -aza and be formed from the names of the catalyzed reactions and their substrates. Each enzyme is assigned an individual code, by which it is easy to determine its position in the hierarchy of enzymes. According to the type of catalyzed reactions, all enzymes are divided into 6 classes:

CF 1: Oxidoreductase, catalyzing redox reactions;

CF 2: Transferases, catalyzing the transfer of chemical groups from one substrate molecule to another;

CF 3: Hydrolases, catalyzing the hydrolysis of chemical bonds;

CF 4: Liase, catalyzing the breaking of chemical bonds without hydrolysis with the formation of a double bond in one of the products;

CF 5: Isomerases, catalyzing structural or geometric changes in the substrate molecule;

CF 6: Ligases, catalyzing the formation of chemical bonds between substrates due to the hydrolysis of the diphosphate bond of ATP or a similar triphosphate.

structural function

Structural proteins of the cytoskeleton, like a kind of armature, give shape to cells and many organelles and are involved in changing the shape of cells. Most structural proteins are filamentous. Collagen and elastin are the main components of the intercellular substance of connective tissue (for example, cartilage), and hair, nails, bird feathers, and some shells are made up of another structural protein, keratin.

Protective function

There are several types of protective functions of proteins:

Physical protection. Physical protection of the body is provided by collagen, a protein that forms the basis of the intercellular substance of connective tissues (including bones, cartilage, tendons, and deep layers of the skin (dermis)); keratin, which forms the basis of horny scutes, hair, feathers, horns, and other derivatives of the epidermis. Usually such proteins are considered as proteins with structural function. Examples of proteins in this group are fibrinogens and thrombins involved in blood clotting.

Chemical protection. The binding of toxins to protein molecules can provide their detoxification. A particularly important role in detoxification in humans is played by liver enzymes that break down poisons or convert them into a soluble form, which contributes to their rapid removal from the body.

Immune protection. Proteins that make up blood and other biological fluids are involved in the body's defense response to both damage and attack by pathogens. Proteins of the complement system and antibodies (immunoglobulins) belong to the proteins of the second group; they neutralize bacteria, viruses or foreign proteins. Antibodies, which are part of the adaptive immune system, attach to substances, antigens, foreign to the given organism, and thereby neutralize them, directing them to the places of destruction. Antibodies can be secreted into the extracellular space or become attached to the membranes of specialized B-lymphocytes called plasma cells.

Regulatory function

Many processes inside cells are regulated by protein molecules, which serve neither as a source of energy nor as a building material for the cell. These proteins regulate the progress of the cell through the cell cycle, transcription, translation, splicing, the activity of other proteins, and many other processes. The regulatory function of proteins is carried out either due to enzymatic activity (for example, protein kinase), or due to specific binding to other molecules.

The most important role in the regulation of intracellular processes is played by protein kinases and protein phosphatases - enzymes that activate or suppress the activity of other proteins by attaching to them or removing phosphate groups.

Signal function

The signaling function of proteins is the ability of proteins to serve as signaling substances, transmitting signals between cells, tissues, organs and organisms. The signaling function is often combined with the regulatory function, since many intracellular regulatory proteins also carry out signal transduction.

The signal function is performed by hormone proteins, cytokines, growth factors, etc.

Hormones are carried in the blood. Most animal hormones are proteins or peptides. The binding of a hormone to its receptor is a signal that triggers a cell response. Hormones regulate the concentration of substances in the blood and cells, growth, reproduction and other processes. An example of such proteins is insulin, which regulates the concentration of glucose in the blood.

Cells interact with each other using signal proteins transmitted through the intercellular substance. Such proteins include, for example, cytokines and growth factors.

Cytokines are peptide signaling molecules. They regulate interactions between cells, determine their survival, stimulate or suppress growth, differentiation, functional activity and apoptosis, and ensure the coordination of actions of the immune, endocrine and nervous systems. An example of cytokines is tumor necrosis factor, which transmits inflammatory signals between body cells.

transport function

Soluble proteins involved in the transport of small molecules must have a high affinity (affinity) for the substrate when it is present in high concentration, and it is easy to release it in places of low substrate concentration.

Some membrane proteins are involved in the transport of small molecules through the cell membrane, changing its permeability. The lipid component of the membrane is waterproof (hydrophobic), which prevents the diffusion of polar or charged (ions) molecules. Membrane transport proteins are commonly classified into channel proteins and carrier proteins. Channel proteins contain internal water-filled pores that allow ions (via ion channels) or water molecules (via aquaporins) to move across the membrane. Many ion channels specialize in the transport of only one ion; thus, potassium and sodium channels often distinguish between these similar ions and allow only one of them to pass through. Carrier proteins bind, like enzymes, every molecule or ion they carry and, unlike channels, can actively transport using the energy of ATP.

Spare (backup) function

These proteins include the so-called reserve proteins, which are stored as a source of energy and matter in plant seeds (for example, 7S and 11S globulins) and animal eggs. A number of other proteins are used in the body as a source of amino acids, which in turn are precursors of biologically active substances that regulate metabolic processes.

Receptor function

Protein receptors can be located both in the cytoplasm and embedded in the cell membrane. One part of the receptor molecule receives a signal, most often a chemical substance, and in some cases, light, mechanical action (for example, stretching), and other stimuli. When a signal is applied to a certain part of the molecule - the receptor protein - its conformational changes occur. As a result, the conformation of another part of the molecule, which transmits the signal to other cellular components, changes. There are several signaling mechanisms. Some receptors catalyze a particular chemical reaction; others serve as ion channels that open or close when a signal is applied; still others specifically bind intracellular messenger molecules. In membrane receptors, the part of the molecule that binds to the signal molecule is located on the cell surface, while the signal-transmitting domain is inside.

Motor (motor) function

A whole class of motor proteins provides movement of the body, for example, muscle contraction, including locomotion (myosin), movement of cells within the body (for example, amoeboid movement of leukocytes), movement of cilia and flagella, as well as active and directed intracellular transport (kinesin, dynein) . Dyneins and kinesins transport molecules along microtubules using ATP hydrolysis as an energy source. Dyneins carry molecules and organelles from the peripheral parts of the cell towards the centrosome, kinesins - in the opposite direction. Dyneins are also responsible for the movement of cilia and flagella in eukaryotes. Cytoplasmic variants of myosin can take part in the transport of molecules and organelles through microfilaments.

The functioning of the human body became clear at the beginning of the 19th century. Scientists designated these substances with the Greek term "proteins", from the word protos - "main, first".

The main feature of these chemical compounds is that they are the basis that the body uses to create new cells. Their other functions are to provide regulatory and metabolic processes; in the performance of transport functions (for example, hemoglobin protein, which distributes oxygen throughout the body with blood flow); in the formation of muscle fibers; in the management of many vital functions of the body ( a prime example serves as the protein insulin) in regulating the process of digestion, energy metabolism; in protecting the body.

The chemical structure of these substances is determined by the number of amino acids that make up the protein molecules. The molecules are quite large in size. These substances are high molecular weight organic matter and are a chain of amino acids linked by a peptide bond. The amino acid composition of proteins is determined by the genetic code. Many variations in the combination of amino acids gives a variety of properties of protein molecules. As a rule, they are interconnected and form complex complexes.

The classification of proteins has not been finalized, since not all proteins have been studied by scientists. The role of many of them continues to be a mystery to people. So far, proteins are divided according to their biological role and according to which amino acids are included in their composition. For our nutrition, it is not the protein itself that is valuable, but the amino acids that make it up. Amino acids are one of the varieties of organic acids. There are more than 100 of them. Without them, metabolic processes are impossible.

The body cannot fully absorb the proteins that come from food. Most of them are destroyed by acidic digestive juices. Proteins are broken down into amino acids. The body “takes” after the breakdown the amino acids it needs and constructs the necessary proteins from them. In this case, the transformation of one amino acid into another can occur. In addition to transformation, they can also be independently synthesized in the body.

However, not all amino acids can be produced by our body. Those that are not synthesized are called irreplaceable, because the body needs them, and can only get them from the outside. Essential amino acids cannot be replaced by others. These include methionine, lysine, isoleucine, leucine, phenylalanine, threonine, valine. In addition, there are other amino acids that are formed exclusively from the essential phenylalanine and methionine. Therefore, the quality of nutrition is determined not by the amount of incoming proteins, but by their qualitative composition. For example, in potatoes white cabbage, beets, cabbage, legumes, bread contains a large amount of tryptophan, lysine, methionine.

The course of protein metabolism in our body depends on a sufficient amount of the necessary proteins. The splitting and transformation of some substances into others occurs with the release of the energy needed by the body.

As a result of the vital activity of the body, there is a constant loss of part of the proteins. Approximately 30 g per day is lost from protein substances coming from outside. Therefore, taking into account the loss, the diet should contain a sufficient amount of these substances to ensure the health of the body.

The consumption of protein substances by the body depends on various factors: performing difficult physical work or being at rest; emotional condition. Per day, the rate of protein intake is a total of at least 50 grams for adults (this is approximately 0.8 grams per kilogram of body weight). Children, due to intensive growth and development, require more proteins - up to 1.9 grams per kilogram of body weight.

However, even a large amount of protein substances eaten does not guarantee a balanced amount of amino acids in them. Therefore, the diet should be varied so that the body can get the most out of it in the form of different amino acids. We are not talking about the fact that if today there was no tryptophan in the food you ate, then tomorrow you will get sick. No, the body "knows how" to store useful amino acids in small quantities and use them if necessary. However, the cumulative capacity of the body is not too high, so the reserves of useful substances must be regularly replenished.

If for personal reasons (vegetarianism) or for health reasons (problems with the gastrointestinal tract and diet food) you have a restriction in the diet, then you need to consult a dietitian to adjust your diet and restore the balance of proteins in the body.
During intensive sports activities, the body needs a large amount of proteins. Specially for such people is produced sports nutrition. However, the intake of proteins should correspond to the physical activity performed. An excess of these substances, contrary to popular belief, will not lead to a sharp increase in muscle mass.

The variety of functions of proteins covers almost all biochemical processes occurring in the body. They can be called biochemical catalysts.
Proteins form the cytoskeleton, which maintains the shape of cells. Without proteins, the successful functioning of the immune system is impossible.

An excellent food source of proteins are meat, milk, fish, grains, legumes, nuts. Fruits, berries and vegetables are less rich in proteins.

The first protein that has been studied to determine its amino acid sequence is insulin. For this achievement, F. Senger received Nobel Prize in the 60s of the last century. And scientists D. Kendrew and M. Perutz at the same time were able to create a three-dimensional structure of myoglobin and hemoglobin using the X-ray diffraction technique. They were also awarded the Nobel Prize for this.

History of study

In the next 30-40 years, studies were carried out on most of the amino acids that make up proteins. In 1894, A. Kossel, a German physiologist, made the assumption that it is amino acids that are the very structural components of proteins, and that they are interconnected by peptide bonds. He tried to study the amino acid sequence of the protein.
In 1926, the dominant role of proteins in the body was finally recognized. This happened when the US chemist D. Sumner proved that urease (an enzyme without which many chemical processes are impossible) is a protein.

It was extremely difficult at that time to isolate pure proteins for the needs of science. That is why the first experiments were carried out using those polypeptides that could be purified in significant quantities at minimal cost - these are blood proteins, chicken proteins, various toxins, enzymes of digestive or metabolic origin, released after slaughtering cattle. In the late 1950s, it was possible to purify bovine pancreatic ribonuclease. It is this substance that has become an experimental object for many scientists.

In modern science, the study of proteins has continued at a qualitatively new level. There is a branch of biochemistry called proteomics. Now, thanks to proteomics, it is possible to study not only isolated purified proteins, but also a parallel, simultaneous change in the modification of many proteins belonging to different cells and tissues. Scientists can now theoretically calculate the structure of a protein from its amino acid sequence. Cryoelectron microscopy methods make it possible to study large and small protein complexes.

Protein properties

Proteins are distinguished by their degree of solubility, most of them are highly soluble in water. However, there are also exceptions. Fibroin (the basis of cobwebs and silk) and keratin (the basis of human hair, as well as wool in animals and feathers in birds), are insoluble.

Denaturation

In some cases, denaturation is reversible; the reverse state of the protein can be restored using ammonium salts. Reversible denaturation is used as a protein purification method.

Simple and complex proteins

According to the chemical nature of complex proteins, five classes are distinguished:

• Glycoproteins.
• Chromoproteins.
• Phosphoproteins.
• Metalloproteins.
• Lipoproteins.

Chromoproteins is the general name for complex proteins, which include flavoproteins, chlorophylls, hemoglobin, and others.

Proteins called phosphoproteins contain residues of phosphoric acid. This group of proteins includes, for example, milk casein.

Metalloproteins are proteins that contain covalently bound ions of certain metals. Among them there are proteins that perform transport and storage functions (transferrin, ferritin).

Complex lipoprotein proteins contain lipid residues in their composition. Their function is the transport of lipids.

Biosynthesis of proteins

The genetic code is made up of codons. A codon is a unit of genetic information consisting of nucleotide residues. Each codon is responsible for attaching one amino acid to a protein. Their total number is 64. Some amino acids are determined not by one, but by several codons.

Functions of proteins in the body

It should be noted that the classification of proteins according to their functions is rather arbitrary, because in some living organisms the same protein can perform several different functions. Proteins perform many functions due to the fact that they have high enzymatic activity. In particular, these enzymes include the motor protein myosin, as well as the regulatory proteins of protein kinase.

catalytic function

More than 4,000 reactions in our body need to be catalyzed. Without the action of enzymes, the reaction proceeds tens and hundreds of times slower.
Molecules that attach to an enzyme during a reaction and then change are called substrates. The enzyme contains many amino acids, but not all of them interact with the substrate, and even more so, not all of them are directly involved in the catalytic process. The part of the enzyme to which the substrate is attached is considered the active site of the enzyme.

structural function

Protective function

Immune defense involves the participation of proteins that make up the blood or other biological fluids in the formation of a protective response of the body to the attack of pathogenic microorganisms or damage. For example, immunoglobulins neutralize viruses, bacteria, or foreign proteins. Antibodies produced by the immune system attach to substances foreign to the body, called antigens, and neutralize them. As a rule, antibodies are secreted into the intercellular space or are fixed in the membranes of specialized plasma cells.

Enzymes and substrate are not interconnected too closely, otherwise the course of the catalyzed reaction may be disturbed. But the stability of the attachment of antigen and antibodies is not limited by anything.

Chemical protection consists in the binding of various toxins by protein molecules, that is, in ensuring the detoxification of the body. The most important role in the detoxification of our body is played by liver enzymes that break down poisons or convert them into a soluble form. Dissolved toxins quickly leave the body.

Regulatory function

Signal function

Cytokines, proteins-hormones perform a signaling function.
Hormones are carried in the blood. The receptor, when bound to a hormone, triggers a response in the cell. Thanks to hormones, the concentration of substances in blood cells is regulated, as well as the regulation of cell growth and reproduction. An example of such proteins is the well-known insulin, which regulates the concentration of glucose in the blood.

Cytokines are small peptide messenger molecules. They act as regulators of interaction between different cells, and also determine the survival of these cells, inhibit or stimulate their growth and functional activity. Without cytokines, the coordinated work of the nervous, endocrine and immune systems is impossible. For example, cytokines can cause tumor necrosis - that is, suppression of the growth and vital activity of inflammatory cells.

transport function

Spare (or back-up) function

Receptor function of proteins

Motor (or motor) function

Proteins in metabolism

Those amino acids that are not synthesized by the body are called essential, therefore, they can only come to us from the outside.

A person receives amino acids from those proteins that are contained in food. Proteins undergo denaturation during digestion under the action of acidic gastric juices and enzymes. Some of the amino acids obtained as a result of the digestive process are used to synthesize the necessary proteins, and the rest of them are converted into glucose during gluconeogenesis or are used in the Krebs cycle (this is a metabolic breakdown process).

The use of proteins as an energy source is especially important in unfavorable conditions, when the body uses the internal "untouchable reserve" - ​​its own proteins. Amino acids are also an important source of nitrogen for the body.

common norms daily requirement not in proteins. The microflora that inhabits the large intestine also synthesizes amino acids, and they cannot be taken into account when compiling protein norms.

The reserves of proteins in the human body are minimal, and new proteins can only be synthesized from decaying proteins coming from body tissues and from amino acids coming with food. Of those substances that are part of fats and carbohydrates, proteins are not synthesized.

Protein deficiency
The lack of protein substances in the diet causes a strong slowdown in growth and development in children. For adults, protein deficiency is dangerous due to the appearance of deep changes in the liver, changes in hormonal levels, impaired functioning of the endocrine glands, impaired absorption of nutrients, impaired memory and performance, and heart problems. All these negative phenomena are due to the fact that proteins are involved in almost all processes of the human body.

In the 70s of the last century, fatal cases were recorded in people who had been following a low-calorie diet with a pronounced protein deficiency for a long time. As a rule, the immediate cause of death in this case was irreversible changes in the heart muscle.

Protein deficiency reduces the resistance of the immune system to infections, as the level of antibody formation decreases. Violation of the synthesis of interferon and lysozyme (protective factors) causes an exacerbation of inflammatory processes. In addition, protein deficiency is often accompanied by a lack of vitamins, which in turn also leads to adverse consequences.

Deficiency affects the production of enzymes and the absorption of important nutrients. It should not be forgotten that hormones are protein formations, therefore, a lack of proteins can lead to severe hormonal disorders.

Any activity of a physical nature harms muscle cells, and the greater the load, the more the muscles suffer. To repair damaged muscle cells, you need a large amount of high-quality protein. Contrary to popular belief, physical activity is only beneficial when enough protein is supplied to the body with food. With intense physical activity protein intake should reach 1.5 - 2 grams per kilogram of weight.

Excess protein

But if a person does not play sports, and at the same time consumes more than 1.75 grams of protein per kilogram of weight, then an excess of protein accumulates in the liver, which is converted into nitrogenous compounds and glucose. The nitrogenous compound (urea) must be excreted by the kidneys from the body without fail.

In addition, with an excess of protein, an acidic reaction of the body occurs, which leads to a loss of calcium due to a change in the drinking regimen. In addition, protein-rich meat foods often contain purines, some of which are deposited in the joints during metabolism and cause the development of gout. It should be noted that disorders associated with excess protein are much less common than disorders associated with protein deficiency.

An assessment of a sufficient amount of protein in the diet is carried out according to the state of nitrogen balance. In the body, the synthesis of new proteins and the release of the end products of protein metabolism are constantly taking place. The composition of proteins includes nitrogen, which is not contained in either fats or carbohydrates. And if nitrogen is deposited in the body in reserve, it is exclusively in the composition of proteins. With protein breakdown, it should stand out along with the urine. In order for the functioning of the body to be carried out at the desired level, it is necessary to replenish the removed nitrogen. Nitrogen balance means that the amount of nitrogen consumed matches the amount excreted from the body.

Protein nutrition

These products are a high-quality source of protein, but you need to remember that they contain a lot of fat, so it is undesirable to abuse their frequency in the diet. In addition to a large amount of protein, an excessive amount of fat will also enter the body.

Preferred high-protein foods: soy cheeses, low-fat cheeses, lean veal, egg whites, low-fat cottage cheese, fresh fish and seafood, lamb, chicken, white meat.
Less preferred foods include: milk and yoghurts with added sugar, red meat (tenderloin), dark chicken and turkey meat, low-fat cuts, homemade cottage cheese, processed meat in the form of bacon, salami, ham.

Egg white is a pure protein with no fat. IN lean meat contains about 50% of kilocalories attributable to proteins; in products containing starch - 15%; in skim milk - 40%; in vegetables - 30%.

The main rule when choosing a protein food is as follows: large quantity protein per calorie unit and a high protein digestibility ratio. It is best to consume foods that are low in fat and high in protein. Calorie data can be found on the packaging of any product. Generalized data on the content of proteins and fats in those products whose calorie content is difficult to calculate can be found in special tables.

Heat-treated proteins are easier to digest, as they become readily available for the action of digestive tract enzymes. However, heat treatment can reduce the biological value of the protein due to the fact that some amino acids are destroyed.

The content of proteins and fats in some foods

Protein metabolism

The body can spend about 15% of the total caloric content of the diet on the assimilation of food.
Food with a high protein content, in the process of metabolism, contributes to increased heat production. Body temperature slightly increases, which leads to additional energy consumption for the process of thermogenesis.

Proteins are not always used as an energy substance. This is due to the fact that their use as an energy source for the body can be unprofitable, because from a certain amount of fats and carbohydrates you can get much more calories and much more efficiently than from a similar amount of protein. In addition, there is rarely an excess of proteins in the body, and if there is, then most of the excess proteins go to carry out plastic functions.

In the event that the diet lacks energy sources in the form of fats and carbohydrates, the body is taken to use the accumulated fats.

A sufficient amount of protein in the diet helps to activate and normalize a slow metabolism in those people who are obese, and also allows you to maintain muscle mass.

If there is not enough protein, the body switches to using muscle proteins. This is because the muscles are not so important for the maintenance of the body. Most of the calories are burned in muscle fibers, and a decrease muscle mass lowers the energy costs of the body.

Very often, people who follow various diets for weight loss choose a diet in which very little protein enters the body with food. As a rule, these are vegetables or fruit diets. In addition to harm, such a diet will not bring anything. The functioning of organs and systems with a lack of proteins is inhibited, which causes various disorders and diseases. Each diet should be considered in terms of the body's need for protein.

Processes such as the absorption of proteins and their use in energy needs, as well as the excretion of products of protein metabolism, require more fluid. In order not to get dehydrated, you need to take about 2 liters of water per day.

Regulatory functions

The regulatory functions of the psyche are aimed at coordinating internal mental processes, managing interaction with objects of the outside world, and establishing relationships with people around a person.

Coordination of internal mental processes is carried out on the basis of unconditioned reflexes, the mechanism of which is innate and, therefore, determined biogenetically. It manifests itself in patterns of instinctive reactions. For example, blinking, constriction or dilation of the pupils, involuntary withdrawal of the hand, etc.

Management of interaction with objects of the external world occurs according to the laws of the dynamics of conditioned reflexes and orienting-research activity in the space of one's being. For example, by the smell of food, you determine the usefulness or harmfulness of eating, by the signal of a traffic light, you stop or cross the street.

Establishing relationships with other people occurs according to the laws of psychological, socio-psychological and social activity. For example, we choose a partner for joint activities who suits us according to specific qualities of his personality.

In all cases, regulatory functions are manifested in bodily movements directed at some object, which are transformed into objective actions, deeds and behavior of a person.

The regulatory functions of the psyche in human relations are manifested through human actions, which always contain a moral component of social behavior. The mechanisms of such behavior are contained in special rules and symbols of social life (rituals, customs, traditions, laws).

The regulation of objective actions and deeds requires a significant volitional effort from a person. Therefore, the will becomes the basic process of the regulatory functions of the psyche. Assimilation of the regulatory functions of the psyche occurs in volitional qualities. Will is the core component structural organization personality. For example, personality disintegration is associated with its weakening (aboulia), which is noted in the clinical practice of mental disorders.

Imlicit functions of the psyche are derived from the nervous activity of the brain. Therefore, they are inherent in the human body and stem from the morphological features of the brain and the patterns of higher nervous activity that the brain carries out. This dependence of mental activity on the activity of the brain is expressed by the formula "the psyche is a function of the brain."

Explicit functions of the psyche

psyche human implicit explicit

A person, thanks to his consciousness, is capable of arbitrary actions, deeds and initiative activities that follow from his subjective activity. Consequently, he himself, at his own discretion, uses his mental potential in the processes of interaction with the outside world. As a result, a person himself transforms his internal mental reserve through the processes of external interaction. This leads to new forms of relations with the reality surrounding him, in which implicit functions are transformed into a number of external (explicit) functions of the psyche: communicative, informational, cognitive, emotive, conative, creative. They reveal the mental potential of a person as a subject of subject-practical and social-labor activities.

In this activity, a person not only transforms his environment, but at the same time his own psychology. In this sense, we can say that the psyche is not only a function of the brain, but also the result of external subjective activity that a person manifests at his own will. This means the dependence of the individual mental development on the person himself, on how successfully he realizes in his life the potential of explicit mental functions.

All six explicit functions of the psyche in the processes of human interaction with the outside world (things and people) are transformed into psychological, socio-psychological, social phenomena of individual, group and social psychology, which is assimilated into the personal organization of a person in the form of roles and psychological qualities.

There are several types of protective functions of proteins:

Physical protection. Collagen takes part in it - a protein that forms the basis of the intercellular substance of connective tissues (including bones, cartilage, tendons and deep layers of the skin) dermis); keratin, which forms the basis of horny shields, hair, feathers, horns, and other derivatives of the epidermis. Usually such proteins are considered as proteins with structural function. Examples of this group of proteins are fibrinogens and thrombins involved in blood clotting.

Chemical protection. The binding of toxins to protein molecules can ensure their detoxification. A particularly important role in detoxification in humans is played by liver enzymes that break down poisons or convert them into a soluble form, which contributes to their rapid elimination from the body.

Immune protection. Proteins that make up the blood and other biological fluids are involved in the body's defense response to both damage and attack by pathogens. Proteins of the complement system and antibodies (immunoglobulins) belong to the proteins of the second group; they neutralize bacteria, viruses or foreign proteins. Antibodies, which are part of the adaptive immune system, attach to substances, antigens, foreign to a given organism, and thereby neutralize them, directing them to the places of destruction. Antibodies can be secreted into the intercellular space or become attached to the membranes of specialized B-lymphocytes called plasma cells. While enzymes have a limited affinity for a substrate, since attachment to a substrate that is too strong can interfere with the catalyzed reaction, the persistence of attachment of antibodies to an antigen is not limited in any way.

Regulatory function

Many processes inside cells are regulated by protein molecules, which serve neither as a source of energy nor as a building material for the cell. These proteins regulate transcription, translation, splicing, as well as the activity of other proteins, etc. The regulatory function of proteins is carried out either due to enzymatic activity (for example, protein kinase), or due to specific binding to other molecules, which, as a rule, affects the interaction with these molecules. enzymes.

Thus, gene transcription is determined by the attachment of transcription factors - activator proteins and repressor proteins to the regulatory sequences of genes. At the level of translation, the reading of many mRNAs is also regulated by the addition of protein factors; the degradation of RNA and proteins is also carried out by specialized protein complexes. The most important role in the regulation of intracellular processes is played by protein kinases - enzymes that activate or inhibit the activity of other proteins by attaching phosphate groups to them.

Signal function

The signaling function of proteins is the ability of proteins to serve as signaling substances, transmitting signals between tissues, cells or organisms. The signaling function is often combined with the regulatory function, since many intracellular regulatory proteins also carry out signal transduction.

The signal function is performed by hormone proteins, cytokines, growth factors, etc.

Hormones are carried in the blood. Most animal hormones are proteins or peptides. The binding of the hormone to the receptor is a signal that triggers a response in the cell. Hormones regulate the concentration of substances in the blood and cells, growth, reproduction and other processes. An example of such proteins is insulin, which regulates the concentration of glucose in the blood.

Cells can communicate with each other at a short distance using signaling proteins transmitted through the intercellular substance. Such proteins include, for example, cytokines and growth factors.

Cytokines are small peptide information molecules. They regulate interactions between cells, determine their survival, stimulate or suppress growth, differentiation, functional activity and apoptosis, and ensure the coordination of actions of the immune, endocrine and nervous systems. An example of cytokines is tumor necrosis factor, which transmits inflammation signals between body cells.