Like other biological macromolecules (polysaccharides, lipids and nucleic acids), proteins are essential components of all living organisms and play a decisive role in the life of the cell. Proteins carry out metabolic processes. They are part of intracellular structures - organelles and cytoskeleton, 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 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 such multifunctionality is lysyl-tRNA synthetase, an enzyme from the class of aminoacyl-tRNA synthetases, which not only attaches a lysine residue to tRNA, but also regulates the transcription of several genes. Proteins perform many functions due to their enzymatic activity. So, enzymes are the motor protein myosin, the regulatory proteins of protein kinase, the transport protein sodium-potassium adenosine triphosphatase, etc.
Molecular model of the urease enzyme of a bacterium Helicobacter pylori
The most well-known function of proteins in the body is the catalysis of 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: for example, the reaction catalyzed by the enzyme orotidine-5 "-phosphate decarboxylase proceeds 10 17 times faster than the non-catalyzed one (the half-reaction period for the decarboxylation of orotic acid is 78 million years without the enzyme and 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 usually consist of hundreds of amino acid residues, only a small part of them interact with the substrate, and even fewer - on average 3-4 amino acid residues, often located far apart in the primary structure - are directly involved in catalysis. . 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 have the ending - aza and be formed from the names of 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:
More: 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: actin and tubulin monomers, for example, are globular, soluble proteins, but after polymerization they form long filaments that make up the cytoskeleton, enabling 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.
More: Protective function of proteins
There are several types of protective functions of proteins:
More: 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 as a building material for the cell. These proteins regulate cell progression 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 kinases), or due to specific binding to other molecules. Thus, transcription factors, activator proteins and repressor proteins, can regulate the intensity of gene transcription by binding to their regulatory sequences. At the level of translation, the reading of many mRNAs is also regulated by the addition of protein factors.
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.
More: 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 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 proteins-hormones, 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, 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.
More: 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 lungs, and besides this, homologous proteins 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.
These proteins include the so-called reserve proteins, which are stored as a source of energy and substances 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.
More: Cell receptor
Protein receptors can be located both in the cytoplasm and embedded in the cell membrane. One part of the receptor molecule receives a signal, 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 specific 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.
A whole class of motor proteins provides body movements, for example, muscle contraction, including locomotion (myosin), cell movement within the body (for example, amoeboid movement of leukocytes), movement of cilia and flagella, and in addition, 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.
in the functioning of the human body became clear in early XIX 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 striking example is 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, potatoes, white cabbage, beets, cabbage, legumes, bread contain 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, due to personal beliefs (vegetarianism) or for health reasons (problems with the gastrointestinal tract and dietary nutrition), you have a dietary restriction, 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.
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) 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, digestive or metabolic enzymes secreted after slaughter 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.
V modern science protein research 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.
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.
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.
According to the chemical nature of complex proteins, five classes are distinguished:
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.
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.
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.
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.
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.
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, suppress 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.
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 adverse conditions when the body uses the internal "emergency reserve" - its own proteins. Amino acids are also an important source of nitrogen for the body.
There are no uniform norms for the daily requirement for 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 exertion, protein intake should reach 1.5 - 2 grams per kilogram of weight.
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.
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 meats.
Less preferred foods include: milk and yogurt 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. Lean meat contains about 50% of the kilocalories that come from protein; in products containing starch - 15%; in skim milk - 40%; in vegetables - 30%.
The main rule when choosing a protein diet is as follows: more 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
| Products | Proteins, grams | Fat, grams |
| Chicken | 20,8 | 8,9 |
| Heart | 15 | 3 |
| Lean pork | 16,3 | 27,8 |
| Beef | 18,9 | 12,3 |
| Veal | 19,7 | 1,2 |
| Doctor's boiled sausage | 13,7 | 22,9 |
| Diet boiled sausage | 12,2 | 13,5 |
| Pollock | 15,8 | 0,7 |
| Herring | 17,7 | 19,6 |
| Sturgeon caviar granular | 28,6 | 9,8 |
| Wheat bread from flour I grade | 7,6 | 2,3 |
| Rye bread | 4,5 | 0,8 |
| Sweet pastries | 7,2 | 4,3 |
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 helps 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 vegetable 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.
Proteins are the basis of all living organisms. It is these substances that act as a component of cell membranes, organelles, cartilage, tendons and horns. However, the protective function of proteins is one of the most important.
Along with lipids, carbohydrates and nucleic acids, proteins are organic substances that form the basis of living beings. All of them are natural biopolymers. These substances are composed of repeatedly repeating structural units. They are called monomers. For proteins, such structural units are amino acids. Connecting in chains, they form a large macromolecule.
A chain of twenty amino acids can form various structures. These are the levels of spatial organization or conformation represented by a chain of amino acids. When it twists into a spiral, a secondary occurs. The tertiary structure arises when the previous conformation is twisted into a coil or globule. But the next structure is the most complex - Quaternary. It consists of several globules.
If the quaternary structure is destroyed to the primary, namely to the chain of amino acids, then a process called denaturation occurs. He's reversible. The chain of amino acids is able to form more complex structures again. But when destruction occurs, i.e. the destruction of the primary can no longer be restored. Such a process is irreversible. Destruction was carried out by each of us when we thermally processed products consisting of protein - chicken eggs, fish, meat.
Protein molecules are very versatile. This causes a wide range of their capabilities, which are determined by the functions of proteins (the table contains necessary information) are a necessary condition for the existence of living organisms.
| Protein function | The meaning and essence of the process | The name of the proteins that perform the function |
Construction (structural) | Protein is a building material for all body structures: from cell membranes to muscles and ligaments. | collagen, fibroin |
| Energy | During the breakdown of proteins, the energy necessary for the implementation of the vital processes of the body is released (1 g of protein - 17.2 kJ of energy). | Prolamine |
| Signal | Protein compounds of cell membranes are able to recognize specific substances from the environment. | Glycoproteins |
| Contractile | Ensuring physical activity. | actin, myosin |
| Reserve | Supply of nutrients. | seed endosperm |
| Transport | Ensuring gas exchange. | Hemoglobin |
| Regulatory | Regulation of chemical and physiological processes in the body. | Protein hormones |
| catalytic | Acceleration of chemical reactions. | Enzymes (enzymes) |
As you can see, the functions of proteins are very diverse and important in their meaning. But we haven't mentioned one more of them. The protective function of proteins in the body is to prevent the penetration of foreign substances that can cause significant harm to the body. If this happens, specialized proteins are able to neutralize them. These defenders are called antibodies or immunoglobulins.
With every breath, pathogenic bacteria and viruses enter our body. They enter the blood, where they begin to multiply actively. However, a significant obstacle stands in their way. These are plasma proteins - immunoglobulins or antibodies. They are specialized and are characterized by the ability to recognize and neutralize substances and structures alien to the body. They are called antigens. This is how the protective function of proteins is manifested. Examples of it can be continued with information about interferon. This protein is also specialized and recognizes viruses. This substance is even the basis of many immunostimulating drugs.
Thanks to the presence protective proteins the body is able to resist pathogenic particles, i.e. he develops immunity. It can be congenital and acquired. All organisms are endowed with the first from the moment of birth, thanks to which life is possible. And the acquired appears after the transfer of various infectious diseases.
Proteins perform a protective function, directly protecting cells and the entire body from mechanical influences. For example, crustaceans play the role of a shell, reliably protecting all contents. Bones, muscles and cartilage form the basis of the body, and not only prevent damage to soft tissues and organs, but also ensure its movement in space.
The process of blood coagulation is also a protective function of proteins. It is possible due to the presence of specialized cells - platelets. When blood vessels are damaged, they collapse. As a result of plasma fibrinogen is converted into its insoluble form - fibrin. This is a complex enzymatic process, as a result of which fibrin strands very often intertwine and form a dense network that prevents blood from flowing out. In other words, a blood clot or thrombus forms. This is a protective reaction of the body. In normal life, this process lasts a maximum of ten minutes. But with - hemophilia, which affects mainly men, a person can die even with a minor injury.
However, if clots form inside a blood vessel, it can be very dangerous. In some cases, this even leads to a violation of its integrity and internal hemorrhage. In this case, drugs are recommended, on the contrary, thinning the blood.
The protective function of proteins is also manifested in the chemical fight against pathogenic substances. And it starts in the mouth. Once in it, food causes reflex salivation. The basis of this substance is water, enzymes that break down polysaccharides and lysozyme. It is the latter substance that neutralizes harmful molecules, protecting the body from their further effects. It is also found in the mucous membranes of the gastrointestinal tract, and in the lacrimal fluid that washes the cornea of the eye. In large quantities, lysozyme is found in breast milk, nasopharyngeal mucus and the protein of chicken eggs.
So, the protective function of proteins is manifested primarily in the neutralization of bacterial and viral particles in the blood of the body. As a result, he develops the ability to resist disease-causing agents. It is called immunity. Proteins, which are part of the external and internal skeleton, protect the internal contents from mechanical damage. And the protein substances found in saliva and other media prevent the action of chemical agents on the body. In other words, the protective function of proteins is to provide the necessary conditions for all life processes.
Proteins are the building material of the body and are involved in the metabolic process. The functions of proteins in the body are of great importance for the maintenance of life.
Proteins - biopolymers, consisting of individual links - monomers, which are called amino acids. They consist of a carboxyl (-COOH), amine (-NH2) group and a radical. Amino acids are linked together by a peptide bond (-C(O)NH-), forming a long chain.
Mandatory chemical elements of amino acids:
Rice. 1. The structure of the protein.
The radical may include sulfur and other elements. Proteins differ not only in the radical, but also in the number of carboxyl and amine groups. Concerning There are three types of amino acids:
In accordance with the possibility of being synthesized inside the body, they secrete two types of amino acids:
TOP 2 articleswho read along with this
About 200 amino acids are known. However, only 20 are involved in building proteins.
Protein biosynthesis occurs on the ribosomes of the endoplasmic reticulum. It's a complicated process consisting of two stages:
Synthesis of the polypeptide network occurs with the help of messenger and transfer RNA. This process is called translation. The second stage includes "work on the mistakes." Parts of the synthesized protein are replaced, removed, or lengthened.
Rice. 2. Protein synthesis.
The biological functions of proteins are presented in the table.
|
Function |
Description |
Examples |
|
Transport |
Carry chemicals to and from cells |
Hemoglobin carries oxygen and carbon dioxide, transcortin is an adrenal hormone in the blood |
|
Motor |
Helps to contract the muscles of multicellular animals |
actin, myosin |
|
Structural |
Provide strength to tissues and cellular structures |
Collagen, fibroin, lipoproteins |
|
Construction |
Participate in the formation of tissues, membranes, cell walls. Make up muscles, hair, tendons |
Elastin, keratin |
|
Signal |
Transfer information between cells, tissues, organs |
Cytokines |
|
enzymatic or catalytic |
Most enzymes in the body of animals and humans are of protein origin. They are a catalyst for many biochemical reactions (accelerate or slow down) |
Enzymes |
|
Regulatory or hormonal |
Hormones of protein origin control and regulate metabolic processes |
Insulin, lutropin, thyrotropin |
|
Gene-regulatory |
Regulate the functions of nucleic acids in the transfer of genetic information |
Histones regulate DNA replication and transcription |
|
Energy |
Used as an additional source of energy. The decay of 1 g releases 17.6 kJ |
Break down after exhaustion of other energy sources - carbohydrates and fats |
|
Protective |
Specific proteins - antibodies - protect the body from infection by destroying foreign particles. Special proteins clot blood to stop bleeding |
Immunoglobulins, fibrinogen, thrombin |
|
Reserve |
Stored to feed cells. Retain substances needed by the body |
Ferritin retains iron, casein, gluten, albumin are stored in the body |
|
Receptor |
Hold various regulators (hormones, mediators) on the surface or inside the cell |
Glucagon receptor, protein kinase |
Proteins can have a poisoning and neutralizing effect. For example, the botulism bacillus secretes a toxin of protein origin, and albumin protein binds heavy metals.
It is worth saying briefly about the catalytic function of proteins. Enzymes or enzymes are isolated into a special group of proteins. They carry out catalysis - the acceleration of a chemical reaction.
According to the structure, enzymes can be:
Enzyme molecules have an active part (active center) that binds a protein to a substance - a substrate. Each enzyme "recognizes" a certain substrate and binds to it. The active site is usually a "pocket" into which the substrate enters.
The binding of the active site and the substrate is described by the model of induced correspondence ("hand-glove" model). The model shows that the enzyme "adjusts" to the substrate. Due to the change in structure, the energy and resistance of the substrate are reduced, which helps the enzyme to more easily transfer it to the product.
Rice. 3. Model "hand-glove".
Enzyme activity depends on several factors:
There are 6 classes of enzymes, each of which interacts with certain substances. For example, transferases transfer a phosphate group from one substance to another.
Enzymes can speed up a reaction 1000 times.
We found out what functions proteins perform in the cell, how they are arranged and how they are synthesized. Proteins are polymer chains made up of amino acids. A total of 200 amino acids are known, but proteins can form only 20. Protein polymers are synthesized on ribosomes. Proteins perform important functions in the body: they carry substances, accelerate biochemical reactions, and control the processes occurring in the body. Enzymes bind the substrate and purposefully transfer it to substances, speeding up reactions by 100-1000 times.
Average rating: 4.6. Total ratings received: 289.
| Parameter name | Meaning |
| Article subject: | Protective function |
| Rubric (thematic category) | cooking |
Allows content to slide from top to bottom
BIBLIOGRAPHY
CONCLUSIONS
Τᴀᴋᴎᴍ ᴏϬᴩᴀᴈᴏᴍ, the main personal qualities of an entrepreneur are: independence; ambition; persistence; diligence; durability. The presence of such personality traits is one of the essential conditions success.
In addition to the actual personal qualities, an entrepreneur must have a set of specific knowledge, skills and abilities in the area in which he works. It is clear that in order to successfully financial transactions an entrepreneur needs at least a minimum set of knowledge in the financial and credit area and accounting, and a person who decides to organize the production of furniture must have a minimum technical education. However, these limitations are not definitive. It often happened that the entrepreneur received special knowledge and skills already during the development of his business, and at its first stages he acted either intuitively or with the help of involved specialists. The main thing here is the desire to learn and improve one's qualifications in order to improve one's business, and such a desire refers to personal qualities (curiosity, perseverance, ambition).
The study of the personality of an entrepreneur with the help of psychological tests not only helps to clarify certain aspects of his personality, but also shows in which direction he should work on himself in order to increase the efficiency of his entrepreneurial activity.
Akperov I. G., Maslikova Zh. V. Psychology of entrepreneurship. - M: Finance and statistics, 2003.
Zavyalova E.K., Posokhova S.T. Entrepreneurship Psychology: Textbook. - St. Petersburg: Ed. St. Petersburg State University, 2004.
Meneghetti A. Psychology of a leader. - M., 2001. - S. 15.
Platonov K.K. Structure and development of personality. - M.: Nauka, 1986. S. 24.
Entrepreneurship: Textbook / Ed. M. L. Lapusty. - M.: INFRA-M, 2003.
Steven J. Train Your Dragons. - St. Petersburg: Peter-press, 1996.
Shcherbatykh Yu.V. Psychology of Entrepreneurship and Business: Textbook. - St. Petersburg: Peter, 2008. S. 45.
Shcherbatykh Yu. V. Psychology of success. - M.: Eksmo, 2005.
The mucosa is fairly smooth
Lubricated with mucus (produced by the mucous glands of the shell itself)
Mucus - envelops m / o, viscosity does not allow penetration into the bloodstream
Accumulation of lymphoid tissue - consists of lymphocytes of varying degrees of maturity. Lymphoid tissue forms clusters:
ü Tonsils - located at the very beginning of the digestive and respiratory tubes:
o Palatine tonsils - on both sides of the pharynx
o Lingual - in the region of the root of the tongue
o Pharyngeal tonsil - m / at the upper and rear wall of the nasopharynx (vault) under the tuberculum faringeum
o Tubal tonsils - near the pharyngeal opening of the auditory tube
ü Single follicles - located throughout the pt, their total weight is about 2 kg;
ü Lymphoid plaques - contain dozens of lymphocytes, are present only in the ileum - Peyer's patches, their number is about 20-30
ü Vermiform appendix - its mucosa contains lymphoid tissue. This intestinal tonsil.
· Alternation of different media throughout the alimentary canal.
When weakened protective devices, reduced immunity!
- chemical processing of food- carried out by digestive juices, which are produced by the digestive glands. Throughout the p.t. there are glands:
By size:
Large
Major salivary glands (parotid, submandibular, sublingual)
Liver - produces bile that enters the duodenum
Pancreas - pancreatic juice, insulin.
Minor salivary glands (labial, buccal, palatine, lingual)
Gastric glands
Intestinal glands - in the mucosa of the small intestine
By localization:
In the thickness of the mucous membrane
Small salivary
Gastric
Glands of the jejunum and ileum of the small intestine
under the mucous layer
Gland 12 of the duodenum
Outside the digestive tube
All large glands
Chemical treatment in the oral cavity - with saliva, in the stomach - with gastric juice, 12 pcs - with bile, pancreatic juice. and iron itself 12pc, in the jejunum and ileum - under the influence of its own juices. Chemical processing ends in the small intestine. In the colon, fiber is broken down under the influence of microorganisms (m / o).
- absorption of nutrients- Nutrients are absorbed into the blood and lymphatic vessels. Absorption begins:
In the oral cavity (dr. Wed, alcohol)
Stomach (l / s, alcohol, nutrients)
The small intestine is the main absorption process
Large intestine - mostly water is absorbed
The small intestine is long, its mucosa has:
1. Circular folds, they increase the suction surface. On the border between the departments form valves
2. Villi - from 1.5 to 4 million, height 1mm, the wall is very thin.
3. Crypts - deepening of the mucosa
4. Epithelial cells have outgrowths - microvilli (up to 300 per cell).
Τᴀᴋᴎᴍ ᴏϬᴩᴀᴈᴏᴍ, mucosal area 1500 m2.
submucosal layer. Consists of loose connective tissue. Purpose:
Fixes the mucous membrane to the muscle;
Provides mobile fixation - the mucous membrane forms folds
Vessels and nerves pass
Muscular sheath. Formed by smooth muscle tissue. But around the oral cavity, the muscles of the pharynx, the upper third of the esophagus, the lower part of the rectum are striated.
The muscular layer of the digestive tube forms two layers:
Longitudinal - external)
shortens the alimentary canal
Straightens curves
Transverse (circular) - internal
Provides peristalsis - wavy narrowing of the intestinal lumen
Forms sphincters - local thickenings between the departments of the p.t. (esophagus - stomach, stomach - 12 pcs, small intestine - large intestine, in the lower part of the rectum).
Sphincters are strengthened by valves - against the sphincter, the mucous membrane forms a circular fold. In the mucous membrane under the valves there are venous plexuses.
Sphincter + Valve + Venous plexus = closing apparatus.
Purpose: prevention of premature emptying of the outgoing department; prevents content from being pushed back.
Only the stomach has three layers (+ oblique layer), as it acts as a reservoir and mixes food. Three layers also have a uterus, bladder, heart - the reservoir must be completely emptied.
Outer shell.
Connective tissue membrane - not in the abdominal cavity: pharynx, esophagus, rectum outside. Consists of a loose connective tissue sheath:
Fixes organs to bones
Connects organs to each other. There are no voids between organs, it is filled with loose connective tissue
Provides organ mobility - provides functional organ mobility
Vessels and nerves pass through it (in the adventitial layers)
The serous membrane is the organs of the abdominal cavity, formed by the peritoneum. The same purpose as the connection-woven sheath.
Protective function - concept and types. Classification and features of the category "Protective function" 2017, 2018.
