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What are polypeptides and how are they obtained. What are peptides? Pancreatic molecules of polypeptide character

Polypeptides are proteins that have an increased condensation degree. They are widely distributed among organisms of both plant and animal origin. That is, here we are talking about components that are mandatory. They are extremely diverse, and there is no clear line between such substances and ordinary proteins. If we talk about the diversity of such substances, then it should be noted that when they are formed, at least 20 amino acids of the protenogenic type are involved in this process, and if we talk about the number of isomers, then they can be infinite.

That is why protein-type molecules have so many possibilities that are practically limitless when it comes to their multifunctionality. So, it is understandable why proteins are called the main of all life that is on Earth. Proteins are also called one of the most complex substances that nature has ever formed, and they are also very unique. Just like protein, proteins contribute to the active development of living organisms.

Speaking as specifically as possible, we are talking about substances that are biopolymers based on amino acids containing at least hundreds of amino acid type residues. Moreover, there is also a division here - there are substances that belong to a low molecular weight group, they include only a few tens of amino acid residues, there are also substances that belong to high molecular weight groups, they contain much more such residues. A polypeptide is a substance that is really very diverse in its structure and organization.

Groups of polypeptides

All these substances are conditionally divided into two groups, with such a division, the features of their structure are taken into account, which have a direct impact on their functionality:

  • The first group includes substances that differ in a typical protein structure, that is, this includes a chain of a linear type and directly amino acids. They are found in all living organisms, and substances with increased activity of the hormonal type are of the greatest interest here.
  • As for the second group, here are those compounds whose structure does not have the most typical features for proteins.

What is a polypeptide chain

The polypeptide chain is a protein structure that includes amino acids, all of which have a strong connection with peptide-type compounds. If we talk about the primary structure, then we are talking about the simplest level of the structure of a protein-type molecule. This organizational form is characterized by increased stability.

When peptide bonds begin to form in cells, the carboxyl-type group of one amino acid first of all activates, and only then does an active connection with another similar group begin. That is, polypeptide chains are characterized by constantly alternating fragments of such bonds. There are a number of specific factors that have a significant impact on the shape of the structure of the primary type, but their influence is not limited to this. There is an active influence on those organizations of such a chain that have the highest level.

If we talk about the features of such an organizational form, then they are as follows:

  • there is a regular alternation of structures belonging to the rigid type;
  • there are sections that have relative mobility, they have the ability to rotate around the bonds. It is features of this kind that affect how the polypeptide chain fits in space. Moreover, various organizational moments can be carried out with peptide chains under the influence of many factors. There may be detachment of one of the structures, when the peptides form into a separate group and are separated from one chain.

Protein structure of secondary type

Here we are talking about a variant of chain folding in such a way that an ordered structure is organized, this becomes possible due to hydrogen bonds between groups of peptides of one chain with the same groups of another chain. If we take into account the configuration of such a structure, then it can be:

  1. Spiral type, this name came about due to its peculiar shape.
  2. Layered-folded type.

If we talk about a helical group, then this is such a protein structure that is formed in the form of a helix, which is formed without going beyond one chain of the polypeptide type. If we talk about the appearance, then it is in many ways similar to the usual electric spiral, which is in a tile that runs on electricity.

As for the layered-folded structure, here the chain is distinguished by a bent configuration, its formation is carried out on the basis of hydrogen-type bonds, and here everything is limited to the limits of one section of a particular chain.


polypeptides, proteins

The biological role of proteins and polypeptides

Polypeptides and proteins are the basic substances of a living organism. "Life is a form of existence of protein bodies" (F. Engels). Their role in metabolism is unique, they perform all the main functions of metabolism:

1) Proteins - the plastic material of tissues;

2) Proteins are one of the three types of nutrients needed by the body;

3) Protein structures are key in the composition of enzymes - biochemical catalysts, "engines" of metabolism;

4) Hormones and substances that regulate the pathways of biochemical transformations are mainly polypeptides and proteins. Tissue receptors for hormones, bioregulators, and drugs are also protein structures.

Primary structure of polypeptides and proteins

Polypeptides and proteins are polymers consisting of amino acid residues linked by peptide bonds.

It is conventionally considered that polypeptides are polymers containing up to 100 amino acid residues, more than 100 residues are proteins. Oligopeptides are especially distinguished - up to 10 amino acid residues.

Polypeptides and proteins are formed as a result of polycondensation of α-amino acids:

Physico-chemical properties of polypeptides and proteins

Molecules of polypeptides and proteins contain ionogenic carboxyl and amino groups and, like amino acids, always carry an electric charge, the sign and value of which depends on the pH of the solution.

All polypeptides and proteins are characterized by a certain isoelectric point (pi) - the pH value at which the total charge of the molecule is zero.

If the pH of the solution below isoelectric point (pH< pI), то молекула в целом имеет positive charge.

If the pH of the solution above isoelectric point (pH > pI), then the molecule as a whole has negative charge.

If the numbers of carboxyl and amino groups in the molecule are the same, then the isoelectric point of the substance is in the region of neutral pH (pI = 7). This neutral polypeptides.

If carboxyl groups predominate in the molecule, then the isoelectric

the point is in the acid pH region (pI< 7). Это sour polypeptides.

If amino groups predominate in the molecule, then the isoelectric point is in the main pH range (pI > 7). This main polypeptides.

The solubility of polypeptides in water depends on their molecular weight.

Oligopeptides and low molecular weight polypeptides, like amino acids, are highly soluble in water.

High molecular weight proteins form colloidal solutions. Their solubility depends on pH (i.e., on the charge of the molecule). At the isoelectric point, the solubility of the protein is minimal and it precipitates. When acidified or alkalized, the molecules acquire a charge again and the precipitate dissolves.

Spatial structure of proteins and polypeptides

High-molecular polypeptides and proteins, in addition to the primary structure, have higher levels of spatial organization - secondary, tertiary and quaternary structures.

PEPTIDE GROUP

secondary structure

1) α-helix

The structure of the peptide group determines the spatial structure of the polypeptide chain.

L. Pauling (1950) showed by calculation that for the α-polypeptide chain one of the most probable is the structure of a right-handed α-helix. Soon this was experimentally confirmed by X-ray diffraction analysis:

Hydrogen bonds are formed between C=O of the 1st and N-H of the 5th amino acid residues, directed almost parallel to the axis of the helix, they hold the helix together. The side radicals R are located along the periphery of the helix.

2) β-pleated structure

In this type of secondary structure, polypeptide chains stretched one along the other form hydrogen bonds with each other:


Many proteins have a secondary structure with alternating fragments of α-helix and β-sheet structure.

Tertiary structure

The α-helix, being sufficiently extended, bends and folds into a ball. This occurs as a result of the interaction of side radicals sufficiently distant from each other. A globule is formed:

Types of interaction that form the tertiary structure

1) Hydrogen bonds

2) Ionic interaction

3) Hydrophobic interaction

4) Disulfide bonds

Quaternary structure

The quaternary structure is an aggregate of subunits - globules. It is formed by the same types of interaction as the tertiary structure:


Quaternary structure of protein Quaternary structure of hemoglobin

Some complex proteins have a quaternary structure - hemoglobin, some enzymes, etc.

LITERATURE:

Main

1. Tyukavkina N.A., Zurabyan S.E., Beloborodov V.L. etc. - Organic chemistry (special course), v. 2 - Bustard, M., 2008, p. 207-227.

2. Tyukavkina N.A., Baukov Yu.I. - Bioorganic chemistry - DROFA, M., 2007, p. 314-315, 345-369.

The human body is a very complex structure, which consists of a large number of cells. Each such cell contains a special type of protein. It is the building material of our body, and also performs other vital functions. Such a protein is called a "peptide".

Peptides are a type of chemical compounds that contain amino acid residues in their molecules.

The number of monomer units of amino acids in one such molecule reaches several tens. Amino acids are connected to each other through "peptide" bonds. This gave the name to the substances.

a brief description of

Peptides are the smallest units of protein molecules. As a rule, they are formed from 2-3 amino acids. There are also oligopeptides. They contain up to two dozen amino acids. After the number of links grows to fifty, the protein itself is formed.

Protein is not only the human body, but also the organisms of other living beings. More than a hundred years ago, scientists described a method that allows you to synthesize proteins in the laboratory. This process occurs due to living human cells, representatives of flora and fauna.

The characteristic properties of peptides and their effect on the human body depend on the following factors:

  • number of amino acid units;
  • sequences of compounds of amino acid residues;
  • secondary structure of peptides.

Today, more than 1500 varieties of these substances are known. Their influence on the human body has been studied at the proper level.

Peptide classification

According to the functions performed, they are divided into several types:

  • hormonal - this group includes prolactin and somatotropin. Produced by the pituitary gland and hypothalamus. Take part in the process of cellular regeneration;
  • neuropeptides - are produced in the central and peripheral nervous systems. Thanks to them, the main physiological processes of the body are carried out;

  • immunological - perform a protective function: prevent toxic effects on the human body;
  • bioregulators - control biological processes and regulate physiological activity.

In turn, bioregulators are divided into several types:

  • regulate the production of hormones;
  • regulate the process of digestion and appetite;
  • have analgesic properties;
  • regulate vascular tone and blood pressure.

There is another classification - according to the size of the molecules:

  • oligopeptides (contain up to 20 amino acid residues);
  • polypeptides (contain more than 20 amino acid residues). This characteristic makes it possible to classify polypeptides as complete proteins.

Impact on the human body

The mechanism of the influence of peptides on the body is well studied. Scientists were able to prove that they are able to regulate the vital processes of cells. It is also known that the rate of aging of the body directly depends on the level of peptides in it.

The functions they perform:

  • stimulate the process of hormone production, which enhances the processes of anabolism and is responsible for muscle growth;
  • eliminate inflammatory reactions;
  • accelerate the healing process of scratches and other skin damage;
  • regulate appetite;
  • improve skin condition by stimulating the production of elastin and collagen;

  • regulate the production of cholesterol;
  • strengthen bones and ligaments;
  • strengthen the immune system;
  • normalize sleep;
  • restore metabolic processes;
  • support the regeneration process;
  • have antioxidant properties.


What are peptides

Peptides and sports

Analyzing the benefits of amino acid chains for the body, we can conclude that they are very important for athletes. Previously used steroid drugs. But now they are banned and doping control will not allow an athlete to compete if there is even the slightest suspicion of using these medications.

Proteins and peptides are of great importance for a person involved in sports:

  • stimulate the process of synthesizing natural hormones (for example, testosterone);
  • contribute to the rapid recovery of muscles;
  • effectively eliminate disruptions in the body at the local level.

The last point needs more details. It is a well-known fact that drugs containing hormones have a detrimental effect on human health. And peptides, in turn, have a positive effect on the body. They direct their energy to a specific organ. This process is selective.

Another advantage of peptides is their relatively low price. They are not prohibited at the legislative level and are freely available. You should also pay attention to the fact that peptides do not leave traces in the body after their use. This allows you not to worry about possible problems before doping control.

If we talk about bodybuilding, then peptides play the following role:

  • control the level of appetite;
  • improve the quality of sleep;
  • normalize emotions;
  • increase libido;
  • strengthen the defenses of the immune system.

We can say that peptides are very important for a person who plays sports. They help to improve physical fitness, but at the same time do not harm the body, as other drugs do.

Peptides and cosmetology

In order to improve and rejuvenate the skin, some types of protein began to be added to cosmetics:

  • keratin;
  • collagen;
  • elastin.

Recently, peptides can also be found in the composition of caring cosmetics. This innovation appeared in cosmetology about 30 years ago.

Regulatory peptides have a direct effect on the ratio of the number of cells at different stages of their maturation. These chains of amino acids penetrate into the center of the nucleus. They simultaneously “monitor” and regulate important stages in the genetic program:

  • control the rate at which stem cells divide;
  • deliver an informative DNA base that regulates the process of cell maturation;
  • support the required number of receptors and enzymes at the cellular level.

Customer reviews of cosmetics with peptides indicate that it reduces the number of wrinkles, tightens and moisturizes the skin of the face, makes it brighter.

Such creams heal the skin from the inside, activate its protective functions, which stops the aging process. Increase skin tone. Facial features become clearer.

fat burning

Today, peptides are used not only in sports, but also for passive weight loss. They act as activity stimulants, which contributes to the effective burning of fat and the removal of excess fluid.

Peptides are natural dietary supplements and can be bought at pharmacies or sports nutrition stores. But before you decide to take such a step, you need to consult a doctor.

For fat burning, the most effective will be. They control appetite, in particular, regulate the amount of sweets consumed.

The peptide lowers the amount of the hunger hormone. The group of fat-burning peptides also includes ipamoneril, which slows down the aging process of the body, improves sleep and improves mood.

If you combine fat burning and active training, then you should pay attention to HGHFrag 176-191. Experienced athletes say that it is excellent for building muscle mass and speeds up the process of muscle recovery after a workout.

The main advantage of this method of losing weight is that the lost kilograms do not come back. Peptides do this much more effectively than any diet.

What foods contain peptides?

A person can remain healthy only when his cells perform their functions properly. To do this, you need to track the level of the necessary substances and replenish their stocks.

In case of a lack of peptides synthesized in the body, they can be replenished with the help of medicines and food. Scientists have proven that regular consumption of foods high in peptides prolongs life by 30%. But only under the condition of a complete rejection of bad habits and with a vision of a healthy lifestyle.

Products that contain a large amount of peptides:

  • milk and dairy products;
  • cereals and legumes;
  • fish and seafood (tuna and sardine);
  • sunflower seeds and soybeans;

  • chicken meat and eggs;
  • greenery;
  • radish.

There are no contraindications to the use of such food. It will be especially useful for the elderly. It is necessary to monitor the reaction of the body after a new product is introduced into the diet.

Side effect

There are cases when peptides have a slight negative effect on the human body. The main features may be:

  • manifestation of autoimmune diseases;
  • retention of excess fluid in the body;
  • a slight increase in blood pressure;

  • weakness;
  • loss of sensitivity of somatic cells;
  • the occurrence of tunnel syndrome.

But these signs are quite minor and do not require long-term treatment. Pass within 3-7 days.

For greater effectiveness, vitamins that support antioxidants and extracts can be used in combination with peptides. When used correctly, peptides can save a person from obesity, reduce the risk of pathologies of the cardiovascular system and diabetes.

Video: Peptides in sports

According to the peptide theory, the polypeptide chain is recognized as the basis of the structure of the protein molecule. This chain is built from several tens and sometimes hundreds of amino acid residues linked by peptide bonds.

Evidence. Synthesis of polypeptides.

Squirrels- high-molecular nitrogen-containing substances that are in cells, mainly in a colloidal state, that is, in a state characterized by extreme instability, the composition of which depends on the properties of the medium.

Mr proteins depends on the number of amino acids in the molecule.

Proteins are monomolecular compounds.

Cytochrome C - 104 amino acid residues, Mr is constant.

Binding of amino acids together

The first assumption about the structure of proteins in 1888 by Danilevsky with alkaline solutions of CuSO 4 all proteins give a blue-violet color. A similar reaction is given by peptones - a product of the breakdown of proteins by protolytic enzymes, similar gives biuret:, malonic acid diamide: There are similar connections: C=O;N-H

In proteins, an amide bond, which is formed due to the interaction of the carboxyl at the 1st amino acid and the amino group of another amino acid

and the proteins themselves are polypeptides

All efforts come together: protecting the amino group and activating the carboxyl group so that what is needed reacts:

    This is the Fischer synthesis of a polypeptide

2. Method of Bergman, Sievers, Curtius.

Zerves protection: benzyl ester of Cl - carbonic acid is used to protect amino groups.

Curtius activation:

it is necessary to remove the protection from the 1st amino acid.

The boundary between polypeptides and proteins is conventional. Proteins include polypeptides with a molecular weight of 6 thousand or more and the number of amino acid residues over 50. This principle of division is based on the ability to dialyze through natural membranes.

A protein molecule may consist of one or more polypeptide chains. Chains can be interconnected by covalent or non-covalent bonds. Proteins consisting of two or more polypeptide chains that are not linked by covalent bonds are called oligomeric and. Individual polypeptide chains in such proteins are called protomers; functionally active parts of the protein - subunits.

2Hemoglobin

HEMOGLOBIN - main. proteins breathe. cycle involved in the transfer of O2 from the respiratory organs to the tissues, and in the opposite direction - CO2. Found in erythrocytes. In the human body, 5-6 liters of blood, where ½ ~ 1/3 are erythrocytes, are in suspension in the blood plasma, which daily carries

Formed from reticulocytes.

Hemoglobin is a complex protein. The protein part is globin, the non-protein part is heme.

Globin consists of 4 pairwise identical polypeptide chains (α-2, β-2). One chain of 146β amino acid residues, the other of 141α.

Gemm - aromatic flat structure containing Fe, which is connected by 6 coordination bonds on one side with globin, on the other side with nitrogen atoms of heme pyrral rings, 1 with the nitrogen atom of histidine, 1 with an oxygen molecule.

Oxyhemoglobin \u003d hemoglobin + O2. Coordination bond with oxygen, iron valency does not change (II). Unstable. This bond is formed as a result of an increase in the partial pressure of oxygen in the lungs. At the same time, the trepical structure of the globin changes. It becomes comfortable to hold

Hemoglobin - carrier of protons and carbon dioxide. The binding of O2 to hemoglobin is affected by the pH of the medium and the concentration of CO 2 . The addition of CO 2 and H + to Hb reduces its ability to bind O2. In peripheral tissues, with a decrease in pH and an increase in CO 2 concentration, the affinity of Hb for O 2 decreases as CO 2 and protons are bound. In the pulmonary capillaries, CO 2 is released and the pH of the medium in the blood rises, therefore, the affinity of Hb to O 2 increases (Bohr effect).

Protons attach to histidine radicals at position 146 of the β-chain and to other histidines in the α-chain. CO 2 attaches to the ring α-amino group of each polypeptide chain. Hb can bind small molecules of CN and CO. It binds with carbon monoxide (II) more easily than with oxygen and carboxyhemoglobin is formed. Under the action of some toxic oxidizing agents (by transferring Fe 2+ → Fe 3+), Hb is oxidized to methemoglobin. The color of the blood changes to brown, it does not tolerate O2, with an increase in it, shortness of breath, easy fatigue, a sharp headache, vomiting, loss of consciousness, an enlarged liver, a gray-blue color of the mucous membranes and skin are observed. Oxidizers: nitro compound, org. nitro compound, amino compound (aniline, aminophenols, aminohydrozine and their derivatives: wax, paints), chlorates, naphthalene, phenones. Redox paints: methylene, blue.

Treatment . The introduction of antidotes - reducing agents: glucose, sulhydryl comp. (β - mercaptoethylalanine, oxygen compression (oxygen cushion)).

This may be a hereditary disease. Occurs if in one of the α chains of globin in position 58 instead of histidine is tyrosine. Tyrosine promotes the formation of a covalent bond instead of a coordinate one and the degree of oxidation of Fe 3+ is fixed

Humans have ~150 types of mutant hemoglobins. The anomaly occurs in 1 in 10,000 people.

Sickle cell anemia. This is a hereditary disease, under the influence of physical exertion there is shortness of breath, taxicardia, .. in the heart. The content of Hb in the blood decreases. Associated diseases occur (kidneys, heart, liver). Erythrocytes in the form of sickles. They become brittle and quickly fail, clog the capillaries. Passed on to children. If only 1 of the parents is sick, the child is a carrier (1%), and if homozygous, then 50% of red blood cells. In Africans, 20% are carriers.

Endemic disease of Africans - malaria, convenient for the virus only round => the main population died out. 8% of the Negro population are carriers of the gene. In the β-chain, in position 6, instead of glutamic acid (polar group), there is valine (non-polar group). Valine is a sticky area to which other sticky areas are attached → deformation of erythrocytes.