B amino acids. Which BCAA ratio is best? Maximizing Fat Burning

STRUCTURE AND PROPERTIES OF AMINO ACIDS INCLUDED IN PROTEINS. PEPTIDE BONDS CONNECTING AMINO ACIDS IN CHAINS

Proteins are polymer molecules in which amino acids serve as monomers. Only 20 α-amino acids are found in proteins in the human body. The same amino acids are present in proteins with different structures and functions. The individuality of protein molecules is determined by the order of alternation of amino acids in the protein. Amino acids can be considered as letters of the alphabet, with the help of which, as in a word, information is written. A word carries information, for example, about an object or action, and the sequence of amino acids in a protein carries information about the construction of the spatial structure and function of this protein.

A. Structure and properties of amino acids

1. General structural features of amino acids that make up proteins

A common structural feature of amino acids is the presence of amino and carboxyl groups connected to the same α-carbon atom. R - amino acid radical - in the simplest case it is represented by a hydrogen atom (glycine), but can have a more complex structure.

IN aqueous solutions at neutral pHα-amino acids exist as bipolar ions.

IN unlike 19 othersα-amino acids, proline is an imino acid, the radical of which is bonded to both the α-carbon atom and the amino group, as a result of which the molecule acquires a cyclic structure.

19 out of 20 amino acids contain an asymmetric carbon atom in the α-position, to which 4 different substituent groups are associated. As a result, these amino acids in nature can be found in two different isomeric forms - L and D. The exception is glycine, which does not have an asymmetric α-carbon atom, since its radical is represented only by a hydrogen atom. Proteins contain only L-isomers of amino acids.

Pure L- or D-stereoisomers can, over a long period of time, spontaneously and non-enzymatically transform into an equimolar mixture of L- and D-isomers. This process is called racemization. Racemization of each L-amino acid at a given temperature occurs at a certain rate. This circumstance can be used to determine the age of people and animals. Thus, hard tooth enamel contains the protein dentin, in which L-aspartate transforms into the D-isomer at human body temperature at a rate of 0.01% per year. During the period of tooth formation, dentin contains only the L-isomer, so the age of the subject can be calculated from the D-aspartate content.

All 20 amino acids in the human body differ in structure, size and physicochemical properties of the radicals attached to the α-carbon atom.

2. Classification of amino acids according to the chemical structure of radicals

According to their chemical structure, amino acids can be divided into aliphatic, aromatic and heterocyclic (Table 1-1).

Aliphatic radicals may contain functional groups that give them specific properties: carboxyl (-COOH), amino (-NH2), thiol

(-SH), amide (-CO-NH2), hydroxyl (-OH) and guanidine groups.

The names of amino acids can be constructed using substitutive nomenclature, but trivial names are usually used (Table 1-2).

Table 1-1. Classification of the main amino acids of proteins according to their chemical structure

Table 1-2. Examples of amino acid names according to substitution nomenclature and corresponding trivial names

Amino acid name	Amino acid formula	Trivial name
by substitution
nomenclature
2-amino-3-
hydroxypropanoic acid
		Methionine
methylthiobutyric acid

To write amino acid residues in peptide and protein molecules, three-letter abbreviations of their trivial names are used, and in some cases, one-letter symbols (see Table 1-1).

Trivial names often come from the name of the source from which they were first isolated, or from the properties of a given amino acid. Thus, serie was first isolated from silk fibroin (from the Latin serieum - silky), and glycine got its name because of its sweet taste (from the Greek glykos - sweet).

3. Classification of amino acids according to the solubility of their radicals in water

All 20 amino acids in the proteins of the human body can be grouped according to the ability of their radicals to dissolve in water. The radicals can be arranged in a continuous series, starting with completely hydrophobic ones and ending with strongly hydrophilic ones.

The solubility of amino acid radicals is determined by the polarity of the functional groups that make up the molecule (polar groups attract water, non-polar groups repel it).

Amino acids with non-polar radicals

Non-polar (hydrophobic) radicals include radicals having aliphatic hydrocarbon chains (alanine, valine, leucine, isoleucine, proline and methionine radicals) and aromatic rings (phenylalanine and tryptophan radicals). The radicals of such amino acids in water tend to each other or to other hydrophobic molecules, as a result of which the surface of their contact with water decreases.

Amino acids with polar uncharged radicals

The radicals of these amino acids are better soluble in water than hydrophobic radicals, since they contain polar functional groups that form hydrogen bonds with water. These include series, threonine and tyrosine, which have

hydroxyl groups, asparagine and glutamine containing amide groups, and cysteine ​​with its thiol group.

Cysteine ​​and tyrosine contain thiol and hydroxyl groups, respectively, capable of dissociation to form H+, but at a pH of about 7.0, maintained in cells, these groups practically do not dissociate.

Amino acids with polar negatively charged radicals

This group includes aspartic and glutamic amino acids, which have an additional carboxyl group in the radical, which dissociates at a pH of about 7.0 to form COO- and H+. Therefore, the radicals of these amino acids are anions. The ionized forms of glutamic and aspartic acids are called glutamate and aspartate, respectively.

Amino acids with polar positively charged radicals

Lysine and arginine have an additional positively charged group in the radical. In lysine, the second amino group, capable of attaching H+, is located in the?- position of the aliphatic chain, and in arginine, the huanidine group acquires a positive charge. In addition, histidine contains a weakly ionized imidazole group, therefore, with physiological fluctuations in pH values ​​(from 6.9 to 7.4) histidine is charged either neutrally or positively. With an increase in the number of protons in the medium, the imidazole group of histidine is able to attach a proton, acquiring a positive charge, and with an increase in the concentration of hydroxyl groups, it can donate a proton, losing the positive charge of the radical. Positively charged radicals are cations (see diagram below).

Polar charged radicals of amino acids have the greatest solubility in water.

4. Change in the total charge of amino acids depending on the pH of the environment

At neutral pH values, all acidic (capable of donating H+) and all basic (capable of adding H+) functional groups are in a dissociated state.

Therefore, in a neutral environment, amino acids containing a non-dissociating radical have a total charge of zero. Amino acids containing acidic functional groups have a total negative charge, and amino acids containing basic functional groups have a positive charge (Table 1-3).

A change in pH toward the acidic side (i.e., an increase in the H+ concentration in the medium) leads to suppression of the dissociation of acid groups. In a highly acidic environment, all amino acids acquire a positive charge.

On the contrary, an increase in the concentration of OH- groups causes the elimination of H+ from the main functional groups, which leads to a decrease in the positive charge. In a highly alkaline environment, all amino acids have a net negative charge.

5. Modified amino acids present in proteins

Only the 20 listed amino acids take part directly in the synthesis of proteins in the human body. However, some proteins contain non-standard modified amino acids - derivatives of one of these 20 amino acids. For example, the molecule of collagen (fibrillar protein of the intercellular matrix) contains hydroxy derivatives of lysine and proline - 5-hydroxylysine and 4-hydroxyproline.

Modifications of amino acid residues are already carried out in the composition of proteins, i.e. only

Modified amino acids found in proteins

after completion of their synthesis. The introduction of additional functional groups into the structure of amino acids gives proteins properties

Scheme. Structure of polar charged amino acids in dissociated form

Table 1-3. Change in the total charge of amino acids depending on the pH of the environment

necessary for them to perform specific functions. Thus, α-carboxyglutamic acid is part of the proteins involved in blood coagulation, and two closely located carboxyl groups in their structure are necessary for the binding of protein factors with Ca2+ ions. Impaired carboxylation of glutamate leads to decreased blood clotting.

6. Chemical reactions used to detect amino acids

The ability of amino acids to enter into certain chemical reactions is determined by the presence of functional groups in their composition. Since all amino acids that make up proteins contain amino and carboxyl groups at the α-carbon atom, they can enter into chemical reactions characteristic of all amino acids. The presence of any functional groups in the radicals of individual amino acids determines their ability to enter into reactions specific to these amino acids.

Ninhydrin reaction to α-amino acids

The ninhydrin reaction can be used to detect and quantify amino acids in solution.

This reaction is based on the fact that colorless ninhydrin, reacting with an amino acid, condenses in the form of a dimer through a nitrogen atom removed from the α-amino group of the amino acid. As a result, a red-violet pigment is formed. At the same time, decarboxylation of the amino acid occurs, which leads to the formation of CO2 and the corresponding aldehyde. The ninhydrin reaction is widely used in studying the primary structure of proteins (see diagram below).

Since the color intensity is proportional to the amount of amino acids in the solution, it is used to measure the concentration of α amino acids.

Ninhydrin reaction used to determine α amino acids

Specific reactions to individual amino acids

Qualitative and quantitative determination of individual amino acids is possible due to the presence of special functional groups in their radicals.

Arginine is determined using a qualitative reaction to the guanidine group (Sakaguchi reaction), and cysteine ​​is detected by the Foll reaction, specific to the SH group of a given amino acid. The presence of aromatic amino acids in a solution is determined by the xanthoprotein reaction (nitration reaction), and the presence of a hydroxyl group in the aromatic ring of tyrosine is determined by the Millon reaction.

B. Peptide bond. Structure and biological properties of peptides

α-Amino acids can be covalently linked to each other using peptide bonds. A peptide bond is formed between the α-carboxyl group of one amino acid and the α-amino group of another, i.e. is an amide bond. In this case, a water molecule is split off (see diagram A).

1. Peptide structure

The number of amino acids in peptides can vary greatly. Peptides containing up to 10 amino acids are called oligopeptides. Often the name of such molecules indicates the number of amino acids included in the oligopeptide: tripeptide, pentapeptide, ocgapeptide, etc.

Peptides containing more than 10 amino acids are called "polypeptides", and polypeptides consisting of more than 50 amino acid residues are usually called proteins. However, these names are conditional, since in the literature the term “protein” is often used to designate a polypeptide containing less than 50 amino acid residues. For example, the hormone glucagon, consisting of 29 amino acids, is called a protein hormone.

Monomers of amino acids that make up proteins are called "amino acid residues". An amino acid residue that has a free amino group is called N-terminal and is written on the left, and one that has a free?-carboxyl group is called C-terminal and is written on the right. Peptides are written and read from the N-terminus. A chain of repeating atoms in a polypeptide chain -NH-CH-CO- is called "peptide backbone"(see diagram B).

When naming a polypeptide, the suffix -yl is added to the abbreviated name of amino acid residues, with the exception of the C-terminal amino acid. For example, the tetrapeptide Ser-Gly-Pro-Ala is read as serylglycylprolylalanine.

The peptide bond formed by the imino group of proline differs from other peptide bonds because the nitrogen atom of the peptide group is not bonded to hydrogen, but to a radical.

Peptides differ in amino acid composition, number and order of amino acids.

Serylglycylprolylalanine

Scheme A. Dipeptide formation

Scheme B. Structure of peptides

Ser-Gis-Pro-Ala and Ala-Pro-Gis-Ser are two different peptides, despite the fact that they have the same quantitative and qualitative amino acid compositions.

2.Characteristics of peptide bond

The peptide bond has the characteristic of a partial double bond, so it is shorter than the other bonds of the peptide backbone and, as a result, has little mobility. The electronic structure of the peptide bond determines the flat, rigid structure of the peptide group. The planes of the peptide groups are located at an angle to each other (Fig. 1-1).

The bond between the α carbon atom and the α-amino group or α-carboxyl group is freely rotatable (although limited by the size and nature of the radicals), allowing the polypeptide chain to adopt different configurations.

Peptide bonds are usually located in the trans configuration, i.e. α-carbon atoms are located on opposite sides of the peptide bond. As a result, the side radicals of amino acids are located at the furthest distance from each other in space (Fig. 1-2).

Peptide bonds are very strong and do not spontaneously break under normal conditions existing in cells (neutral environment, body temperature). In laboratory conditions, the hydrolysis of protein peptide bonds is carried out in a sealed ampoule with concentrated (6 mol/l) hydrochloric acid, at a temperature of more than 105 ° C, and complete hydrolysis of the protein to free amino acids takes place in about a day.

In living organisms, peptide bonds in proteins are broken with the help of special proteolytic enzymes (from English, protein - protein, lysis - destruction), also called proteases, or peptide hydrolases.

To detect proteins and peptides in solution, as well as for their quantitative determination, the biuret reaction is used ( positive result for substances containing at least two peptide bonds).

3.Biological role of peptides

The human body produces many peptides that participate in the regulation of various biological processes and have high physiological activity.

Rice. 1-1. Planes of location of peptide groups and α-carbon atoms in space.

Rice. 1-2. Trans configuration of peptide bonds. Functional groups-CO- and -NH-,

forming peptide bonds, are not ionized, but are polar, and can participate in the formation of hydrogen bonds.

The number of amino acid residues in the structure of biologically active peptides can vary from 3 to 50. Some of the “smallest” peptides include thyrotropin-releasing hormone and glutathione (tripeptides), as well as enkephalins, which contain 5 amino acids. However, most biologically active peptides contain more than 10 amino acids, for example, neuropeptide Y (appetite regulator) contains 36 amino acids, and corticoliberin - 41 amino acids.

Some of the peptides, in particular most peptide hormones, contain peptide bonds formed by the α-amino group and the α-carboxyl group of neighboring amino acids. Typically, they are synthesized from inactive protein precursors in which specific proteolytic enzymes break down specific peptide bonds.

Angiotensin II is an octapeptide formed from the large plasma protein angiotensinogen as a result of the sequential action of two proteolytic enzymes.

The first proteolytic enzyme, renin, cleaves from angiotensinogen from the N-terminus a peptide containing 10 amino acids, called angiotensin I. The second proteolytic enzyme, carboxydipeptidyl peptidase, cleaves from the C-terminus

Lecture No. 1

TOPIC: "Amino acids".

Lecture outline:

1. Characteristics of amino acids

2. Peptides.

Characteristics of amino acids.

Amino acids are organic compounds, derivatives of hydrocarbons, the molecules of which include carboxyl and amino groups.

Proteins consist of amino acid residues connected by peptide bonds. To analyze the amino acid composition, protein hydrolysis is carried out followed by the isolation of amino acids. Let's consider the basic patterns characteristic of amino acids in proteins.

It has now been established that proteins contain a constantly occurring set of amino acids. There are 18 of them. In addition to those indicated, 2 more amino acid amides were discovered - asparagine and glutamine. They all got the name major(frequently occurring) amino acids. They are often figuratively called "magical" amino acids. In addition to major amino acids, there are also rare ones, those that are not often found in natural proteins. They are called minor.

Almost all protein amino acids belong to α – amino acids(the amino group is located at the first carbon atom after the carboxyl group). Based on the above, for most amino acids the general formula is valid:

N.H. 2 -CH-COOH

Where R are radicals with different structures.

Let's look at the formulas of protein amino acids, table. 2.

All α - amino acids, except aminoacetic (glycine), have an asymmetric α - carbon atom and exist in the form of two enantiomers. With rare exceptions, natural amino acids belong to the L series. Amino acids of the D genetic series were found only in the cell walls of bacteria and in antibiotics.

The rotation angle is 20-30 0 degrees. Rotation can be right (7 amino acids) or left (10 amino acids).

H― *―NH 2 H 2 N―*―H

D - configuration L-configuration

(natural amino acids)

Depending on the predominance of amino or carboxyl groups, amino acids are divided into 3 subclasses: Acidic amino acids.

Carboxyl (acidic) groups predominate over amino groups (basic), for example, aspartic, glutamic acids. Neutral amino acids

The number of groups is equal. Glycine, alanine, etc. Basic amino acids.

In terms of physical and a number of chemical properties, amino acids differ sharply from the corresponding acids and bases. They dissolve better in water than in organic solvents; crystallize well; have high density and exceptionally high melting points. These properties indicate the interaction of amine and acid groups, as a result of which amino acids in the solid state and in solution (over a wide pH range) are in zwitterionic form (i.e., as internal salts). The mutual influence of groups is especially pronounced in α - amino acids, where both groups are in close proximity.

H 2 N - CH 2 COOH ↔ H 3 N + - CH 2 COO -

zwitterion

The zwitter ionic structure of amino acids is confirmed by their large dipole moment (at least 5010 -30 C  m), as well as the absorption band in the IR spectrum of a solid amino acid or its solution.

Amino acids are capable of entering into polycondensation reactions, leading to the formation of polypeptides of different lengths, which constitute the primary structure of the protein molecule.

H 2 N–CH(R 1)-COOH + H 2 N– CH(R 2) – COOH → H 2 N – CH(R 1) – CO-NH– CH(R 2) – COOH

Dipeptide

The C–N bond is called peptide communication

In addition to the 20 most common amino acids discussed above, some other amino acids have been isolated from hydrolysates of some specialized proteins. All of them are, as a rule, derivatives of ordinary amino acids, i.e. modified amino acids.

4-hydroxyproline , found in fibrillar protein collagen and some plant proteins; 5-oxylysine is found in collagen hydrolysates, desmozi n and isodesmosine isolated from hydrolysates of the fibrillar protein elastin. It appears that these amino acids are only found in this protein. Their structure is unusual: the 4th lysine molecules, connected by their R-groups, form a substituted pyridine ring. It is possible that due to this particular structure, these amino acids can form 4 radially diverging peptide chains. The result is that elastin, unlike other fibrillar proteins, is able to deform (stretch) in two mutually perpendicular directions. Etc.

From the listed protein amino acids, living organisms synthesize a huge number of diverse protein compounds. Many plants and bacteria can synthesize all the amino acids they need from simple inorganic compounds. In the body of humans and animals, approximately half of the amino acids are also synthesized. The other part of the amino acids can enter the human body only with dietary proteins.

- essential amino acids - are not synthesized in the human body, but are supplied only with food. Essential amino acids include 8 amino acids: valine, phenylalanine, isoleucine, leucine, lysine, methionine, threonine, tryptophan, phenylalanine.

- essential amino acids - can be synthesized in the human body from other components. Nonessential amino acids include 12 amino acids.

Both types of amino acids are equally important for humans: non-essential and essential. Most of the amino acids are used to build the body’s own proteins, but without essential amino acids the body cannot exist. Proteins, which contain essential amino acids, should make up about 16-20% of the adult diet (20-30g with a daily protein intake of 80-100g). In children's nutrition, the share of protein increases to 30% for schoolchildren, and to 40% for preschoolers. This is due to the fact that the child’s body is constantly growing and, therefore, needs a large amount of amino acids as plastic material for building proteins in muscles, blood vessels, the nervous system, skin and all other tissues and organs.

In these days of fast food and the general craze for fast food, the diet is often dominated by foods high in easily digestible carbohydrates and fats, and the share of protein foods is noticeably reduced. If there is a lack of any amino acids in the diet or during fasting in the human body for a short time, the proteins of connective tissue, blood, liver and muscles can be destroyed, and the proteins obtained from them “ construction material" - amino acids are used to maintain the normal functioning of the most important organs - the heart and brain. The human body may experience a shortage of both essential and non-essential amino acids. Deficiency of amino acids, especially essential ones, leads to poor appetite, retarded growth and development, fatty liver and other severe disorders. The first “harbingers” of amino acid deficiency may be decreased appetite, deterioration of skin condition, hair loss, muscle weakness, fatigue, decreased immunity, and anemia. Such manifestations may occur in individuals who, in order to lose weight, follow a low-calorie, unbalanced diet with a sharp restriction of protein foods.

More often than others, vegetarians who intentionally avoid including complete animal protein in their diet face manifestations of a lack of amino acids, especially essential ones.

Excess amino acids are quite rare these days, but can cause the development of serious diseases, especially in children and adolescence. The most toxic are methionine (provokes the risk of heart attack and stroke), tyrosine (can provoke the development of arterial hypertension, lead to disruption of the thyroid gland) and histidine (can contribute to copper deficiency in the body and lead to the development of aortic aneurysm, joint diseases, early gray hair). , severe anemia). Under normal conditions of functioning of the body, when there is a sufficient amount of vitamins (B 6, B 12, folic acid) and antioxidants (vitamins A, E, C and selenium), excess amino acids are quickly converted into useful components and do not have time to “cause damage” to the body. An unbalanced diet causes a deficiency of vitamins and microelements, and an excess of amino acids can disrupt the functioning of systems and organs. This option is possible with long-term adherence to protein or low-carbohydrate diets, as well as with uncontrolled intake by athletes of protein-energy products (amino acid-vitamin cocktails) to increase weight and develop muscles.

Among the chemical methods, the most common method is amino acid score (scor - counting, counting). It is based on comparison of the amino acid composition of the protein of the product being evaluated with the amino acid composition standard (ideal) protein. After quantitative chemical determination of the content of each of the essential amino acids in the protein under study, the amino acid score (AS) for each of them is determined according to the formula

AC = (m ak . research / m ak . perfect ) 100

m ac. research - the content of essential amino acids (in mg) in 1 g of the protein being studied.

m ac. ideal - the content of essential amino acids (in mg) in 1 g of standard (ideal) protein.

Amino acid pattern FAO/WHO

Simultaneously with the determination of the amino acid score, limiting essential amino acid for a given protein , that is the one for which the speed is the smallest.

Peptides.

Two amino acids can be joined covalently by peptide connection with the formation of a dipeptide.

Three amino acids can be joined through two peptide bonds to form a tripeptide. A few amino acids form oligopeptides, and a large number of amino acids form polypeptides. Peptides contain only one α-amino group and one α-carboxyl group. These groups can be ionized at certain pH values. Like amino acids, they have characteristic titration curves and isoelectric points at which they do not move in an electric field.

Like other organic compounds, peptides participate in chemical reactions that are determined by the presence of functional groups: free amino group, free carboxy group and R-groups. Peptide bonds are susceptible to hydrolysis by a strong acid (for example, 6M HC1) or a strong base to form amino acids. Hydrolysis of peptide bonds is necessary stage in determining the amino acid composition of proteins. Peptide bonds can be broken by enzymes proteases.

Many naturally occurring peptides have biological activity at very low concentrations.

Peptides are potentially active pharmaceuticals, there are three ways receiving them:

1) isolation from organs and tissues;

2) genetic engineering;

3) direct chemical synthesis.

In the latter case, high demands are placed on the yield of products at all intermediate stages.

Amino acids are the structural chemical units or "building blocks" that make up proteins. Amino acids consist of 16% nitrogen, this is their main chemical difference from the other two essential nutrients - carbohydrates and fats. The importance of amino acids for the body is determined by the enormous role that proteins play in all life processes.

Every living organism, from the largest animals to tiny microbes, is made up of proteins. Various forms of proteins take part in all processes occurring in living organisms. In the human body, muscles, ligaments, tendons, all organs and glands, hair, and nails are formed from proteins. Proteins are found in fluids and bones. Enzymes and hormones that catalyze and regulate all processes in the body are also proteins. A deficiency of these nutrients in the body can lead to an imbalance of water balance, which causes swelling.

Each protein in the body is unique and exists for specific purposes. Proteins are not interchangeable. They are synthesized in the body from amino acids, which are formed as a result of the breakdown of proteins found in food products. Thus, it is amino acids, and not proteins themselves, that are the most valuable nutritional elements. In addition to the fact that amino acids form proteins that make up the tissues and organs of the human body, some of them act as neurotransmitters (neurotransmitters) or are their precursors.

Neurotransmitters are chemicals that transmit nerve impulses from one nerve cell to another. Thus, some amino acids are essential for normal brain function. Amino acids ensure that vitamins and minerals adequately perform their functions. Some amino acids directly provide energy to muscle tissue.

In the human body, many amino acids are synthesized in the liver. However, some of them cannot be synthesized in the body, so a person must obtain them from food. These essential amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Amino acids that are synthesized in the liver: alanine, arginine, asparagine, aspartic acid, citrulline, cysteine, gamma-aminobutyric acid, glutamine and glutamic acid, glycine, ornithine, proline, serine, taurine, tyrosine.

The process of protein synthesis occurs constantly in the body. If at least one essential amino acid is missing, protein formation stops. This can lead to a variety of serious problems, from poor digestion to depression and slow growth.

How does this situation arise? Easier than you might imagine. Many factors lead to this, even if your diet is balanced and you consume enough protein. Malabsorption in the gastrointestinal tract, infection, trauma, stress, taking certain medicines, the aging process and imbalances of other nutrients in the body can all lead to essential amino acid deficiencies.

Keep in mind that all of the above does not mean that consuming a lot of protein will solve any problem. In reality, it is not conducive to maintaining health.

Excess protein creates additional stress for the kidneys and liver, which need to process the products of protein metabolism, the main one being ammonia. It is very toxic to the body, so the liver immediately processes it into urea, which then travels through the bloodstream to the kidneys, where it is filtered and excreted.

As long as the amount of protein is not too high and the liver is functioning well, the ammonia is neutralized immediately and does not cause any harm. But if there is too much of it and the liver cannot cope with its neutralization (as a result of poor diet, digestive disorders and/or liver disease), toxic levels of ammonia are created in the blood. In this case, a lot of serious health problems can arise, including hepatic encephalopathy and coma.

Too high a concentration of urea also causes kidney damage and back pain. Therefore, it is not the quantity, but the quality of proteins consumed in food that is important. Currently, it is possible to obtain essential and non-essential amino acids in the form of biologically active food additives.

This is especially important for various diseases and when using reduction diets. Vegetarians need supplements containing essential amino acids to ensure that the body receives everything it needs for normal protein synthesis.

Available different types supplements containing amino acids. Amino acids are part of some multivitamins and protein mixtures. There are commercially available formulas containing complexes of amino acids or containing one or two amino acids. They come in various forms: capsules, tablets, liquids and powders.

Most amino acids exist in two forms, the chemical structure of one being a mirror image of the other. These are called D- and L-forms, for example D-cystine and L-cystine.

D stands for dextra (right in Latin) and L stands for levo (left). These terms indicate the direction of rotation of the helix, which is the chemical structure of a given molecule. Animal proteins and plant organisms created mainly by L-forms of amino acids (with the exception of phenylalanine, which is represented by D, L forms).

Nutritional supplements containing L-amino acids are considered more suitable for the biochemical processes of the human body.
Free, or unbound, amino acids are the purest form. Therefore, when choosing an amino acid supplement, preference should be given to products containing L-crystalline amino acids standardized by the American Pharmacopoeia (USP). They do not require digestion and are absorbed directly into the bloodstream. After oral administration, they are absorbed very quickly and, as a rule, do not cause allergic reactions.

Individual amino acids are taken on an empty stomach, preferably in the morning or between meals with a small amount of vitamins B6 and C. If you are taking a complex of amino acids that includes all the essential ones, it is best to do this 30 minutes after or 30 minutes before meals. It is best to take both individual essential amino acids and a complex of amino acids, but in different time. Amino acids alone should not be taken for long periods of time, especially in high doses. It is recommended to take it for 2 months with a 2-month break.

Alanin

Alanine helps normalize glucose metabolism. A relationship has been established between excess alanine and infection with the Epstein-Barr virus, as well as chronic fatigue syndrome. One form of alanine, beta-alanine is a component of pantothenic acid and coenzyme A, one of the most important catalysts in the body.

Arginine

Arginine slows down the growth of tumors, including cancer, by stimulating immune system body. It increases the activity and size of the thymus gland, which produces T lymphocytes. In this regard, arginine is useful for people suffering from HIV infection and malignant neoplasms.

It is also used for liver diseases (cirrhosis and fatty degeneration), it promotes detoxification processes in the liver (primarily the neutralization of ammonia). Seminal fluid contains arginine, so it is sometimes used in the complex treatment of infertility in men. Connective tissue and skin also contain large amounts of arginine, so taking it is effective for various injuries. Arginine is an important component of metabolism in muscle tissue. It helps maintain optimal nitrogen balance in the body, as it participates in the transportation and neutralization of excess nitrogen in the body.

Arginine helps with weight loss because it causes a slight decrease in fat stores in the body.

Arginine is part of many enzymes and hormones. It has a stimulating effect on the production of insulin by the pancreas as a component of vasopressin (a pituitary hormone) and helps in the synthesis of growth hormone. Although arginine is synthesized in the body, its production may be reduced in newborns. Sources of arginine include chocolate, coconuts, dairy products, gelatin, meat, oats, peanuts, soybeans, walnuts, white flour, wheat and wheat germ.

People having viral infections, including Herpes simplex, should not take arginine in the form of dietary supplements and should avoid consuming foods rich in arginine. Pregnant and breastfeeding mothers should not take arginine supplements. Taking small doses of arginine is recommended for diseases of the joints and connective tissue, impaired glucose tolerance, liver diseases and injuries. Long-term use is not recommended.

Asparagine

Asparagine is necessary to maintain balance in the processes occurring in the central nervous system: it prevents both excessive excitation and excessive inhibition. It is involved in the processes of amino acid synthesis in the liver.

Since this amino acid increases vitality, a supplement based on it is used for fatigue. She also plays important role in metabolic processes. Aspartic acid is often prescribed for diseases of the nervous system. It is useful for athletes, as well as for liver dysfunction. In addition, it stimulates the immune system by increasing the production of immunoglobulins and antibodies.

Aspartic acid in large quantities found in proteins plant origin, obtained from sprouted seeds and in meat products.

Carnitine

Strictly speaking, carnitine is not an amino acid, but its chemical structure is similar to that of amino acids, and therefore they are usually considered together. Carnitine is not involved in protein synthesis and is not a neurotransmitter. Its main function in the body is the transport of long-chain fatty acids, the oxidation of which releases energy. This is one of the main sources of energy for muscle tissue. Thus, carnitine increases the conversion of fat into energy and prevents the deposition of fat in the body, primarily in the heart, liver, skeletal muscles.

Carnitine reduces the likelihood of complications diabetes mellitus associated with disorders of fat metabolism, slows down fatty liver degeneration in chronic alcoholism and the risk of heart disease. It has the ability to reduce triglyceride levels in the blood, promotes weight loss and increases muscle strength in patients with neuromuscular diseases and enhances the antioxidant effect of vitamins C and E.

Some variants of muscular dystrophy are believed to be associated with carnitine deficiency. With such diseases, people must receive more of this substance than is required according to the norms.

It can be synthesized in the body in the presence of iron, thiamine, pyridoxine and the amino acids lysine and methionine. Carnitine synthesis occurs in the presence of sufficient amounts of vitamin C. Insufficient amounts of any of these nutrients in the body leads to carnitine deficiency. Carnitine enters the body with food, primarily meat and other products of animal origin.

Most cases of carnitine deficiency are associated with a genetically determined defect in the process of its synthesis. Possible manifestations of carnitine deficiency include impaired consciousness, heart pain, muscle weakness, and obesity.

For men due to greater muscle mass requires more carnitine than women. Vegetarians are more likely to be deficient in this nutrient than non-vegetarians due to the fact that carnitine is not found in plant-based proteins.

Moreover, methionine and lysine (amino acids necessary for the synthesis of carnitine) are also not found in plant products in sufficient quantities.

To get the required amount of carnitine, vegetarians should take supplements or eat lysine-fortified foods such as cornflakes.

Carnitine is presented in dietary supplements in various forms: in the form of D, L-carnitine, D-carnitine, L-carnitine, acetyl-L-carnitine.
It is preferable to take L-carnitine.

Citrulline

Citrulline is predominantly found in the liver. It increases energy supply, stimulates the immune system, and is converted into L-arginine during metabolism. It neutralizes ammonia, which damages liver cells.

Cysteine ​​and cystine

These two amino acids are closely related, each cystine molecule consists of two cysteine ​​molecules connected to each other. Cysteine ​​is very unstable and easily transforms into L-cystine, and thus one amino acid can easily change into another when needed.

Both amino acids are sulfur-containing amino acids and play an important role in the formation of skin tissue and are important for detoxification processes. Cysteine ​​is part of alpha keratin - the main protein of nails, skin and hair. It promotes collagen formation and improves skin elasticity and texture. Cysteine ​​is also found in other proteins in the body, including some digestive enzymes.

Cysteine ​​helps neutralize certain toxic substances and protects the body from the damaging effects of radiation. It is one of the most powerful antioxidants, and its antioxidant effect is enhanced when taken simultaneously with vitamin C and selenium.

Cysteine ​​is a precursor to glutathione, a substance that has a protective effect on liver and brain cells from damage by alcohol, certain medications and toxic substances contained in cigarette smoke. Cysteine ​​dissolves better than cystine and is quickly utilized in the body, so it is often used in the complex treatment of various diseases. This amino acid is formed in the body from L-methionine, with the obligatory presence of vitamin B6.

Additional intake of cysteine ​​is necessary for rheumatoid arthritis, arterial diseases, and cancer. It accelerates recovery after operations, burns, binds heavy metals and soluble iron. This amino acid also accelerates fat burning and muscle tissue formation.

L-cysteine ​​has the ability to destroy mucus in the respiratory tract, which is why it is often used for bronchitis and emphysema. It accelerates healing processes in respiratory diseases and plays an important role in activating leukocytes and lymphocytes.

Since this substance increases the amount of glutathione in the lungs, kidneys, liver and red bone marrow, it slows down the aging process, for example, reducing the number of age spots. N-acetylcysteine ​​is more effective at increasing glutathione levels in the body than cystine or even glutathione itself.

People with diabetes should be careful when taking cysteine ​​supplements as it has the ability to inactivate insulin. If you have cystinuria, a rare genetic condition that leads to the formation of cystine stones, you should not take cysteine.

Dimethylglycine

Dimethylglycine is a derivative of glycine, the simplest amino acid. It is a constituent of many important substances, such as the amino acids methionine and choline, some hormones, neurotransmitters and DNA.

Dimethylglycine is found in small quantities in meat products, seeds and grains. Although there are no symptoms associated with dimethylglycine deficiency, taking dimethylglycine supplements has a number of benefits, including improved energy and mental performance.

Dimethylglycine also stimulates the immune system, reduces cholesterol and triglycerides in the blood, helps normalize blood pressure and glucose levels, and also helps normalize the function of many organs. It is also used for epileptic seizures.

Gamma-aminobutyric acid

Gamma-aminobutyric acid (GABA) functions as a neurotransmitter in the central nervous system in the body and is essential for metabolism in the brain. It is formed from another amino acid - glutamine. It reduces neuronal activity and prevents overexcitation of nerve cells.

Gamma-aminobutyric acid relieves anxiety and has a calming effect; it can also be taken as tranquilizers, but without the risk of addiction. This amino acid is used in the complex treatment of epilepsy and arterial hypertension. Since it has a relaxing effect, it is used in the treatment of sexual dysfunctions. In addition, GABA is prescribed for attention deficit disorder. Excess gamma-aminobutyric acid, however, can increase anxiety, causing shortness of breath and trembling of the limbs.

Glutamic acid

Glutamic acid is a neurotransmitter that transmits impulses in the central nervous system. This amino acid plays an important role in carbohydrate metabolism and promotes the penetration of calcium through the blood-brain barrier.

This amino acid can be used by brain cells as an energy source. It also neutralizes ammonia by removing nitrogen atoms in the process of forming another amino acid - glutamine. This process is the only way to neutralize ammonia in the brain.

Glutamic acid is used in the correction of behavioral disorders in children, as well as in the treatment of epilepsy, muscular dystrophy, ulcers, hypoglycemic conditions, complications of insulin therapy for diabetes mellitus and mental development disorders.

Glutamine

Glutamine is the amino acid most commonly found in free form in muscles. It very easily penetrates the blood-brain barrier and in brain cells passes into glutamic acid and vice versa, in addition, it increases the amount of gamma-aminobutyric acid, which is necessary to maintain normal brain function.

This amino acid also maintains normal acid-base balance in the body and a healthy state gastrointestinal tract, necessary for the synthesis of DNA and RNA.

Glutamine is an active participant in nitrogen metabolism. Its molecule contains two nitrogen atoms and is formed from glutamic acid by adding one nitrogen atom. Thus, glutamine synthesis helps remove excess ammonia from tissues, primarily from the brain, and transport nitrogen within the body.

Glutamine is found in large quantities in muscles and is used to synthesize proteins in skeletal muscle cells. Therefore, nutritional supplements with glutamine are used by bodybuilders and in various diets, as well as to prevent muscle loss in diseases such as malignant neoplasms and AIDS, after operations and during long-term bed rest.

Additionally, glutamine is also used in the treatment of arthritis, autoimmune diseases, fibrosis, gastrointestinal diseases, peptic ulcers, and connective tissue diseases.

This amino acid improves brain activity and is therefore used for epilepsy, chronic fatigue syndrome, impotence, schizophrenia and senile dementia. L-glutamine reduces pathological cravings for alcohol, therefore it is used in the treatment of chronic alcoholism.

Glutamine is found in many foods of both plant and animal origin, but it is easily destroyed by heating. Spinach and parsley are good sources of glutamine, as long as they are consumed raw.

Dietary supplements containing glutamine should only be stored in a dry place, otherwise glutamine will convert into ammonia and pyroglutamic acid. Do not take glutamine if you have liver cirrhosis, kidney disease, or Reye's syndrome.

Glutathione

Glutathione, like carnitine, is not an amino acid. According to its chemical structure, it is a tripeptide obtained in the body from cysteine, glutamic acid and glycine.

Glutathione is an antioxidant. Most glutathione is found in the liver (some of it is released directly into the bloodstream), as well as in the lungs and gastrointestinal tract.

It is necessary for carbohydrate metabolism, and also slows down aging due to its effect on lipid metabolism and prevents the occurrence of atherosclerosis. Glutathione deficiency primarily affects the nervous system, causing problems with coordination, mental processes, and tremors.

The amount of glutathione in the body decreases with age. In this regard, older people should receive it additionally. However, it is preferable to use nutritional supplements containing cysteine, glutamic acid and glycine - that is, substances that synthesize glutathione. Taking N-acetylcysteine ​​is considered the most effective.

Glycine

Glycine slows down the degeneration of muscle tissue, as it is a source of creatine, a substance contained in muscle tissue and used in the synthesis of DNA and RNA. Glycine is necessary for the synthesis of nucleic acids, bile acids and non-essential amino acids in the body.

It is part of many antacid medications used for stomach diseases; it is useful for restoring damaged tissue, as it is found in large quantities in the skin and connective tissue.

This amino acid is necessary for the normal functioning of the central nervous system and the maintenance of good prostate health. It functions as an inhibitory neurotransmitter and thus can prevent epileptic seizures.

Glycine is used in the treatment of manic-depressive psychosis, and it can also be effective for hyperactivity. Excess glycine in the body causes a feeling of fatigue, but adequate quantity provides the body with energy. If necessary, glycine can be converted into serine in the body.

Histidine

Histidine is an essential amino acid that promotes tissue growth and repair, is part of the myelin sheaths that protect nerve cells, and is also necessary for the formation of red and white blood cells. Histidine protects the body from the damaging effects of radiation, promotes the removal of heavy metals from the body and helps with AIDS.

Too high a histidine content can lead to stress and even mental disorders (agitation and psychosis).

Inadequate levels of histidine in the body worsen the condition of rheumatoid arthritis and deafness associated with damage to the auditory nerve. Methionine helps lower the level of histidine in the body.

Histamine, a very important component of many immunological reactions, is synthesized from histidine. It also promotes sexual arousal. In this regard, the simultaneous use of dietary supplements containing histidine, niacin and pyridoxine (necessary for the synthesis of histamine) may be effective for sexual disorders.

Since histamine stimulates the secretion of gastric juice, the use of histidine helps with digestive disorders associated with low acidity of gastric juice.

People suffering from manic depression should not take histidine unless a deficiency of this amino acid is clearly established. Histidine is found in rice, wheat and rye.

Isoleucine

Isoleucine is one of the BCAA amino acids and essential amino acids necessary for the synthesis of hemoglobin. It also stabilizes and regulates blood sugar levels and energy supply processes. Isoleucine metabolism occurs in muscle tissue.

Combined use with isoleucine and valine (BCAA) increases endurance and promotes muscle tissue recovery, which is especially important for athletes.

Isoleucine is necessary for many mental illnesses. A deficiency of this amino acid results in symptoms similar to hypoglycemia.

Food sources of isoleucine include almonds, cashews, chicken, chickpeas, eggs, fish, lentils, liver, meat, rye, most seeds, and soy proteins.

There are biologically active food supplements containing isoleucine. In this case, it is necessary to maintain the correct balance between isoleucine and two other branched BCAA amino acids - leucine and valine.

Leucine

Leucine is an essential amino acid, together with isoleucine and valine, one of the three branched BCAA amino acids. Acting together, they protect muscle tissue and are sources of energy, and also promote the restoration of bones, skin, and muscles, so their use is often recommended during the recovery period after injuries and operations.

Leucine also slightly lowers blood sugar levels and stimulates the release of growth hormone. Food sources of leucine include brown rice, beans, meat, nuts, soy flour and wheat flour.

Dietary supplements containing leucine are used in combination with valine and isoleucine. They should be taken with caution to avoid causing hypoglycemia. Excess leucine can increase the amount of ammonia in the body.

Lysine

Lysine is an essential amino acid that is part of almost any protein. It is necessary for normal bone formation and growth in children, promotes the absorption of calcium and maintains normal nitrogen metabolism in adults.

This amino acid is involved in the synthesis of antibodies, hormones, enzymes, collagen formation and tissue repair. Lysine is used during the recovery period after operations and sports injuries. It also lowers serum triglyceride levels.

Lysine has an antiviral effect, especially against viruses that cause herpes and acute respiratory infections. Taking supplements containing lysine in combination with vitamin C and bioflavonoids is recommended for viral diseases.

A deficiency of this essential amino acid can lead to anemia, hemorrhages in the eyeball, enzyme disorders, irritability, fatigue and weakness, poor appetite, slow growth and weight loss, as well as reproductive system disorders.

Food sources of lysine include cheese, eggs, fish, milk, potatoes, red meat, soy and yeast products.

Methionine

Methionine is an essential amino acid that helps process fats, preventing their deposition in the liver and on the walls of arteries. The synthesis of taurine and cysteine ​​depends on the amount of methionine in the body. This amino acid promotes digestion, provides detoxification processes (primarily the neutralization of toxic metals), reduces muscle weakness, protects against radiation exposure, and is useful for osteoporosis and chemical allergies.

This amino acid is used in complex therapy of rheumatoid arthritis and toxicosis of pregnancy. Methionine has a pronounced antioxidant effect, as it is a good source of sulfur, which inactivates free radicals. It is used for Gilbert's syndrome and liver dysfunction. Methionine is also necessary for the synthesis of nucleic acids, collagen and many other proteins. It is useful for women receiving oral hormonal contraceptives. Methionine lowers histamine levels in the body, which may be useful in schizophrenia when the amount of histamine is elevated.

Methionine in the body is converted into cysteine, which is a precursor to glutathione. This is very important in case of poisoning, when large amounts of glutathione are required to neutralize toxins and protect the liver.

Food sources of methionine: legumes, eggs, garlic, lentils, meat, onions, soybeans, seeds and yogurt.

Ornithine

Ornithine helps release growth hormone, which helps burn fat in the body. This effect is enhanced when ornithine is used in combination with arginine and carnitine. Ornithine is also essential for the immune system and liver function, participating in detoxification processes and the restoration of liver cells.

Ornithine in the body is synthesized from arginine and, in turn, serves as a precursor for citrulline, proline, and glutamic acid. High concentrations of ornithine are found in the skin and connective tissue, so this amino acid helps repair damaged tissue.

Dietary supplements containing ornithine should not be given to children, pregnant and nursing mothers, or to persons with a history of schizophrenia.

Phenylalanine

Phenylalanine is an essential amino acid. In the body, it can be converted into another amino acid - tyrosine, which, in turn, is used in the synthesis of two main neurotransmitters: dopamine and norepinephrine. Therefore, this amino acid affects mood, reduces pain, improves memory and learning ability, and suppresses appetite. It is used in the treatment of arthritis, depression, menstrual pain, migraines, obesity, Parkinson's disease and schizophrenia.

Phenylalanine occurs in three forms: L-phenylalanine (the natural form and is found in most proteins human body), D-phenylalanine (synthetic mirror form, has an analgesic effect), DL-phenylalanine (combines beneficial features two previous forms, it is usually used for premenstrual syndrome.

Dietary supplements containing phenylalanine should not be given to pregnant women, persons with anxiety attacks, diabetes, high blood pressure, phenylketonuria, or pigmented melanoma.

Proline

Proline improves skin condition by increasing collagen production and reducing its loss with age. Helps restore cartilaginous surfaces of joints, strengthens ligaments and heart muscle. To strengthen connective tissue, proline is best used in combination with vitamin C.

Proline enters the body mainly from meat products.

Serin

Serine is necessary for the normal metabolism of fats and fatty acids, the growth of muscle tissue and the maintenance of a normal immune system.

Serine is synthesized in the body from glycine. As a moisturizing agent, it is included in many cosmetic products and dermatological preparations.

Taurine

Taurine is found in high concentrations in the heart muscle, white blood cells, skeletal muscles, and the central nervous system. It is involved in the synthesis of many other amino acids, and is also a major component of bile, which is necessary for the digestion of fats, the absorption of fat-soluble vitamins and for maintaining normal blood cholesterol levels.

Therefore, taurine is useful for atherosclerosis, edema, heart disease, arterial hypertension and hypoglycemia. Taurine is necessary for the normal metabolism of sodium, potassium, calcium and magnesium. It prevents the removal of potassium from the heart muscle and therefore helps prevent certain heart rhythm disorders. Taurine has a protective effect on the brain, especially during dehydration. It is used in the treatment of anxiety and agitation, epilepsy, hyperactivity, and seizures.

Dietary supplements with taurine are given to children with Down syndrome and muscular dystrophy. In some clinics, this amino acid is included in complex therapy for breast cancer. Excessive excretion of taurine from the body occurs in various conditions and metabolic disorders.

Arrhythmias, disorders of platelet formation, candidiasis, physical or emotional stress, intestinal diseases, zinc deficiency and alcohol abuse lead to taurine deficiency in the body. Alcohol abuse also impairs the body's ability to absorb taurine.

In diabetes, the body's need for taurine increases, and vice versa, taking dietary supplements containing taurine and cystine reduces the need for insulin. Taurine is found in eggs, fish, meat, milk, but is not found in plant proteins.

It is synthesized in the liver from cysteine ​​and from methionine in other organs and tissues of the body, provided there is a sufficient amount of vitamin B6. In case of genetic or metabolic disorders that interfere with the synthesis of taurine, it is necessary to take a dietary supplement with this amino acid.

Threonine

Threonine is an essential amino acid that helps maintain normal protein metabolism in the body. It is important for the synthesis of collagen and elastin, helps the liver and is involved in fat metabolism in combination with aspartic acid and methionine.

Threonine is found in the heart, central nervous system, skeletal muscles and prevents the deposition of fats in the liver. This amino acid stimulates the immune system as it promotes the production of antibodies. Threonine is found in very small quantities in grains, so vegetarians are more likely to be deficient in this amino acid.

Tryptophan

Tryptophan is an essential amino acid required for the production of niacin. It is used to synthesize serotonin, one of the most important neurotransmitters, in the brain. Tryptophan is used for insomnia, depression and to stabilize mood.

It helps with hyperactivity disorder in children, is used for heart disease, to control body weight, reduce appetite, and also to increase the release of growth hormone. Helps with migraine attacks, helps reduce the harmful effects of nicotine. Deficiency of tryptophan and magnesium can increase spasms of the coronary arteries.

The richest food sources of tryptophan include brown rice, country cheese, meat, peanuts and soy protein.

Tyrosine

Tyrosine is a precursor to the neurotransmitters norepinephrine and dopamine. This amino acid is involved in mood regulation; a lack of tyrosine leads to a deficiency of norepinephrine, which in turn leads to depression. Tyrosine suppresses appetite, helps reduce fat storage, promotes melatonin production and improves adrenal, thyroid and pituitary function.

Tyrosine is also involved in phenylalanine metabolism. Thyroid hormones are formed when iodine atoms are added to tyrosine. Therefore it is not surprising that low content plasma tyrosine is associated with hypothyroidism.

Symptoms of tyrosine deficiency also include low blood pressure, low temperature body and restless leg syndrome.

Dietary supplements with tyrosine are used to relieve stress and are believed to help with chronic fatigue syndrome and narcolepsy. They are used for anxiety, depression, allergies and headaches, as well as for drug withdrawal. Tyrosine may be helpful in Parkinson's disease. Natural sources of tyrosine include almonds, avocados, bananas, dairy products, pumpkin seeds and sesame seeds.

Tyrosine can be synthesized from phenylalanine in the human body. Dietary supplements with phenylalanine are best taken before bed or with foods containing large amounts of carbohydrates.

During treatment with monoamine oxidase inhibitors (usually prescribed for depression), you should almost completely avoid foods containing tyrosine and not take dietary supplements with tyrosine, as this can lead to an unexpected and sharp rise in blood pressure.

Valin

Valine is an essential amino acid with a stimulating effect, one of the BCAA amino acids, and therefore can be used by muscles as an energy source. Valine is necessary for muscle metabolism, repair of damaged tissues and for maintaining normal nitrogen metabolism in the body.

Valine is often used to correct severe amino acid deficiencies resulting from drug addiction. Its excessively high level in the body can lead to symptoms such as paresthesia (pins and needles sensation) and even hallucinations.
Valine is found in the following foods: grains, meat, mushrooms, dairy products, peanuts, soy protein.

Valine supplementation should be balanced with the other branched chain amino acids BCAA L-leucine and L-isoleucine.

Among the variety of amino acids, only 20 are involved in intracellular protein synthesis ( proteinogenic amino acids). Also, about 40 more non-proteinogenic amino acids have been found in the human body. All proteinogenic amino acids are α- amino acids and their example can be shown additional ways classifications.

According to the structure of the side radical

Highlight

• aliphatic(alanine, valine, leucine, isoleucine, proline, glycine),
• aromatic(phenylalanine, tyrosine, tryptophan),
• sulfur-containing(cysteine, methionine),
• containing OH group(serine, threonine, tyrosine again),
• containing additional COOH group(aspartic and glutamic acids),
• additional NH 2 group(lysine, arginine, histidine, also glutamine, asparagine).

Usually the names of amino acids are abbreviated to a 3-letter designation. Molecular biology professionals also use single-letter symbols for each amino acid.

Structure of proteinogenic amino acids

According to the polarity of the side radical

Exist non-polar amino acids (aromatic, aliphatic) and polar(uncharged, negatively and positively charged).

According to acid-base properties

According to their acid-base properties they are divided into neutral(majority), sour(aspartic and glutamic acids) and basic(lysine, arginine, histidine) amino acids.

By irreplaceability

According to the need for the body, those that are not synthesized in the body and must be supplied with food are isolated - irreplaceable amino acids (leucine, isoleucine, valine, phenylalanine, tryptophan, threonine, lysine, methionine). TO replaceable include those amino acids whose carbon skeleton is formed in metabolic reactions and is capable of somehow obtaining an amino group to form the corresponding amino acid. The two amino acids are conditionally irreplaceable (arginine, histidine), i.e. their synthesis occurs in insufficient quantities, especially for children.

Amino acids are heterofunctional compounds that necessarily contain two functional groups: an amino group - NH 2 and a carboxyl group - COOH, associated with a hydrocarbon radical. The general formula of the simplest amino acids can be written as follows:

Because amino acids contain two different functional groups that influence each other, the characteristic reactions differ from those of carboxylic acids and amines.

Properties of amino acids

The amino group - NH 2 determines the basic properties of amino acids, since it is capable of attaching a hydrogen cation to itself via a donor-acceptor mechanism due to the presence of a free electron pair at the nitrogen atom.

The -COOH group (carboxyl group) determines the acidic properties of these compounds. Therefore, amino acids are amphoteric organic compounds. They react with alkalis as acids:

With strong acids - like bases - amines:

In addition, the amino group in an amino acid interacts with its carboxyl group, forming an internal salt:

The ionization of amino acid molecules depends on the acidic or alkaline nature of the environment:

Since amino acids in aqueous solutions behave like typical amphoteric compounds, in living organisms they play the role of buffer substances that maintain a certain concentration of hydrogen ions.

Amino acids are colorless crystalline substances that melt and decompose at temperatures above 200 °C. They are soluble in water and insoluble in ether. Depending on the R- radical, they can be sweet, bitter or tasteless.

Amino acids are divided into natural (found in living organisms) and synthetic. Among natural amino acids (about 150), proteinogenic amino acids (about 20) are distinguished, which are part of proteins. They are L-shapes. About half of these amino acids are irreplaceable, because they are not synthesized in the human body. Essential acids are valine, leucine, isoleucine, phenylalanine, lysine, threonine, cysteine, methionine, histidine, tryptophan. These substances enter the human body with food. If their quantity in food is insufficient, the normal development and functioning of the human body is disrupted. In certain diseases, the body is unable to synthesize some other amino acids. Thus, in phenylketonuria, tyrosine is not synthesized. The most important property of amino acids is the ability to enter into molecular condensation with the release of water and the formation of the amide group -NH-CO-, for example:

The high-molecular compounds obtained as a result of this reaction contain a large number of amide fragments and are therefore called polyamides.

These, in addition to the synthetic nylon fiber mentioned above, include, for example, enant, formed during the polycondensation of aminoenanthic acid. Amino acids with amino and carboxyl groups at the ends of the molecules are suitable for producing synthetic fibers.

Alpha amino acid polyamides are called peptides. Depending on the number of amino acid residues, they are distinguished dipeptides, tripeptides, polypeptides. In such compounds, the -NH-CO- groups are called peptide groups.