Amino acid properties can be divided into two groups: chemical and physical.

Chemical properties of amino acids

Depending on the compounds, amino acids can exhibit different properties.

Interaction of amino acids:

Amino acids as amphoteric compounds form salts with both acids and alkalis.

As carboxylic acids, amino acids form functional derivatives: salts, esters, amides.

Interaction and properties of amino acids with grounds:
Salts are formed:

NH 2 -CH 2 -COOH + NaOH NH 2 -CH 2 -COONa + H2O

Sodium salt of + 2-aminoacetic acid Sodium salt of aminoacetic acid (glycine) + water

Interaction with alcohols:

Amino acids can react with alcohols in the presence of hydrogen chloride gas, converting into ester... Esters of amino acids do not have a bipolar structure and are volatile compounds.

NH 2 -CH 2 -COOH + CH 3 OH NH 2 -CH 2 -COOCH 3 + H 2 O.

Methyl ester / 2-aminoacetic acid /

Interaction ammonia:

Amides are formed:

NH 2 -CH (R) -COOH + H-NH 2 = NH 2 -CH (R) -CONH 2 + H 2 O

Interaction of amino acids with strong acids:

We get salts:

HOOC-CH 2 -NH 2 + HCl → Cl (or HOOC-CH 2 -NH 2 * HCl)

These are the basic chemical properties of amino acids.

Physical properties of amino acids

We list the physical properties of amino acids:

• Colorless
• Are crystalline
• Most amino acids have a sweet taste, but depending on the radical (R) may be bitter or tasteless
• Well soluble in water, but poorly soluble in many organic solvents
• Amino acids have the property of optical activity
• Melts with decomposition above 200 ° C
• Non-volatile
• Aqueous solutions of amino acids in an acidic and alkaline environment conduct an electric current

Amino acids are organic amphoteric compounds. They contain two opposite functional groups in the molecule: an amino group with basic properties and a carboxyl group with acidic properties. Amino acids react with both acids and bases:

H 2 N -CH 2 -COOH + HCl → Cl [H 3 N-CH 2 -COOH],

H 2 N -CH 2 -COOH + NaOH → H 2 N-CH 2 -COONa + H 2 O.

When amino acids are dissolved in water, the carboxyl group eliminates a hydrogen ion, which can attach to the amino group. In this case, an internal salt is formed, the molecule of which is a bipolar ion:

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

Acid-base transformations of amino acids in various media can be depicted by the following general scheme:

Aqueous solutions of amino acids have a neutral, alkaline or acidic environment, depending on the number of functional groups. So, glutamic acid forms an acidic solution (two groups —COOH, one —NH 2), lysine — alkaline (one group —COOH, two —NH 2).

Like primary amines, amino acids react with nitrous acid, whereby the amino group is converted to a hydroxo group, and the amino acid to a hydroxy acid:

H 2 N-CH (R) -COOH + HNO 2 → HO-CH (R) -COOH + N 2 + H 2 O

Measuring the volume of nitrogen released allows you to determine the amount of amino acid ( Van Slike method).

Amino acids can react with alcohols in the presence of gaseous hydrogen chloride, converting into an ester (more precisely, into a hydrochloric ester salt):

H 2 N-CH (R) -COOH + R'OH H 2 N-CH (R) -COOR '+ H 2 O.

Esters of amino acids do not have a bipolar structure and are volatile compounds.

The most important property of amino acids is their ability to condense to form peptides.

Qualitative reactions.

1) All amino acids are oxidized by ninhydrin

with the formation of products colored blue-violet. The imino acid proline gives a yellow color with ninhydrin. This reaction can be used to quantify amino acids by spectrophotometry.

2) When aromatic amino acids are heated with concentrated nitric acid, the benzene ring is nitrated and yellow-colored compounds are formed. This reaction is called xanthoprotein(from the Greek xanthos - yellow).

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Amino acids are organic substances consisting of a hydrocarbon skeleton and two additional groups: amine and carboxyl. The last two radicals determine the unique properties of amino acids - they can exhibit the properties of both acids and alkalis: the first - due to the carboxyl group, the second - due to the amino group.

So, we found out what amino acids are from the point of view of biochemistry. Now let's consider their effect on the body and their use in sports. For athletes, amino acids are important for their participation in. It is from individual amino acids that our body is built - muscle, skeletal, liver, connective tissue. In addition, some amino acids are directly involved in metabolism. For example, arginine is involved in the ornithine urea cycle, a unique mechanism for detoxifying ammonia produced in the liver during protein digestion.



• From tyrosine in the adrenal cortex, catecholamines are synthesized - adrenaline and norepinephrine - hormones whose function is to maintain the tone of the cardiovascular system, an instant response to a stressful situation.
• Tryptophan is a precursor of the sleep hormone melatonin, which is produced in the pineal gland of the brain - the pineal gland. With a lack of this amino acid in the diet, the process of falling asleep becomes more complicated, insomnia and a number of other diseases caused by it develop.

It is possible to list for a long time, but let us dwell on the amino acid, the value of which is especially great for athletes and people who are moderately involved in sports.

What is glutamine for?

- an amino acid that limits the synthesis of the protein that makes up our immune tissue - lymph nodes and individual formations of lymphoid tissue. The importance of this system is difficult to overestimate: without proper resistance to infections, there is no need to talk about any training process. Moreover, every workout - no matter whether professional or amateur - is a dosed stress for the body.

Stress is a necessary condition to move our "point of balance", that is, to cause certain biochemical and physiological changes in the body. Any stress is a chain of reactions that mobilize the body. In the interval characterizing the regression of the cascade of reactions of the sympathoadrenal system (namely, they are stress), there is a decrease in the synthesis of lymphoid tissue. For this reason, the decay process exceeds the rate of synthesis, which means that immunity is weakened. So, the additional intake of glutamine minimizes this extremely undesirable but inevitable effect of physical activity.



Essential and nonessential amino acids

To understand what essential amino acids are for in sports, you need to have a general understanding of protein metabolism. The proteins consumed by humans at the level of the gastrointestinal tract are processed by enzymes - substances that break down the food we have consumed.

In particular, proteins break down first to peptides - individual chains of amino acids that do not have a quaternary spatial structure. And already the peptides will break down into individual amino acids. Those, in turn, are assimilated by the human body. This means that amino acids are absorbed into the bloodstream and only from this stage can they be used as products for the synthesis of body protein.



Looking ahead, we will say that the intake of individual amino acids in sports shortens this stage - individual amino acids will be immediately absorbed into the bloodstream and synthesis processes, and the biological effect of amino acids will come faster.

There are twenty amino acids in total. In order for the process of protein synthesis in the human body to become possible in principle, the full spectrum must be present in the human diet - all 20 compounds.

Irreplaceable

From this moment on, the concept of irreplaceability appears. Essential amino acids are those that our body is unable to synthesize on its own from other amino acids. And this means that they will appear, except from food, nowhere. There are 8 such amino acids plus 2 partly replaceable ones.

Consider in the table in which foods each essential amino acid is contained and what is its role in the human body:

Name	What products contain	Role in the body
	Nuts, oats, fish, eggs, chicken,	Reduces blood sugar
	Chickpeas, lentils, cashews, meat, fish, eggs, liver, meat	Restores muscle tissue
	Amaranth, wheat, fish, meat, most dairy products	Takes part in the absorption of calcium
	Peanuts, mushrooms, meat, legumes, dairy products, many grains	Takes part in nitrogen exchange processes
Phenylalanine	, nuts, cottage cheese, milk, fish, eggs, various legumes	Improving memory
Threonine	Eggs, nuts, beans, dairy products	Synthesizes collagen
	, eggs, meat, fish, legumes, lentils	Takes part in protection from radiation
Tryptophan	Sesame, oats, legumes, peanuts, pine nuts, most dairy products, chicken, meat, fish, dried	Improves and deeper sleep
Histidine (partially non-replaceable)	Lentils, soybeans, peanuts, salmon, beef and chicken fillets, pork tenderloin	Takes part in anti-inflammatory reactions
(partially replaceable)	Yogurt, sesame seeds, pumpkin seeds, Swiss cheese, beef, pork, peanuts	Promotes the growth and repair of body tissues

Amino acids are found in sufficient quantities in animal sources of protein - fish, meat, poultry. In the absence of such in the diet, it is highly advisable to take the missing amino acids as supplements in sports nutrition, which is especially important for vegetarian athletes.

The latter should focus on supplements such as BCAAs, a blend of leucine, valine, and isoleucine. It is for these amino acids that a "drawdown" is possible in a diet that does not contain animal protein sources. For an athlete (both a professional and an amateur), this is absolutely unacceptable, since in the long term it will lead to catabolism from the internal organs and to diseases of the latter. First of all, the liver suffers from a lack of amino acids.



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Replaceable

Replaceable amino acids and their role are considered in the table below:

What happens to amino acids and proteins in your body

Amino acids that enter the bloodstream are primarily distributed to the tissues of the body, where they are most needed. If you have drawdowns on certain amino acids, taking in extra protein rich in them or taking in extra amino acids will be especially beneficial.

Protein synthesis occurs at the cellular level. Every cell has a nucleus - the most important part of the cell. It is in it that genetic information is read and reproduced. In fact, all information about the structure of cells is encoded in a sequence of amino acids.

How to choose amino acids for an ordinary amateur who moderately goes in for sports 3-4 times a week? No way. He just doesn't need them.

The following recommendations are more important for a modern person:

1. Start eating regularly at the same time.
2. Balance the diet for proteins, fats and carbohydrates.
3. Remove fast food and low-quality food from the diet.
4. Start drinking enough water - 30 ml per kilogram of body weight.
5. Give up refined sugar.

These simple manipulations will bring much more than adding any kind of additives to the diet. Moreover, supplements without observing these conditions will be absolutely useless.

Why know what amino acids you need if you are eating something you don't understand? How do you know what the cutlets in the dining room are made of? Or sausages? Or what is the meat in the burger cutlet? We will not say anything about the pizza toppings.

Therefore, before making a conclusion about the need for amino acids, you need to start eating simple, clean and healthy foods and follow the recommendations described above.

The same goes for supplemental protein intake. If you have protein in your diet, in the amount of 1.5-2 g per kilogram of body weight, you do not need any additional protein. Better to spend your money buying quality food.

It is also important to understand that protein and amino acids are not pharmaceuticals! These are just sports nutrition supplements. And the key word here is additives. Add them as needed.

To understand if there is a need, you need to control your diet. If you have already gone through the steps above and realized that supplements are still necessary, the first thing you should do is go to a sports nutrition store and select the appropriate product in accordance with your financial capabilities. The only thing that beginners should not do is buy amino acids with a natural taste: it will be difficult to drink them due to the extreme bitterness.

Harm, side effects, contraindications

If you have a disease characterized by intolerance to one of the amino acids, you know about it from birth, just like your parents. This amino acid should be avoided further. If this is not the case, there is no point in talking about the dangers and contraindications of additives, since these are completely natural substances.

Amino acids are a constituent part of protein, protein is a familiar part of the human diet. Everything that is sold in sports nutrition stores is not pharmacological! Only amateurs can talk about some kind of harm and contraindications. For the same reason, it makes no sense to consider such a concept as the side effects of amino acids - with moderate consumption, there can be no negative reactions.

Take a sober approach to your diet and sports training! Be healthy!

DEFINITION

Amino acids are complex organic compounds that simultaneously contain an amino group and a carboxyl group in their molecule.

Amino acids are crystalline solids with high melting points and decompose when heated. They dissolve well in water. These properties are explained by the possibility of the existence of amino acids in the form of internal salts (Fig. 1).

Rice. 1. Internal salt of aminoacetic acid.

Getting amino acids

The starting compounds for the production of amino acids are often carboxylic acids, into the molecule of which an amino group is introduced. For example, obtaining them from halogenated acids

CH 3 -C (Br) H-COOH + 2NH 3 → CH 3 -C (NH 2) H-COOH + NH 4 Br.

In addition, aldehydes (1), unsaturated acids (2) and nitro compounds (3) can serve as the starting material for the production of amino acids:

CH 3 —C (O) H + NH 3 + HCN → CH 3 —C (NH 2) H — C≡H + H 2 O;

CH 3 -C (NH 2) H-C≡H + H 2 O (H +) → CH 3 -C (NH 2) H-COOH + NH 3 (1).

CH 2 = CH-COOH + NH 3 → H 2 N-CH 2 -CH 2 -COOH (2);

O 2 N-C 6 H 4 -COOH + [H] → H 2 N-C 6 H 4 -COOH (3).

Chemical properties of amino acids

Amino acid as heterofunctional compounds undergoes most of the reactions characteristic of carboxylic acids and amines. The presence of two different functional groups in amino acid molecules leads to the appearance of a number of specific properties.

Amino acids are amphoteric compounds. They react with both acids and bases:

NH 2 -CH 2 -COOH + HCl → Cl

NH 2 -CH 2 -COOH + NaOH → NH 2 -CH 2 -COONa + H 2 O

Aqueous solutions of amino acids have a neutral, alkaline and acidic environment, depending on the number of functional groups. For example, glutamic acid forms an acidic solution, since it contains two carboxyl groups and one amino group, and lysine is an alkaline solution, because it contains one carboxyl group and two amino groups.

Two amino acid molecules can interact with each other. In this case, the splitting off of the water molecule occurs and a product is formed in which the fragments of the molecule are linked to each other by a peptide bond (-CO-NH-). For example:

The resulting compound is called a dipeptide. Substances built from many amino acid residues are called polypeptides. Peptides are hydrolyzed by acids and bases.

Use of amino acids

The amino acids necessary for building the body, both humans and animals, are obtained from food proteins.

γ-Aminobutyric acid is used in medicine (aminalon / gammalon) for mental illness; on its basis, a number of nootropic drugs have been created, i.e. influencing the processes of thinking.

ε-Aminocaproic acid is also used in medicine (hemostatic agent), and in addition, it is a large-scale industrial product used to obtain synthetic polyamide fiber - nylon.

Anthranilic acid is used for the synthesis of dyes, such as indigo blue, and is also involved in the biosynthesis of heterocyclic compounds.

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

By the nature of hydrocarbon substituents, amines are divided into

General structural features of amines

As in the ammonia molecule, in the molecule of any amine, the nitrogen atom has a lone electron pair directed to one of the vertices of the distorted tetrahedron:

For this reason, amines, like ammonia, have significant basic properties.

So, amines, similarly to ammonia, react reversibly with water, forming weak bases:

The bond of the hydrogen cation with the nitrogen atom in the amine molecule is realized using the donor-acceptor mechanism due to the lone electron pair of the nitrogen atom. Limit amines are stronger bases than ammonia, because in such amines, hydrocarbon substituents have a positive inductive (+ I) effect. In this regard, the electron density on the nitrogen atom increases, which facilitates its interaction with the H + cation.

Aromatic amines, if the amino group is directly connected to the aromatic nucleus, exhibit weaker basic properties than ammonia. This is due to the fact that the lone electron pair of the nitrogen atom is shifted towards the aromatic π-system of the benzene ring, as a result of which, the electron density on the nitrogen atom decreases. In turn, this leads to a decrease in basic properties, in particular the ability to interact with water. So, for example, aniline reacts only with strong acids, and practically does not react with water.

Chemical properties of saturated amines

As already mentioned, amines react reversibly with water:

Aqueous solutions of amines have an alkaline reaction of the medium, due to the dissociation of the resulting bases:

Saturated amines react with water better than ammonia due to their stronger basic properties.

The basic properties of saturated amines increase in series.

Secondary saturated amines are stronger bases than primary saturated amines, which in turn are stronger bases than ammonia. As for the basic properties of tertiary amines, then if we are talking about reactions in aqueous solutions, then the basic properties of tertiary amines are expressed much worse than in secondary amines, and even slightly worse than in primary ones. This is due to steric hindrances, which significantly affect the rate of protonation of the amine. In other words, three substituents “block” the nitrogen atom and interfere with its interaction with H + cations.

5interaction with acids

Both free saturated amines and their aqueous solutions interact with acids. In this case, salts are formed:

Since the basic properties of saturated amines are more pronounced than those of ammonia, such amines react even with weak acids, for example, carbonic:

Amine salts are solids that are readily soluble in water and poorly soluble in non-polar organic solvents. The interaction of amine salts with alkalis leads to the release of free amines, in the same way as ammonia is displaced under the action of alkalis on ammonium salts:

2. Primary saturated amines react with nitrous acid to form the corresponding alcohols, nitrogen N 2 and water. For example:

A characteristic feature of this reaction is the formation of gaseous nitrogen, in connection with which it is of high quality for primary amines and is used to distinguish them from secondary and tertiary ones. It should be noted that most often this reaction is carried out by mixing the amine not with a solution of nitrous acid itself, but with a solution of a salt of nitrous acid (nitrite) and then adding a strong mineral acid to this mixture. When nitrites interact with strong mineral acids, nitrous acid is formed, which then reacts with an amine:

Secondary amines give oily liquids under similar conditions, the so-called N-nitrosamines, but this reaction does not occur in real USE tasks in chemistry. Tertiary amines do not interact with nitrous acid.

Complete combustion of any amines leads to the formation of carbon dioxide, water and nitrogen:

Interaction with haloalkanes

It is noteworthy that absolutely the same salt is obtained by the action of hydrogen chloride on a more substituted amine. In our case, when hydrogen chloride interacts with dimethylamine:

Getting amines:

1) Alkylation of ammonia with haloalkanes:

In case of a lack of ammonia, instead of amine, its salt is obtained:

2) Reduction by metals (to hydrogen in the range of activity) in an acidic environment:

followed by treatment of the solution with alkali to release the free amine:

3) Reaction of ammonia with alcohols when passing their mixture through heated alumina. Depending on the proportions of alcohol / amine, primary, secondary or tertiary amines are formed:

Chemical properties of aniline

Aniline - the trivial name of aminobenzene, which has the formula:

As can be seen from the illustration, in the aniline molecule, the amino group is directly attached to the aromatic ring. For such amines, as already mentioned, the basic properties are much weaker than for ammonia. So, in particular, aniline practically does not react with water and weak acids such as carbonic acid.

Interaction of aniline with acids

Aniline reacts with strong to medium strength inorganic acids. In this case, phenylammonium salts are formed:

Interaction of aniline with halogens

As already mentioned at the very beginning of this chapter, the amino group in aromatic amines is drawn into the aromatic ring, which in turn reduces the electron density on the nitrogen atom, and as a result increases it in the aromatic nucleus. An increase in the electron density in the aromatic nucleus leads to the fact that electrophilic substitution reactions, in particular, reactions with halogens, proceed much easier, especially in the ortho and para positions relative to the amino group. So, aniline easily interacts with bromine water, forming a white precipitate of 2,4,6-tribromoaniline:

This reaction is qualitative for aniline and often identifies it among other organic compounds.

Interaction of aniline with nitrous acid

Aniline reacts with nitrous acid, but in view of the specificity and complexity of this reaction, it does not occur in the real USE in chemistry.

Aniline alkylation reactions

By successive alkylation of aniline at the nitrogen atom with halogenated hydrocarbons, secondary and tertiary amines can be obtained:

Getting aniline

1. Reduction of nitrobenzene with metals in the presence of strong non-oxidizing acids:

C 6 H 5 -NO 2 + 3Fe + 7HCl = + Cl- + 3FeCl 2 + 2H 2 O

Cl - + NaOH = C 6 H 5 -NH 2 + NaCl + H 2 O

Any metals up to hydrogen in the range of activity can be used as metals.

Reaction of chlorobenzene with ammonia:

С 6 H 5 −Cl + 2NH 3 → C 6 H 5 NH 2 + NH 4 Cl

Chemical properties of amino acids

Amino acids are called compounds in the molecules of which there are two types of functional groups - amino (-NH 2) and carboxy- (-COOH) groups.

In other words, amino acids can be considered as derivatives of carboxylic acids, in the molecules of which one or more hydrogen atoms are replaced by amino groups.

Thus, the general formula of amino acids can be written as (NH 2) x R (COOH) y, where x and y are most often equal to one or two.

Since there is both an amino group and a carboxyl group in amino acid molecules, they exhibit chemical properties similar to both amines and carboxylic acids.

Acidic properties of amino acids

Formation of salts with alkalis and alkali metal carbonates

Esterification of amino acids

Amino acids can enter into an esterification reaction with alcohols:

NH 2 CH 2 COOH + CH 3 OH → NH 2 CH 2 COOCH 3 + H 2 O

Basic properties of amino acids

1. Formation of salts by interaction with acids

NH 2 CH 2 COOH + HCl → + Cl -

2. Interaction with nitrous acid

NH 2 -CH 2 -COOH + HNO 2 → HO-CH 2 -COOH + N 2 + H 2 O

Note: interaction with nitrous acid proceeds in the same way as with primary amines

3. Alkylation

NH 2 CH 2 COOH + CH 3 I → + I -

4. Interaction of amino acids with each other

Amino acids can react with each other to form peptides - compounds containing the peptide bond -C (O) -NH- in their molecules

At the same time, it should be noted that in the case of a reaction between two different amino acids, without observing some specific synthesis conditions, the formation of different dipeptides occurs simultaneously. So, for example, instead of the reaction of glycine with alanine above, leading to glycylananine, a reaction leading to alanylglycine can occur:

In addition, the glycine molecule does not necessarily react with the alanine molecule. Peptization reactions also occur between glycine molecules:

And alanine:

In addition, since the molecules of the resulting peptides, like the original amino acid molecules, contain amino groups and carboxyl groups, the peptides themselves can react with amino acids and other peptides, due to the formation of new peptide bonds.

Individual amino acids are used to produce synthetic polypeptides or so-called polyamide fibers. So, in particular, using the polycondensation of 6-aminohexanoic (ε-aminocaproic) acid, nylon is synthesized in industry:

The nylon resin obtained as a result of this reaction is used for the production of textile fibers and plastics.

Formation of internal salts of amino acids in aqueous solution

In aqueous solutions, amino acids exist mainly in the form of internal salts - bipolar ions (zwitterions):

Getting amino acids

1) Reaction of chlorinated carboxylic acids with ammonia:

Cl-CH 2 -COOH + 2NH 3 = NH 2 -CH 2 -COOH + NH 4 Cl

2) Cleavage (hydrolysis) of proteins under the action of solutions of strong mineral acids and alkalis.