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The biological role of amino acids and their application

What is the biological role of amino acids? Let's try together to find the answer to this question. We reveal the peculiarities of the structure of this class of organic substances, their chemical properties, the main fields of application.

Historical background

The first open amino acid was glycine. It was synthesized in 1820 by acid hydrolysis of gelatin. Decipher the amino acid composition of protein molecules was only possible by the middle of the last century, it was then revealed an amino acid - threonine.

Main functions

At the moment there is information about 300 amino acids, performing various functions in the body.

What is the main biological role of amino acids? Twenty of them are considered standard (proteinogenic), because they are part of the main protein molecules.

These compounds are part of certain proteins. Oksiprilin is the basis of collagen, elastin is formed by desmosin.

They can be intermediate substances in metabolic processes. This function is performed by citrulline, ornithine.

The biological function of amino acids also consists in the synthesis of nucleotides, polyamides. The carbon chain of these compounds is used to form other organic substances:

  • Glucose is synthesized from glucogenic amino acids;
  • Lipids are formed by ketogenic compounds.

The biological role of amino acids lies in the possibility of their use for the determination of functional groups. Cysteine is used in the detection of the sulfate group. Aspartate is used in the detection of an amino group.

Nomenclature Features

How correctly to name amino acids? The structure, classification, biological role of these compounds are considered even in the course of the school curriculum.

Amino acids are derivatives of carboxylic acids, in which one hydrogen atom is replaced by an amino group.

Depending on the location of this functional group, one compound may have several isomers. Chemists use at once three different nomenclatures: rational, trivial, systematic.

The trivial names of these compounds are related to the source from which they were isolated. Serin is included in the fibroin silk, glutamine is found in the gluten of cereal plants. Cystine is present in the stones of the bladder.

The rational name is associated with the carboxylic acid derivative, and the abbreviated designation is used to indicate the sequence of amino acids in the protein molecule. In biochemistry, the abbreviated and trivial names of these compounds are used.

Classification of amino acids

In order to understand the biological role of amino acids and their application, let us dwell in more detail on the types of classification of these organic compounds.

Currently, several types of classification are used:

  • By the radical;
  • By the degree of its polarity;
  • On the variant of synthesis in the body.

By the structure of the radical in organic chemistry different types of amino acids are isolated.

Aliphatic compounds can contain one carboxyl and an amino group, in which case they are monoaminocarbon compounds.

In the presence of two COOH and one amino group, the substances are called monoamino dicarboxylic substances.

Also, diaminomonocarboxylic and diaminodicarboxylic forms of amino acids are isolated.

Cyclic species differ not only in the number of cycles, but also in their qualitative composition.

According to Lenin, amino acids are divided into four groups according to the specific features of the interaction of the hydrocarbon radical with water:

  • Hydrophobic;
  • Hydrophilic;
  • Negatively charged;
  • Positively charged.

Depending on the ability of amino acids to synthesize in the human body, indispensable (come with food), as well as interchangeable species.

Numerous scientific experiments have proved the biological role of alpha-amino acids.

Physical properties

What are the characteristics of amino acids? The nomenclature, properties, biological role of these compounds is offered to school leavers at the uniform state examination in chemistry. These organic acids are highly soluble in water, have a high melting point.

Their optical activity is explained by the presence in the molecules of an asymmetric carbon atom (except glycine alone). That is why L- and D-stereoisomers of amino acids were discovered.

L-series isomers are found in animal proteins. The value of the hydrogen index for these compounds is in the range of 5.5-7.

Chemical properties

Let us consider in more detail amino acids. The structure, chemical properties, the biological role of these organic substances must be known.

The specificity of the chemical properties of amino acids lies in their duality. The cause of amphotericity is the presence of two functional groups in these organic acids.

The presence of a carboxyl group COOH gives these compounds an acidic character. They easily interact with active metals, basic oxides, alkalis. Also, the acidity of the properties of these organic compounds is manifested in the esterification reaction (with esters form esters).

Amino acids can also enter into chemical interaction with salts formed by weak mineral acids. As an example of such a reaction, one can consider the interaction of amino acids with bicarbonates and carbonates.

The main properties of this class are the ability of amino acids to react with other acids on the amino group. In this case, salts are formed.

The biological role of decarboxylation of amino acids is that a neutral medium is formed, which is absolutely safe for a living organism.

Ninhydrin reaction allows detecting amino acids in a solution. The essence of the reaction is that a colorless solution of ninhydrin interacting with an amino acid will condense in the form of a dimer through a nitrogen atom which is split off from the amino group of the corresponding acid.

The resulting pigment has a red-philolite shade, in addition, decarboxylation of the amino acid results in the formation of a certain aldehyde and carbon monoxide (4).

It is the ninhydrin reaction used by biologists in the analysis of the primary structure of protein molecules. By the intensity of the color, it is possible to detect the quantitative content of amino acids in the initial solution, so such an analysis is appropriate when determining the concentration of amino acids.

Specific reactions

In amino acids, in addition to carboxyl and amino groups, additional functional groups may be present. To determine them in the research laboratories carry out qualitative reactions.

Arginine can be detected in the mixture by performing a qualitative Sakaguchi reaction (on the guanidine group). Cysteine can be determined by the Fole method, specific for the SH group.

The nitration reaction (xantoprotein reaction) makes it possible to confirm the presence of an aromatic amino acid in the mixture. The Millon reaction is designed to detect the hydroxyl group in the aromatic ring of tyrosine.

Features of peptide bonding

What are the characteristics of sulfur-containing amino acids? Their biological role is associated with the formation of peptide molecules. When several molecules of amino acids interact with each other, water molecules are cleaved, and amino acid residues form peptides using peptide (amide) bonds.

The number of amino acid residues forming the polypeptide varies significantly. Those peptides that contain no more than ten amino acid residues are called oligopeptides. The name of the resulting compound is often indicated by the amount of amino acid residues.

If the substance contains more than ten amino acid residues, the compounds are called polypeptides. For those compounds that contain more than fifty amino acid residues, the product of their synthesis is called protein.

So, the hormone glucagon, which contains 29 amino acids, is called a hormone. Amino acid residues are considered monomers of the initial organic acids from which the protein compounds are formed.

That amino acid residue that is written to the left has an amino group, is called N-terminal, the fragment having a carboxyl group is considered C-terminal, it is customary to write it on the right.

When the polypeptide is named, the abbreviated names of the amino acids from which it is formed are used. For example, if glycine, serine, alanine were involved in the interaction, the resulting tripeptide would be read as glycilserilalanine.

The Importance of Some Amino Acids

Glycine (aminoacetic acid) is a donor of carbon fragments, which are necessary for the formation of hemoglobin, pyrrole, choline, nucleotides, and also for the synthesis of creatine.

Serin is present in the active centers of enzymes. This amino acid is needed for the process of synthesis of phosphoprotein (casein of natural milk).

Glucogenic acid is needed to form a secondary, tertiary structure of the protein molecule. In this compound there is the most reactive-active functional group, therefore the substance easily enters the redox processes, binds heavy metals in the form of insoluble compounds. It is she who performs the function of the donor of the sulfate group, which is in demand for the synthesis of sulfur-containing substances.


Amino acids are amphoteric organic compounds having an important biological significance. It is the amino acid residues in the synthesis that form a sequence that is the primary structure of the protein molecule. Depending on how exactly the amino acid fragments are built, a protein specific for each living organism is synthesized.

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