Amino acids, the formulas of which are discussed in the high school chemistry course, are important substances for the human body. Proteins, consisting of amino acid residues, are necessary for a person to fully function.
Definition
Amino acids, the formulas of which will be discussed below, are organic compounds whose molecules contain amino and carboxyl groups. Carboxyl consists of a carbonyl and a hydroxyl group.
You can consider amino acids as derivatives of carboxylic acids, where the hydrogen atom is replaced by an amino group.
Features of chemical properties
Amino acids, whose general formula can be represented as CnH2nNH2COOH, are amphoteric chemical compounds.
The presence of two functional groups in their molecules explains the possibility of these organic substances displaying basic and acidic properties.
Their aqueous solutions have the properties of buffer solutions. A zwitterion is an amino acid molecule where the amino group is NH3+ and the carboxyl is -COO-. A molecule of this type has a significant dipole moment, whilethe total charge is zero. Crystals of many amino acids are built on such molecules.
Among the most important chemical properties of this class of substances, polycondensation processes can be distinguished, as a result of which polyamides are formed, including proteins, peptides, nylon.
Amino acids, the general formula of which is CnH2nNH2COOH, react with acids, bases, metal oxides, s alts of weak acids. Of particular interest are the interactions of amino acids with alcohols related to esterification.
Features of isomerism
In order to write down the structural formulas of amino acids, we note that many amino acids involved in biochemical transformations contain an amino group in the a-position from the carboxyl group. Such a carbon atom is a chiral center, and amino acids are considered optical isomers.
The structural formula of amino acids gives an idea of the location of the main functional groups that make up a given substance, relative to the active carbon atom.
Natural amino acids that are part of protein molecules are representatives of the L-series.
Optical isomers of amino acids are characterized by spontaneous slow non-enzymatic racemization.
Features of a-compounds
Any formula of substances of this type assumes the location of the amino group at the second carbon atom. 20 amino acids, the formulas of which are considered even in a school biology course, are alsobelong to this species. For example, these include alanine, asparagine, serine, leucine, tyrosine, phenylalanine, valine. It is these compounds that make up the human genetic code. In addition to standard connections? non-standard amino acids, which are their derivatives, were also found in protein molecules.
Classification by synthesis
How can the essential amino acids be separated? Formulas of this class are subdivided according to the physiological basis into semi-replaceable, capable of being synthesized in the human body. Ordinary compounds synthesized in any living organism are also isolated.
Division for radical and functional groups
The amino acid formula differs in the structure of the radical (side group). There is a division into non-polar molecules containing a hydrophobic non-polar radical, as well as into charged polar groups. Aromatic amino acids are considered as a separate group in biochemistry: histidine, tryptophan, tyrosine. Depending on the functional groups, several groups are distinguished. Aliphatic compounds are represented by:
- monoaminomonocarboxylic compounds, which can be considered glycine, valine, alanine, leucine;
- oxymonocaminocarboxylic substances: threonine, serine;
- monoaminocarboxylic: glutamic, aspartic acid;
- sulfur-containing compounds: methionine, cysteine;
- diaminomonocarboxylic substances: lysine, histidine, arginine;
- heterocyclic: proline, histidine,tryptophan/
Any amino acid formula can be written in general terms, only radical groups will differ.
Qualitative definition
In order to detect small amounts of amino acids, a ninhydrin reaction is carried out. In the process of heating amino acids with an excess of ninhydrin, a purple product is obtained if the acid has a free a-amino group, and a yellow product is typical for a protected group. This method has high sensitivity and is used for colorimetric detection of amino acids. On its basis, the method of partition chromatography on paper, introduced by Martin in 1944, was created.
The same chemical reaction is used in an automatic amino acid analyzer. The device, created by Moore, Shpakman, Stein, is based on the separation of an amino acid mixture in columns filled with ion-exchange resins. From the column, the eluent current enters the mixer, ninhydrin also goes here.
The quantitative content of amino acids is judged by the intensity of the resulting color. The readings are recorded by a photoelectric colorimeter, recorded by a recorder.
Similar technology is currently used in clinical practice for blood, cerebrospinal fluid and urine tests. It allows you to give a complete picture of the qualitative composition of amino acids contained in biological fluids, to identify non-standard nitrogen-containing substances in them.
Features of the nomenclature
How to name correctlyamino acids? The formulas and names of these compounds are given according to the international IUPAC nomenclature. The position of the amino group is added to the corresponding carboxylic acid, starting from the hydrocarbon at the carboxyl group.
For example, 2-aminoethanoic acid. In addition to the international nomenclature, there are trivial names used in biochemistry. Thus, aminoacetic acid is a glycine used in modern medicine.
If there are two carboxyl groups in the molecule, the suffix -dionic is added to the name. For example, 2-aminobutanedioic acid.
For all representatives of this class, structural isomerism is characteristic, due to changes in the structure of the carbon chain, as well as the location of the carboxyl and amino groups. In addition to glycine (the simplest representative of this class of oxygen-containing organic substances)? the remaining compounds have mirror antipodes (optical isomers).
Application
Amino acids are common in nature, they are the basis for building animal and vegetable proteins. These compounds are used in medicine in case of severe exhaustion of the body, for example, after complex surgical operations. Glutamic acid helps fight nervous diseases, and histidine is used to treat stomach ulcers. In the synthesis of synthetic fibers (capron, enanth), aminocaproic and aminoenanthic acids act as raw materials.
Conclusion
Amino acids are organic compounds that in theirhave two functional groups. It is the structural features that explain the duality of their chemical properties, as well as the specifics of their use. Based on the results of research experiments, it was possible to establish that the biomass of living organisms that live on our planet totals 1.8 1012-2.4 1012 tons of dry matter. Amino acids are the initial monomers in the biosynthesis of protein molecules, without which the existence of humans and animals is impossible.
Depending on physiological characteristics, there is a division of all amino acids into essential substances, the synthesis of which is not carried out in the human body and mammals. In order to avoid disturbances in metabolic processes, it is important to eat foods that contain these amino acids.
It is these compounds that are a kind of "bricks" that are used to build biopolymers-proteins. Depending on which amino acid residues, in what sequence they will line up in the protein structure, the resulting protein has certain physical and chemical properties and applications. Thanks to qualitative reactions to functional groups, biochemists determine the composition of protein molecules, looking for new ways to synthesize individual biopolymers necessary for the human body.
