Among the huge variety of natural substances, amino acids occupy a special place. It is explained by their exceptional importance both in biology and in organic chemistry. The fact is that molecules of simple and complex proteins are composed of amino acids, which are the basis of all forms of life on Earth without exception. It is for this reason that science pays serious attention to the study of issues such as the structure of amino acids, their properties, production and use. These compounds are also of great importance in medicine, where they are used as medicinal preparations. For those people who are serious about their own he alth and lead an active lifestyle, protein monomers are a form of food (the so-called sports nutrition). Some of their types are used in the chemistry of organic synthesis as a feedstock in the production of synthetic fibers - enanth and capron. As you can see, aminocarboxylic acids play a very important role both in nature and in the life of human society, so let's get to know them in more detail.
Structure featuresamino acids
Compounds of this class belong to amphoteric organic substances, that is, they contain two functional groups, and, therefore, exhibit dual properties. In particular, the molecules contain hydrocarbon radicals combined with NH2 amino groups and COOH carboxyl groups. In chemical reactions with other substances, amino acids act either as bases or as acids. The isomerism of such compounds is manifested due to a change in either the spatial configuration of the carbon skeleton or the position of the amino group, and the classification of amino acids is determined based on the structural features and properties of the hydrocarbon radical. It can be in the form of a straight or branched chain, and also contain cyclic structures.
Optical activity of aminocarboxylic acids
All monomers of polypeptides, and their 20 species, presented in organisms of plants, animals and humans, belong to L-amino acids. Most of them contain an asymmetric carbon atom that rotates a polarized light beam to the left. Two monomers, isoleucine and threonine, have two such carbon atoms, and aminoacetic acid (glycine) has none. The classification of amino acids according to their optical activity is widely used in biochemistry and molecular biology when studying the process of translation in protein biosynthesis. Interestingly, the D-forms of amino acids are never part of the polypeptide chains of proteins, but are present in bacterial membranes and in the metabolic products of actinomycete fungi, thenthere are, in fact, they are found in natural antibiotics, for example, in gramicidin. In biochemistry, substances with a D-form spatial structure, such as citrulline, homoserine, ornithine, are widely known, which play an important role in cell metabolism reactions.
What are zwitterions?
Recall once again that protein monomers contain functional groups of amines and carboxylic acids. Particles -NH2 and COOH interact with each other inside the molecule, which leads to the appearance of an internal s alt called a bipolar ion (zwitterion). This internal structure of amino acids explains their high ability to interact with polar solvents, such as water. The presence of charged particles in solutions determines their electrical conductivity.
What are α-amino acids
If the amino group is located in the molecule at the first carbon atom, counting from the location of the carboxyl, this amino acid is classified as an α-amino acid. They occupy a leading place in the classification, because it is from these monomers that all biologically active protein molecules are built, for example, such as enzymes, hemoglobin, actin, collagen, etc. The structure of amino acids of this class can be considered using the example of glycine, the same which is widely used in neurological practice as a sedative in the treatment of mild forms of depression and neurasthenia.
The international name for this amino acid is α-aminoacetic, ithas an optical L-shape and is proteinogenic, that is, it participates in the translation process and is part of protein macromolecules.
The role of proteins and their monomers in metabolism
It is impossible to imagine the normal functioning of the organism of mammals, including humans, without hormones consisting of protein molecules. The chemical structure of the amino acids that make up their composition confirms their belonging to α-forms. For example, triiodothyronine and thyroxine are produced by the thyroid gland. They regulate metabolism and are synthesized in its cells from the α-amino acid tyrosine. In simple and complex proteins, there are both 20 basic monomers and their derivatives. Carboxyglutamic acid is present in prothrombin, which regulates blood clotting, methyllysin is found in myosin (muscle protein), and selenocysteine is found in the peroxidase enzyme.
Nutritional value of proteins and their monomers
Considering the structure of amino acids and their classification, let us dwell on the gradation based on the ability or impossibility of protein monomers to be synthesized in cells. Alanine, proline, tyrosine and other compounds are formed in plastic metabolism reactions, while tryptophan and seven other amino acids should enter our body only with food.
One of the indicators of proper and balanced nutrition is the level of human consumption of protein foods. It should be at least a quarter of the total amount of food that has entered the body per day. Especiallyit is important that proteins contain valine, isoleucine and other essential amino acids. In this case, the proteins will be called complete. They enter the human body from plant foods or foods containing mushrooms.
The essential protein monomers themselves cannot be synthesized in mammalian cells. If we consider the structure of amino acid molecules that are indispensable, we can make sure that they belong to different classes. So, valine and leucine belong to the aliphatic series, tryptophan belongs to aromatic amino acids, and threonine belongs to hydroxyamino acids.
