Belkov called nitrogenous high-molecularorganic matter. They are built of amino acids. Proteins fulfill fundamental tasks in the vital activity and structure of organisms, being their main and necessary component. It is thanks to these organic compounds that there is a metabolism, energy transformations.
Due to the relatively large sizemolecules, the complexity of the structure, as well as a lack of information on the structural composition of most substances, did not establish a rational unified classification of proteins. The existing system of separation is largely conditional. In its construction, the physical and chemical properties of proteins, sources of their production, biological activity and other, often random, signs are taken as a basis.
So, globular and fibrillar,hydrophobic (insoluble) and hydrophilic (soluble) substances. This separation is based on the physicochemical properties of the compounds. Depending on the source of production, proteins of the nervous tissue, blood serum, muscles, and others are isolated. There are also bacterial, animal and plant compounds. In accordance with biological activity, proteins-hormones, protein-enzymes, contractile and structural proteins, antibodies and others are secreted. It should be noted that there are separate compounds that can not be assigned to any of the above groups. This is due to the imperfection of the classification system and the exceptional diversity of the proteins themselves.
It is accepted to divide connections into complex(proteids) and simple (proteins). Simple proteins are only amino acid polymers. Complex compounds, besides amino acid residues, contain non-proteinaceous inclusions.
Each cell contains thousands of organichigh-molecular compounds. Due to the fact that during the life of the body these substances are destroyed sooner or later, the cell must carry out continuous protein synthesis to restore its organoids, membranes and other components. Along with this, a large number of cells carry out the formation of organic compounds for the whole organism. Such a "production" is engaged, for example, cells in the glands of internal secretion, producing hormones. Here the synthesis of protein is the most intense.
The production of compounds requires considerable energy costs. A source providing not only protein synthesis, but also all cellular processes, is ATP.
It should be noted that the variety of functions andproblems of compounds is formed in accordance with their primary structure - the amino acid sequence in the molecule. Hereditary data on the primary protein structure are contained in the nucleotide chain of the DNA molecule. The portion of deoxyribonucleic acid that contains information about the amino acid sequence of one compound is called a gene.
The synthesis of protein occurs on ribosomes, in the cellularcytoplasm. In the cytoplasm from the nucleus, information about the structure of the compound comes in the form of i-RNA (information RNA). To perform the synthesis of the i-RNA molecule, "unwinding" (despiralization) of the DNA site occurs. The subsequent process is based on the principle of complementarity. With the help of enzymes on one of the DNA strings, RNA molecules are synthesized.
The cytoplasm must containa certain set of amino acids. It is necessary for protein synthesis. The formation of these amino acids is due to the breakdown of food organic compounds. In addition, the amino acid can enter the site of direct synthesis (into the ribosome), adhering to a special transport RNA (t-RNA).
