Biochemistry

The NH 3 and C0 2 released as a result of these reactions are used for the biosynthesis of urea, nitrogen bases, decarboxylation processes and other reactions. 9.2 PROTEIN BIOSYNTHESIS Protein biosynthesis takes place in all cells of a living organism and ensures renewal of the protein composition, metabolic processes and their regulation, as well as the growth and differentiation of organs and tissues. Proteins are synthesized in tissues from free amino acids with the participation of nucleic acids. They are in the process of constant digestion and synthesis. Proteins of blood plasma, liver, kidneys, mucous membrane of the small intestine and pancreas are restored faster. Within nine days, about 50% of the liver proteins are renewed. Slower this process occurs in the muscles (every 120 days), the skin and especially the nervous system. An average, all proteins are updated in the body in about 135-155 days. An average of 1.3 g of protein per I kg of body weight is synthesized per person per day, which with an average weight of 70 kg is about 90 g. Consequently, to ensure protein biosynthesis needs adequate intake food substances. The protein biosynthesis process proceeds with the energy consumption accumulated in the form of ATP. This ensures the formation of certain proteins of a strictly specific structure, which is encoded in DNA. The process of protein synthesis can be divided into three main stages. At the first stage, which is called transcription (from lat. transcriptio - reading), M-RNA molecules is synthesis on DNA, after which M-RNAs enter the ribosomes. In this way, information about the structure of the synthesized protein is transmitted to ribosomes - the place of their direct formation. The second stage - recognition (from lat. recognition - recognition) - is the combination of amino acids necessary for the synthesis of polypeptide chains with specific T-RNAs and their delivery to ribosomes. The third stage - translation (from lat. translation - translation) consists in translating the nucleotide sequence of M-RNA into the amino acid sequence of the polypeptide chain during protein synthesis on ribosomes. The reproduction of proteins in all organisms occurs according to the principle of matrix synthesis with the participation of nucleic acids. Matrix synthesis refers to the process of reproducing proteins in exact accordance with the program. DNA is a carrier and keeper of genetic information. The information is programmed in the DNA with nucleotide sequence, i.e., a matrix is compiled in accordance with which a specific protein is synthesized. 182