Biochemistry

The combination of a nitrogenous base (e.g., adenine) with pentose is called a nucleoside. Nucleosides are bicomponent substances, adding phosphoric acid they turn into mononucleotides - ternary compounds. Phosphoric acid binds to nucleosides due to ester bonds with pentose alcohol hydroxyl. According to the composition of carbohydrates included in nucleic acids, deoxyribonucleic (DNA) and ribonucleic (RNA) acids are distinguished . Deoxyribonucleic acid (DNA) is localized mainly in the nuclei of cells (in chromosomes) and only a small amount of it is found in mitochondria and chloroplasts. The molecular weight is (0.5-20) x 10 6 Da and more. The main function of DNA is that it is a storage medium for genetic information . It encodes all the hereditary properties of the body, primarily all protein structures and, consequently, the characteristics of metabolism. This is due to a certain sequence of arrangement of nitrogenous bases in the structure of DNA.. The composition of DNA includes nitrogenous bases: adenine (A), guanine (G), thymine (T) and cytosine (C), carbohydrate - deoxyribose and phosphoric acid . The primary structure of the molecule is a unique sequence connected with the fight mononucleotides connection type 3,5. The nucleotide phosphodiester linkages found which are formed between the OH group in position 5' deoxyribose nucleotide and one OH-group in the position of 3' another pentose (Fig. 5.1). Figure 5.1 - Fragment of the primary structure of DNA In this case, nitrogenous bases in a certain way are interconnected according to the principle of complementarity (additions): purine bases complement pyrimidine ones. For example, adenine always connects only with thymine, and guanine with cytosine. 118