. Nucleic acids The inherent characteristics of each and every species are transmitted from one generation to the next. It has been observed that the particles in nucleus of the cell are responsible for the transmission of these characteristics. They are called chromosomes and are made up of proteins and another type of biomolecules called nucleic acids.
There are mainly two types nucleic acids, the deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). They are the molecular repositories that carry genetic information in every organism. . .
Composition and structure of nucleic acids Nucleic acids are biopolymers of nucleotides. Controlled hydrolysis of DNA and RNA yields three components namely a nitrogenous base, a pentose sugar and phosphate group. Nitrogen base These are nitrogen containing organic compounds which are derivatives of two parent XII XII - - - - compounds, pyrimidine and purine . Both DNA and RNA have two major purine bases, adenine (A) and guanine (G).
In both DNA and RNA, one of the pyrimidines is cytosine (C), but the second pyrimidine is thymine (T) in DNA and uracil (U) in RNA. NH NH Purine Adenine Guanine Tymine (T) NH Cytosine (C) Uracil (U) HC CH CH Pyrimidine XII XII - - - - Pentose sugar: Nucleic acids have two types of pentoses. The recurring deoxyribonucleotide units of DNA contain ’-deoxy-D-ribose and the ribonucleotide units of RNA contain D-ribose . In nucleotides, both types of pentoses are in their β-furanose (closed five membered rings) form.
CH OH ' ' ' ' Ribose CH OH ' ' ' ' ' ' Deoxyribose P Phosphate group Phosphoric acid forms phospho diester bond between nucleotides. Based on the number of phosphate group present in the nucleotides, they are classified into mono nucleotide, dinucleotide and trinucleotide. Nucleosides and nucleotides: The molecule without the phosphate group is called a nucleoside . A nucleotide is derived from a nucleoside by the addition of a molecule of phosphoric acid.
Phosphorylation occurs generally in the ’ OH