Structure of Nucleic Acids

Structure of Nucleic Acids

Nucleic acids are the biomolecules which play a very important role in the process of Inheritance.

Two types of nucleic acids exist: DNA (Deoxyribo Nucleic Acid) and RNA (Ribo Nucleic Acid).

DNA has a double-stranded structure. It is a polynucleotide whose monomer units are deoxyribonucleotide. Length of DNA is determined by number of nucleotides in it.

RNA, on the other hand, has a single-stranded structure. It is also a polymer whose monomer units are ribonucleotide.

 

A nucleotide has 3 components:                     

• Pentose sugar
  • Monosaccharide with 5 Carbon atoms
  • Ribose sugar in RNA
  • Deoxyribose sugar in DNA

• Nitrogenous base
  • Nitrogen containing compound with properties of a base
  • 2 types: Purines, Pyrimidines
    • Purine
      • Heterocyclic aromatic organic compound
      • 9-membered ring
      • Examples: Adenine, Guanine
  •  
    • Pyrimidine
      • Heterocyclic aromatic organic compound
      • 6-membered ring
      • Examples: Cytosine, Uracil, Thymine

 

• Phosphate group
  • Inorganic salt of phosphorus
  • Forms backbone of polynucleotide chain along with the sugar

 

Formation of a polynucleotide takes place using the following linkages:

1. Nitrogenous base is linked to the pentose sugar through a N-glycosidic bond to form a nucleoside
2. A phosphate group is linked to 5'-OH of a nucleoside through phosphoester bond to form a nucleotide
3. Multiple nucleotides are joined together through 3'-5' phosphodiester bond to form a polynucleotide