NUCLEIC ACID: CLASSIFICATION,ITS MONOMER AND FORMATION OF POLYNUCLEOTIDE

NUCLEIC ACID:

Nucleic acid was first reported in(1869) by a swiss physician when he isolated a new compound from the nuclei of pus cell(WHITE BLOOD CELLS). This compound was neither a PROTEIN nor LIPID nor a CARBOHYDRATE; therefore, it was a novel type of BIOLOGICAL MOLECULE He named this molecule NUCLEIN because it was located in nucleus. The basic structure and chemical nature of this nuclein  was determined in 1920 and was renamed as NUCLEIC ACID because of its acidic nature

CHEMICAL STRUCTURE OF NUCLEIC ACID:

Now it has been cleared that nucleic acid has two types
1-DNA(Deoxyribo nucleic acid)
2-RNA(Ribonucleic acid)
actually ribose is a aldopentose. It is monosaccaride. the difference between DNA and RNA is that RNA conatin ribose sugar and DNA contain deoxyribose Sugar(mean from ribose OH group was removed from carbon number 2)
Both nucleic acids are linear unbranched polymers. The monomer of nucleic acid is NUCLEOTIDE

COMPOSITION OF NUCLEOTIDE:

Nucleotide is a monomer of nucleic acid. Nucleotide of DNA is know DEOXYRIBONUCLEOTIDES and nucleotide of RNA is known as RIBONUCLEOTIDES. Each nucleotide consist of
1-Pentose Sugar
2-Phosphoric acid
3-Nitrogen containing ring structures called BASES
Pentose sugar in case of DNA is deoxyribose and pentose sugar in case of RNA is ribose. Phosphoric acid is common component of both DNA and RNA it provides acidic nature to them. There are two major classification of nitrogen bases
1- Pyrimidine(Single ring)
2-Purines(Double ring)
Pyrimidine bases are of three type
1-Cytosine

2-Thymine(Only found in DNA)

3-Uracil(Only found in RNA)

Purines bases are also of two types
1-Adenine

2-Guanine

                                             During the formation of nucleic acid first nitrogen base attach to first carbon of pentose sugar. Such combination is called NUCLEOSIDE. when phophoric acid attach to five carbon of nucleoside nucleotide forms. Nucleotides which take part in the formation of DNA or RNA will must have three phosphates. During incorporation into DNA or RNA two terminal phosphates from nucleotide remove

FORMATION OF POLYNUCLEOTIDE:

WE know that by condensation biomolecules join and during condensation water molecule released. Nucleotide also join by condensation but the molecule which is released is not water but pyrophosphate(Two phosphate group bound togeather). When pyrophosphate cleaved by the addition of water, a great deal of energy release which drive the process. In this way nucleotides begin to link and bond form between them known as PHOTODIESTER BOND