VPB 112: General Veterinary Biochemistry (1+1)

INTRODUCTION

• Nucleic acids are nitrogen-containing compounds of higher molecular weight found in association with proteins in the cell.
• Nucleic acids account for 0.5 – 1 % of dry weight of the cell.
• They are conjugated proteins. The nucleic acid and protein complex is known as Nucleoproteins.
• The nucleoproteins can be separated into proteins and nucleic acids by treatment with acids or salts of higher concentration.
• The protein is usually a basic protein ( they contain more of arginine and lysine) such as protamines and histones.
• The nucleic acid is acidic due to the presence of phosphate group and are –vely charged under physiological condition.
• The 2 main groups of nucleic acids are Ribonucleic acid (RNA) and Deoxyribo nucleic acid (DNA).
• Hydrolysis of DNA and RNA under controlled conditions yield nucleotides and further hydrolysis of nucleotides yields nucleosides and phosphates.
• Hydrolysis of nucleosides then produces sugars, which may be either a ribose or a deoxyribose and a number of purine and pyrimidine bases. In nucleosides,the bases are linked to the pentose sugar by β-configuration.
• Purine bases are adenine and guanine. Pyrimidine bases are uracil, thymine and cytosine.
• A nucleic acid molecule is constructed of monomeric units called nucleotides joined together by phosphodiester bond.
• Nucleotides are composed of 3 parts, namely, nitrogenous base which may be a purine or a pyrimidine, a sugar molecule, which may be ribose or a deoxyribose and a phosphate group.
• Polynucleotide structure is written from the left to right(5’→ 3’). The 5’ end is phosphorylated and 3’ end has a free hydroxyl group.
• At neutral pH, the purines and pyrimidines are hydrophobic and insoluble in water. At acidic or alkaline pH, the bases become charged and their solubility is increased in water.
• The length of the DNA is expressed as bp. Kb is a unit of 1000 bases in DNA or RNA sequence. In double stranded DNA it is kilo base pair ( kbp).