Nucleic acids


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Nucleic acids

  1. 1. Nucleic Acids : RNA and DNANucleoproteins – are conjugated proteins, theprosthetic group of which are nucleic acidsNucleic acids – are macromolecules found abundantin tissues possessing closed packed cells with bignuclei like thymus, liver, spleen, kidney, andpancreas - also found in bacteria, bacteriophages, chromosomes and constitute the whole make-up of the simple filterable virusesThe protein components of the nucleoproteins aresimple proteins, albumins, histones and protaminsProperties of Nucleoproteins 1. acidic, soluble in alkalis and hot water forming salts 2. insoluble in alcohol 3. slightly soluble in cold water 4. precipitated by acetic acid but are redissolved by dilute HCL
  2. 2. Importance of Nucleoproteins 1. closely associated with the chromosomes of the cells 2. act as co-factors to the enzymes – catalytic activities 3. play a role in the energy transfer in living organismsTypes of Nucleic acids 1. RNA – less strictly org. than DNA; exists as a single strand Types of RNA a. messenger RNA (mRNA) – 3% - contains genetic code transcribed from DNA; also called template RNA or information RNA b. transfer RNA (tRNA)- 10-20% of cellular RNA; “soluble RNA” c. ribosomal RNA (rRNA) -80% - provides the working area for protein synthesis d. viral RNA (vRNA) – forms the chemical nature of viruses; ex. RNA viruses in poliomyelitis, common colds, influenza 2. DNA – similar to RNA , acid, alkali, heat, and low ionic strength can cause denaturation of DNA
  3. 3. Melting temperature – temperature at which 50% of the molecule is denaturated Renaturation (annealing) of DNA – if the temperature of the melted DNA is lowered or below the melting temperature, so double bond is reformed RNA DNA1. functions Protein Storage and synthesis transmission of genetic material2. sugar d- ribose d- deoxyribosecomposition3. Pyrimidine uracil thyminebasecomposition4. structure Single strand Double helix5. source Isolated Tissues with large from yeast nuclei- thymus,liver, spleen,kidney,pancreasFeulgen test – differentiates the DNA from RNA
  4. 4. Properties of purines and pyrimidines 1. they have limited solubilities in water 2. they exist in lactam-lactim form (keto-enol) tautomeric forms 3. absorb UV light- maximum absorption occurring around 260nm. This property is frequently used for the detection and quantitative determination of nucleic acidNucleoproteins when treated with weak acid, alkaliand enzymes will undergo degradation into variousproducts. NucleoproteinsSimple proteins Nucleic acids Nuclease Nucleotides Nucleotidase Phosphates Nucleosides Nucleosidase Sugar N2 Base d- ribose pyrimidine d-deoxyribose purine adenine guanine