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Explain about thecomposition and structureof nucleicacids . |
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Answer» Solution :(i) Nucleic acids arebiopolymers of nucleotides. Controlledhydrolysis of DNA and RNA YIELDS three componentsnamely a nitrogeneousbase , a pentosesugarand phosphategroup. (ii) Nitrogenbase: - (a) Theseare nitrogen containing organic compounds whichare derivatives of tow parentcompounds , pyrimidine and purine . (b)BothDNAand RNA havetwo majorpurinebases,ADENINE (A) andguanine (G). In both DNAand RNA , oneof the pyrimidinesis cytosine (C),but thesecondpyrimidineisthymine (T) in DNA and uracil (U) in RNA. (iii) Pentose Sugar : -Nucleicacidshave two types ofpentoses. The recurring deoxyribonucleotide units of DNA contain 2- deoxy - D- riboseand theribonucleotide units of RNA containD - ribose . In nucleotides, bothtypes of pentoseare in their `beta` - furanose form. (IV) Phosphate group : - Phosphoricacidformsphsophor diester bondbetweennucleotides . Basedon the numberof phsphate group presentin thenucleotides, theyare classsifiedmono nucleotide, dinucleotide and trinucleotide . The molecule withoutthe phosphate group is calleda nucleoside. Anucelotide is derivedform a nucleulewithout the phosphategroup is calleda nucleoside . Anucleotideis derivedforma nucleoside by theaddtiton ofa molecule ofphosphoricacid . (vi) Sugare + Base `to`Nucleoside . Nucleoside +Phosphate `to` Nucleotide. Nucelotide`to` Polynucelotide(Nucleic ACID ). |
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