Question #536d0

Nucleic acids are made up of nucleotides(monomers). Nucleotides can be either ribonucleotides#("in RNA")# or deoxyribonucleotides. In case of #"DNA"# the repeating units or monomers are deoxyribonucleotides.

Structure of deoxyribonucleotide

Each deoxyribonucleotide comprises three components:

• Deoxyribose sugar ** :
  #"DNA"# contains a five carbon sugar or pentose sugar which lack an oxygen atom because of replacement of hydroxyl group#(OH)# with hydrogen atom#(H)#. That's why called as #color(red)"doeoxy"#ribose sugar.

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• Phosphate group:
  Phophate group #(PO4^(3-))# of one deoxyribonucleotide interact with deoxyribose sugar of another deoxyribonucleotide forming a phosphodiester bond b/w them. So these help to maintain structure of #"DNA"# and to help the deoxyribonucleotide subunits to make longer stands of #"DNA"# double helix.

The phosphate groups together with doexyribose sugars form backbone of #"DNA"# molecule.

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• Nitrogenous bases:
  #"DNA"# contains four nitrogenous bases i.e adenine & guanine(purines) and cytosine & thymine(pyrimidines). These bases are linked by hydrogen bonds and are salient in maintaining helical structure of #"DNA"# molecule.
  Guanine#(G)# form #3# hydrogen bonds with cytosine#(C)#.
  Adenine#(A)# form #2# hydrogen bonds with thymine#(T)#.

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Thus overall structure of single deoxyribonucleotide unit can be expressed as:

Hope it helps...