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5.1.4. Nucleotides


The nucleotides are formed by bonding by ester linkage of a molecule of phosphoric acid and nucleoside, by the group hydroxyl of the fifth (carbon 5') of the pentose.

Nucleotides therefore have a strong acid character.

Nucleoside + phosphoric acid = Nucleotide

Bonds in nucleotides

  • N-glucosidic bond, between the pentose and the nitrogenous base, forming a nucleoside.
  • Phosphoester bond, between the phosphate group and the pentose (of the nucleoside), releasing a water molecule between an OH of the phosphate and another OH of the pentose.
  • Phosphodiester bond, bond between two consecutive nucleotides.

Each nucleotide is made up of three components:

  • Nitrogenous bases: derived from purine and pyrimidine.
    • Puric nitrogenous bases: they are adenine (A) and guanine (G). Both are part of DNA and RNA, and have a structure formed by two cycles similar to purine.
    • Pyrimidine nitrogenous bases: they are thymine (T), cytosine (C) and uracil (U). They have a single ring structure similar to pyrimidine.
      • In DNAthymine and cytosine.
      • In RNAcytosine and uracil.
  • Pentose: The five carbon monosaccharide can be ribose (RNA) or deoxyribose (DNA).
  • Phosphoric acid, H3PO4: Each nucleotide can contain one (like AMP), two (like ADP), or three (like ATPphosphate groups.

Depending on the nucleotide having ribose or deoxyribose, they are called ribonucleotides and deoxyribonucleotides.

Nucleotides are named by removing the final "a" from the nucleoside name and adding the term "5'-monophosphate" So we have to:

  • The nucleotides of RNA are adenosine-5'-monophosphate (AMP), guanosine-5'-monophosphate (GMP), cytidine-5-monophosphate (CMP) and uridine-5'-monophosphate (UMP).
  • The DNA nucleotides are the monophosphate deoxyadenosine-5'- (dAMP), the deoxyguanosine-5'-monophosphate (dGMP), the deoxycytidine 5'-monophosphate (dCMP) and deoxythymidin-5'-monophosphate (dTMP).

But normally, to name each nucleotide, we will use the initial of each nitrogenous base (A, G, C, T).

Fundamental ideas about nucleotides

The nucleosides are formed by bonding a ribose or a deoxyribose, a nitrogenous base, by a N-glycosidic bond .

The nucleotides are formed by bonding by ester bond, of a molecule of phosphoric acid and nucleoside.

Two consecutive nucleotides are joined by a phosphodiester bond

  • Composition of nucleotides:
    • The DNA nucleotides are formed by:
      • Deoxyribose
      • Phosphoric acid H3PO4.
      • Nitrogenous bases:
        • Adenine.
        • Cytosine.
        • Thymine.
        • Guanine.
    • The RNA nucleotides are formed by:
      • Ribose.
      • Phosphoric acid H3PO4.
      • Nitrogenous bases:
        • Adenine.
        • Cytosine.
        • Uracil.
        • Guanine.
  • Localization of nucleic acids:
  • Nucleic acid functions