3. NUCLEOTIDE
Nucleotides are organic molecules consisting of a
nucleoside( contain one nitrogenous base & a
pentose sugar) and one or more phosphate group.
Nucleotides are the monomer of DNA
(Deoxyribonucleic acid) and RNA (Ribonucleic acid)
both of which are essential bio-molecules within all
life-forms on Earth.
4. • Pentose sugar : Deoxyribose sugar
and Ribose sugar.
• Phosphate : Two nucleotide link-
up by phosphate group and create
polynucleotide.Ex-DNA,RNA.
• Nitrogenous base: One or two ring bases that contains Nitrogen
in the ring.Two types-
1. Purine base - larger double ring structure. Ex:
Adenine(A),Guanine(G).
2. Pyrimidine base – single ring structure. Ex:
Cytosine(C),Thymine(T),Uracil(U).
6. Pathways for the biosynthesis of nucleotides: Nucleotide
biosynthesis in the cell can be grouped into two broad classes –
1. De-novo synthesis (synthesis from scratch): It is a biochemical
pathway in which nucleotides are synthesized new from simple
precursor molecules.Such as sugar or amino acids.
2. Salvage pathway ( recycle pathway): This pathway is used to
recover bases and nucleosides formed during the degradation of
RNA and DNA.
10. ANTICANCER DRUGS
Structural analogues purine synthesis inhibitors:
This structural analogues act as competitive
inhibitor of the naturally occurring nucleotides
that are used to synthesized DNA.when wrong
Bases are in corporated the DNA becomes
functionally inactive. There by cell division is
Arrested,so they are useful as anticancer drug.
Example :
Mercaptopurine
Azaserine
Inhibits the conversion of
IMP to GMP & AMP
Glutamine antagonist
