(Nucleotides and Nucleic Acids ( Session 4

Nucleic Acids: DNA and RNA
There are two chemically distinct types of nucleic acids:
•Deoxyribonucleic acid (DNA): is polymer of deoxyribonucleotides covalently
linked by phosphodiester bond 3´? 5? that function as carring the genetic
information in all cellular forms of life and some viruses.
• Ribonucleic acid (RNA): is polymer of ribonucleotides covalently linked by
phosphodiester bond 5´? 3´ that function as an intermediary in the transfer
of genetic information from DNA to protein.

Nucleotides
Nucleotides : are basic building block of nucleic acids (DNA and RNA)
Each nucleotide consists of three components:
•Nitrogenous base
•A sugar (ribose or deoxyribose)
•A Phosphate molecule
While nucleoside composed of only :
•Nitrogenous base
•A sugar (ribose or deoxyribose)

?A sugar : There are two types of a sugar including
( Ribose in RNA and Deoxyribose in DNA )
?Phosphate molecule: The phosphate groups are strongly acidic and
are the reason DNA and RNA are called acids