Biochemistry Lecture No. 22: Introduction To DNA & RNA
Tuesday October 30 , 2012
Major Functions Of DNA & RNA:
-Major in the flow of genetic material, both DNA and RNA play key roles in the human body. While DNA
is responsible for carrying genetic material, RNA provides a template for producing proteins (mRNA),
makes up much of the ribosome (rRNA), and also carries amino acids to the ribosome (tRNA).
Building Blocks Of RNA:
-Ribonucleotides are composed of three parts: a sugar, a nitrogenous base, and a phosphate. Once a
nitrogenous base is added to a sugar, the resulting molecule is called a nucleoside (e.g. cytidine). The
base and the sugar are structurally held together by an N-glycosidic bond since the anomeric carbon is
joined to a nitrogen atom in the base. This leaves the anomeric carbon stuck in its β configuration (all
nucleic acids in our cells have their sugar in the β configuration). A prime (‘) is used to denote numbering
in a sugar that is part of a nucleoside.
-As phosphate groups are added to the nucleoside at the 5’ carbon in its sugar, you start to see the
development of a nucleotide. Phosphoanhydride bonds are excellent bonds for storing energy (e.g.
ATP). In DNA, the sugar is a deoxyribose, which always loses an oxygen atom from the hydroxyl group on
the 2’ carbon.
Nitrogenous Bases – Purines & Pyrimidines:
-Purines are nitrogenous bases in DNA and RNA