RNAs, Structure and Function

RNA structure
Ribonucleic acid or RNA is a biopolymer macromolecule along with DNA. It consists if small subunits called nucleotides which are composed by: The nucleobase is attached on the D-ribose by an N-glycosidic bond, the ribose is bonded on the phospate group through ester bonds, and the backbone bonding between phosphate group and an adjacent ribose sugar through phosphodiester bonds.A phosphate group is attached to the 3' position of one ribose and the 5' position of the next. RNA is relatively unstable in comparison with the DNA molecule as it contains a 2'-OH hydroxyl group that acts as a nucleophil enhancing the cleavage of the phosphodiester bond between adjacent nucleotides.
 * Purine(adenine, guanine) or pyrimidine (cytosine,uracil) nucleobase
 * D-ribose pentose sugar
 * Phosphate group

RNA / DNA differences
RNA and DNA are very similar in structure but they differ in 4 major points:
 * 1) DNA nucleotides include adenine, guanine, thymine or cytosine whereas RNA nucleotides instead of thymine they involve uracil.
 * 2) DNA is always in a double helix structure with 2 strands always running in antiparallel orientation whereas RNA usually exists as a single strand but it has the ability to form a double strand structure too.
 * 3) DNA has a 2'-deoxy-D-ribose pentose sugar whereas RNA has a D-ribose.
 * 4) DNA has equal portions of adenine-thymine and guanine-cytosine nucleobases as it exists as a double stranded molecule where as RNA does not as it usually exists in a single stranded form