Nucleotides are important for several reasons.
The genetic information is coded in the sequence of nucleotides in a DNA molecule. Polymers of nucleotides such as DNA and the several types of RNA in the body are called nucleic acids. Nucleotides and related compounds are also important energy carrying compounds. These two molecules AMP and CMP illustrate the two basic types of nucleotides. CMP's nitrogen bearing base has one ring and that kind of base is called a pyrimidine.