Are adenine and guanine purines or pyrimidines?
Adenine is a purine.
Cytosine is a pyrimidine.
Nucleotides called purines include adenine (A) and guanine (G). These nucleotides have a structure containing both hexagon and pentagon rings. These are the larger nucleotides that make up DNA molecules.
Nucleotides called pyrimidines include cytosine (C) and thymine (T). These nucleotides are smaller because they have a structure of just a single hexagon ring.
This video gives a quick review of base pairing rules in DNA and shows the difference in structure of the four nitrogenous bases.
Hope this helps!