What type of nitrogenous bases are adenine and guanine classified as?

Adenine and guanine are classified as purines, which is a type of nitrogenous base. Purines are characterized by their two-ring structure, which distinguishes them from pyrimidines, the latter of which have a single-ring structure. In the context of nucleic acids, purines pair with pyrimidines to form the rungs of the DNA ladder, specifically pairing with thymine (in DNA) and uracil (in RNA) for adenine, and cytosine for guanine.

Understanding the classification of adenine and guanine as purines is essential because it highlights their role in forming the genetic code and reflects on their chemical properties, such as their size and bonding capabilities. This classification also helps in understanding the structure of DNA and RNA, where the type of nitrogenous base plays a critical role in base pairing and the stability of the nucleic acid structure.