Purines

Definition

Purines are a type of nitrogenous base found in nucleotides, which are the building blocks of DNA and RNA. They include adenine (A) and guanine (G).

5 Must Know Facts For Your Next Test

1. Purines have a double-ring structure consisting of a six-membered and a five-membered nitrogen-containing ring fused together.
2. Adenine pairs with thymine in DNA and with uracil in RNA via two hydrogen bonds.
3. Guanine pairs with cytosine in both DNA and RNA via three hydrogen bonds.
4. Purines are larger than pyrimidines due to their double-ring structure.
5. The synthesis and breakdown of purines involve complex biochemical pathways that are crucial for cellular metabolism.

Review Questions

• What are the two purines found in DNA?
• How do purines differ structurally from pyrimidines?
• Which bases do adenine and guanine pair with in DNA?

Related terms

Pyrimidines: Nitrogenous bases that have a single-ring structure, including cytosine, thymine, and uracil.

Nucleotide: The basic structural unit of nucleic acids such as DNA and RNA, consisting of a nitrogenous base, a sugar molecule, and one or more phosphate groups.

Hydrogen Bonds: Weak bonds that form between complementary nitrogenous bases in the DNA double helix.