Lecture : Bio Notes 240 - Purines
Document Summary
Purines are one of the two categories of nitrogenous bases found in nucleic acids, the other being pyrimidines. Purines consist of a six-membered ring fused to a five-membered ring, and are larger than pyrimidines, which consist only of a six-membered ring. There are two purine bases found in dna and rna: adenine (a) and guanine (g). Adenine forms two hydrogen bonds with thymine (t) in dna or uracil (u) in rna, while guanine forms three hydrogen bonds with cytosine (c) in both dna and rna. These base pairings are crucial for the stability and integrity of the dna double helix and are the basis for the genetic code. Purines are synthesized de novo from simpler precursors in the body, starting with the amino acids glycine, glutamine, and aspartate. The purine ring is built up stepwise by the addition of carbons, nitrogen, and hydrogens, and the final product is inosine monophosphate (imp), which is a precursor to both amp and gmp.
