Facilitating understanding of the purine nucleotide cycle and the one-carbon pool: Part I: The purine nucleotide cycle.

Some metabolic processes are readily understood because they are circumscribed in metabolic pathways that have clearly identifiable beginning points, end products, and other features. Other metabolic pathways that do not appear to be straightforward pose difficulties for students. One such metabolic process, the purine nucleotide cycle, is discussed here.