Final answer:
The big picture in purine synthesis involves the de novo synthesis of purine nucleotides, which includes the formation of the purine ring and the attachment of the ribose sugar provided from the HMP pathway.
Step-by-step explanation:
The big picture in purine synthesis involves the de novo synthesis of purine nucleotides, which includes the formation of the purine ring and the attachment of the ribose sugar provided from the HMP pathway. The precursors for the purine ring come from various sources such as aspartate, glutamine, formate, glycine, and carbon dioxide. This pathway is regulated by feedback inhibition at the first step, which is generally irreversible.