<prompt> Nitrogen-9 of purine ring is provided by ?GlycineAspaateGlutamineCO2  <response>: In de novo synthesis, purine ring is formed from variety of precursors is assembled on ribose-5-phosphate. Precursors for de novo synthesis are - i Glycine provides C4, C5 and N7 ii Aspaate provides N1 iii Glutamine provides N3 and N9 iv Tetrahydrofolate derivatives furnish C2 and C8 v Carbon dioxide provides C6 