This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
Nitrogen atoms in purines are derived from all except 
Select and explain. 
A. Aspaate, B. Glutamine, C. THF, D. Glycine
C: THF
Answer: C: THF 
Explanation: The N atoms at positions 3 and 9 are derived from the amide nitrogen glutamine Ref-Sathyanarayana 4/e