This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Biochemistry
First purine nucleotide, which is synthesized in purine biosynthesis ? 
Select and explain. 
A. AMP, B. GMP, C. IMP, D. UMP
C: IMP
Answer: C: IMP 
Explanation: The biosynthesis of purine begins with ribose-5-phosphate, derived from pentose phosphate pathway (PPP). First intermediate formed in this pathway, 5-phosphoribosyl-pyrophosphate (PRPP), is also an intermediate in purine salvage pathway. REF: Lippincott book of biochemistry 6th ed.