First purine nucleotide, which is synthesized in purine biosynthesis ?: (A) AMP, (B) GMP, (C) IMP, (D) UMP
Answer is C. 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.