De novo purine ring synthesis incorporates atoms from several precursors. Which single precursor contributes three different atoms to the completed purine ring?
- A Aspartate
- B Glutamine
- C Glycine ✓
- D Carbon dioxide
Correct answer: C. Glycine
Explanation
Glycine is incorporated intact and supplies three atoms of the purine ring: B4, B5, and N7. Glutamine donates only two nitrogens (N3 and N9), aspartate donates a single nitrogen (N1), and CO2 supplies only B6. Formyl-tetrahydrofolate contributes B2 and B8. Knowing that an entire amino acid is inserted as a unit explains why glycine is the largest single contributor to the ring.
Reference: Lippincott's Illustrated Reviews: Biochemistry, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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