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Module 8 Nucleotide Metabolism — Test 1
Q1. During pyrimidine biosynthesis, which of the following contributes the most atoms to the pyrimidine ring?✓ Aspartate
Q2. The N1 and N3 atoms of the purine ring are contributed by:✓ N1 – aspartate & N3 – glutamine
Q3. Methotrexate, an anticancer drug, is an inhibitor of:✓ Dihydrofolate reductase
Q4. What general pathway(s) can a eukaryotic cell use to synthesize nucleotides?✓ Salvage and de novo pathways
Q5. The end product of AMP and GMP catabolism in normal humans is:✓ Uric acid
Q6. Which statement is true regarding the regulation of purine nucleotide biosynthesis?✓ Adenylosuccinate synthase is inhibited by AMP only
Q7. Which statement is true regarding the regulation of purine nucleotide biosynthesis? (variant)✓ Adenylosuccinate synthase is inhibited by AMP only
Q8. Identify the correct statement about the reaction catalyzed by ribonucleotide reductase (RNR):✓ RNR converts NDP to dNDP
Q9. Purine synthesis differs from pyrimidine synthesis. Which statement is true?✓ Purine ring is synthesized directly on the pentose sugar
Q10. The precursor molecule for pyrimidine biosynthesis is:✓ Carbamoyl phosphate
Q11. The atoms of the pyrimidine ring are derived from:✓ N1,C4,C5,C6 – aspartate; C2 – bicarbonate; N3 – glutamine
Q12. During de novo biosynthesis, the C-2 and N-3 atoms in the pyrimidine ring come from:✓ Carbamoyl phosphate
Q13. De novo synthesis of pyrimidine nucleotides is repressed by:✓ UTP
Q14. Lesch–Nyhan syndrome is a defect in the salvage pathway of nucleotide synthesis. Which nitrogen bases show increased concentration?✓ Hypoxanthine–guanine