Preparatory Guide on Biochemistry, Molecular Biology, Physiology, Microbiology, Immunology, Pharmacology & Drug Discovery

Purine and Pyrimidine Metabolism: MCQ

July 22, 2018
Questions on Purine Metabolism
1. The function of nucleotide includes:
a) Second Messenger
b) Energy currency and high energy equivalents
c) Regulators of intermediary metabolism
d) All of the above

2. Purines and Pyrimidines are the nitrogen bases present on the nucleotides. Which of the following is a purine base?
a) Adenosine
b) Cytosine
c) Thymine
d) Uracil

3. Nucleotides are:
a) Purine bases
b) Nitrogen bases+ Pentose Sugar
c) Nitrogen bases + Pentose sugar + Phosphate
d) None of the above

4. Which of the following is not the precursor for the denovo purine biosynthesis?
a) Aspartic Acid
b) Glycine
c) Glutamine
d) Arginine

5. Which of the following serves as the cofactor for the denovo synthesis of purine metabolism?
a) Thiamine
b) Biotin
c) Folate
d) Flavin

6. What is an activator of the enzyme “Glutamine: Phosphoribosylpyrophosphate amidotransferase” a committed step of de novo biosynthesis of purines?
a) Adenosine Monophosphate
b) Guanosine Monophosphate
c) Inosine Monophosphate
d) Phosphoribosyl Pyrophosphate

7. Which of the following is the correct statement regarding Sulfonamides?
a) Structural analogs of PABA that competitively inhibit bacterial synthesis of folic acid
b) Structural analogs of PABA that competitively inhibit the human synthesis of folic acid
c) Structural analogs of PABA that competitively inhibit the bacterial and human synthesis of folic acid
d) None of the above

8. Trimethoprim is a potent antibacterial compound that selectively inhibits bacterial:
a) Formyltransferase
b) PRPP synthetase
c) Dihydrofolate reductase
d) None of the above

9. Which of the following is the coenzyme for the synthesis of deoxyribonucleotides catalyzed by an enzyme ribonucleotide reductase?
a) Glutathione
b) Thioredoxin
c) NADPH
d) FADH

10. Severe combined immunodeficiency disease is caused by the deficiency of the following enzymes?
a) AMP deaminase
b) Adenosine deaminase
c) PRPP synthetase
d) None of the above

Answers
1-d
2-a
3-c
4-d
5-c
6-d
7-a
8-c
9-b
10-b

Questions on Pyrimidine Metabolism 

1) Carbamoyl phosphate synthetase II (CPS-II) is the committed step in the formation of carbamoyl phosphate is:
a) Activated by PRPP
b) Inhibited by UMP
c) Activated by ATP
d) All of the above are correct

2) Which of the following cofactor is used during the conversion of uracil to thymine?
a) S-Adenosyl Methionine
b) Tetrahydrofolate
c) Tetrahydrobiopterin
d) Biotin

3) Which of the following cofactor/coenzyme is NOT utilized in the conversion of ribose to deoxyribose?
a) NADPH
b) FADH2
c) UMP
d) Thioredoxin

4) Followings are the example of nucleosides EXCEPT:
a) Adenosine
b) Cytidine
c) Cytosine
d) Uridine

5) The nitrogens of a purine molecule are derived from all of the following amino acids:
a) Aspartic Acid and Glutamine
b) Asparagine and Glutamine
c) Glutamate and Alanine
d) Glycine and Alanine

6) Which of the following steps of pyrimidine biosynthesis occurs in mitochondria?
a) Synthesis of carbamoyl phosphate catalyzed by CPS II
b) Conversion of carbamoyl phosphate to carbamoyl aspartate catalyzed by aspartate transcarbamoylase
c) Synthesis of dihydroorotate catalyzed by dihydroorotase
d) Formation of orotic acid catalyzed by dihydroorotase dehydrogenase

7) Methotrexate inhibits which of the following enzyme:
a) ribonucleotide reductase
b) thymidylate synthase
c) dihydrofolate reductase
d) PRPP‑amidotransferase
8) Orotic aciduria is an inherited genetic disorder caused by a deficiency of the following enzyme:
a) CPS II
b) Aspartate transcarbamoylase
c) Dihydroorotase dehydrogenase
d) UMP synthase
9) Fluorouracil is an anti-tumor agent that binds and irreversibly inhibit which of the following enzyme:
a) ribonucleotide reductase
b) thymidylate synthase
c) dihydrofolate reductase
d) PRPP‑amidotransferase

10) Which of the following is the degradation product of pyrimidines?
a) beta -alanine
b) Uric acid
c) Allantoin
d) Glycine
Answers
1- d
2- b
3- c
4- c
5- a
6- d
7- b
8- d
9- b
10- a





Purine and Pyrimidine Metabolism: MCQ Purine  and Pyrimidine Metabolism: MCQ Reviewed by Biotechnology on July 22, 2018 Rating: 5
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