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NUCLEIC ACIDS- Part 8
See all quizzes of NUCLEIC ACIDS- Part 8 here:
1 The enzyme common to catabolism of all
the purines is
(A) Adenosine deaminase
(B) Purine nucleoside phosphorylase
(C) Guanase
(D) None of these
2. Uric acid is the end product of purine as
well as protein catabolism in
(A) Man (B) Fish
(C) Birds (D) None of these
3. Daily uric acid excretion in adult men is
(A) 2–6 mg (B) 20–40 mg
(C) 150–250 mg (D) 40–600 mg
4. Dietary purines are catabolised in
(A) Liver (B) Kidneys
(C) Intesitnal mucosa (D) All of these
5. De novo synthesis of pyrimidine nucleotides
occurs in
(A) Mitochondria (B) Cytosol
(C) Microsomes (D) Ribosomes
6. An enzyme common to de novo synthesis
of pyrimidine nucleotides and urea is
(A) Urease
(B) Carbamoyl phosphate synthetase
(C) Aspartate transcarbamoylase
(D) Argininosuccinase
7. The nitrogen atoms of pyrimidine nucleus
are provided by
(A) Glutamate
(B) Glutamate and aspartate
(C) Glutamine
(D) Glutamine and aspartate
8. The carbon atoms of pyrimidine nucleus
are provided by
(A) Glycine and aspartate
(B) CO2 and aspartate
(C) CO2 and glutamate
(D) CO2 and glutamine
NUCLEIC ACIDS 249
9. Nitrogen at position 1 of pyrimidine nucleus
comes from
(A) Glutamine (B) Glutamate
(C) Glycine (D) Aspartate
10. Nitrogen at position 3 of pyrimidine nucleus
comes from
(A) Glutamine (B) Glutamate
(C) Glycine (D) Aspartate
11. The carbon atom at position 2 of pyrimidine
nucleus is contributed by
(A) CO2 (B) Glycine
(C) Aspartate (D) Glutamine
12. Aspartate contributes the following
carbon atoms of the pyrimidine nucelus:
(A) C2 and C4 (B) C5 and C6
(C) C2, C4 and C6 (D) C4, C5 and C6
13. The first pyrimidine nucleotide to be
formed in de novo synthesis pathway is
(A) UMP (B) CMP
(C) CTP (D) TMP
14. Conversion of uridine diphosphate into
deoxyuridine diphosphate requires all
the following except
(A) Ribonucleotide reductase
(B) Thioredoxin
(C) Tetrahydrobiopterin
(D) NADPH
15. Amethopterin and aminopterin decrease
the synthesis of
(A) TMP (B) UMP
(C) CMP (D) All of these
16. For synthesis of CTP and UTP, the amino
group comes from
(A) Amide group of Asparagine
(B) Amide group of glutamine
(C) α-Amino group of glutamine
(D) α-Amino group of glutamate
17. CTP synthetase forms CTP from
(A) CDP and inorganic phosphate
(B) CDP and ATP
(C) UTP and glutamine
(D) UTP and glutamate
18. For the synthesis of TMP from dump, a
coenzyme is required which is
(A) N10- Formyl tetrahydrofolate
(B) N5- Methyl tetrahydrofolate
(C) N5, N10- Methylene tetrahydrofolate
(D) N5- Formimino tetrahydrofolate
20. All the enzymes required for de novo
synthesis of pyrimidine nucleotides are
cytosolic except
(A) Carbamoyl phosphate synthetase
(B) Aspartate transcarbamoylase
(C) Dihydro-orotase
(D) Dihydro-orotate dehydrogenase
21. During de novo synthesis of pyrimidine
nucleotides, the first ring compound to be
formed is
(A) Carbamoyl aspartic acid
(B) Dihydro-orotic acid
(C) Orotic acid
(D) Orotidine monophosphate
22. Tetrahydrofolate is required as a coenzyme
for the synthesis of
(A) UMP (B) CMP
(C) TMP (D) All of these
23. All of the following statements about
thioredoxin reductase are true except:
(A) It requires NADH as a coenzyme
(B) Its substrates are ADP, GDP, CDP and UDP
(C) It is activated by ATP
(D) It is inhibited by dADP
24. De novo synthesis of pyrimidine nucleotides
is regulated by
(A) Carbamoyl phosphate synthetase
(B) Aspartate transcarbamoylase
(C) Both (A) and (B)
(D) None of these
25. Cytosolic carbamoyl phosphate synthetase
is inhibited by
(A) UTP (B) CTP
(C) PRPP (D) TMP
250 MCQs IN BIOCHEMISTRY
235. Cytosolic carbamoyl phosphate synthetase
is activated by
(A) Glutamine (B) PRPP
(C) ATP (D) Aspartate
26. Aspartate transcarbamoylase is inhibited
by
(A) CTP (B) PRPP
(C) ATP (D) TMP
27. The following cannot be salvaged in human
beings:
(A) Cytidine (B) Deoxycytidine
(C) Cytosine (D) Thymidine
28. β -Aminoisobytyrate is formed from catabolism
of
(A) Cytosine (B) Uracil
(C) Thymine (D) Xanthine
29. Free ammonia is liberated during the
catabolism of
(A) Cytosine (B) Uracil
(C) Thymine (D) All of these
30. β -Alanine is formed from catabolism of
(A) Thymine
(B) Thymine and cytosine
(C) Thymine and uracil
(D) Cytosine and uracil
