1.
5-Phosphoribosyl-1-pyrophosphate
(PRPP) is a substrate for which of the following enzymes?
A)
ribonucleotide reductase
B)
thymidylate synthase
C)
carbamoyl phosphate synthetase-II
D) Curidine
kinase
E)
hypoxanthine-guanine phosphoribosyl transferase (HGPRT)
2.
A
42-year-old male cancer patient undergoing radiation therapy (which kills lots
of cells and leads to degradation of their intracellular contents) develops
severe pain in his right big toe. Laboratory analyses indicate an elevated
serum uric acid level and urate crystals in his urine. This patient's pain is
caused by the overproduction of the end product of which of the following
metabolic pathways?
A)
Pyrimidine nucleotide catabolism
B)
Ketone body synthesis
C)
Pentose phosphate pathway
D)
B-oxidation of fatty acids
E)
Purine nucleotide catabolism
3.
IMP
is:
A) A
product of pyrimidine degradation
B)
Precursor to urea
C)
An intermediate in purine synthesis which has only 1 ring of the purine nucleus
D) A
precursor to AMP and GMP
E)
The product of PRPP and glutamine
4.
NOT
an enzyme involved in purine biosynthesis:
A)
Orotate phosphoribosyl transferase
B)
IMP dehydrogeanse
C)
Glutamine PRPP amidotransferase
D)
IMP synthase
E)
GAR synthetase
5.
NOT
a method of de novo purine synthesis regulation
A)
Inhibition of IMP dehydrogenase by GMP
B)
Inhibition of adenylosucinate synthetase by AMP
C)
Inhibition of adenylosuccinate synthetase by GMP
D)
Inhibition of glutamine PRPP amidotransferase by IMP, GMP and AMP
E)
Inhibition of PRPP synthetase by IMP, GMP and AMP
6.
Reaction
involved in de novo synthesis of pyrimidines
A)
Formation of N-carbamoylaspartate from aspartate and carbon dioxide
B)
Addition of a ribose 5-phosphate side chain from ribulose 5-phosphate
C)
Phosphorylation of uridylate (UMP) to UTP
D)
Phosphorylation of cytidylate (CMP) to CTP
E)
Formation of CTP from UTP using aspartate
7.
Source
of carbon atoms in the pyrimidine ring
A)
Alanine
B)
Glycine
C)
Phenylalanine
D)
glutamate
8.
A
patient develops severe pain in his big toe. Laboratory tests find elevated
serum uric acid and urate-crystals in his urine. The patient's pain is caused
by the overproduction of the end product of which metabolic pathway?
A)
De novo pyrimidine biosynthesis
B)
De novo purine biosynthesis
C)
Pyrimidine degradation
D)
Purine degradation
9.
A
one year old female patient is weak and anemic. Her weight and height are below
average. There are elevated orotic acid levels in her urine. Which compound is
most likely to alleviate the symptoms?
A)
Thymidine B) Uridine C) Hypoxanthine D) Guanine 1 E) Adenine
10.
Which
of the following is NOT a useful chemotherapeutic agent?
A)
Fluorouracil
B)
Methotrexate
C)
Trimethoprim
D)
Allupurinol
E)
Azaserine
11.
NOT
an enzyme involved in purine degradation
A.
Xanthine oxidase
B.
Aminotransferase
C.
Guanine deaminase
D.
Adenosine deaminase
12.
Which
of these is NOT involved in thymidylate synthesis?
A.
Xanthine oxidase
B.
Dihydrofolate reductase
C.
Thymidylate synthase
D.
DUMP
E.
N5,N10-methylene THF
13.
Which
enzyme is used to convert GMP into GDP?
A.
Thioredoxin kinase
B
Adenylate kinase
C.
Guanylate kinase
D.
NTP kinase
14.
NOT
an enzyme involved in nucleotide salvage
A.
Phosphorylases
B.
nucleotidases
C.
Nucleoside kinases
D.
Phosphoribosyl oxidase
15.
After
several weeks of methotrexate chemotherapy, a patient's tumour begins to show
signs of resistance to treatment. Which of the following is likely to explain
this?
A.
Overproduction of dihydrofolate reductase
B.
Overproduction of xanthine oxidase
C.
Deficiency of PRPP synthase
D.
Deficiency of thymidine kinase
E.
Deficiency of thymidylate synthase
16.
Orotic
aciduria results from deficiency of 2 enzymes which convert orotate to UMP. One
of these enzymes acts as a:
A.
Decarboxylase
B.
Dehydrogenase
C.
Transcarbamoylase
D.
Phosphatase
17.
A
drug which prevents uric acid synthesis by inhibiting the enzyme xanthine
oxidase is
A.
Aspirin
B.
Allopurinol
C.
Colchicine
D.
Probenecid
18.
Carbamoyl
phosphate synthetase I and II are similar for:
A.
Carbon source
B.
Nitrogen source
C.
Intracellular location
D.
Regulation by N-acetyl glutamate.
19.
Lesch-Nyhan
syndrome has an enzyme deficiency that catalyzes conversion of:
A.
Adenine to AMP
B.
Guanine to GMP
C.
Adenosine to AMP
D.
Guanosine to GMP.
20.
Carbamoyl
phosphate synthetase I and II are similar for:
A.
Carbon source.
B.
Nitrogen source.
C.
Intracellular location.
D.
Regulation by N-acetyl glutamate.
21.
The
only organelle contains its own DNA is
A.
Ribosomes
B.
Cytoplasm
C.
Mitochondria
D.
Cell membrane