Download 2009 Dental Biochemistry (Questions)

Practice questions Exam. II
What is the location of telomeric sequences found in eukaryotic chromosomes?
A) At or near the centromere
B) In the long arm of chromosome
C) In the short arm of Chromosome
D) At both ends of chromosome
E) At the break point in chromosomal DNA( recombination site)
Which of the following eukaryotic DNA polymerases bind to PCNA in order to gain
speed in the rate of DNA synthesis?
A) DNA polymerase alpha
B) DNA polymerase B
C) DNA polymerase Delta
D) DNA polymerase Gamma
E) Telomerase
Termination of RNA synthesis in prokaryotes is greatly aided by the presence of this
factor
A) Sigma factor
B) Rho factor
C) B clamp
D) TATA factor
E) TF II
The ribosomal RNA in eukaryotes is synthesized in the nucleolus. Which is the major
enzyme responsible for its synthesis?
A) RNA polymerase I
B) RNA polymerase II
C) RNA polymerase III
D) RNA polymerase Delta
E) rRNA polymerase
When the amino acid valine undergoes transamination with the oxoacid co-substrate
pyruvate, the amino nitrogen of the valine becomes the amino nitrogen of
A) glutamate.
B) glycine.
C) alanine.
D) aspartate.
E) serine.
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The importance of glutamate being formed as the result of transamination is that
A) this can lead directly to the production of ATP.
B) this occurs in the mitochondrion under conditions of prolonged starvation.
C) this leads to the production of glutamine in the kidney, which is the way
humans generate energy in the absence of adequate intake of proteins.
D) glutamate can undergo a reaction that produces ammonia that can, in turn,
enter the urea cycle.
E) this becomes a signal to up regulate the urea cycle since 2-oxoglutarate is the
allosteric effector for the enzyme that catalyzes the rate-determining step (RDS)
of the urea cycle.
The rate-determining step (RDS) of the urea cycle requires
A) glutamine, 2 ATP, ornithine.
B) glutamate, 2 ATP, bicarbonate.
C) ammonia, bicarbonate, aspartate.
D) arginine, ornithine, 2 ATP.
E) ammonia, bicarbonate, 2 ATP.
Carbon atoms derived from phenylalanine or tyrosine can become those of acetoacetate.
Acetoacetate is
A) virtually absent in the blood of the uncontrolled diabetic.
B) readily oxidized in the brain in response to excessive intake of carbohydrates.
C) the “ketone body” that can be converted into the other two ketone bodies.
D) present only in the liver mitochondrion where it is used for energy production
during fasting.
E) a precursor in the biosynthesis of N-acetylglutamate.
The biosynthesis of the “ATP reservoir” creatine requires the amino acids glycine,
methionine, and
A) cysteine.
B) glutamate
C) glutamine.
D) arginine.
E) serine.
The second messenger nitric oxide (NO) is involved in the signaling that
A) leads to Type I diabetes.
B) leads to most oral cancers.
C) mediates the suppression of pulp-cell growth
D) leads to the activation of adenylyl cyclase and the production of cyclic AMP.
E) promotes the onset of stroke.
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What is the dietary precursor of prostaglandins and other eicosanoid molecules?
a. oleic acid
b. alpha linolenic acid
c. palmitic acid
d. acetic acid
e. linoleic acid
Which of the following nonselective NSAID-related adverse effects can be minimized by
switching to a selective COX-2 inhibitor?
A.
Dyspepsia
B.
GI bleeding
C.
Hypertension
D.
Renal impairment
Feedback inhibition of cholesterol synthesis by dietary cholesterol is defective in patients
with hyperlipoproteinemia. These patients have high cholesterol levels, in part, due to
defective inhibition of a key rate limiting reaction in cholesterol biosynthesis catalyzed
by which one of the following enzymes?
a.
b.
c.
d.
e.
21-hydroxylase
Acetyl CoA synthetase
HMG CoA reductase
Monooxygenase
Desmolase
All of the carbons of cholesterol are derived from which initial compound in the
cholesterol biosynthetic pathway?
a.
b.
c.
d.
e.
bile salts
malate
oxaloacetate
glycerol
acetyl CoA
Bile salts, the major product of cholesterol metabolism, are synthesized in
a.
b.
c.
d.
e.
kidney
gall bladder
liver
small intestine
spleen
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Addison’s disease is characterized by
a. excess adrenal androgen production
b. increased glycolysis
c. obesity
d. hypofunctioning of the adrenal cortex leading to increased ACTH production and
skin darkening which first appears in the gums.
e. hyperfunctioning of the adrenal cortex resulting in excess production of cortisol
Steroid hormones act
a.
b.
c.
d.
e.
via receptors at the plasma membrane
via receptors in the nucleus to affect transcription
via receptors at the cytoskeleton
at the mitochondrial membrane
by activating enzymes
Which one of the following enzymes is required for the synthesis of testosterone?
a. 18 hydroxylase
b. 11 hydroxylase
c. 21 hydroxylase
d. 24 hydroxylase
e. 17 hydroxylase
Which one of the following has anti-inflammatory actions and increases the activity of
four gluconeogenic enzymes?
a. cortisol
b. dehydroepiandrosterone
c. aldosterone
d. androstenedione
e. progesterone
Deamination of cytosine results in the formation of
A. uracil
B. guanine
C. adenine
D. thymine
E. cytidine
In the synthesis of purine nucleotides from phosphoribosyl pyrophosphate, the first compound
to be formed is
A. a methyl derivative.
B. an amine.
C. an ester.
D. a phosphate.
E. a sulfate.
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In purine nucleotide synthesis, the compounds that serve directly as sources of nitrogen atoms
are glycine, glutamine and
A. aspartate.
B, cysteine.
C. serine.
D. proline.
E. alanine.
In gout the condition can be ameliorated by inhibition of the formation of uric acid from
A. thymine and uracil.
B. cytosine
C. hypoxanthine and xanthine.
D. pyruvate and lactate.
E. serine and threonine.
In pyrimidine nucleotide synthesis phosphoribosyl pyrophosphate (PRPP) is required in a
reaction in which the other substrate is
A. aspartic acid.
B. uric acid.
C. glutamic acid.
D. formic acid.
E. orotic acid.
In mammalian cells, feedback inhibition of carbamoyl phosphate synthetase II is exerted
by elevated concentrations of
A.
B.
C.
D.
E.
ATP.
GTP.
IMP.
UTP.
AMP.
N5N10-methylene-tetrahydrofolate is a coenzyme required for the reaction catalyzed by
A. AMP kinase.
B. uricase.
C. thymidylate synthase.
D. adenosine deaminase.
E. ribonucleotide reducatase.
The Lesch-Nyhan syndrome is caused by a lack of the enzyme
A.
B.
C.
D.
E.
xanthine oxidase.
hypoxanthine guanine phosphoribosyl transferase.
adenosine deaminase.
aspartate transcarbamoylase.
dihydrofolate reductase.
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Which of the following types of molecules would accurately describe the Epidermal
Growth Factor Receptor (EGFR)?
a)
b)
c)
d)
e)
G-Protein Coupled receptor
Receptor Serine-Threonine Kinase
Receptor Tyrosine Kinase
Guanine Nucleotide Exchange Protein
Growth Factor Transporter.
Which ONE of the following most accurately describes Ras? It is a
a)
b)
c)
d)
e)
Ca2+ channel that lets Ca2+ enter cells.
protein kinase that causes protein phosphorylation in the presence of growth
factor.
regulator of phospholipase C.
GTPase that modulates the activity of other proteins.
transcription factor that binds the Myc promoter
Which of the following motifs on the Nerve Growth Factor (NGF) Receptor would most
likely interact with the Src homology 2 (SH2) domain of Grb2? Note that pY is
phosphotyrosine, pT is phosphothreonine, pS is phosphoserine, P is Proline, A is
Alanine, and L is Leucine.
a)
b)
c)
d)
e)
pYALP
YALP
PALP
pTALP
pSALP
Which one of the following BEST describes signaling by the Nerve Growth Factor?
a)
b)
c)
d)
Autocrine.
Paracrine.
Juxtacrine.
Holocrine.
All the statements concerning cellular membrane structure are correct except one. Which
one is the exception? Cellular membranes
A.
B.
C.
D.
E.
consist of phospholipids and proteins.
surround cells and intracellular organelles
control the entry and exit of inorganic ions, and nutrients.
have same phospholipid composition on the inner and outer bilayers.
maintain concentration gradients across and inside the cells
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Integral membrane proteins
A.
B.
C.
D.
E.
are bound to the outer bilayers of membranes.
are bound to the inner bilayers of membranes.
may interact with membranes by electrostatic interactions.
may transverse the bilayers one or more times.
are usually very hydrophilic.
Proteins that make up the cell membrane serve as
A.
transporters.
B.
enzymes.
C.
receptors.
D.
mediators.
E.
all of the above.
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