Quiz: Basic Principles of Protein
Score for this attempt: 68 out of 80
Submitted Aug 27 at 3:14pm
This attempt took 79 minutes.
Question 1
2 / 2 pts
What form of the folate coenzyme is required for the conversion of
homocysteine to methionine?
dihydrofolate
methylene-tetrahydrofolate
formyl-tetrahydrofolate
C !
methyl-tetrahydrofolate
methenyl-tetrahydrofolate
Question 2
2 / 2 pts
Which of the following amino acids is properly paired with the amino acid
from which it is derived?
Pro: Ala
Arg: Lys
C !
Tyr: Phe
Ser: Cys
Gln: Asp
Question 3
2 / 2 pts
Which of the following describes the general three-dimensional structure of a
tRNA?
since all tRNAs have very different three-dimensional structure, it is difficult
describe a general shape
a cloverleaf shape with the anticodon and acceptor stem on "leaves" that are
opposite each other
a large loop with the anticodon and 3′ end in very close proximity to each
other
an elongated cylinder shape with the anticodon and acceptor stem at
opposite ends
C !
an L shape with the anticodon at one end of the L and the acceptor stem at
the other
Question 4
2 / 2 pts
The disease gout is characterized by high levels of ________, which forms
crystal deposits of ________, resulting in painful joints
uric acid; urea
urea; uric acid
C !
uric acid; sodium urate
sodium urate; urea
none of the above
Question 5
0 / 2 pts
Which of the following is a function of the ribosome?
I. bind mRNA and allow codon recognition
II. mediate the binding of proteins necessary for initiation, elongation, and
termination
III. catalyze synthesis of peptide bonds
IV. translocate such that multiple codons can be read
Y Answered
I, IV
I only
II only
Correct Answer
I, II, III, IV
I, II
Question 6
2 / 2 pts
Which of the following is true regarding the interaction of EF-Tu with
aminoacyl-tRNAs?
the interaction always involves the anticodon loop
EF-Tu binds charged and uncharged tRNAs with the same affinity
the higher the occurrence of an amino acid in a protein, the stronger the
interaction
free aminoacyl-tRNAs can only bind to the ribosome in vitro
C !
binding occurs with about equal affinity for all aminoacyl-tRNAs
Question 7
2 / 2 pts
Why does the mRNA adopt a sharp bend as it moves through the ribosome?
in order to maximize base pairing with the 23S rRNA
C !
so the tRNAs in both the A and P site can interact with their appropriate
codons
to prevent dissociation of the 30S and 50S subunits
so that the mRNA can enter the 30S subunit and exit the 50S subunit
all of the above
Question 8
2 / 2 pts
In E. coli translation, ________ aids with binding of the fMet-tRNA to the 30S
subunit while ________ blocks the A site.
IF-1; IF-3
C !
IF-2; IF-1
IF-1; IF-2
IF-3; IF-1
IF-2; IF-3
Question 9
0 / 2 pts
The amino acids metabolized by the branched chain keto acid
dehydrogenase complex are ________.
Pro, Leu and Met
Correct Answer
Val, Leu and Ile
Ile, Thr and Pro
Y Answered
Thr, Val and Pro
none of the above
Question 10
2 / 2 pts
What amino acid is the precursor for the neurotransmitters epinephrine and
norepinephrine?
aspartate
serine
glutamate
tryptophan
C !
tyrosine
Question 11
2 / 2 pts
The amino acids Ala, Cys, Gly, and Ser are all degraded to the metabolic
intermediate ________ and are considered ________.
pyruvate; ketogenic
acetoacetate; ketogenic
acetyl-CoA; glucogenic
C !
pyruvate; glucogenic
acetyl-CoA; ketogenic
Question 12
0 / 2 pts
Attachment of ________ to a Lys residue of a protein targets it for transport
into the nucleus.
SRP
ubiquitin
Y Answered
DnaK
Correct Answer
SUMO
trigger factor
Question 13
2 / 2 pts
A mutation in GDH of patients with HI/HA (hypoglycemia/hyperammonemia)
results in a decrease in allosteric control of GDH via GTP. Which of the
following will be observed in the patients?
an increase in ammonia
an increase in glutamate
an increase in NADH
A and B
C !
A and C
Question 14
2 / 2 pts
What molecule is used to reduce ribonucleotide reductase back to its
catalytically active state?
FADH2
NADPH
C !
thioredoxin
ferredoxin
NADH
Question 15
2 / 2 pts
Signal recognition particle is a ________ whose function is to ________.
chaperone; aid in protein folding
C !
ribonucleoprotein; direct proteins to the membrane or endoplasmic reticulum
DNA-protein complex; transport proteins into the eukaryotic nucleus
glycosylase; catalyze posttranslational modification
none of the above
Question 16
2 / 2 pts
Chaperones such as trigger factor generally bind to what regions of a
polypeptide?
C !
hydrophobic regions
acidic regions
basic regions
neutral polar regions
both acidic and basic regions
Question 17
2 / 2 pts
What nucleotide is methylated to produce dTMP?
dAMP
C !
dUMP
dGMP
dCMP
both dCMP and dUMP can be converted to dTMP
Question 18
0 / 2 pts
Transfer RNA molecules are involved in ________.
replication
Correct Answer
translation
reverse transcription
post-translational processing
Y Answered
transcription
Question 19
2 / 2 pts
The activity of glutamine synthetase is
I. regulated allosterically by tryptophan.
II. inhibited allosterically by glucosamine-6-phosphate.
III. activated by nine allosteric feedback inhibitors.
IV. altered by covalent modification.
I, II
I, III
C !
I, II, III, IV
III, IV
I, IV
Question 20
2 / 2 pts
Which of the following glycolytic intermediates is the common precursor to
serine, cysteine and glycine?
C !
3-phosphoglycerate
pyruvate
dihydroxyacetone phosphate
glyceraldehyde-3-phosphate
fructose-6-phosphate
Question 21
2 / 2 pts
Which of the following is the only tRNA loop that is exclusively single
stranded RNA?
TψC loop
anticodon loop
D loop
acceptor step
C !
none of the above
Question 22
2 / 2 pts
The genetic code is said to be ________ because several codons may
correspond to the same amino acid.
decadent
deteriorate
C !
degenerate
despicable
depraved
Question 23
2 / 2 pts
Which of the following tRNA binding sites is correctly defined?
T site: site that is briefly occupied while the tRNA is passed from the A site to
P site
E site: entrance site for initial tRNA binding
P site: site occupied by the tRNA that accepts the growing peptide chain
C !
A site: accepts incoming aminoacyl-tRNA
all of the above
Question 24
2 / 2 pts
The term rRNA refers to ________ RNA.
C !
ribosomal
recombinant
rho factor
retroviral
Question 25
2 / 2 pts
Which of the following aids in protein folding by completely sequestering a
polypeptide from its environment?
ubiquitin
heat shock protein
signal recognition particle
trigger factor
C !
chaperonin
Question 26
2 / 2 pts
What is the similarity between the amino acids that have only one codon
each?
they are neutral polar amino acids
C !
they occur very infrequently in proteins
they are the sulfur containing amino acids
they are aromatic amino acids
none of the above
Question 27
2 / 2 pts
What are the products of the following transamination reaction?
α-ketoglutarate + alanine ⇌ ________ + ________
glutamate; oxaloacetate
aspartate; oxaloacetate
aspartate; pyruvate
C !
glutamate; pyruvate
none of the above
Question 28
2 / 2 pts
Which of the following initiation steps results in GTP hydrolysis?
binding of IF-2 to the 30S subunit
binding of mRNA to the 30S subunit
binding of IF-1 to the A site
C !
binding of the 50S subunit to the 30S subunit
binding of the fMet-tRNA to the ribosome
Question 29
2 / 2 pts
Which of the following best describes the preparation of fMet-tRNA for
translation in prokaryotes?
fMet isn't used in prokaryotes, only in eukaryotes
Met is first formylated, then added to a tRNA specific for the start codon and
differs from the tRNA designed to carry Met
C !
Met is first added to a tRNA specific for the start codon that differs from that
designed to carry Met, then formylated
Met is first formylated, then added to a "regular" tRNAMet; the fact that it has
the formyl group allows use in the initiation codon
Met is first added to a "regular" tRNAMet, then formylated; the fact that it has
the formyl group allows use in the initiation codon
Question 30
2 / 2 pts
How many ATP and electrons are required for the reduction of one molecule
of nitrogen to two molecules of ammonia in the reaction catalyzed by
nitrogenase?
C !
16 ATP and 8 electrons
8 ATP and 16 electrons
8 ATP and 8 electrons
16 ATP and 6 electrons
16 ATP and 16 electrons
Question 31
0 / 2 pts
Which of the following amino acids is a source of both carbon and nitrogen
for UMP?
Y Answered
Gly
Correct Answer
Asp
Asn
Glu
Gln
Question 32
2 / 2 pts
Which of the following amino acids is a source of both carbon and nitrogen
for IMP?
C !
Gly
Asn
Gln
Asp
Glu
Question 33
2 / 2 pts
The kidney has a small amount of gluconeogenic activity. Which of the
following explains the source of carbon for gluconeogenesis?
conversion of citrate into acetyl-CoA and oxaloacetate
conversion of aspartate into oxaloacetate
conversion of odd-chain fatty acids into succinyl-CoA
C !
conversion of glutamine into glutamic acid, then to α-ketoglutarate
conversion of alanine into pyruvate
Question 34
2 / 2 pts
Hydrolysis of GTP by EF-Tu is thermodynamically required for ________.
aminoacyl-tRNA binding to the ribosomal A site
transpeptidation
C !
proofreading
translocation
none of the above
Question 35
2 / 2 pts
Threonine is considered both ketogenic and glucogenic because it is
converted to ________ and ________.
carbamoyl phosphate; acetoacetate
pyruvate; acetyl-CoA
C !
glycine; acetyl-CoA
glycine; glutaryl-CoA
ammonia; acetoacetate
Question 36
2 / 2 pts
What enzyme is responsible for the conversion of nucleotides to
deoxynucleotides?
C !
ribonucleotide reductase
ribonucleotide deoxidase
ribonucleotide dehydrogenase
ribonucleotide oxidase
ribonucleotide dehydratase
Question 37
2 / 2 pts
Polypeptide synthesis proceeds from the ________ to the ________.
C-terminus; N-terminus
peptidyl site; aminoacyl site
entrance site; exit site
50S subunit; 30S subunit
C !
N-terminus; C-terminus
Question 38
2 / 2 pts
What enzyme catalyzes the conversion of phenylalanine to tyrosine?
phenylalanine decarboxylase
phenylalanine hydrolase
C !
phenylalanine hydroxylase
phenylalanine desaturase
phenylalanine oxidase
Question 39
2 / 2 pts
What coenzyme is required for the conversion of serine to glycine?
pyridoxal phosphate
cobalamin
biotin
lipoic acid
C !
tetrahydrofolate
Question 40
0 / 2 pts
In the mechanism of ribonucleotide reductase, a ________ is generated at C3′
to stabilize the ________ that is formed at C2′.
radical; carbanion
Correct Answer
radical; carbocation
carbocation; radical
Y Answered
carbanion; radical
carbanion; carbocation
a,
Quiz Score: 68 out of 80
