Transcript In Anfinsen`s experiment, RNAse was denatured with urea and β

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BC367, Fall 2009
Exam 2 Review Questions
+ In Anfinsen’s experiment, RNAse was denatured with
urea and β-mercaptoethanol. After dialysis and
treatment with oxygen, the enzyme’s activity was
restored. What conclusions can be made from this?
a) Urea and β-mercaptoethanol are ineffective
denaturants.
b) All the necessary information for protein folding is in
the primary structure of RNAse.
c) RNAse is particularly resistant to denaturation.
d) The odds of the enzyme spontaneously folding
correctly, with appropriate disulfide linkages, are
close to 1.
e) There must have been molecular chaperones present
to facilitate proper folding.
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Emperor penguins can remain submerged for up to
18 minutes, diving to a depth of 535 m. What does the
oxygen-hemoglobin dissociation curve look like for an
emperor penguin compared to the domestic duck?
a. The same. The birds have no difference in O2 binding affinity.
b. The dissociation curve is shifted left because the emperor
penguin has a higher O2 binding affinity.
c. The dissociation curve is shifted right because the emperor
penguin has a lower O2 binding affinity.
d. The dissociation curve is shifted left because the emperor
penguin has a lower O2 binding affinity.
e. There is no dissociation curve because birds do not have
hemoglobin.
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You have been invited to join a prestigious relay
team competing in a high-altitude 4 x 5k relay.
Which of the following would be most helpful so you
won’t disappoint your teammates and they’ll want to
invite you back again next year?
a. Traveling everyday to train at the course up in the Rockies
so you can acclimate to the terrain and altitude
b. A mutation of His146  Val in the β chain
c. Sleeping in a hyperbaric chamber so your body gets used
to different pressures
d. Renting a house in Denver, but traveling to do most your
serious workouts in New Orleans
e. Hyperventilating right before the race to decrease your
blood pH and help prevent cramps
+ Which is the most likely phenotypic result of
Hb mutation Arg141α -> Cys (Hb Nunobiki)?
a) Cyanotic
b) Flushed
c) Pale
d) Normal
e) Death
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Assuming equal enzyme concentrations and based
upon the kinetics plot for the substrate S, which of the
following enzymes (A, B, C, or D) would have the highest
kcat/Km value?
A.) A
B.) B
C.) C
D.) D
E.) Not enough information to predict
-Lactamase is an enzyme that conveys resistance to -lactam
antibiotics such as penicillins. For penicillin G, the KM for -lactamase
is 13 μM. Which of the following plots represents inhibition of the
reaction of -lactamase with penicillin G by clavulcanic acid, a
competitive inhibitor? (Concentration units are μM in all cases.)
A.
B.
1/v = 1000(1/[S]) + 130
D.
C.
1/v = 1300(1/[S]) + 100
1/v = 1000(1/[S]) + 130
E.
1/v = 1000(1/[S]) + 130
1/v = 1300(1/[S]) + 100
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Which of the following is false about the amino
acids involved in the active site of chymotrypsin?
a) Ser195 acts as a nucleophile.
b) His57 acts as a general acid.
c) His57 acts as a general base.
d) Asp102 influences the pKa of His57 in the presence of
substrate.
e) None of the above is false.
+ Which of the following is false about
enzymes that are made from zymogens?
A.
Proteolysis results in an active form of the protein.
B.
Digestive enzymes and blood clotting enzymes are examples of
such proteins.
C.
The protein is inactivated by returning to the proprotein
conformation.
D.
The proprotein may have properties that differ greatly from the
final protein.
E.
Some undergo more than one cleavage event to produce
multiple active forms.