BC367,%20Fall%202009

1
BC367, Fall 2009

• Exam 2 Review Questions

2
In Anfinsens experiment, RNAse was denatured
with urea and ß-mercaptoethanol. After dialysis
and treatment with oxygen, the enzymes activity
was restored. What conclusions can be made from
this?

• a) Urea and ß-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.

3
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.

4
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 wont disappoint your teammates and theyll
want to invite you back again next year?

1. Traveling everyday to train at the course up in
   the Rockies so you can acclimate to the terrain
   and altitude
2. A mutation of His146 ? Val in the ß chain
3. Sleeping in a hyperbaric chamber so your body
   gets used to different pressures
4. Renting a house in Denver, but traveling to do
   most your serious workouts in New Orleans
5. Hyperventilating right before the race to
   decrease your blood pH and help prevent cramps

5
Which is the most likely phenotypic result of Hb
mutation Arg141a -gt Cys (Hb Nunobiki)?

• a) Cyanotic
• b) Flushed
• c) Pale
• d) Normal
• e) Death

6
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
7
?-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.
C.
1/v 1300(1/S) 100
1/v 1000(1/S) 130
1/v 1000(1/S) 130
D.
E.
1/v 1300(1/S) 100
1/v 1000(1/S) 130
8
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.
9
Which of the following is false about enzymes
that are made from zymogens?

1. Proteolysis results in an active form of the
   protein.
2. Digestive enzymes and blood clotting enzymes are
   examples of such proteins.
3. The protein is inactivated by returning to the
   proprotein conformation.
4. The proprotein may have properties that differ
   greatly from the final protein.
5. Some undergo more than one cleavage event to
   produce multiple active forms.