BC367, Fall 2009

1. BC367, Fall 2009 Exam 2 Review Questions

2. 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.

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 won’t disappoint your teammates and they’ll want to invite you back again next year? • Traveling everyday to train at the course up in the Rockies so you can acclimate to the terrain and altitude • A mutation of His146  Val in the β chain • Sleeping in a hyperbaric chamber so your body gets used to different pressures • Renting a house in Denver, but traveling to do most your serious workouts in New Orleans • Hyperventilating right before the race to decrease your blood pH and help prevent cramps

5. a) Cyanotic b) Flushed c) Pale d) Normal e) Death Which is the most likely phenotypic result of Hb mutation Arg141α -> Cys (Hb Nunobiki)?

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 = 1000(1/[S]) + 130 1/v = 1300(1/[S]) + 100 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? • Proteolysis results in an active form of the protein. • Digestive enzymes and blood clotting enzymes are examples of such proteins. • The protein is inactivated by returning to the proprotein conformation. • The proprotein may have properties that differ greatly from the final protein. • Some undergo more than one cleavage event to produce multiple active forms.