Bio301 Biochemistry I
Final Examination, January 15, 2007
Questions 1 to 22 (each 2 points)
Questions 23-26 (each 10 points), 27 (16 points). bonus question (4 points).
Question 1. What is the common strategy by which catalysis occurs?
A) increasing the probability of product formation
B) shifting the reaction equilibrium
C) stabilization of transition state
D) all of the above
E) none of the above
Question 2. The Gibbs free energy of activation is
A) the difference between the substrate and the transition state.
B) the difference between the substrate and the product.
C) the difference between the product and the transition state.
D) all of the above.
E) none of the above.
Question 3. In this type of inhibition the enzyme can form a complex with either the
substrate (ES) or the inhibitor (EI), but not both.
A) Competitive
D) All of the above
B) Non-competitive
E) None of the above
C) Mixed
Question 4. Which amino acids in chymotrypsin are found in the active site and are
participants in substrate cleavage?
A) his, ser, asp B) his, ser C) asp, lys D) lys, arg E) his, ser, arg
Question 5. The metal most commonly found at the active site of metalloproteases is
A) zinc. B) calcium. C) selenium. D) magnesium. E) sodium.
Question 6. Nucleotide monophosphate kinases function to
A) transfer the phosphate from NTP to NDP.
B) transfer the phosphate from NTP to NMP.
C) transfer the phosphate from NMP to NDP.
D) phosphorylate NADH.
E) transfer the phosphate from NTP to water.
Question 7. What is the Bohr effect?
A) the ability of hemoglobin to retain oxygen when in competition with myoglobin
B) the regulation of hemoglobin binding by hydrogen ions and carbon dioxide
C) the alteration of hemoglobin conformation during low oxygen stress
D) all of the above
E) none of the above
Question 8. How is trypsin activity turned off?
A) by dephosphorylation D) all of the above
B) by an inhibitor protein E) none of the above
C) by a second cleavage
Question 9. An aldehyde and alcohol can react to form a
A) hemiaketal.
D) all of the above.
B) hemiketal.
E) none of the above.
C) hemiacetal.
Question 10. Furanose rings are in a(n) ____ conformation.
A) chair B) envelope C) boat D) all of the above E) none of the above
Question 11. Which of the following membranes would be the most fluid?
A) a bilayer made of lipids with polyunsaturated 18 carbon-fatty acids
B) a bilayer made of lipids with saturated 18 carbon-fatty acids
C) a bilayer made of lipids with saturated 16 carbon-fatty acids
D) a bilayer made of lipids with polyunsaturated 16 carbon-fatty acids
E) All of the above are equivalent in fluidity.
Question 12. RNA Polymerase I transcribes the genes for
A) mRNA precursors.
D) all of the above.
B) 18S, 5.8 S, and 28S rRNA.
E) none of the above.
C) most tRNA.
Question 13. Given are five Km values for the binding of substrates to a particular
enzyme. Which has the strongest affinity when k−1 is greater than k2?
A) 150 mM B) 0.15 mM C) 150 μM D) 1.5 nM E) 15000 pM
Question 14. Which of the following is not true?
A) Enzymes force reactions to proceed in only one direction.
B) Enzymes alter the equilibrium of the reaction.
C) Enzymes alter the standard free energy of the reaction.
D) All of the above are true.
Question 15. Binding of a water molecule to the zinc ion induces
A) a hydronium ion to form.
B) a large conformation change in the binding site.
C) ionization of a his residue, which functions as a strong nucleophile.
D) a lowered pK for water, which leads to formation of a zinc bound hydroxide ion.
E) an altered Km value.
Question 16. If you carried out site-directed mutagenesis of subtilisin, changing serine
221 to isoleucine, what would you expect?
A) a large change in Km D) a and c
B) a small change in Km E) b and c
C) a large change in Kcat
Question 17. The relaxed form of an allosteric enzyme has _________ affinity for the
substrates.
A) higher B) equal C) lower D) no E) none of the above
Question 18. Why is the peptide bond planar?
A) Bulky side chains prevent free rotation around the bond.
B) It contains partial double bond character, preventing rotation.
C) Hydrogen bonding between the NH and C=O groups limits movement.
D) None of the above.
E) All of the above.
Question 19. Amino acids to which sugars are commonly linked.
A) tyrosine and asparagine
D) serine and threonine
B) serine, threonine, and asparagine
E) a and d
C) serine, tyrosine, and asparagines
Question 20. Carbohydrates are
A) aldehydes with multiple hydroxyl groups.
B) ketones with multiple hydroxyl groups.
C) acids with multiple hydroxyl groups.
D) a and b.
E) none of the above.
Question 21. The most common motif found in membrane spanning proteins is
A) α helices of nonpolar amino acids that pass through the membrane.
B) α helices of charged amino acids that form channels via extensive hydrogen bonding.
C) triple helix of α helices.
D) a helix-turn-helix arrangement of the peptide strands.
E) none of the above.
Question 22. The low incidence of protein or lipid flip-flop in a membrane preserves
A) membrane fluidity.
D) all of the above.
B) membrane melting temperatures.
E) none of the above.
C) membrane asymmetry.
Question 23. Fill in the blanks.
a) Mirror images of each other are called ____________.
b) Sugars that vary at a single asymmetric carbon are called __________.
c) Substituents on the ring carbon atoms in chair conformations can be
equitorial or ____________.
d) The storage form of glucose in animals____________..
e) Enzymes that do not have the required cofactor bound are called________________
f) A tightly bound cofactor might be called a ___________.
g) Kcat is often referred to as the _________________.
h) Proteases function by what common mechanism? ____________.
i) _A technique that permits rapid monitoring of enzyme kinetics. ____________.
j) The metal ion frequently found at active sites containing phosphate
groups. ____________.
Question 24. Draw a fatty acid called cis-9-hexadecenoate. Show and name the carbons
C, C2,C3, also C, C, and C
Question 25. Draw and label a typical phospholipids, i.e. phosphatidyl serine. (show the
chemical structure around the attachment sites, the rest can be shown as –R.
Question 26. Describe the significant differences between eukaryotic and prokaryotic
translation.
Question 27. An enzyme is present at 1x10-8M in a reaction. It has a Km of 4.7x10-5 M
for its substrate. If the Vmax of the preparation is 22 micromolesxliter-1xmin-1. A) what
velocity would be observed in the presence of
2x 10-4M substrate and 5x10-4M of a competitive inhibitor (with a Ki of 3x10-4 M).
B) What is the degree of inhibition (as a percentage of original activity) at this
concentration of substrate and inhibitor.
C) What happens to the Vma of the reaction, and to the degree of inhibition if the
enzyme concentration is doubled.
Bonus question: (5 points)
The son received a Nobel Prize this year in Chemistry whose father was also a Nobel
Laurate for his discovery of mechanisms in DNA and RNA synthesis. Who are these
father and son?