BCH Exam 2 Questions
In the free energy diagram to the right, which reaction is most likely to occur at the fastest rate? - correct
answer ✔✔c
The main difference between a catalyzed and an uncatalyzed reaction is that _ - correct answer ✔✔The
activation energy of the catalyzed reaction is lo
Which of the following features is NOT associated with a peptide bond? - correct answer ✔✔Hydrolysis
of the peptide bond has a positive ∆G
In a reaction with a negative ∆G and diagramed as E + S ES E + P, the ES complex_________
a) lowers the energy of the transition state.
b) forms a transition state in which the substrate may be subject to strain, distortion and desolvation
c) forms a transition state which has a lower energy than would occur in an un-catalyzed reaction
d) a and b
e) all of the above - correct answer ✔✔all of the above
Under standard conditions (i.e. no "extras"), Aspartate Transcarbamoylase has an apparent KM of 10
mM aspartate.However, this reaction can be regulated by CTP (an end product of the pyrimidine
pathway initiated by thetranscarbamoylase reaction) and ATP (an end product of the purine biosynthetic
pathway). Which of the following is most likely not correct for this reaction? - correct answer ✔✔c) 0.4
mM CTP would shift the apparent KM to 5 mM
6. Which of the following best describes positive cooperativity?
a) Binding of one substrate molecule inhibits the binding of a second substrate
b) Binding of one substrate molecule enhances the binding of a second substrate
c) Competitive inhibition by an inhibitor
d) US Congress - correct answer ✔✔b) Binding of one substrate molecule enhances the binding of a
second substrate
, For the enzyme enhanced reaction, CO2 + H2O <--> H2 CO3 <--> H+ + HCO3- , which of the following
would most likely help increase the rate of catalysis - correct answer ✔✔Zn2+
Based on the chymotrypsin protease inhibitor TPCK (Tosyl-phenylalanyl-chloromethyl-ketone), which of
thefollowing changes would be most likely to create a suicide inhibitor more specific for trypsin? -
correct answer ✔✔c) Change the phenylalanine-like feature to be more like lysine
The critical serine residue in the active site of chymotrypsin is initially ionized because of the following
residue that accepts a proton from the serine's hydroxyl group: - correct answer ✔✔His
For a solution of Cys (C), at what pH would the net charge = 0? - correct answer ✔✔(1.9+8.4)/2 = 5.5
For a solution of Lysine (K), what percentage of the side chain Rgroup would be ionized at pH = 10.5? -
correct answer ✔✔50%
For a short peptide with the sequence "HELP", which of thefollowing would be closest to the overall
charge if this peptide were foundin normal human blood? - correct answer ✔✔-1
Which of the following peptides will bind most strongly to a cation exchange column at pH 7? (hint,
matrix is negative)
a) MLVSFYAGLATTVIGAM
b) DETYLTFWELDELIEDPE
c) KIRGRVLIGRHARRAKTR - correct answer ✔✔c)KIRGRVLIGRHARRAKTR
Which of the following would be the most appropriate unit for a KM ? - correct answer ✔✔moles / liter
If an enzyme can reach the upper limits of catalytic efficiency, it is referred to as ________. - correct
answer ✔✔c) Achieving Kinetic Perfection (kcat / KM = ~108 - 109 s-1 M-1 )
In the free energy diagram to the right, which reaction is most likely to occur at the fastest rate? - correct
answer ✔✔c
The main difference between a catalyzed and an uncatalyzed reaction is that _ - correct answer ✔✔The
activation energy of the catalyzed reaction is lo
Which of the following features is NOT associated with a peptide bond? - correct answer ✔✔Hydrolysis
of the peptide bond has a positive ∆G
In a reaction with a negative ∆G and diagramed as E + S ES E + P, the ES complex_________
a) lowers the energy of the transition state.
b) forms a transition state in which the substrate may be subject to strain, distortion and desolvation
c) forms a transition state which has a lower energy than would occur in an un-catalyzed reaction
d) a and b
e) all of the above - correct answer ✔✔all of the above
Under standard conditions (i.e. no "extras"), Aspartate Transcarbamoylase has an apparent KM of 10
mM aspartate.However, this reaction can be regulated by CTP (an end product of the pyrimidine
pathway initiated by thetranscarbamoylase reaction) and ATP (an end product of the purine biosynthetic
pathway). Which of the following is most likely not correct for this reaction? - correct answer ✔✔c) 0.4
mM CTP would shift the apparent KM to 5 mM
6. Which of the following best describes positive cooperativity?
a) Binding of one substrate molecule inhibits the binding of a second substrate
b) Binding of one substrate molecule enhances the binding of a second substrate
c) Competitive inhibition by an inhibitor
d) US Congress - correct answer ✔✔b) Binding of one substrate molecule enhances the binding of a
second substrate
, For the enzyme enhanced reaction, CO2 + H2O <--> H2 CO3 <--> H+ + HCO3- , which of the following
would most likely help increase the rate of catalysis - correct answer ✔✔Zn2+
Based on the chymotrypsin protease inhibitor TPCK (Tosyl-phenylalanyl-chloromethyl-ketone), which of
thefollowing changes would be most likely to create a suicide inhibitor more specific for trypsin? -
correct answer ✔✔c) Change the phenylalanine-like feature to be more like lysine
The critical serine residue in the active site of chymotrypsin is initially ionized because of the following
residue that accepts a proton from the serine's hydroxyl group: - correct answer ✔✔His
For a solution of Cys (C), at what pH would the net charge = 0? - correct answer ✔✔(1.9+8.4)/2 = 5.5
For a solution of Lysine (K), what percentage of the side chain Rgroup would be ionized at pH = 10.5? -
correct answer ✔✔50%
For a short peptide with the sequence "HELP", which of thefollowing would be closest to the overall
charge if this peptide were foundin normal human blood? - correct answer ✔✔-1
Which of the following peptides will bind most strongly to a cation exchange column at pH 7? (hint,
matrix is negative)
a) MLVSFYAGLATTVIGAM
b) DETYLTFWELDELIEDPE
c) KIRGRVLIGRHARRAKTR - correct answer ✔✔c)KIRGRVLIGRHARRAKTR
Which of the following would be the most appropriate unit for a KM ? - correct answer ✔✔moles / liter
If an enzyme can reach the upper limits of catalytic efficiency, it is referred to as ________. - correct
answer ✔✔c) Achieving Kinetic Perfection (kcat / KM = ~108 - 109 s-1 M-1 )
