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PASS BIOL 2020 Mock Test #1
PASS Leader: Aisha Nasim
Disclaimer: This mock test was prepared by a PASS
leader. It is not reflective of all of the material that you
are required to learn for the evaluation.
Do not substitute this mock test for studying. This
test is also SOS-PROPERTY. SALE OR
REDISTRIBUTION IS PROHIBITED.
PASS BIOL 2020 Schedule:
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PASS BIOL 2020 WINTER 2019
PART 1 - Multiple Choice Questions
2. 2
1) Which change would most likely disrupt the tertiary structure of amino acids?
a) lysine to histidine
b) leucine to trytophan
c) phenylalanine to tyrosine
d) asparagine to glutamine
e) serine to cysteine
2) All of the following about an alpha helix are false EXCEPT
a) Pro is usually found in the bends of the helices
b) The side chain can doesn't have a large effect on the molecule
c) There are 10 amino acids per turn
d) The helix is mainly supported by the H-bonds of the R group
e) Gly is not common in helices
3) Acetic acid has a Ka of 1.8 x 10^-5 while hydrogen fluoride has a pKa is 3.17. Which
statement is true?
a) Acetic acid has a higher Ka so it H ions will dissociate less then hydrogen fluoride
b) Hydrogen fluoride has a higher pKa so H ions will dissociate more then acetic acid
c) Hydrogen fluoride has a lower Ka so H ions will dissociate less then acetic acid
d) Acetic acid has a higher pKa so it H ions will dissociate less then hydrogen fluoride
e) More then one answer is correct
4) All of the following statements are true EXCEPT:
a) Lowering the pH will shift the dissociation curve to the right
b) With a more acidic environment, hemoglobin will bind more tightly to O2
c) Decreasing the BPG content will shift the current to the left
d) At higher altitudes, less O2 will be bound to hemoglobin then at sea level
e) More then one is false
5) A new organic substance, Vitamin B10L has been found in newly discovered species of
plants in southern Asia. It is found to help the plant make more food by binding permanently
to a system of glucose producing enzymes. Looking at all the known facts, how would you
BEST describe this new molecule as?
a) Cofactor
b) Coenzyme
c) Prosthetic group
d) Allosteric effector
e) Holoenzyme
6.
3. 3
Protein Molecular weight or amino acid
composition
pI
1 430,000 Da 3.4
2 230 kDa 10.7
3 3000 amino acids 9.2
4 45,000 Da 6.5
5 320 amino acids 12.8
This mixture was put through a column filled with DAEA-cellulose, a positively charged
resin, at pH of 8, after which the proteins that remained bound were run through SDS-PAGE.
Which protein would be found at the top of the gel?
a) 1
b) 2
c) 3
d) 4
e) 5
7. Which of these statements about Lineweaver-Burk and Michaelis-Menten plots is correct?
a) The Lineweaver-Burk plot is a rectangular hyberbolic plot
b) Using the Michaelis-Menten plot, you can find the Vmax by drawing extrapolating a
straight line
c) The Lineweaver-Burk plot requires fewer data points
d) The X-intercept on the Lineweaver-Burk graph is 1/Km
e) The Y-axis on the Michaelis-Menten plot is v0
8. When plotting 1/V against 1/[S] for an enzyme, the presence of a competitive inhibitor will
affect
a) Vmax
b) The Y-intercept of the graph
c) The amount of product formed
d) The X-intercept of the graph
e) Raises the asymptote on the graph
9. Given an enzyme with KM of 0.5mM. At what substrate concentration will the velocity of
the enzyme reach ¼ of the Vmax? Vmax=200mmols
a) 0.5mM
b) 0.17mM
c) 0.12mM
d) 0.20mM
4. 4
10. Which of the following characteristics are true for enzymes in reaction?
a) No covalent bonds can form in active site
b) The most prevalent theory is that substrates make a tight fit with the enzyme
c) They work by lowering the activation energy so that reactions can be more spontaneous
d) They can increase the equilibrium constant for a reaction immensely
e) Their activity is directly related to the substrate concentration
11. Which of the following about isoelectric focusing is correct?
a) Proteins separated by isoelectric focusing can be tested for biological activity
b) The separation of proteins by isoelectric focusing is only based on size
c) SDS gel electrophoresis and isoelectric focusing together make up the process of 2D
gel electrophoresis
d) Isoelectric focusing elutes smaller sample first
e) Two of the of the above
12. Which plot on the bottom (Figure 2) corresponds with the equation shown in Figure 1
Figure 1:
Figure 2:
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13. Which of the following represents the predominant form of Asn at a pH of 7?
14. You perform an enzyme experiment and plot the results on a Lineweaver-Burk plot. You
know the Vmax is 5 sec/mol, the x-intercept is -2.5 mM^-1, and the v0 value of the system is
0.2 sec/mol. What is the Km value?
a) 0.4 mM
b) 5 mM
c) 5 uM
d) 4 mM
e) Not enough information
15. What could be a possible reason of adding Beta Mercaptoethanol to the SDS page?
a) It can act as an oxidizing agent, that can oxidize alcohol groups in protein sample
b) It can act as a reducing agent, that can reduce disulfide bonds in protein sample
c) It can act as a Lewis base allowing all protein chains to migrate as monomers
d) It can act as a Lewis acid allowing all protein chains to migrate as monomers
16. A scientist isolates a protein from sample. Which of the following characteristics would
suggest that it is a fibrous protein?
a) It is water soluble
b) It is mainly a structural protein that forms a tight triple helix intertwined with each
other
c) Its structure is supported by the formation of covalent bonds, which is dependent on
Flavin mononucleotide (vitamin B12)
d) All of above would suggest that this protein is fibrous
17. In which lab technique will the smaller sample elute first?
a) Gel electrophoresis
b) Isoelectric focusing
c) Ion exchange chromatography
d) Size exclusion chromatography
e) Two of the above
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18. When will hemoglobin have the highest affinity for oxygen?
a) When pH is low
b) When carbon monoxide levels are high
c) At high elevations
d) When 2,3-bisphosphoglycerate levels are low
e) Two of the above
19. Which of the following are correct statements?
a) An iron atom in the heme group is capable of five coordination bonds
b) Four heme groups can bind to four oxygen molecules
c) Both myoglobin and hemoglobin are made up of four peptide chains
d) H+ is a negative allosteric inhibitor of hemoglobin because protonation of histidine in
the heme group stabilizes T conformation
e) Two of the above
20. Which of the following functional groups is not present in the structure shown below?
a) Alcohol
b) Phenyl
c) Carbonyl
d) Aldehyde
e) Ether
f) Amino
22. Determine the isoelectric point of the tripeptide shown below. The pKa is shown beside
the functional group.
a) 7.0
b) 3.25
c) 2.2
d) 9.7
23. what is the overall charge of the tripeptide shown in previous question at pH = 6.6?
a) +1
b) -1
c) 0
d) -2
e) more information is needed
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24. How is SDS-PAGE different from PAGE?
A) They are the same process
B) You can estimate the size of the protein in SDS-PAGE
C) You can estimate the size of the protein in PAGE
D) Mobility of proteins depends on charge only in PAGE
E) Mobility of proteins depends on charge only in SDS-PAGE
25. In electrophoresis protein will move until
A) its pH is greater than PI
B) its pH is smaller than PI
C) its pH is equal to PI
D) PI is greater than pH
26. Select the correct statement.
A) When running hemoglobin down an SDS Page, 2 bands will be visible.
B) Only proteins have catalytic activities.
C) Enzymes lower the free energy of the system
D) Reactions with transition states at lower energy levels are spontaneous
E) Enzymes destabilize the transition state
F) None of the above
27. If the first purification step had 18, 000 g of protein and a total activity of 150,000 unit,
what is the specific activity? If the second purification process had 3,000 g of protein and a
total activity of 80,000, how much was the yield?
A) 0.12, 63%
B) 8.3, 53%
C) 150,000, 20%
D) none of the above
28. NaOH is added to a 500mL of 2M acetic acid. If the pKa value of acetic acid is
approximately 4.8, what volume of 2M NaOH must be added so that the pH of the solution is
4.8?
A) 1 L
B) 2 L
C) 250 mL
D) 500 mL
29. Select the correct statement
A) A prosthetic group is a non-peptide component that transiently associates with the protein
B) Beta subunit of the hemoglobin contain a lot of beta pleated sheets
C) Hemoglobin is an alpha beta dimer
D) Heme is an example of a ligand
E) Iron coordinates with 4 nitrogen atoms in the heme group and one nitrogen in proximal
lysine group
F) none of the above
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30. Consider the diagram on the right. It is representing the binding of oxygen to two
different enzymes. Select the correct statement.
a) Curve A represents a parabolic curve
b) Curve B represents a sigmoidal curve
c) Curve B shows a higher affinity than curve A
d) Both curves show positive cooperativity
e) The Y-axis represents the concentration of oxygen
f) More than one of the above
31. What allows fetal hemoglobin to have greater affinity for
oxygen?
a) High concentrations of 2,3-BPG
b) High concentrations of oxygen
c) Amino acid replacement in the beta subunit
d) None of the above
32. Which allosteric effectors would favour T state of the hemoglobin?
a) Oxygen
b) 2,3-BPG
c) H+
d) H2O
e) O2
f) More than one of the above
33. What kind of an inhibitor am I? I reduce Vmax and increase Km and I like to bind to near
the active site.
a) Pure non-competitive
b) competitive
c) mixed non-competitive
d) uncompetitive
e) two of the above are possible
35. Exclusion of water in the active site
a) increases the dielectric constant
b) decreases the dielectric constant
c) enhances electrostatic interactions
d) disrupts electrostatic interactions
e) A & C
f) B & C
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36. In order to perform degradation of a protein sequence, which of the following amino
acids will be ubiquitinated?
a)
b)
c)
d)
37. Which of the following apply to hemoglobin?
A) positive cooperativity
B) heterotropic allosterism
C) isoenzyme
D) two of the above
E) all of the above
