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Name: ____________________
Student ID: _______________________
__) (1pt) Which amino acid(s) do(es) not posses a chiral alpha carbon.
__________glycine / Gly / G________________________
__) (1pt) What is the pH of 0.1 M NaOH?
The pH is ___13_____.
__) (4pts) Compute the net charge of the following tripeptide: Glu-Glu-Glu (where the
Glu pK value of its main chain carboxylate group is 2.2, that of its main chain amino
group is 9.2 and that of its side chain carboxylate group is 4.2).
(a) The net charge on this peptide at pH 7.0 is ___-3______
(b) The net charge on this peptide in 0.1 M NaOH is ___-4______
(c) The net charge on this peptide in 1 M HCl is ___+1_____
(d) The isoelectric point of this peptide is ____3.2_______
__) (2pts) Your 199 supervisor asks you to prepare pH 6.0 buffer. You already have
1 M KH2PO4. What concentration of K2HPO4 do you need? (pKa = 6.9) Show your
work!
HA = KH2PO4; A- = K2HPO4
pH = pKa + log ([A-] / [HA]
6.0 = 6.9 + log ([K2HPO4]/1.0 M)
-0.9 = log ([K2HPO4]/1.0 M)
10^(-0.9) M = 0.13 M = [K2HPO4]
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Name: ____________________
Student ID: _______________________
__) (1pt) The tertiary structure of many proteins is stabilized by covalent bonds
between the side chains of ___cysteines / Cys _____________
__) (1pt) Enzymes accelerate reactions by ____(circle one)_____ of the reaction.
decreasing ΔG‡ / increasing ΔG‡ / decreasing ΔG° / increasing ΔG° / decreasing ΔG
__) (2pts) If a protein at a concentration of 0.02 mM has an UV absorbance at 280 nm
of 0.5, what is its molar extinction coefficient? Assume the path length of the cuvette is 1
cm. Remember the units!
A = ε c l or ε = A / (c l); c = 0.00002 M, l = 1 cm
ε = 0.5 / (0.00002 M 1 cm) = 25,000 M-1 cm-1= 25 mM-1 cm-1
The molar extinction coefficient is ___25,000 M-1 cm-1___.
__) (1pt) The approximate molecular weight of a protein with 600 amino acid residues
is ____66,000 Da / 66 kDa___________ (don’t forget the units!)
__) (1pt) The term that bests describes the characteristics of detergents is (circle one)
hydrophilic / hydrophobic / amphipathic / nucleophilic /
zwitterionic
__) (1pt) The strongest, angle-independent force of attraction between the side-chains
of aspartate and arginine within a protein is likely to be (circle one)
H-bonding / hydrophobic interaction / van der Waals / a peptide bond / electrostatic
_____
Name: ____________________
Student ID: _______________________
_____
Name: ____________________
Student ID: _______________________
__) (2pts) In a reaction which observes Michaelis Menten kinetics, a Lineweaver-Burk
plot shows a y-axis intercept of ___1/Vmax__________. This corresponds to a substrate
concentration [S] of __infinity________.
__) (1pt) Plant starch is a polymer of (circle one)
detergents / polysaccharides / monosaccharides / fatty acids / amino acids
__) (1pt) The overall efficiency of an enzyme performing a reaction can be expressed
as (circle one)
A. Vmax/Km
B. Km/pKa
C. Km/Vmax
D. kcat/Km
E. Km/kcat
__) (1pt) Which of the following would be least soluble in water? (circle one)
A. Phenylalanine
B. Arginine
C. Lysine
D. Glycine
E. Aspartate
_____
Name: ____________________
Student ID: _______________________
__) (a) (4pts) Without drawing any graph, estimate the Km and Vmax (with units) from
this table of kinetic data (with units).
Km = ______~0.2 µM __________
Vmax = __~48-50 µM/min________
(b) (1pt) A competitive inhibitor was added to the above reaction. The Km (apparent) of
the substrate increased / decreased in the presence of the inhibitor. Circle the
correct answer.
__) (a) (1pt) If we have a mixture of 20 kDa and a 50 kDa protein protein, what type of
chromatography would we use to separate them for structural studies?
Affinity / Ionic-Exchange / Size-Exclusion / Isoelectric focusing / MS-MS
(b) (1pt) To verify that we separated them, we run an SDS-PAGE gel to observe the
proteins. The larger protein will run slower / faster than the smaller protein. Circle the
correct one.
_____
Name: ____________________
Student ID: _______________________
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