There are 7 pages in this exam, counting the cover sheet and scrap page. Please count them
tions:
• There are 7 pages in this exam, counting the cover sheet and scrap page. Please count them
before you start to make sure they are all there.
• For those questions labeled SC (for SCantron), please bubble in your response on your UCD
2000 scantron form. You will not get credit for any answer that is not bubbled in on the scantron.
• Write your name on your scantron and bubble in your student ID number AND test identifier
(Version A, B, or C) – 2 points will be subtracted if either piece of info is omitted
The following information may be useful for the questions on the exam.
R= 8.3 x 10-3 kJ/K•mol
25°C = 298 K
37°C = 310
Amino Acid amino group (-NH3) carboxyl group (-COOH) R-group
Ala, Gly, Ile, Leu, Val
Asn, Gln
Met, Ser, Trp
9.7
9.0
9.3
2.3
2.1
2.3
—-
—-
—-
Phe
Pro
Thr
9.1
10.6
10.4
1.8
2.0
2.6
—-
—-
—-
Asp
Glu
His
9.8
9.7
9.2
2.1
2.2
1.8
3.9
4.2
6.0
Cys
Tyr
Lys
Arg
10.8
9.1
9.0
9.0
1.8
2.2
2.2
2.2
8.3
10.0
10.5
12.5
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For the multiple choice questions, please select the BEST answer and bubble in on your scantron.
SC1. (2 points) A scientist successfully purifies a membrane-associated protein by treating isolated cell
membranes with a buffer containing a high concentration of NaCl. Which of the following is most likely
true about this protein?
A. It is an integral membrane protein with seven transmembrane helices.
B. It is a lipid-anchored protein attached via a covalently bonded lipid.
C. It is a peripheral membrane protein that interacts with the charged head groups of
phospholipids.
D. It is a glycoprotein with extensive N-linked oligosaccharides facing the extracellular space.
SC2. (2 points) During the initial stages of apoptosis (programmed cell death), the phospholipid
phosphatidylserine (PS), which is normally restricted to the inner leaflet of the plasma membrane,
becomes exposed on the outer leaflet. This event signals to phagocytic cells that the cell is dying. This
change is most likely due to:
A. Increased activity of Flippases.
B. Increased activity of Floppases.
C. Inhibition of Flippases.
D. The action of a Scramblases.
E. Both C and D could likely be contributing factors.
SC3. (2 points) You are tasked with separating two proteins of identical molecular weight and overall
shape. However, Protein A is rich in aspartate and glutamate residues, while Protein B is rich in lysine
and arginine residues. Which technique would be most effective for separating them in preparative scale?
A. SDS-PAGE
B. Ion Exchange Chromatography
C. Size Exclusion (Gel Filtration) Chromatography
D. Affinity Chromatography using an ATP-linked resin
E. Isoelectric Focusing
SC4. (2 points) To determine if your purified protein exists as a 120 kDa monomer or a dimer of two 60
kDa subunits, which two techniques would be most informative to compare?
A. Ion Exchange Chromatography and Affinity Chromatography
B. Size Exclusion Chromatography and SDS-PAGE
C. Isoelectric Focusing and SDS-PAGE
D. Size Exclusion Chromatography and Isoelectric Focusing
E. Affinity Chromatography and SDS-PAGE
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SC5. (2 points) Which protein separation technique separates proteins based on their intrinsic net charge
in an electric field, but is generally used for analytical purposes only due to low capacity?
A. Ion Exchange Chromatography
B. Size Exclusion Chromatography
C. SDS-PAGE
D. Affinity Chromatography
E. Isoelectric Focusing
SC6. (2 points) The bacterium Vibrio cholerae lives in aquatic environments with fluctuating
temperatures. When the water temperature drops significantly, how would you expect the composition of
its membrane lipids to change to maintain fluidity?
A. An increase in the proportion of long-chain, saturated fatty acids.
B. An increase in the proportion of short-chain fatty acids and unsaturated fatty acids.
C. A decrease in the amount of triacylglycerols incorporated into the membrane.
D. An increase in the proportion of trans-unsaturated fatty acids.
E. The composition would not change, as it is genetically determined.
SC7. (2 points) Which of the following pairs of amino acid R-groups could form a salt bridge to stabilize
the tertiary structure of a protein at physiological pH (~7.4)?
A. Alanine and Valine
B. Asparagine and Glutamine
C. Phenylalanine and Tryptophan
D. Lysine and Aspartate
E. Cysteine and Cysteine
SC8. (2 points) Coconut oil is a solid at room temperature, whereas olive oil is a liquid. This is because,
compared to olive oil, coconut oil contains a higher proportion of:
A. Long-chain, unsaturated fatty acids.
B. Short-chain, unsaturated fatty acids.
C. Long-chain, saturated fatty acids.
D. Polyunsaturated fatty acids.
E. Odd-numbered fatty acid chains.
SC9. (2 points) You are purifying the enzyme Hexokinase from yeast. You perform several purification
steps and collect the following data.
Procedure Fraction volume (mL) Total protein (mg) Activity (units)
1. Isolate crude cellular extract 500 mL 20,000 80,000
2. Precipitation with Ammonium
Sulfate
100 mL 5,000 75,000
3. Ion exchange chromatography 50 mL 200 60,000
4. Affinity chromatography on
glucose resin.
10 mL 10 50,000
5. Size exclusion chromatography 20 mL 8 48,000
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Which single purification step yielded the greatest fold-increase in specific activity compared to the
preceding step?
A. Ammonium Sulfate Cut
B. Ion Exchange Chromatography
C. Affinity (Glucose resin)
D. Size Exclusion Chromatography
E. Both B and C resulted in the same fold purification.
SC10. (2 points) Which lipid is least likely to be found in the plasma membrane of erythrocytes (red
blood cells)?
A. phosphatidylethanolamine
B. phosphatidylserine
C. cholesterol
D. glycosphingolipids
E. triacylglycerol
SC11. (2 points) Which of the following amino acids would be LEAST likely to be found in an alphahelix that spans a lipid bilayer?
A. Leucine
B. Phenylalanine
C. Arginine
D. Valine
E. Isoleucine
SC12. (2 points) A researcher discovers that a particular protein can be modified by phosphorylation. This
modification adds a phosphate group to a serine residue. Which technique would be best to
analytically separate the phosphorylated and unphosphorylated forms of the protein, assuming
they have nearly identical mass?
A. SDS-PAGE
B. Size Exclusion Chromatography
C. Affinity chromatography
D. Isoelectric Focusing
E. None of these techniqu
OR