NATIONAL UNIVERSITY OF SINGAPORE DEPARTMENT OF BIOCHEMISTRY ADVANCED PLACEMENT TEST (SAMPLE)

NATIONAL UNIVERSITY OF SINGAPORE
DEPARTMENT OF BIOCHEMISTRY
ADVANCED PLACEMENT TEST
(SAMPLE)
LSM1101
BIOCHEMISTRY OF BIOMOLECULES
MMM-YYYY---Time Allowed : 2 hours
INSTRUCTIONS TO CANDIDATES
1. This paper contains a total of THIRTY EIGHT (38) questions and comprises NINE (9)
printed pages including this cover page.
2. This is a CLOSED BOOK test.
3. There are 2 parts (Part I and Part II) in this paper.
4. Part I contains 35 Multiple Choice Questions (MCQs).
5. Shade the answers onto the ANSWER SHEET provided. No marks will be given if you
do not fill the answer sheet.
6. Fill in the appropriate circle COMPLETELY using a 2B pencil. Do not use a pen or a
light pencil as marks will not be given if the response is not detected properly due to
incomplete or improper shading.
7. Be sure to WRITE and SHADE your matriculation number on the answer sheet. No
attempt will be made to trace the individual if the matriculation number is not
written correctly or not written at all.
8. Part II contains 3 short questions. For Part II, write all your answers in the answer
booklet(s) provided.
9. Only Non-Programmable calculators are allowed to be used.
10. No Helpsheet(s) or Formula Sheet(s) will be provided.
PART I (Multiple Choice Questions)
1. Which of the following statements about the biophysical property of water is INCORRECT?
A. Water molecule forms H-bonds
B. Water retains heat well
C. Water is dielectrict
D. Water at freezing point has the highest density
E. Water is polar
2. Which of the following is NOT a strong electrolyte and acts as a buffer?
A. Adipic acid.
B. Sulphuric acid.
C. Nitrous acid.
D. Ammonium hydroxide.
E. Potassium hydroxide.
3. Which acid is NOT found in biological systems?
A. Hydrochloric acid.
B. Carbonic acid.
C. Carboxylic acid.
D. Nitric acid.
E. Tetraethylamino acid
4. In the isoelectric form of a pentapeptide,
A. both extreme termini are not charged.
B. two internal amino acids of the pentapeptide are not ionized.
C. the total net charge is zero.
D. there are five ionic charges.
E. only the amino and carboxyl termini contribute charges.
5. In the tripeptide, Asp-His-Glu, which of the following group is NOT free to ionize?
A. β-carboxyl of aspartic acid
B. γ-carboxyl group of glutamic acid
C. carboxyl group of histidine
D. α-amino of aspartic acid
E. carboxyl of glutamic acid
6. Which of the following statements about hydroxylysine in collagen is CORRECT?
A. Hydroxylysine is negatively charged at neutral pH
B. Hydroxylysine is a neutral molecule at neutral pH
C. Hydroxylysine is produced by transcription
D. Hydroxylysine is produced by post-translational modifications
E. Hydroxylysine is produced by post-transcriptional modifications.
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7. Which of the following statement is FALSE?
A. Metalloenzyme uses metal for activity.
B. A lipoprotein contains lipid covalently linked to the protein.
C. A glycoprotein contains glycogen covalently linked to the protein.
D. A hemoprotein contains iron.
E. A flavoprotein contains flavin dinucleotide.
8. Which of the following statement about amino acid is FALSE?
A. Some amino acids contain oxygen.
B. Some amino acids contain iron.
C. Some amino acids contain sulphur.
D. Some amino acids contain phosphates.
E. Some amino acids have modified carboxlate groups.
9. Primary structure are determined by
A. hydrophobic interactions.
B. ionic bonds.
C. Van der Waals forces.
D. hydrogen bonds.
E. arrangements of amino acids.
10. All of the amino acids EXCEPT _________ have both free α-amino and free α-carboxyl
groups.
A. aspartic acid
B. proline
C. asparagine
D. arginine
E. alanine
11. Which reagent effectively denatures proteins?
A. Buffer at pH 6.5
B. Guanidinium
C. Acetic acid
D. Water
E. Oxygen
12. Which protein is most abundantly found in human tissues?
A. Crystalline
B. Serum
C. Collagen
D. Actin
E. Hemoglobin
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13. What is this amino acid?
A.
B.
C.
D.
E.
Aspartic acid
Arginine
Glycine
Glutamine
Cysteine
14. How many helices make up tropocollagen?
A. One
B. Two
C. Three
D. Four
E. Five
15. Which of the following amino acids may alter the direction of polypeptide chains and interrupt
α-helices?
A. Glu
B. Trp
C. Phe
D. Ala
E. Pro
16. If the rate constant for the enzyme catalyzed reaction is 2 × 105/sec and the rate constant for
the uncatalyzed reaction is 2 × 10-7/sec, the catalytic power of the enzyme is
A. 1012
B. 2 × 10-12
C. 10-11
D. 10-1
E. 2 × 10-1
17. Which one of the following statements is FALSE?
A. Enzymes typically act under milder conditions of temperature and pH than chemical
catalysts.
B. Hemoproteins contains copper.
C. Ribozymes are RNA molecules with catalytic functions.
D. Effectors can either stimulate or inhibit the activities of allosteric enzymes
E. Metalloenzyme use metal for activity.
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18. How do catalysts work to accelerate a chemical reaction?
A. They raise the average free energy of the products.
B. They provide a means of acceleration by being completely consumed in the reaction.
C. They lower the energy of activation.
D. They lower the overall free energy change of the reaction.
E. They decrease the average free energy of the reactants.
19. In uncompetitive inhibition,
A. inhibitor combines only with ES.
B. inhibitor combines only with E.
C. inhibitor combines with E and ES.
D. inhibitor combines with EP.
E. inhibitor combines with ES and EP.
20. The function of glycogen phosphorylase is
A. the conversion of glucose-6-phosphate to glucose-1-phosphate.
B. to stimulate the buildup of glycogen.
C. to catalyze the phosphorolysis of glucose-1-phosphate from glycogen molecules.
D. to inhibit the production of glucose-1-phosphate.
E. to break down ATP.
21. Sickle cell anemia is due to
A. the interaction of oxy-HbS with the cell membrane.
B. the formation of oxy-HbS complexes and subsequent cell disruption.
C. the precipitation of hybrid molecules, HbA-HbS.
D. the precipitation of deoxy-HbS into long, chain-like fibers.
E. formation of oxy-HbA complexes within the red blood cells.
22. For an enzyme-catalyzed reaction, the initial velocity was determined at two different
concentrations of the substrate. Estimate the value of Km
[S] (mM)
1.0
4.0
A.
B.
C.
D.
E.
V o (mM/min)
2.0
3.2
1 mM
5.7 mM
2.7 mM
0.6 mM
1.7 mM
23. It is known that glucokinase has a K m value of 10.0 mM, whereas hexokinase has a K m value
of 0.1 mM. Which one of the following statements is TRUE?
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A.
B.
C.
D.
E.
Glucokinase acting on glucose at low concentrations.
Glucokinase acting on glucose at high glucose concentrations.
Glucokinase phosphorylation of most of the glucose at low glucose levels.
Hexokinase acting on glucose at high levels of glucose.
Hexokinase acting at about half-maximal velocity at glucose concentrations of 4-5 mM.
24. To calculate the turnover number of an enzyme, you need to know
A. the enzyme concentration.
B. the initial velocity of the catalyzed reaction at [S] >> Km.
C. the initial velocity of the catalyzed reaction at low [S].
D. the Km for the substrate.
E. both A and B.
25. Which of the following is not a ligand to the porphyrin ring Fe2+ ion in oxymyoglobin?
A. His E7
B. His F8
C. Nitrogen atoms in the porphyrin ring
D. Oxygen
E. Carbon monoxide
26. In A-DNA
A. the major grove and the ninor groove have the same width.
B. the major groove is wider than the minor groove.
C. the minor groove is wider than the major groove.
D. there is no major groove.
E. there is no minor groove.
27. The DNA microarray technique is useful for
A. paternity identification.
B. DNA mismatch repair.
C. cloning an animal.
D. gene regulation study.
E. DNA synthesis.
28. For lipids,
A. the transition point is higher than the melting point.
B. the melting point is higher than the transition point.
C. the melting point and transition point are identical.
D. there is no melting point.
E. there is no transition point.
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29. The hydropathy plot can be calculated
A. only for membranes.
B. only for fatty acids.
C. only for transmembrane proteins.
D. only for peripheral proteins.
E. for all proteins.
30. To withstand / regulate the high salt concentration of sea water, the sea fish
A. does not drink water at all.
B. drinks water and absorbs all salt ions.
C. drinks water but expels all salt ions.
D. apart from (A), it uses a mechanism that does not involve water at all.
E. drinks water but chemically converts the salt to other types of molecules.
31. The major component of snake venom is
A. phospholipase a2 enzyme.
B. phosphate salts.
C. phosphorylated proteins.
D. Phospholipids.
E. carbohydrates.
32. Optical activity of a sugar molecule is referred to
A. its color / hue.
B. its shining / brightness.
C. its affinity with proteins.
D. how it interacts with polarized light.
E. how it interacts with unpolarized light.
33. Cellulose is a
A. modified amino acid.
B. monosaccharide.
C. polysaccharide.
D. olidosaccharide.
E. disaccharide.
34. Cells convert glucose to pyruvate by
A. gyucogenesis.
B. glycogenolysis.
C. gluconeogenesis.
D. glycolysis.
E. glycosylation.
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35. ADP is converted to ATP in
A. translation.
B. transcription.
C. β-oxidation.
D. the tca cycle.
E. oxidative phosphorylation.
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PART II. Short Answer Questions
1. Answer all the questions below.
a. Draw the structure of a pentapeptide consisting of : Cys-Phe-Phe-Gly_Leu-Met-NH2.
b. Which amino acid/s can be oxidized?
c. Draw the structure of the sulphonate form of Met.
d. Describe how a covalently linked homodimer can be formed.
2. A researcher was studying the kinetic properties of β-galactosidase using an assay in which οnitrophenol-β-galactoside (ONPG), a colorless substrate, is converted to galactose and onitrophenolate, a brightly-colored, yellow compound. Upon addition of 0.25 mM substrate to a
fixed amount of enzyme, o-nitrophenolate (ONP) production was monitored at 410nm in a cuvette
of 1-cm path length. The following data were collected:
Time
(sec)
0
15
30
45
60
75
90
150
210
270
330
390
450
510
A 410 nm
0.00
0.16
0.27
0.36
0.43
0.48
0.53
0.65
0.72
0.77
0.81
0.83
0.85
0.86
(a) Convert A 410 nm to concentration of o-nitrophenolate, [ONP], using
ε = 3.76 mM-1cm-1 as the extinction coefficient. (2 marks)
(b) Plot [ONP] versus time. (2 marks)
(c) Determine the initial velocity of the reaction. (2 marks)
(d) Explain why the curve is nearly linear initially and later approaches a plateau. (2 marks)
(e) Describe how K m and V max for β-galactosidase can be determined with additional
experimentation. (2 marks)
3. The location of a gene is denoted by 9p21.2. Draw a diagram and explain all the terms.
(10 marks)
~ End of Paper ~
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