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Biochemistry and Molecular Biology (BCMB 20002) 2017 Exam Questions
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lOMoARcPSD|23478024EXAM 2017 BIOCHEMISTRY UNIVERSITY OF
MELBOURNE
Biochemistry And Molecular Biology (University of Melbourne)
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Student ID ________________
Semester Two Assessment, 2017
Faculty / Dept: Biochemistry and Molecular Biology
Subject Number BCMB20002
Subject Name Biochemistry and Molecular Biology
Writing time 3 hours
Reading 15 minutes
Open Book status No
Number of pages (including this page) 26
Authorised Materials:
No authorised materials.
Instructions to Students:
CLEARLY PRINT your STUDENT NUMBER on the cover page and where indicated, as well as on the Multiple
Choice Answer Sheet.
All pages of the paper MUST be submitted.
There are SEVEN (A - G) SECTIONS to the paper: Sections A and B contain multiple choice questions;
Section C contains extended matching questions and sections D - G contain short answer questions. ALL
questions should be attempted.
Read the instructions at the top of each section and follow them carefully.
This paper contributes 70% of the marks for the subject BCMB20002. Marks are indicated for each section
and question.
Pages are printed single sided and the reverse sides are blank. These blank pages can be used for scrap or
extended answers/diagrams. If you wish any additional material to be considered please indicate this
clearly (e.g. "answer continues on back of page").
Instructions to Invigilators:
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Paper to be held by Baillieu Library: Yes No x
Extra Materials required (please supply)
Graph paper _____ Multiple Choice form _
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STUDENT NUMBER
SECTION A (60 minutes)
To be answered on the FRONT of the Multiple Choice Answer Sheet
2 marks per question
1. A peptide five residues long contains: one threonine, one asparagine, one arginine and two glutamic
acid residues. At pH 7, this peptide would have ______ positive charge(s), ______ negative charge(s)
and have an overall charge of ______.
A. 1, 2, positive 1.
B. 2, 1, negative 1.
C. 2, 3, negative 1.
D. 3, 2, positive 1.
2. Which combination of two of the following statements best describes an α-helix?
1. Hydrogen bonds lie parallel to the helical axis.
2. Hydrogen bonds lie perpendicular to the helical axis.
3. φ (phi) = -50°, ϕ (psi) = +60°
4. φ (phi) = -50°, ϕ (psi) = -60°
A. 1 and 3.
B. 1 and 4.
C. 2 and 4.
D. 2 and 3.
3. The alignment of the amino acid sequences of two small proteins 26 and 22 amino acids long is
shown below. A gap has been introduced to allow optimal alignment of the two proteins.
Residue Number 1 10 20
Protein A (human) ANYDYRSKLRGSLSFKKGERLQIVQS
| | :| | | | | : | :|||
Protein B (yeast) ALYPWRAK----LNFNKNDVLTVVQS
Select an option from A-D to complete the following: From the alignments above we may expect the
insertion to be _____________; in addition, the alignment suggests the proteins are _____________.
A. a type I β-turn; paralogues.
B. a type II β-turn; orthologues.
C. a type I β-turn; orthologues.
D. a type II β-turn; paralogues.
4. Which of the following statements regarding protein domains is INCORRECT?
A. A protein consisting of two domains will usually show close packing between the two
hydrophobic cores of the domains.
B. A domain from a protein containing only β-strands is likely to have two β-sheets.
C. Protein domains are units of tertiary protein structure.
D. Protein domains vary in sequence length, from approximately 50 to more than 200 residues.
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SECTION A (continued)
5. During protein folding, the entropy of water:
A. decreases.
B. increases.
C. is zero.
D. is equal to the change in entropy of the protein.
6. The role of myoglobin is to store oxygen in the muscles. Aquatic diving mammals (e.g otters and
dolphins) have much higher muscle concentrations of myoglobin than non-diving mammals (e.g. cats
and dogs). The oxygen binding curve for myoglobin is shown below.
Which of the following is most likely to be correct?
A. The oxygen partial pressure in the muscles of diving mammals must drop significantly lower
than that in non-diving mammals (~4 kPa).
B. Diving mammals must have lower muscle BPG concentrations than non-diving animals, so that
their myoglobin releases more oxygen.
C. The oxygen partial pressure in the lungs of diving mammals must be higher than that of non-
diving mammals (~13 kPa).
D. The increased Bohr Effect in the muscles of diving mammals causes myoglobin to release more
oxygen.
7. Compared to the uncatalysed reversible reaction S ↔ P, in the enzyme-catalysed reaction:
A. P binds the enzyme strongly to prevent the back reaction of P to S.
B. Weak interactions between S and the enzyme lower the free energy of the transition state.
C. The enzyme decreases the standard free energy change, ∆G′°, for the conversion of S to P.
D. The equilibrium between S and P is shifted to the right, so that formation of P is more
favourable.
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SECTION A (continued)
8. Which of the following is most likely to be responsible for the reduced activity of α-chymotrypsin
above pH 8.5?
A. Protonation of His57 in the catalytic triad.
B. Protonation of the Asp102 in the catalytic triad.
C. Deprotonation of Ser195 in the catalytic triad.
D. Deprotonation of the primary amine of Ile16, the N-terminal residue of the B-chain.
9. Which of the processes DNA replication, transcription and translation require DNA-RNA base pairing?
A. Only DNA replication.
B. Only transcription.
C. DNA replication and transcription.
D. All three of them.
10. What is the importance of the 3’ to 5’ exonuclease activity of DNA polymerase I during DNA
replication?
A. It can remove a nucleotide that DNA polymerase I has incorrectly inserted.
B. It can remove a nucleotide that DNA polymerase III has incorrectly inserted.
C. It removes an RNA nucleotide from the primer and replaces it with a DNA nucleotide before
removing the next RNA nucleotide from the primer.
D. It removes all of the RNA nucleotides from the primer before replacing them with DNA
nucleotides.
11. Which of the following enzymes is used in the base excision repair pathway to begin to repair a
deaminated 5-methylcytosine?
A. AP endonuclease.
B. Helicase.
C. DNA glycosylase.
D. DNA polymerase I.
12. Which type of DNA damage is most likely to result in mutation when it is repaired?
A. Double-stranded DNA break.
B. Single-stranded DNA break.
C. Hydrolytic attack removing a guanine base.
D. Formation of a thymine dimer.
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SECTION A (continued)
13. How does the ribosome catalyse formation of the peptide bond?
A. rRNA catalyses a reaction in which the bond holding the polypeptide to the tRNA in the A site
is broken.
B. rRNA catalyses a reaction in which the bond holding the polypeptide to the tRNA in the P site is
broken.
C. Ribosomal protein catalyses a reaction in which the bond holding the polypeptide to the tRNA
in the A site is broken.
D. Ribosomal protein catalyses a reaction in which the bond holding the polypeptide to the tRNA
in the P site is broken.
14. Which histone sits outside the eight core histones and locks the nucleosomes in place once they have
formed?
A. Histone 1.
B. Histone 2a.
C. Histone 2b.
D. Histone 3.
15. Plasmid DNA is extracted from a bacteria that contains only one type of plasmid. When this DNA is
run on an agarose gel, multiple bands can be seen. Why?
A. Different numbers of histone proteins are bound to the DNA.
B. Different numbers of topoisomerase proteins are bound to the DNA.
C. The plasmids have recombined in the bacteria to generate different sized plasmids.
D. Different amounts of supercoiling cause it to migrate at different speeds.
16. After a G protein has transmitted the signal from an activated G protein-coupled receptor, what
stops the signal?
A. The G protein releases GDP and binds GTP.
B. The G protein releases GTP and binds GDP.
C. The G protein hydrolyses GTP to GDP.
D. The GAP protein hydrolyses GTP to GDP.
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SECTION A (continued)
17. Upon binding of a ligand, what is the first action of a typical receptor tyrosine kinase?
A. Cross-phosphorylation of the dimerising partner.
B. Phosphorylation of a G protein.
C. Phosphorylation of an intracellular signalling molecule.
D. Phosphorylation of a transcription factor.
18. Which one of the following statements about carbohydrates is CORRECT?
A. Glucose residues in glycogen are joined by β-1,4 glycosidic linkages.
B. Glycosyltransferases catalyse the biosynthesis of oligosaccharides by transfer of a
monosaccharide from a nucleotide sugar to a carbohydrate acceptor.
C. O-glycans are attached to the side chains of asparagine residues in proteins.
D. Up to 11 different disaccharides can be generated using the two monosaccharides D-glucose
and D-galactose.
19. Which of the following is expected to decrease membrane fluidity?
A. Increasing the temperature of the membrane environment.
B. Increased content of phospholipids with long, saturated fatty acyl chains.
C. Increased content of peripheral membrane proteins.
D. Increased content of phospholipids with short, unsaturated fatty acyl chains.
20. The addition of free fatty acid molecules to an aqueous solution at physiological temperatures
favours the formation of:
A. bilayers.
B. liposomes.
C. micelles.
D. a mixture of different lipid structures
21. Which one of the following statements about ABO blood groups is CORRECT?
A. Blood group AB has both the A and the B antigen on the same oligosaccharide structure.
B. Blood group A contains a terminal galactose residue.
C. Blood groups A and B are synthesized by glycosyltransferases that recognise different
carbohydrate acceptors.
D. The O allele is expressed and encodes an inactive enzyme.
22. The sodium/potassium ATPase:
A. mediates passive transport of sodium and potassium ions across membranes.
B. pumps sodium and potassium ions out of the cell.
C. can be dissociated from the membrane by extraction with low pH buffers.
D. undergoes conformational changes in the reaction cycle that are induced by phosphorylation
and dephosphorylation.
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SECTION A (continued)
23. Which of the following represent plausible hydrogen bonding interactions at pH 9?
A. 1 and 2.
B. 1 and 3.
C. 2 and 3.
D. 1, 2 and 3.
24. If the pKa of a carboxylate group is 4.5, which statement is CORRECT?
A. At pH = 3, the predominant state will be positively charged.
B. At pH = 4.5, the predominant state will be neutral.
C. At pH = 7, the predominant state will be negatively charged.
D. The ionisation state of the group depends on acid strength, not on pH.
25. The conversion of L-malate to oxaloacetate by malate dehydrogenase has a ∆G′° value of 29.7
kJ/mol. Under which initial conditions will the production of oxaloacetate be most favoured?
A. Low L-malate and high oxaloacetate concentrations.
B. High L-malate and high oxaloacetate concentrations.
C. Low L-malate and low oxaloacetate concentrations.
D. High L-malate and low oxaloacetate concentrations.
26. Which statement about the production of pyruvate in the final step of glycolysis is CORRECT?
A. Pyruvate kinase transfers a phosphate group from ATP to PEP to generate pyruvate and ADP.
B. The unfavourable conversion of PEP to pyruvate is driven largely by the highly favourable
standard free energy change for the hydrolysis of ATP to ADP.
C. The standard free energy change for the conversion of PEP to pyruvate is very highly
favourable to counteract the unfavourable phosphorylation of ADP to ATP.
D. The production of pyruvate yields two ATP molecules per glucose that enters glycolysis,
because fructose 1,6-bisphosphate contains two phosphate groups.
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SECTION A (continued)
27. Glycogen is an efficient source of energy during high intensity exercise, such as sprinting, because:
A. glycogen breakdown in the liver can supply glucose to muscles via the bloodstream.
B. the debranching enzyme produces glucose, which does not require the phosphoglucomutase
to convert it to glucose 6-phosphate.
C. glycogenin is both the primer on which new glycogen chains are synthesised and the enzyme
that catalyses their assembly.
D. the highly branched glycogen particle has many non-reducing ends.
28. Which statement about the following reaction is CORRECT?
A. Succinate dehydrogenase links the Krebs cycle with glycolysis because it is used in both
pathways.
B. It can drive glycolysis or gluconeogenesis because the forward and reverse reactions are
favoured equally.
C. It is coupled to the production of ∼1.5 ATP per succinate oxidised.
D. It is critical under anaerobic conditions because it regenerates FADH2 for use in glycolysis.
29. After a carbohydrate-rich meal, when the blood glucose concentration more than doubles, which of
the following glucose transporters would be operating closest to its Vmax?
A. GLUT4, because its Kt is most similar to normal blood glucose levels.
B. GLUT3, because it has a very low Kt, which protects the brain under starvation conditions.
C. GLUT2, because it has a very high Kt, which helps regulate insulin production and removal of
glucose from the blood.
D. GLUT1, because it has a moderately low Kt, which provides a constant flow of glucose into
most cells of the body to maintain their basal cellular functions.
30. Glucagon release from the pancreas leads to:
A. an increase in gluconeogenesis, but decrease in glycogenesis.
B. an increase in glycogenolysis and increase in glycolysis.
C. a decrease in glycolysis, but increase in glycogenesis.
D. an increase in glycolysis and increase in glycogenesis.
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STUDENT NUMBER
SECTION B (14 minutes)
To be answered on the FRONT of the Multiple Choice Answer Sheet
1 mark per question
Questions 31-39 refer to Fig. 1 and the information in the figure legend.
Figure 1. Structure of an enzyme involved in glycolysis. The enzyme is composed of four subunits. Certain
sites on the enzyme are indicated with shaded ovals and rectangles. The sites at the front are shown with
solid lines and the sites at the back are shown with dashed lines. The sites indicated with ovals bind
fructose 6-phosphate. The sites indicated with rectangles bind fructose 2,6-bisphosphate. Interestingly, ATP
can bind to both sets of sites (ovals and rectangles), but ADP can only bind to the sites shown as rectangles.
31. The enzyme depicted in Fig. 1 catalyses the:
A. cleavage of fructose 2,6-bisphosphate into DHAP and GA-3-P.
B. conversion of glucose 6-phosphate to fructose 6-phosphate.
C. phosphorylation of fructose 6-phosphate to fructose 1,6-bisphosphate.
D. transfer of phosphate from PEP to ADP to generate pyruvate and ATP.
32. The reaction catalysed by the enzyme depicted in Fig. 1 is important because it:
A. is the first committed step of, and the most important control element in, glycolysis.
B. is freely reversible and hence the enzyme can be used in glycolysis and gluconeogenesis.
C. generates two ATP molecules per glucose molecule that enters glycolysis.
D. generates two 3-carbon molecules from a 6-carbon molecule, so that the pay-off phase of
glycolysis occurs twice.
33. Choose the best option to complete the sentence: The ovals indicate ________ and the rectangles
indicate________.
A. allosteric sites, catalytic sites.
B. catalytic sites, allosteric sites.
C. where allosteric activators bind, where allosteric inhibitors bind.
D. where allosteric inhibitors bind, where allosteric activators bind.
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