ID Num____________ 1 Medical Biochemistry Comprehensive Examination January 30, 1995 Kresge Auditorium Please follow these directions: 1. Do not begin the exam until all students have received a copy of the exam. You will be instructed as to when to break the seal. 2. The exam consists of 146 questions on 38 pages, with this title page considered page 1. If you are missing any questions or any pages please see an Instructor. 3. Place your ID number on every page of the exam and on the answer sheets you will hand in. If you do not remember your ID number use your name. 4. Two computer graded answer sheets will be used for this exam. Fill in both your ID number and your name in the indicated areas of the answer sheets. You should convert your number to a three digit number (001, 010, etc) and use the three leftmost boxes to insert your number. When using the answer sheets use a No. 2 pencil only. Fill in the circle for the correct answer(s) completely. If you wish to change an answer, be sure to erase cleanly. Make sure that you use your biochemistry ID number to fill in the ID box. The first answer sheet is to be used for the first 66 questions. The second answer sheet is to be used for the next 78 questions. Answers to questions 79 and 80 in part two are to be answered within the exam booklet. Every question has a defined number of answers! 5. When you are finished with the exam return both the test booklet and the answer sheet. Both will be returned to you when the grading is finished. Your experience in Medical Biochemistry is now complete. 6. Questions will not be allowed during the exam. If you believe there is a typographical error do the best you can with the information available. Do not spend extra time on the question. If it is determined that the information presented is ambiguous, or in error, then the question will not be counted in the final scoring. 7. There are two pages at the end of the exam for you to mark your answers so that you can check them against the posted answers (outside of room 3109 MSB). This sheet can be kept by you as you leave the exam. Answers will be posted once we are certain that all first year students have taken the exam. 8. You will have 4.5 hours (until 5:00) to complete this exam. Good luck.
Transcript
ID Num____________
1
Medical Biochemistry Comprehensive Examination
January 30, 1995Kresge Auditorium
Please follow these directions:
1. Do not begin the exam until all students have received a copy of the exam. You will beinstructed as to when to break the seal.
2. The exam consists of 146 questions on 38 pages, with this title page considered page1. If you are missing any questions or any pages please see an Instructor.
3. Place your ID number on every page of the exam and on the answer sheets you willhand in. If you do not remember your ID number use your name.
4. Two computer graded answer sheets will be used for this exam. Fill in both your IDnumber and your name in the indicated areas of the answer sheets. You shouldconvert your number to a three digit number (001, 010, etc) and use the threeleftmost boxes to insert your number. When using the answer sheets use a No. 2pencil only. Fill in the circle for the correct answer(s) completely. If you wish tochange an answer, be sure to erase cleanly. Make sure that you use your biochemistryID number to fill in the ID box. The first answer sheet is to be used for the first 66questions. The second answer sheet is to be used for the next 78 questions. Answersto questions 79 and 80 in part two are to be answered within the exam booklet. Everyquestion has a defined number of answers!
5. When you are finished with the exam return both the test booklet and the answersheet. Both will be returned to you when the grading is finished. Your experience inMedical Biochemistry is now complete.
6. Questions will not be allowed during the exam. If you believe there is a typographicalerror do the best you can with the information available. Do not spend extra time onthe question. If it is determined that the information presented is ambiguous, or inerror, then the question will not be counted in the final scoring.
7. There are two pages at the end of the exam for you to mark your answers so that youcan check them against the posted answers (outside of room 3109 MSB). This sheetcan be kept by you as you leave the exam. Answers will be posted once we are certainthat all first year students have taken the exam.
8. You will have 4.5 hours (until 5:00) to complete this exam. Good luck.
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2
Answer questions 1-66 (pages 2-17) on Answer Sheet 1.
1. (1 point) Which one of the following statements is incorrect with respect to theproperties of water?
A. Water acts in the biosphere as a general thermal buffer.B. Water has both a high heat of fusion and vaporization.C. Water is dipolar due to the differences in electronegativity between hydrogen
and oxygen.D. The high heat of vaporization of water is largely explained by its hydrogen
bonding capability.E. There are large changes in network hydrogen bonding in the transition from
water to ice.
2. (1 point) Which one of the following amino acids react with nerve gas (DFP) to form acovalent bond?
A. HistidineB. LysineC. ThreonineD. SerineE. Glutamine
3. (1 point) Which residues constitute the catalytic triad in the digestive enzymechymotrypsin?
4. (1 point) The pK (-COOH), pK (-NH ) and pK (R) for glutamic acid are 2.19, 9.67 and1 2 3 3
4.25 respectively. What is the pH of the isolectric point for glutamic acid?
A. 6.05B. 3.22C. 5.93D. 6.96E. 10.5
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5. (2 points) Which one of the following statements concerning the heme in hemoglobinis incorrect?
A. Carbon monoxide affinity to the iron atom is reduced by stearic interference bythe distal His of hemoglobin.
B. The proximal histidine forms a coordinate-covalent bond with the iron atom.C. The distal His forms one of the six ligands to the iron atom.D. Heme interactions with the protein are mediated by largely hydrophobic forces.E. When the iron atom is in a +3 valence state, it prefers H O binding instead of2
O .2
6. (2 points) Which one of the following statements concerning the Bohr effect isincorrect?
A. A significant fraction of the Bohr effect cannot be explained by changes in ionicbonding.
B. The lower pH of the tissues causes the oxygen saturation curve of hemoglobinto shift to the right.
C. Protonation of a histidine residue results in stabilization of the deoxy form.D. Dissolved CO in the tissue raises the pH at the tissue level, thus causing2
dissociation of oxygen.E. CO released in the lung raises the pH and increases the affinity of hemoglobin2
for oxygen.
7. (2 points) Concerning the binding of 2,3 bisphosphoglycerate (BPG) to hemoglobin,which one of the following statements is incorrect?
A. BPG forms ionic bonds in the central cavity of the hemoglobin tetramer.B. BPG stabilizes the deoxy form of hemoglobin.C. The binding of BPG is weaker to fetal hemoglobin than to the adult form.D. BPG binding to hemoglobin moves the oxygen saturation curve to the left.E. The stoichiometry of BPG is one molecule per hemoglobin tetramer.
8. (2 points) Which one of the following statements concerning sickle-cell disease isincorrect?
A. The solubility of the deoxy form of sickle-cell hemoglobin is greatly reduced.B. The mutation is in the $-6 position.C. The point mutation substitutes glutamic acid for valine.D. Sickle cell formation is favored in the capillaries due to lower pH values.E. The mutation causes the formation of a new surface protein-protein binding site.
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9. (1 point) All of the following amino acids are found in collagen except for which one?
A. CysteineB. HydroxylysineC. HydroxyprolineD. glycineE. proline
10. (1 point) Which one of the following statements concerning collagen is incorrect?
A. Cross linking can occur through hydroxylysine residuesB. Formation of the left hand single chain left-handed helix is dictated by stearic
compression.C. Collagen is stabilized by inter-chain hydrogen bond.D. Collagen is further stabilized by intra-chain ionic bonds.E. Collagen consists of three left-handed helices wound into a right-handed
superhelix.
11. (1 point) A proteoglycan consists of all the following constituents except for whichone?
A. Link proteinsB. Chondroitin sulfateC. Hyaluronic acidD. Core proteinsE. N-acetyl glucosamine
A
O
OH B
N
N
H
HN
H H
O
COH
O
NN
NN
H
N
H
H
H
D
H
N
N
HH3C
O
O
E
NN
NN
H
H
NH H
F
O
N
N
O
H H
H
O
NN
NN
H
H
O
NN
N N
H
N
H
H
H
O
P OC H2O
O
OH
O
OH
O
OH
O
OH
O
OH
O
OH
O
OH OH G
O
P OCH2O
O
O
P OC H2O
O
O
P OC H2O
O
O
P OCH2O
O
O
P OCH2O
O
O
P O CH2O
O
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Questions 12 and 13 (1 point each) require you to identify some of the following structures:
12. Which structure is GMP?
13. Which structure is dCMP?
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14. (1 point) Which ONE of the following statements best characterizes the mechanism bywhich AZT inhibits replication of HIV?
A. The azido group chemically cross-links to DNA polymerase and inhibits itsactivity
B. Since AZT only has a single phosphate on its 5' hydroxyl, it cannot be cappedproperly
C. Since AZT has no 2' hydroxyl group it inhibits reverse transcriptaseD. Since AZT has no 3' hydroxyl group it inhibits chain elongation after
incorporation into DNAE. When incorporated into DNA it creates a hot-spot for repair.
15. (1 point) Chargaff's base composition rule states that in double stranded DNA, A = Tand G = C. What can one say about the relative base composition of single strandedDNA?
A. A + T = G + CB. A + G = C + TC. A = 25%, C = 25%, G = 25%, T = 25%D. A + C + G + T = 100%E. None of the above
16. (1 point) Xeroderma is a DNA repair deficiency syndrome caused by which ONE of thefollowing?
A. A defective proofreading pathwayB. A defective nucleotide excision pathwayC. A defective DNA ligase geneD. A defective thymine-DNA glycosylase proteinE. A defective mismatch repair system
Questions 17-26 (1 point each) should be answered either TRUE or FALSE. Indicate which bydarkening either T or F on the answer sheet.
17. Both ATP and GTP are used during protein synthesis
18. In eukaryotes, polyadenylation is required before ANY species of message can betransported from the nucleus to the cytoplasm
19. Many forms of sickle cell anemia arise because of globin gene splicing defects
20. Eukaryotic gene regulatory elements are frequently composites of numerous individualnuclear factor binding sites
21. Nonsense mutations represent a specific class of missense mutations
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(True/False, continued)
22. In eukaryotes, termination factors are bound by both RNA polymerase II in transcriptionand by the ribosomal complex in translation
23. Transcription and translation initiate at ATG and AUG triplets respectively.
24. A phosphodiester linkage is one where a single phosphate group is esterified to twoindividual hydroxyl groups
25. Base pairs are stacked parallel to the helical axis of DNA
26. Under low glucose/low lactose conditions, lac repressor will effectively inhibittranscription of the lac operon
27. (1 point) All of the following statements concerning the lac operon are true except forwhich ONE?
A. Transcription initiation and translation start sites are not identicalB. The lac mRNA consists of three separate, but overlapping, protein-encoding
cistronsC. Inhibition of transcription occurs via a lac repressor-mediated loop in the DNA of
the operonD. Transcriptional activation via cAMP-CRP complex cannot overcome active
repressor-mediated inhibitionE. The inducer allolactose binds to the lacI protein in the initial stage of lac operon
activation
28. (2 points) Concerning the process of DNA replication, which TWO of the followingstatements are true?
A. Bidirectional synthesis means DNA is made both 5' to 3' and 3' to 5'B. Leading strand synthesis is discontinuousC. In bacteria, DNA polymerase III synthesizes DNA on both strandsD. DNA polymerase III initiates Okazaki fragment synthesisE. RNA primers are degraded by the proofreading activity of DNA polymerase IF. DNA polymerase I lays down new sequence in place of the RNA primer
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29. (2 points) Pick TWO choices from the options below which best complete the followingstatement:
Mismatch repair in prokaryotes is a process in which......
A. DNA polymerase at the replication fork continuously checks its workB. All mistakes in RNA synthesis are repairedC. The presence of methylated bases is required in order for it to work
correctlyD. Incorrect bases in the template strand are eliminatedE. A complex of repair proteins scan newly synthesized DNA for errors in DNA
base pairingF. A complex of repair proteins scans cellular DNA for damage inflicted by the
environment
30. (2 points) Which TWO of the following statements are a possible consequenceresulting from the deletion of a single nucleotide at the 3'-most position of exon 1 in agene that contains 3 exons (assuming that translation initiates normally well upstreamof this position)?
A. Production of a longer mRNAB. Production of a substantially shorter mRNAC. Production of a longer proteinD. Production of a shorter proteinE. Production of no mRNAF. Production of no protein
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31. (1 point) All of the following are associated with myosin EXCEPT for which ONE?
A. it self-assembles into dimersB. it binds actinC. it binds Ca which triggers muscle contraction+2
D. it possesses ATPase activity
32. (1 point) Which of the following TWO proteins would be expected to be found in the "Iband" of a striated muscle sarcomere?
A. dystrophinB. troponin CC. myosinD. a-actinin
33. (1 point) Which ONE sequence would most likely be an endonuclease restriction site?
A. TCGGCTAGCCGA
B. GAATTCCUUAAG
C. ATCGATTAGCTA
D. TACTACATGATG
34. (1 point) All of the following properties about recombinant DNA cloning vectors are trueEXCEPT for which ONE?
A. their DNA integrates into their bacterial host genomeB. their DNA can be separated and purified easily from their host genomeC. foreign DNA can be inserted and propagated in the cloning vectorD. they often encode antibiotic resistance genes to aid in selection of clones
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The picture below refers to questions 35 through 38. Below is shown a clone of a genomic DNAfragment from the mouse cardiac actin gene subcloned into a pUC plasmid vector. The distancebetween restriction endonuclease sites is indicated in parentheses. The vector without insert is2600 bp long and the position of restriction sites in the clone is shown. The genomic fragment iscloned into the pUC vector at the "R" restriction site located 500 bp from "T" restriction site. Theboxes represent exon sequences.
35. (1 point) How many bandswould you expect if the cloneis fully digested with therestrictions enzymes "S" and"X" simultaneously?
A. 2B. 3C. 4D. 5
36. (1 point) If you isolate the "R - R" genomic DNA fragment and then partially restrict theDNA with enzyme "X", how many DNA fragments would you expect to see?
A. 2B. 3C. 5D. 6
Questions 37-38 are True False (1 point each). Darken either T or F on the answer sheet.
37. You would expect a hybridizing band to be visible if the 250 bp "X - X" DNA fragmentwere radiolabeled and used to probe a Northern blot of mouse heart tissue?
38. You would expect a hybridizing band to be visible if the 250 bp "X - X" DNA fragmentwere radiolabeled and used to probe a mouse genomic Southern blot?
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Questions 39-40 are True False (1 point each). Darken either T or F on the answer sheet.
39. Glycoprotein complexes in the sarcolemma of the striated muscle fiber are affected inDuchenne's muscular dystrophy patients.
40. Duchenne's muscular dystrophy often results from deletions in the dystrophin locuscausing nonsense codons or frameshifts in the amino acid translational reading frameresulting in the lack of a functional protein, whereas Becker's muscular dystrophy oftenresults from an in-frame deletion such that a shorter protein is produced and is partiallyfunctional.
41. (1 point) Bacteriphage are often used in constructing genomic libraries because
A. multiple phage can infect a single bacterium, thus increasing the amount ofDNA which can be analyzed.
B. the average insert size of foreign DNA is 100 - 500 kb.C. isolated clones reflect genes which are expressed in the specific tissue from
which the library was constructed.d. none of the above.
42. (1 point) Which ONE of the following species of DNA will take the longest tocompletely re-nature in solution, under appropriate conditions of ionic strength, pH, andtemperature?
A. T4 bacteriophage DNAB. E. coli DNAC. mouse cell nonrepetitive genomic DNAD. human cell repetitive genomic DNA
43. (1 point) Southern blot hybridization utilizes all of the following EXCEPT for whichONE?
A. converting double-stranded DNA into single-stranded DNAB. irreversibly binding denatured DNA to a membrane filterC. hybridizing single-stranded DNA probes to RNAD. slowly allowing complementary single-stranded nucleic acid bases to renature
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44. (1 point ) The following properties are true about cDNA clones EXCEPT for whichONE?
A. when used to probe a genomic Southern blot of the same species, one wouldexpect to detect at least 1 band
B. when used to probe a Northern blot containing RNA from the same tissue and developmental stage as the cDNA source material, one would expect to detectat least 1 band
C. they reflect mRNAs which are expressed in a specific tissue at a specific timeD. they contain intron sequences which can be used for "chromosomal walking"
45. (1 point) The following reagents are used during M13 DNA sequencing reactionsEXCEPT for which ONE?
A. deoxyribonucleotides and dideoxyribonucleotidesB. single-stranded DNA template and DNA polymerase (Klenow fragment)C. DNA ligase and reverse transcriptased. a DNA oligonucleotide primer
46. (1 point) The polymerase chain reaction (PCR) is associated with which ONE of thefollowing:
A. a number of cycles, with each cycle comprised of a denaturation, ligation, andsynthesis step
B. four dideoxyribonucleotidesC. two synthetic oligonucleotide primers that are complementary to regions on the
same DNA strandD. a renaturation step that allows oligonucleotide primers to reanneal with their
complementary sequences
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47. (1 point) A man and his dizygotic (fraternal) twin come for genetic counseling. They haveeach had children with unrelated spouses and their two offspring, one boy and one girl,have fallen madly in love and wish to get married and have children. If you know that theson of one fraternal twin carries a lethal recessive trait, what is the probability that thedaughter of the other fraternal twin carries the same lethal recessive trait?
A. 50%B. 25%C. 15%D. 12½%
48. (1 point) A man with Klinefelter's syndrome (chromosomal constitution 47, XXY) has afather with hemophilia A (an X-linked recessive) disease. His risk of having manifestationsof hemophilia A are:
A. No chance at all.B. About the same as any of his sisters.C. The same as any other male in the general population.D. About the same as his brothers.
49. (1 point) Which one of the following statements describes the number of active X-chromosomes in a cell?
A. The number of Barr bodiesB. One less than the number of Barr bodies C. One more than the number of Barr bodiesD. One
50. (1 point) The Lyon hypothesis includes which one of the following statements?
A. In females, the maternal X-chromosome is imprinted randomly in cells at about the16-cell stage of embryogeneses.
B. X-inactivation is maintained and is clonally propagated following the initial randomX-inactivation.
C. In females the inactivated X is never reactivated even in oogonia. D. X-inactivation occurs randomly during each cell division.
51. (1 point) At a LOD score equal to 4, which one of the following values for 2 values wouldbe most consistent with tight linkage of an anonymous probe and the gene of interest?
A. 0.3B. 0.5C. 0.01D. 0.1
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52. (1 point) Genetic imprinting violates which one of the following Mendelian assumptions?
A. Differential expression of maternal or paternal genes at the same locus.B. Random inactivation of maternal or paternal genes at a given locus.C. A method for dosage compensation.D. Gene expression is independent of parental origin
53. (1 point) The physical basis for the number termed, 2, the recombination fraction, isderived from which one of the following physical processes?
A. Sister chromatid exchangeB. Exchange of genetic material on non-homologous chromosomes during meiosis
I.C. Reciprocal translocation of genetic material from homologous chromosomes D. Homologous crossovers between chromosomes during meiosis I.
54. (2 points) The gene frequency for a particular autosomal recessive trait in the populationis 1:100. Under Hardy-Weinberg equilibrium assumptions, the heterozygote frequencyis:
A. 1:50B. 1:2500C. 1:625D. 1:25
55. (2 points) Duchenne Muscular dystrophy, an X-linked recessive disease, has a genefrequency for mutant alleles of 1:10,000 in the general population. What is the frequencyof affected males in that population?
A. 1:106
B. 1:10,000C. 1:5,000 D. 1:100
56. (1 point) The use of retroviral vectors for gene therapy in human diseases has severalconcerns. These include which one of the following?
A. genome integrationB. insertional mutagenesisC. Cytoplasmic replicationD. mitochondrial targeting
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57. (1 point) Most current gene therapy protocols require the ex-vivo manipulation of culturedcells prior to installation of transformed cells containing the gene therapy product. Whichone of the following requires administration of the vectors directly into the disease organ?
A. Adenosine deaminaseB. Gaucher diseaseC. Phenylketonuria D. Hemophilia A
58. (1 point) Once determined, the sequence of the human genome should make readilyapparent the location and organization of genes. For this statement to be true, all of thefollowing EXCEPT for which one will likely be needed?
A. computer programs for identification of exonsB. detailed knowledge about murine and drosophila genomesC. a library containing cosmid clones for each region of the human genomeD. detailed knowledge of homologous sequences in various organisms
59. (1 point) A couple has an affected girl with congenital heart disease, a multifactorial trait.That girl has surgery and grows up happy and healthy. She and her spouse (who has nofamily history of congenital heart disease) come for genetic counseling to determine theirrisk of having a child affected with congenital heart disease. Compared to the girl'sparents, she and her spouse have a risk of an affected child that is:
A. greaterB. lessC. the sameD. no conclusions can be made.
60. (1 point) An important concept in gene therapy, organoid usage and enzyme therapy isthat of tropism. Which one of the following best describes this concept?
A. cellular migration along axonal pathwaysB. cell specific receptor mediated endocytosisC. cell specific podocytosis D. electrostatic lipid interactions
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61. (2 points) A patient shows up in your clinic and is diagnosed with osteogenesisimperfecta. Although the gene causing this disease has not been cloned, a geneticlinkage test is available. The patient insists on having the test as she and her spouseintend to have children in the near future. You now have to explain the limitations of thistype of test. These are:
A. Requirement for samples from many or all family members.B. The need to test all samples for possible non-paternity.C. The possibility of genetic heterogeneity might mean that the available genetic test
might not be useful.D. The possibility that the marker might not be informative in this particular family.E. All of the above.
62. (2 points) A PCR assay has shown that individual #1, who is severely affected bymyotonic dystrophy has an expansion of -2 kb in the CTG triplet in the 3' untranslatedregion. Which TWO of the following methods can also be used to detect suchexpansions?
A. Southern blotB. Northern blotC. Western blotD. Eastern Blot
63. (2 points) The Huntington disease (HD) locus was found to be tightly linked to apolymorphic marker G8. However, the same study also showed that the G8 marker wasnot, itself, the gene for HD. The one best piece of evidence for this conclusion would be:
A. The detection of different polymorphisms at the HD locus.B. The detection of a “recombinant” between the HD locus and G8.C. The fact that no “recombinants” were seen between the HD locus and G8.D. The lack of large families to test for better genetic linkage.E. None of the above.
64. (2 points) Individuals affected by cystic fibrosis are reproductively impaired and almostnever have children. To a casual observer, this might suggest that mutant CF allelebearing chromosomes will eventually be lost from the population. If the populationstructure (proportion of different groups that comprise the population) remains unchanged,your best estimate of the carrier frequency for CF ten generations from now would be:
A. Carrier frequency for CF will significantly decreaseB. Carrier frequency for CF will significantly increaseC. Carrier frequency for CF will not change muchD. Information to make such predicitons is currently unavailable
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65. (2 points) For a positional cloning strategy to be successful, the order in which differenttechniques are used is crucial. Which of the following is the one most likely to work?
66. (2 points) Which one of the following best describes the role of the retinoblastoma (Rb)gene product?
A. It plays a role in control of DNA damage in the cell.B. It plays a role in the control of the cell cycle.C. Has kinase domains that suggests that it phosphorylates serine and threonine
residues.D. Other than the fact that it is a cytoplasmic protein, not much is known about its
4. (2 points) Which of the following are found in high concentration in the urine of goutpatients treated with allopurinol?
A. carbamoyl phosphate and dihydroorotateB. hypoxanthine and xanthineC. inosine and guanosineD. uric acid and allantoinE. uric acid and uricaseF. xanthine and uric acid
5. (2 points) Both 5-fluorouracil and 5-fluoro-2-deoxy-uridine are potent inhibitors of DNAsynthesis. Their action as inhibitors involves their intracellular conversion to 5-fluorodeoxyuridine monophosphate which binds irreversibly to one of the enzymes of denovo pyrimidine biosynthesis. When first incubated with cultured cells at low doses andthen applied at increasing doses, a population of cells is selected for that is resistant to thedrugs. These cells have become resistant because they overproduce
6. (1 point) Mixed micelles in the intestinal lumen contain 2-monoacylglycerol andunesterified fatty acids. After endocytosis of the micelles, the fatty acids are converted tofatty acyl-CoA by fatty acyl-CoA synthetase and then acyl transferases attach the fattyacids to 2-monoacylglycerol to form triacylglycerol.
How accurate are the two sentences above? Note: any misstatement in a sentencemakes the entire sentence incorrect.
A. Both are correctB. Only one is correctC. Neither is correct
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7. (2 points) You are diagnosed with type Ia hyperlipoproteinemia and allowed to see theresults of your fasting serum lipid profile. Your physician tells you that you will be treatedwith a drug that inhibits the rate limiting step of cholesterol biosynthesis. You tell thephysician that either his diagnosis or treatment strategy is incorrect. The physician tellsyou the “facts” listed below. You explain that one of his “facts” is wrong and win theargument!Which one of the following “facts” is INCORRECT?
A. HMG-CoA reductase catalyzes the rate limiting step in cholesterol biosynthesis.B. Hypertriglyceridemia is typically associated with increased levels of serum
chylomicrons and/or VLDLs.C. VLDLs are produced in the liver and contain many lipids including cholesterol.D. Your lipid profile indicates that you have an abnormally high level of beta-
lipoproteins, therefore, by definition, you have type I hyperlipoproteinemia.
8. (2 points) Increased plasma insulin can result in which one of the following?
A. decreased fat cell hexokinase activity.B. increased fat cell adenylate cyclase activity.C. increased lipoprotein lipase production.D. increased liver carnitine.E. increased numbers of insulin receptors on fat cells.
9. (2 points) A 43 year old female with a history of heart disease has a 3-fold elevatedplasma triglyceride level compared to normal, and a slightly elevated plasma cholesterollevel. A serum lipid profile demonstrated a great excess of pre-beta-lipoproteins andnormal chylomicron levels. Lowering the patient’s dietary fat intake did not effect thehyperlipidemia; however, it was effectively treated by lowering carbohydrate intake.This patients hyperlipoproteinemia:
A. is of the exogenous type.B. is probably a result of a defect in lipoprotein lipase activity.C. is probably the result of an increase in VLDL production by the liver.D. is typical of type IV hyperlipoproteinemiasE. reflects an inability to digest and absorb fat.
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10. (1 point) Peter Minimus, a 22 year old male medical student, was diagnosed with chronicuremia (excess urea in the blood). After initiation of maintenance hemodialysis, hissymptoms subsided; however, it was discovered that Peter had suddenly developedhypertriglyceridemia. Which one of the following explanations is most likely?
A. Peter suffers from a genetic deficiency of apoprotein B-100.B. Peter's chronic uremia is caused a liver dysfunction which resulted in the over
secretion of bile acids.C. During the dialysis procedure, a significant amount of heparin is removed from the
plasma.D. Peter suffers from a genetic deficiency of apoprotein C-1.E. During the dialysis procedure, lipoprotein lipase is damaged.F. Peter's chronic uremia caused a pancreatic dysfunction which reduced the
production of pancreatic digestive enzymes.G. Peter’s kidneys are beginning to fail and no longer remove chylomicron remnants
from the blood.
11. (2 points) When ketone bodies are being produced by the liver
A. HMG-CoA reductase is not phosphorylated and is activeB. HMG-CoA reductase is not phosphorylated and is inactiveC. HMG-CoA reductase is phosphorylated and is activeD. HMG-CoA reductase is phosphorylated and is inactive
12. (2 points) The first steps of de novo cholesterol biosynthesis occur in the
A. cytoplasmB. endoplasmic reticulumC. Golgi apparatusD. mitochondriaE. peroxisomes
13. (2 points) Fran Roundbody, a 26 year old female, was diagnosed as having a geneticdisease that results in a deficiency of the enzyme acyl-CoA: cholesterol acyl transferase.Fran’s enzyme deficiency would result in
A. a decrease in mature HDL particles.B. a decreased ability to store cholesterol esters in the cell.C. a increase in nascent HDL particles.D. a increase in the cholesterol ester content of chylomicrons.E. an inability to form cholesterol esters in the plasma.
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14. (2 points) True statements about the synthesis of the bile acids and salts include:
A. Secondary bile acids can be formed from primary bile salts by removal of aconjugated amino acid and removal of the 7-alpha-hydroxy group.
B. Synthesis of bile acids can occur in the absence of dietary cholesterol.C. The rate limiting step in biosynthesis involves hydroxylation of free cholesterol at
the 7-alpha position. D. All of the aboveE. None of the above
15. (2 points) The decarboxylation of phosphatidylserine results in the production of:
A. PhosphatidateB. Phosphatidic acidC. PhosphatidylcholineD. PhosphatidylethanolamineE. PhosphatidylglycerolF. None of the above
16. (2 points) Which one of the following statements is FALSE?
A. Less than 20% of the phosphatidylinositol found in humans is polyphosphorylated.B. Phosphatidylinositol is typically present at a higher concentration in the cytoplasmic
leaflet of the plasma membrane as compared to the outer leaflet.C. The activation of protein kinase C by tumor promoters results in the activation of
cellular enzymes by the removal of covalently bound phosphate groups.D. The cleavage of phosphatidylinositol-4,5-bisphosphate results in the activation of
a protein kinase and an increase in the concentration of intracellular free calcium.E. The PI cycle is initiated by the activation of a phospholipase C located at the
plasma membrane.
17. (2 points) Which one of the following enzymes catalyzes the degradation ofphosphatidylglycerol to phosphatidate and glycerol?
A. Phospholipase A1
B. Phospholipase A2
C. Phospholipase BD. Phospholipase CE. Phospholipase DF. Phospholipase EG. None of the above
ID NUM___________
24
18. (1 point) Which one of the following diseases is caused by a defect in phospholipiddegradation?
A. Gaucher's diseaseB. Farber's diseaseC. Fabry's diseaseD. Niemann-Pick diseaseE. None of the above
19. (2 points) Jake is back. Having enjoyed the fruits of California for several years JakeLipidhead has returned to Cincinnati to head the Center for Fat Control. The Center’s firstclinical study is aimed at understanding the action of compound 1691, a new drug thatsupposedly inhibits the production of triacylglycerol. Some current findings about thecompound are presented below.
Rats injected with compound 1691 produce 50% less radiolabeled triglyceride 30minutes after feeding them C-glycerol as compared to rats injected with saline.14
Rats injected with either compound 1691 or saline produce the same amount ofradiolabeled triglyceride 2 minutes after feeding them C-2-monoacylglycerol (label in the14
glycerol moiety).Rats injected with compound 1691 produce more radiolabeled phosphatidic acid
30 minutes after feeding them C-glycerol as compared to rats injected with saline.14
Rats injected with either compound 1691 or saline produce the same amount ofradiolabeled phosphatidic acid 2 minutes after feeding them C-2-monoacylglycerol (label14
in the glycerol moiety).Diacylglycerol acyltransferase activity is identical in rats injected with either
compound 1691 or saline.
Based on these findings, Jake has proposed that compound 1691 acts by inhibiting a singleenzyme. Are you as smart as Jake? Which one of the following enzymes is inhibited by the newcompound?
20. (1 point) The signal peptide found at the amino end of proteins destined to be secretedfrom eukaryotic cells:
A. binds to docking proteins present in the trans Golgi apparatus.B. consists entirely of hydrophilic amino acids.C. contains the signal protease activityD. is added to the polypeptide chain post-translationally.E. is cleaved off prior to the translocation of the completed protein to the extracellular
space.
21. (2 points) During lysosomal enzyme biosynthesis
A. the enzymes attach to the mannose 6-phosphate receptor in the trans Golgi.B. lysosomal enzymes are released from the mannose 6-phosphate receptor in
CURL-like sorting vesicles.C. lysosomal enzymes migrate to the cis Golgi where mannose residues are
phosphorylated.D. most of the mannose 6-phosphate residues lose the phosphate before the
enzymes are delivered to lysosomes.E. All of the aboveF. None of the above
22. (1 point) Proteins having a GPI-anchor
A. are located mainly in lysosomesB. are used by the US navy to remove obscene tattoosC. can be either membrane bound or exist free in the cytosol.D. have the "anchor" attached to the C-terminal amino acid residue.E. have the "anchor" attached to the N-terminal amino acid residue.F. None of the above
23. (2 points) Which one of the following statements is true concerning uncontrolled diabetes?
A. High levels of acetyl-CoA in liver cytosol may be diverted toward the production ofcholesterol; therefore, many diabetics have elevated serum cholesterol levels.
B. Increased lipolysis caused by ACTH and glucagon occurs, so that production offatty acids and glycerol is greatly increased.
C. Low serum levels of insulin prevent adipose tissue from using glucose to producetriacylglycerols.
D. Surplus fatty acids are transported to the liver, where they enter the beta-oxidationspiral to form acetyl CoA.
E. All of the above.F. None of the above.
ID No: __________
26
24. (2 points) A high protein diet will not necessarily cause you to use weight. Surplus dietaryprotein can be converted into triacylglycerol. Which one of the following statementsconcerning the metabolism of protein to fat are correct?
A. Degradation of all the ketogenic aminoacids results in the production of acetyl-CoA.B. Many amino acids are degraded to pyruvate, which after entering the mitochondria
may be acted upon by pyruvate carboxylase or pyruvate dehydrogenase.C. The NADPH required for fatty acid biosynthesis may arise from the pyruvate /
malate cycle or the pentose phosphate pathway.D. The citrate shuttles acetyl-CoA from the mitochondria to the cytosol where fatty
acid biosynthesis takes place.E. Triglyceride biosynthesis may occur by either acylation of glyceraldehyde-3-
phosphate or dihydroxyacetone phosphate.F. When proteins are converted to fat, the essential precursors for fatty acid
synthesis, namely a carbon source (acetyl-CoA) and biosynthetic reducing power(NADPH), must be formed.
G. All of the aboveH. None of the above
25. (2 points) Which of the following statements about the net biosynthesis of glucose inhumans is true?
A. Glucose can be synthesized from all species of phosphatidylcholine.B. Glucose can be synthesized from alpha-ketoglutarate.C. Glucose can be synthesized from odd chain fatty acids.D. Glucose can be synthesized from triglyceride.E. All of the aboveF. None of the above
26. (2 points) Which TWO of the following statements concerning glycogen metabolism areINCORRECT?
A. The regulation of glycogen metabolism can occur through either covalentmodification of key enzymes, or allosteric regulation of the same enzymes.
B. The synthesis of glycogen requires a nucleotide sugar.C. The cofactor pyridoxal phosphate is required for the synthesis of glycogen.D. In the synthesis of glycogen from pyruvate in the liver, radioactivity derived from
carbon dioxide would be found in the glycogen which is newly synthesized.E. The immediate product of glycogen degradation is glucose-6-phosphate.F. In the degradation of glycogen a phosphorolysis reaction is required for
approximately 90% of the process, whereas a hydrolysis is used the other 10% ofthe time.
ID No: __________
27
27. (2 points) The regulation of glycolysis is very complex. Which TWO of the followingstatements most correctly describe the regulation of this pathway?
A. The regulated steps of glycolysis are those in which either ATP is formed orhydrolyzed, as well as the step which produces NADH.
B. Glucose-6-phosphate, ATP, and alanine are all negative allosteric effectors of atleast one of the regulated steps of glycolysis.
C. Phosphorylation of key enzymes by Protein Kinase A is important in the regulationof glycolysis in the liver, but not in the muscle.
D. Glucagon administration activates glycolysis in the muscle as well as the liver.E. Under conditions in which ketone body formation is favored in the liver glycolysis
in the liver will also be activated, in order to provide adequate substrates for ketonebody formation.
F. Under conditions of adequate energy supplies glycolysis in the liver is allostericallyactivated to provide substrates for fatty acid biosynthesis.
28. (2 points) Which TWO of the following statements concerning the role ofphosphofructokinase-2 in the regulation of glycolysis are correct?
A. The major role of PFK-2 is to phosphorylate fructose-6-phosphate, to formfructose-1,6-bisphosphate.
B. Regulation of PFK-2 in the liver links the glycolytic pathway in the liver to hormonalcontrol.
C. The major product of the PFK-2 reaction also will feed-forward and stimulate theactivity of another regulated step, that catalyzed by pyruvate kinase.
D. PFK-2, which catalyzes a reversible reaction, is regulated by the concentration ofglucose-6-phosphate, which strongly activates the enzyme.
E. Fructose-1,6-bisphosphatase is reciprocally regulated from PFK-2.F. The major product of the PFK-2 reaction is the most potent activator of the key
regulated step of glycolysis
29. (2 points) Which TWO of the following statements are INCORRECT concerning the TCAcycle?
A. The major regulatory allosteric factors for the enzymes of the cycle are the energycharge and the levels of reduced cofactors present within the mitochondria.
B. A major function of the cycle is to oxidize acetyl-CoA to carbon dioxide and water.C. Two of the enzymes within the cycle itself carry out oxidative decarboxylation
reactions which require five different cofactors.D. For each turn of the cycle 12 molecules of ATP can eventually be obtained.E. All of the enzymes of the cycle are found within the matrix of the mitochondria
except for one, which is membrane bound.F. The cycle cannot operate in the presence of an uncoupler.
ID No: __________
28
30. (2 points) Which TWO of the following statements can be considered correct accordingto the oncogene hypothesis?
A. Normal cells should contain DNA sequences related to the transforming genesfound in RNA tumor viruses.
B. Cancer results from the simultaneous activation of most of the genes found in acell.
C. RNA tumor viruses are the cause of greater than 85% of human tumors.D. Transformation of eukaryotic cells can be brought about by adapting cells to grow
in culture.E. Oncogenes have arisen spontaneously in prokaryotic cells, and have since been
found to be expressed in eukaryotic cells as well.F. Oncogenes are frequently mutated forms of the proto-oncogenes.
31. (2 points) Based upon current knowledge transformation can result from all of thefollowing EXCEPT for which TWO?
A. Constitutive expression of certain nuclear proteins.B. Increased expression of a plasma membrane protein which regulates glucose
transport.C. Increased activity of intracellular tyrosine kinases.D. Increased activity of the enzymes hexokinase, phosphofructokinase-1, and
pyruvate kinase.E. Altered regulation of the MAP kinase cascade.F. Altered regulation of a small GTP binding protein named ras.
32. (2 points) Which TWO of the following statements are correct concerning the potentialfate of pyruvate in metabolism?
A. It can form lactate in order to regenerate NAD such that glycolysis can continue+
under anaerobic conditions.B. It can form acetyl-CoA in order to enter the TCA cycle for eventual energy
production.C. It can be transaminated to form the amino acid serine.D. It can form malate in a reaction which requires GTP and biotin.E. It can react with a second molecule of pyruvate to form acetoacetate.F. It can initiate gluconeogenesis and go directly back to phosphoenolpyruvate in a
one step reaction.
ID No: __________
29
33. (2 points) Which TWO of the following statements concerning gluconeogenesis areINCORRECT?
A. Gluconeogenesis is the reversal of the reactions of glycolysis, using all of the sameenzymes which catalyze the reactions of glycolysis.
B. In the conversion of lactate to phosphoenolpyruvate, three enzymes and thehydrolysis of two high energy bonds are required.
C. The conversion of glucose-6-phosphate to glucose occurs primarily in the liver. D. Phosphorylation of PEP carboxykinase by protein kinase A is an important
regulatory step in gluconeogenesis.E. Under conditions which favor ketone body formation in the liver, gluconeogenesis
will also be favored.F. Under conditions in which glycogen degradation is enhanced in the liver,
gluconeogenesis in the liver will also be enhanced.
34. (2 points) Which TWO enzymes would be phosphorylated and inactive under conditonswhich favor ketone body formation in the liver?
A. Phosphofructokinase-1B. Phosphofructokinase-2C. Phosphorylase KinaseD. Protein-phosphatase 1E. Insulin-stimulated protein kinaseF. Hormone-sensitive lipaseG. Acetyl-CoA carboxylase
35. (2 points) Which TWO enzymes would NOT BE required in the biosynthesis of glutamicacid starting with ribose-5-phosphate as the sole carbon source?
36. (2 points) Which TWO of the following events are required for the liver to produce ketonebodies?
A. Allosteric inhibition of PEP carboxykinase.B. Excessive fatty acid oxidation, leading to elevated levels of acetyl-CoA within the
mitochondrial matrix.C. Phosphorylation of HMG-CoA reductase, to allow the irreversible step of ketone
body formation to proceed.D. The ratio of $-hydroxybutyrate to acetoacetate will be dependent on the
NADH/NAD ratio within the mitochondria.+
E. Acetoacetate synthetase is activated by phosphorylation by protein kinase A.F. Glycogen degradative enzymes are not activated.
ID No: __________
30
37. (2 points) Which TWO statements are correct concerning the concept of “coupling”oxidation to phosphorylation?
A. Coupling refers to coupling factor 1, which is required for the transport of protonsthrough the F portion of the ATPase, and which couples the energy from protono
entry to the rotation of the F subunit of the ATPase.1
B. Coupling refers to the discovery that if the phosphorylation of ADP to form ATP isblocked in any way then respiration will also stop.
C. Coupling refers to the rate at which the TCA cycle produces reduced cofactorswhich couple to the electron transfer chain.
D. Uncouplers uncouple oxidation from phosphorylation by inhibiting electron flowfrom complex II to complex III, but not complex I to complex III, which still allowsoxidation to occur in the absence of phosphorylation.
E. Coupling refers to the tight complexing of the cytochromes within each electrontransfer complex.
F. Uncouplers uncouple oxidation from phosphorylation by equilibrating theconcentration of protons across both sides of the inner mitochondrial membrane.
38. (2 points) Under conditions of vigourous exercise certain key enzymes are altered in theiractivity by phosphorylation. Which TWO of the following enzymes would bephosphorylated and inactive under these conditions?
A. Phosphorylase kinase (both liver and muscle)B. Phosphorylase (muscle)C. Phosphorylase (liver)D. Phosphofructokinase-1(liver)E. Pyruvate kinase (liver)F. Hormone-sensitive lipaseG. Glycogen synthase (liver)
39. (2 points) Which TWO of the following statements concerning the HMP shunt areINCORRECT?
A. The HMP shunt allows for the conversion of six carbon sugars to five carbonsugars.
B. The HMP shunt is regulated by the ratio of reduced NADPH to oxidized NADP .+
C. The non-oxidative reactions of the HMP shunt require the breakage and formationof carbon-carbon bonds.
D. Transaldolase will transfer two carbon units, and transketolase will transfer threecarbon units.
E. Transaldolase requires a cofactor in order to catalyze its reaction.F. Both four and seven carbon intermediates are produced during the course of the
non-oxidative reactions.
ID No: __________
31
40. (2 points) Which TWO of the following statements are correct concerning signaltransduction?
A. Activation of raf by the growth factor receptor and ras lead to the eventualphosphorylation of the transcription factor jun.
B. Activation of phospholipase-C-( by phosphorylation on a serine residue leads tothe eventual activation of protein kinase C.
C. Oncogenic ras proteins lead to the constitutive activation of the MAP kinasecascade pathway because this form of ras is refractory to regulation by GAP.
D. All growth factors must activate protein kinase C in order to stimulate cellproliferation in the target cell.
E. The MAP kinase kinase is similar to growth factor receptors, in that it is exclusivelya tyrosine kinase, and activates other proteins by phosphorylating critical tyrosineresidues on the substrates.
F. The use of GRB2 and SOS is specific for insulin signalling, and those proteins arenot used with any other growth factor signalling pathways.
41. (1 point) The ATP yield from substrate-level phosphorylation in the conversion of onemoleucule of glucose to 2 molecules of pyruvate using exclusively the glycolytic pathwayis:
A. 1 molecule of ATP.B. 2 molecules of ATP.C. 3 molecules of ATP.D. 4 molecules of ATP.E. 5 molecules of ATP.F. None of the above.
ID No: __________
32
Questions 42-48 are matching questions worth 1 point each. Consider an individual whohas been fasting for 8 hours. Answer the following questions concerning the phosphorylationstate of various enzymes using the matching key, with the lettered choices. There is ONE correctanswer for each question, and a lettered choice will need to be used more than once to answerall of the questions.
42. Phosphorylase Kinase (liver) A. The enzyme is phosphorylated and
43. Phosphorylase (liver)
44. Hormone-sensitive lipase and is active under these conditions.
45. Pyruvate kinase (liver) C. The enzyme is phosphorylated and
46. Acetyl-CoA carboxylase
47. Pyruvate carboxylase and is inactive under these
48. Protein inhibitor I
active under these conditions.
B. The enzyme is not phosphorylated
inactive under these conditions.
D. The enzyme is not phosphorylated
conditions.
49. (2 points) Which ONE of the following statements most correctly defines the Michealisconstant, K ?m
A. The affinity of the substrate for the enzyme.B. The substrate concentration at which one-half the maximal velocity is reached.C. The rate of the forward reaction, in which the enzyme-substrate complex is
converted to enzyme and product.D. The maximal rate at which the enzyme can work (ie, the rate obtained when all of
the enzyme is in the enzyme-substrate complex).E. K is a combined constant of all of the rate constants involved in the derivation, inm
which the product of three constants are divided by the expression (k + k ).1 2
50. (1 point) After long periods of exercise muscle cramping can occur due to the buildup ofan organic acid. The acid which brings about the cramping is:
During the discussions on metabolism a large number of diseases were discussed.Questions 51-57 (1 point each) are based on the matching format below. Match the appropriatesymptoms with the ONE best enzyme defect.
51. Enlarged liver, hypoglycemia under A. Activation of vitamin B1fasting conditions, normal glycogen B. Activation of vitamin B12structure. C. Adenosine deaminase
52. Enlarged liver, abnormal glycogen E. Carbomyl-phosphate synthetase Istructures, leads to liver damage and F. Debranching enzymedeath. G. Glucose-6-phosphatase
53. No visible signs of disease, dehydrogenasesusceptible to oxidizing agents such I. Glyceraldehde-3-phosphatethat hemolytic anemia results. dehydrogenase
54. Loss of a viable immune system, K. Lactate dehydrogenasepatient dies from simple infections. L. Ornithine transcarbamoylase
55. Elevated levels of homocysteine and N. Propionyl-CoA carboxylasemethyl-malonic acid. O. Purine nucleotidase
56. Elevated levels of ammonia andorotic acid. Can lead to death if nottreated.
57. Lack of pigmentation; albinism.
D. Branching enzyme
H. Glucose-6-phosphate
J. HGPRT
M. Phenylalanine hydroxylase
P. Tyrosinase
58. (1 point) Which ONE of the following equations correctly represents the Michealis-Mentonequation?
ID No: __________
34
59. (1 point) This question refers to theFigure shown to the right. WhichONE statement is correct concerningthe graphs shown in this figure?
A. Graph A represents a Hillplot, whereas graph Drepresents an Eadie-Hofsteeplot.
B. Graph E represents a Hillplot, whereas graph Brepresents a Scatchard plot.
C. Graph C represents non-competitive inhibition,whereas Graph B representsa Hill plot.
D. Graph A is used to measureligand binding to its receptor,whereas graph F representsthe effects of an inhibitor onthe kinetics of an enzymecatalyzed reaction.
E. Graph E represents aScatchard plot, whereasgraph A represents a Hillplot.
Questions 60-64 (1 point each) refer to the matching questions below. Many enzymes inbiochemical pathways require cofactors in order to function. Pick TWO cofactors from the letteredlist below which match the pathways (or substrate conversions) asked in the question. Note thatwhile each answer consists of two cofactors, a cofactor can be used for more than one pathway.
60. The conversion of glucose to acetyl- A. BiotinCoA using primarily the enzymes of B. NAD /NADHglycolysis C. NADP /NADPH
61. The biosynthesis of palmitic acid from D. Pyridoxal Phosphateacetyl-CoA E. SAM
62. Hexose monophosphate shunt F. Tetrahydrobiopterinpathway (both the oxidative and non- G. Tetrahydrofolateoxidative portions of this pathway) H. Thiamine Pyrophosphate
63. TCA cycle64. The biosynthesis of glycine from
phosphopyruvate
+
+
ID No: __________
35
65. (2 points) Individuals on an alcoholic diet (ie no other carbon sources) can becomehypoglycemic due to an inability to produce glucose. This inability to produce glucose isdue primarily to which one of the following?
A. Lack of glycogen in the liverB. Lack of a needed cofactor in the gluconeogenic pathwayC. Lack of substrates for gluconeogenesisD. Lack of a needed cofactor for the TCA cycle to operateE. Inhibition of glucose-6-phosphatase by acetaldehydeF. Inhibition of pyruvate dehydrogenase by acetyl-CoA
66. (1 point) The reactions of fatty acid degradation are cyclical. Which ONE of the followingstatements best describes the nature of this cycle?
A. The first reaction is a reduction, followed by hydration, a second reduction, andthen carbon-carbon bond breakage.
B. The first reaction is an oxidation, followed by a dehydration, then a secondoxidation, and finally carbon-carbon bond breakage.
C. The first reaction is an oxidation of the substrate, followed by hydration of theoxidized bond, then a second oxidation, followed by carbon-carbon bond breakage.
D. The first reaction is hydration, followed by two oxidations, then carbon-carbon bondbreakage.
E. The first reaction is an oxidation reaction, followed by hydration, then a reduction,followed finally by carbon-carbon bond breakage.
67. (1 point) Glutamate plays a number of very important roles in nitrogen metabolism. WhichONE of the following statements is INCORRECT concerning the role of glutamate in thegathering and disposal of nitrogen?
A. Glutamate can “fix” ammonia in an ATP dependent reaction.B. Glutamate and glutamine are the primary nitrogen carriers in the blood under
normal conditions.C. Glutamate can lose its nitrogen group to form "-ketoglutarate in a reaction
catalyzed by glutamate dehydrogenase.D. Glutamate is the precursor of ornithine, an important component of the urea cycle.E. Glutamate and oxaloacetate are the primary transamination pair utilized to funnel
nitrogens into glutamate.
ID No: __________
36
Certain key enzymes are required for the regulation of various pathways. For questions68-73 (1 point each) match the ONE BEST appropriate regulated enzyme to the biochemicalpathway.
68. Glycolysis A. Acetyl-CoA carboxylase
69. HMP shunt C. Argininosuccinate lyase
70. Fatty acid biosynthesis E. Carbamoyl-phosphate synthetase II
71. Fatty acid degradation G. Enolase
72. TCA cycle I. Glucose-6-phosphate
73. Nitrogen disposal J. Glyceraldehyde-3-phosphate
B. "-ketoglutarate dehydrogenase
D. Carbamoyl-phosphate synthetase I
F. Carnitine acyltransferase
H. Fatty acid synthase
dehydrogenase
dehydrogenaseK. Phosphofructokinase-1
74. (1 point) Which TWO of the following statements concerning metabolic pathways andreaction types are correct?
A. Glycogen synthesis and degradation require carbon-carbon bond formation andbreakage.
B. The pathway of fatty acid degradation of unsaturated fatty acids can involve bothoxidation and reduction reactions.
C. The TCA cycle reactions are similar to those of the oxidation of saturated fattyacids.
D. The synthesis of ATP during the operation of the glyoclytic pathway is an exampleof oxidative phosphorylation.
E. An oxidative decarboxylation reaction, requiring 5 different cofactors, is foundamongst the reaction types in the oxidative portion of the HMP shunt pathway.
F. Urea biosynthesis (consider only the reactions of the urea cycle) requires carbon-carbon bond breakage.
75. (1 point) Citrate plays a number of important roles in intermediary metabolism. Which ONEof the following statements is INCORRECT concerning the role of citrate in metabolism?
A. Citrate is an allosteric inhibitor of phosphofructokinase-1.B. Citrate is an allosteric activator of a key enzyme of fatty acid biosynthesis.C. Citrate is a key intermediate of the TCA cycle.D. Citrate is used as a carrier to transport acetyl-CoA equivalents across the
mitochondrial membrane into the cytosol for use in fatty acid biosynthesis.E. Citrate is an allosteric activator of pyruvate kinase, a key regulated step of
glycolysis.
C
H
COOH
NH2
CH2CH
CH3
CH3
C
H
COOH
NH2
CH2CH2CH2N
H
C
NH
NH2
C
H
COOH
NH2
NH2CH2CH2CH2CH2
C
H
COOH
NH2
HOCH2
C
H
COOH
NH2
H C
H
COOH
NH2
CH3
C
H
COOH
NH2
CH2HO C
H
COOH
NH2
CH2CH2C
H2N
O
A.
B.
C.
D.
E.
F.
G.
H.
ID No: __________
37
Questions 76-78 (1 point each) should be answered from the lettered list of structuresbelow. Match the appropriate structure with the question. Each question has TWO correctanswers, and an answer may be used more than once.
76. These are essential (for the adult human diet) amino acids.
77. These amino acids are designated by the letters “R” and “Q”.
78. These amino acids are involved in the catalytic site of important enzymes, and actuallyform a covalent intermediate with the substrate of the reaction.
ID No: __________
38
79. (2 points) You have isolated some perfectly intact mitochondria from rabbit muscle. At alltimes sufficient ADP is present to allow ATP synthesis to occur within the mitochondria.The compounds added are shown below:
Indicate on the graph below what the shape of the oxygen consumption curve would beas each compound is added.
80. (3 points) On the next page is an abbreviated metabolic chart. There are some errors inthe chart. Circle THREE errors, and also indicate why what you have circled is incorrect.Certain cofactors have been left out of the chart by design, so absence of a requiredcofactor does not make a reaction incorrect. However, if a cofactor for a reaction is listed,and is incorrect, then that would qualify as an error. Additionally, the directions of thearrows (ie reversible or non-reversible reaction) is included by design, and if incorrectwould also qualify as an answer.
ID No: __________
39
ID No: __________
40
Answer Sheet 1
1. E 32. B, D 63. B
2. D 33. C 64. C
3. E 34. A 65. D
4. B 35. C 66. B
5. C 36. D
6. D 37. F
7. D 38. T
8. C 39. T
9. A 40. T
10. D 41. D
11. E 42. C
12. C 43. C
13. B 44. D
14. D 45. C
15. D 46. D
16. B 47. D
17. T 48. B
18. F 49. D
19. F 50. B
20. T 51. C
21. T 52. D
22. F 53. D or C
23. F 54. A
24. T 55. B
25. F 56. B
26. T 57. C
27. B 58. C
28. C, F 59. C
29. C, E 60. B
30. C, D 61. E
31. C 62. A, B
ID No: __________
41
Answer Sheet 2
1. C 32. A, B 63. B, H
2. C 33. A, D 64. D, G
3. C 34. B, G 65. C
4. B 35. B, F 66. C
5. G 36. B, D 67. E
6. B 37. B, F 68. K
7. D 38. E, G 69. I
8. C 39. D, E 70. A
9. Either C or D 40. A, C 71. F
10. E 41. B 72. B
11. D 42. A 73. D
12. A 43. A 74. B, C
13. B 44. A 75. E
14. D 45. C 76. A, E
15. D 46. C 77. B, H
16. C 47. B 78. E, F
17. E 48. A
18. D 49. B
19. I 50. C
20. E 51. F or G
21. E 52. D
22. D 53. H
23. E 54. C
24. G 55. B
25. E 56. L
26. Any 2 of C,D,E 57. P
27. B, C 58. A
28. B, F 59. D
29. C, F 60. B, H
30. A, F 61. A, C
31. B, D 62. C, H
ID No: __________
42
79. Answer
ID No: __________
43
80. Answer
Potential errors are:
1. Glucose-1-P to Glucose-6-P is reversible, not one way as indicated in the figure.
2. Xyulose-5-P is NOT reversibly converted to Ribose-5-P. X5P is reversibly converted to
Ru5P, which is reversibly converted to R5P.
3. PEP is not reversibly converted to 3-PG. 3-PG is isomerized (reversibly) to 2-PG, which is
then dehydrated (reversibly) to form PEP.
4. The conversion of succinate to fumarate requires FAD (being converted to FADH2) instead
of NAD to NADH, as indicated in the figure.
5. The conversion of alpha-KG to glutamate is reversible (glutamate DH), and does NOT
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