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MedBiochem Exam 2, 1995
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MedBiochem Exam 2, 1995
For each of the following questions, choose the
one best answer.
(Answer key at bottom of page.)
1. Each of the following contains a methyl group that can be derived
from S-adenosyl methionine EXCEPT which one?
A. choline
B. sphingomyelin
C. phosphatidyl ethanolamine
D. carnitine
E. phosphatidyl choline
2. A deficiency of lipoprotein lipase is associated with which of the
following hyperlipoproteinemias?
A. Type I
B. Type IIa
C. Type IIb
D. Type III
E. Type IV
3. Which of the following hyperlipoproteinemias would display a
normal electrophoretic pattern (i.e., no bands present that are not
normally found) when serum is obtained from a fasted patient.
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A. Type I
B. Type IIa
C. Type IIb
D. Type III
E. Type IV
4. Tay-Sachs disease is associated with accumulation of which of the
following?
A. cerebroside
B. lecithin
C. sphingomyelin
D. ganglioside
E. cephalin
5. Concerning cholesterol biosynthesis:
A. Eight isoprene units are required.
B. The rate of synthesis is controlled by the rate of production of
HMG-CoA.
C. Oxygen is incorporated into the molecule at the C-17 position.
D. NADPH is required for the formation of HMG-CoA.
E. HMG-CoA reductase is down-regulated by cholesterol.
6. Which of the following statements concerning bile acids is true?
A. Bile acids inhibit the formation of additional bile acids by
inhibiting cholesterol 7α -hydroxylase.
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B. Glycodeoxycholic acid is conjugated with glucose.
C. Bile acids are deconjugated in the small intestine by a pancreatic
hydrolase.
D. Chenodeoxycholic acid is a secondary bile acid.
E. Bile acids are formed from cholesterol in the pancreas.
7. Concerning the metabolism of alcohol:
A. Oxidation of alcohol leads to an increase in the ratio of
NADH:NAD only in the cytosol.
B. Hyperglycemia can result from the excessive production of lactate.
C. The MEOS is located in the mitochondria.
D. Excess blood lactate leads to inhibition of uric acid excretion by the
kidney.
E. Alcohol inhibits drug metabolism because NADH is depleted.
8. A non-familial Type IV hyperlipoproteinemia often results from
the continued use of alcohol BECAUSE:
A. Epinephrine inhibits the oxidation of fatty acids.
B. The proliferation of smooth endoplasmic reticulum leads to the
increased production of VLDL.
C. High NADH:NAD ratio leads to an increased rate of fatty acid
synthesis.
D. Uptake of vitamins A, D, E and K is defective.
E. High NADH:NAD ratio leads to an increased rate of conversion of
pyruvate to lactate.
9. Alcohol metabolism:
A. Leads to proliferation of smooth endoplasmic reticulum enzymes.
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B. Causes excessive production of NADPH.
C. Causes excessive utilization of NADH.
D. Leads to excessive fat storage due to high levels of circulating of
epinephrine.
E. Leads to the inhibition of glycolysis by the inhibition of
phosphofructokinase.
10. Which vitamin is required for enzymes catalyzing transamination
reactions?
A. thiamine
B. folic acid
C. pyridoxal phosphate
D. B12
E. biotin
11. The α -keto acid that is produced by transamination of alanine is:
A. oxalic acid
B. pyruvic acid
C. oxaloacetic acid
D. α -keto butyric acid
E. homocysteine
12. The α -keto acid produced upon the transamination of aspartic
acid is an important component of which of the following pathways?
A. glycolysis
B. tricarboxylic acid cycle
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C. glycogenesis
D. glycogenolysis
E. hexose monophosphate shunt
13. Each of the following statements about glutamic acid
dehydrogenase is true EXCEPT:
A. It is important for the production of ammonia for urea synthesis.
B. It is important for the adjustment of the size of the amino acid pool.
C. It is found mainly in liver.
D. α -ketoglutarate is an important product of the reaction catalyzed
by this enzyme.
E. Pyridoxal phosphate is required for the reaction catalyzed by this
enzyme.
14. Which of the following vitamins (or cofactors) is required for the
conversion of serine to glycine?
A. pyridoxal phosphate
B. tetrahydrofolate
C. thiamine pyrophosphate
D. biotin
E. CoA
15. Which enzyme is deficient in the most common form of
phenylketonuria?
A. phenylalanine hydroxylase
B. tyrosine hydroxylase
C. dihydrofolate reductase
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D. dihydrobiopterin reductase
E. 7α -hydroxylase
16. The following amino acids are non-essential EXCEPT:
A. alanine.
B. arginine.
C. glutamic acid.
D. aspartic acid.
E. asparagine.
17. Urea production:
A. is stimulated during times when fatty acids are being oxidized and
when amino acids are being used for the production of glucose.
B. occurs mainly in muscle where amino acids are released from
muscle proteins.
C. starts with the synthesis of creatine phosphate.
D. is inhibited if carnitine is absent.
E. is blocked when one essential amino acid is absent.
18. The following statements about carnitine are true EXCEPT
A. Carnitine is synthesized from lysine.
B. Carnitine synthesis requires S-adenosyl methionine.
C. Carnitine deficiency leads to ketosis.
D. Carnitine deficiency leads to fatty liver.
E. Carnitine deficiency leads to fatty muscles.
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19. Twenty four hours after a meal, the primary source of glucose for
the brain is:
A. dietary glucose.
B. muscle glycogen.
C. liver glycogen.
D. fatty acids.
E. gluconeogenesis.
20. The metabolic state in which glycogen and gluconeogenesis (from
lactate and alanine) are the main sources of new glucose for the blood
without appreciable release of fatty acids from adipose tissue would
be described as which state?
A. well fed (2-3 h postprandial)
B. early fasted (3-12 h postprandial)
C. late fasted (12-24 h postprandial)
D. early refed (0-2 h after refeeding)
21. Each of the following enzymes is a site of allosteric regulation of
metabolism EXCEPT
A. phosphofructokinase.
B. acetyl CoA carboxylase.
C. glucokinase.
D. fructose 1,6 bisphosphatase.
E. pyruvate carboxylase.
22. During uncontrolled insulin-dependent diabetes mellitus, ketosis
results primarily from
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A. excessive utilization of fatty acids.
B. excessive release of glucose from glycogen.
C. inability to produce glucose from lactate.
D. excessive uptake of triglycerides from serum by adipocytes.
E. excessive synthesis of muscle proteins.
23. All of the following enzymes are regulated by covalent
modification EXCEPT:
A. glycogen phosphorylase.
B. glycogen synthetase.
C. pyruvate dehydrogenase complex.
D. acetyl CoA carboxylase.
E. glucokinase.
24. Thyroid hormone receptors
A. are histone proteins localized in the chromatin of target cells.
B. are intrinsic non-histone chromosomal proteins.
C. initially bind triiodothyronine in the cytoplasm and after
undergoing a conformational change translocate to the nucleus.
D. are enzymes that deiodinate thyroxine to triiodothyronine.
E. have higher affinity for thyroxine than triiodothyronine.
25. After a steroid hormone enters a target cell, it can exist as all of
the following EXCEPT which one?
A. free hormone in the cytoplasm
B. hormone-receptor complex in the cytoplasm
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C. hormone-receptor complex in the nucleus
D. free hormone bound to chromatin
26. Calmodulin
A. is a calcium binding protein.
B. mediates group translocation.
C. is the regulatory subunit of cAMP-dependent protein kinase.
D. is an integral membrane protein.
E. can release calcium from internal stores.
27. Compared to normal cells, the cells of a rapidly growing tumor
are likely to be characterized by all of the following EXCEPT
A. loss of contact inhibition.
B. requirement of growth factors.
C. absence of anchorage dependence.
D. rounded morphology.
E. indefinite lifespan.
28. Which of the following steroids is the only one that could serve as
an intermediate in the formation of testosterone, estradiol, cortisol,
and aldosterone?
A. corticosterone
B. dehydroepiandrosterone
C. estriol
D. 11-deoxycorticosterone
E. progesterone
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29. Which of the following has a high binding affinity for this steroid?
A. androgen receptor
B. estrogen receptor
C. progesterone receptor
D. glucocorticoid receptor
E. mineralocorticoid receptor
30. Acetylcholine, glutamate and GABA are best classified as which
one of the following types of transmitters?
A. excitatory
B. ionotropic
C. inhibitory
D. metabotropic
E. peptidergic
31. Which of the following is a correct statement pertinent to insulin
biosynthesis and/or storage?
A. Synthesis of insulin prohormone from amino acids occurs in the
membranes of the Golgi body.
B. The first known polypeptide in insulin biosynthesis is proinsulin.
C. Storage vesicles of pancreatic beta cells contain insulin and Cpeptide in a 1:1 ratio.
D. The disulfide across-links between A and B chains of insulin are
normally formed after independent synthesis of the two polypeptides.
E. Insulin is extensively modified in the Golgi body by
phosphorylation and the addition of carbohydrate chains.
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32. Retinal phosphodiesterase is to light as adipose tissue adenylate
cyclase is to
A. ATP.
B. calcium ion.
C. epinephrine.
D. GTP binding protein.
E. phosphatidylinositol 4,5-bisphosphate.
33. Which of the following chemical interactions accounts for the
inactivation of acetylcholinesterase?
A. organophosphate-serine
B. organophosphate-glutamic acid
C. pyridine aldoximethiodide (2 PAM)-tyrosine
D. tubocurarine-serine
E. hydroxylamine-leucine
34. During the agonist induced phosphoinositide pathway for
hormone signaling, binding of hormone to the receptor
stimulates_______; leading to the production of______; which in turn
activate(s)________.
A. C kinase; Ca++ calmodulin; phosphatidyl inositol kinase.
B. phospholipase C; diacylglycerol and phosphatidyl inositol
bisphosphate; C kinase.
C. phospholipase A2; diacylglycerol and phosphatidyl inositol
bisphosphate; C kinase.
D. Gs dependent adenylate cyclase; active protein kinase; C kinase.
E. phospholipase C; diacylglycerol and phosphatidyl inositol
bisphosphate; adenylate cyclase.
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35. What are histones?
A. Basic proteins associated with RNA.
B. Basic proteins associated with nucleosomes.
C. Acidic proteins which bind chromosomal nucleoprotein.
D. Proteins exclusively found in the spliceosomes.
E. Proteins which help to form ribosomes.
36. All of the molecules below are nucleosides EXCEPT which one?
A. adenosine
B. uridine
C. inosine
D. guanosine
E. thymidine
37. A DNA segment of the sequence 5'TAGCAT3' on the template
strand is incubated with RNA polymerase and all the necessary
components to produce RNA molecules. This RNA product is then
used to direct protein synthesis. The final protein product will have
which of the following amino acid sequences? (Codon for asp: GAU,
GAC; tyr: UAU, UAC; leu: CUA, CUU; ile: AUC; val: GUA)
A. asp-val
B. ile-val
C. tyr-asp
D. met-leu
E. asp-tyr
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38. All of the following statements about ribosomes are correct
EXCEPT which one?
A. The larger subunits of all ribosomes have the enzyme peptidyl
transferase which is a ribozyme.
B. Eukaryotic cells have 80S ribosomes, and protein synthesis on these
ribosomes can be inhibited by cycloheximide.
C. Prokaryotic cells have 70S ribosomes, and protein synthesis on
these ribosomes can be inhibited by chloramphenicol.
D. Mitochondria have 80S ribosomes, and protein synthesis on these
ribosomes can be inhibited by cycloheximide.
E. All ribosomes have two subunits.
39. The RNA primer in DNA replication differs from other RNA in
that it:
A. contains modified bases.
B. is formed by DNA polymerase III.
C. exists only in a DNA-RNA double-stranded hybrid.
D. becomes a permanent part of the DNA.
E. is synthesized in the 3' --> 5' direction.
40. The prokaryotic repressor protein binds to:
A. the promoter.
B. the operator.
C. regulatory gene.
D. the sigma factor.
E. RNA polymerase.
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41. The reaction of hypoxanthine and PRPP (5'phosphoribosylpyrophosphate) leads directly to the formation of:
A. xanthine.
B. AMP.
C. GMP.
D. IMP.
E. uric acid.
42. The first committed, essentially irreversible step in purine
nucleotide biosynthesis is the formation of:
A. carbamoyl phosphate.
B. inosine monophosphate.
C. orotic acid.
D. phosphoribosylpyrophosphate.
E. 5-phosphoribosylamine.
43. The role of elongation factor 2 (or EF-G) in protein biosynthesis is
to:
A. translocate amino acyl-tRNA from the P site to the A site on the
ribosome.
B. catalyze the formation of peptide bonds.
C. catalyze the ejection of free tRNA from the A site on the ribosome.
D. translocate peptidyl-tRNA from the A site to the P site on the
ribosome.
E. promote the recognition of termination codons by release factors.
44. A metabolite of folic acid is required in mammalian tissues as a
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coenzyme in the de novo synthesis of all of the following EXCEPT:
A. dTMP.
B. ATP.
C. GTP.
D. dUTP.
E. xanthine.
45. Restriction endonucleases:
A. digest DNA duplex molecules from the 5'-OH ends.
B. attack only single stranded DNA.
C. have base sequence specificity for palindromes.
D. digest double stranded DNA molecules randomly.
E. can only act on DNA-RNA double helices.
46. Codons on mRNA may be accurately described by all of the
following EXCEPT:
A. they are read in a non-overlapping fashion.
B. they can form hydrogen bonds with tRNA.
C. they may specify only one amino acid.
D. in some cases they may be recognized by proteins rather than by
tRNAs.
E. one codon hybridizes with the Shine-Dalgarno sequence.
47. When a solution of double-stranded DNA which has been heated
0
to 95 C is slowly cooled a decrease in optical density at 260 nm
occurs. Each of the following processes is associated with the physical
change the DNA is undergoing EXCEPT which one?
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A. Hydrogen bonds are being formed.
B. 5’ to 3’ phosphodiester bonds are being formed.
C. Helical structure is being formed.
D. Complementary bases are pairing with each other.
E. Hydrophobic interactions between bases are occurring.
48. In the gene for a protein containing 300 amino acids, which of the
following mutations would be the LEAST likely to result in a faulty
protein?
A. Insertion of a single base in the codon for amino acid 12.
B. A single base change such that amino acid 12 is now leucine rather
than isoleucine.
C. Deletion of two bases from the codon for amino acid 19.
D. A nonsense mutation in the codon for amino acid 37.
49. When E. coli is grown in a medium containing both glucose and
lactose as the carbon sources:
A. the lac repressor is able to bind tightly to the lac operator.
B. RNA polymerase is unable to transcribe the lac operon.
C. the catabolite activator protein is activated.
D. the allolactose-repressor complex binds to the lac operator site.
E. -galactosidase activity will be increased along with the glycolytic
pathway.
50. All of the following are true for DNA polymerase and RNA
polymerase EXCEPT which one?
A. Both require a template.
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B. Both reactions produce pyrophosphate as a product.
C. Both add 5' nucleotides to 3' hydroxyl groups.
D. Both utilize 5'-nucleoside triphosphates as substrates.
E. Both proofread as they synthesize the new chain.
51. Which modification of DNA is inversely correlated with gene
activity?
A. acetylation
B. methylation
C. phosphorylation
D. dephosphorylation
E. deamination
52. Molecular cloning of eukaryotic mRNA sequences utilizes all of
the following EXCEPT
A. DNA polymerase.
B. reverse transcriptase.
C. restriction endonucleases.
D. RNA polymerase.
E. oligo dT primers.
53. A cloned cDNA copy of -globin mRNA could direct the
biosynthesis of a complete and correct peptide in E. coli while the
corresponding cloned chromosomal gene could not because
A. bacterial polymerases can not transcribe intervening sequences.
B. intervening sequences contain codons that are not recognized by
cellular tRNA.
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C. bacteria do not have the enzymatic machinery necessary for
splicing eukaryotic mRNA precursors.
D. intervening sequences form hairpin loops which block the progress
of ribosomes during translation.
E. bacterial protein processing machinery is not capable of processing
the protein precursor to its correct size.
54. Southern blot hybridization analysis is best used to
A. detect specific protein molecules.
B. detect specific RNA molecules.
C. detect antigen-antibody reactions.
D. detect specific DNA molecules.
E. detect GC composition.
55. Which of the following temporal sequences of enzyme activities is
required for nucleotide excision-repair of DNA?
A. Ligase, exonuclease, polymerase
B. Exonuclease, endonuclease, polymerase, ligase
C. Exonuclease, endonuclease, ligase
D. Polymerase, endonuclease, ligase
E. Endonuclease, exonuclease, polymerase, ligase
56. A break of a phosphodiester bond in one strand of a doublestranded DNA molecule can be repaired by
A. AP endonuclease.
B. transmethylase.
C. DNA polymerase.
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D. DNA ligase.
E. DNA polymerase.
57. Puromycin is an inhibitor of protein biosynthesis because it
A. prevents the recognition of "initiator" regions on mRNA by the
30S ribosomal subunit.
B. causes premature chain termination.
C. prevents the interaction of fmet-tRNA with the preinitiation
complex.
D. inhibits the peptidyl transferase reaction.
E. inhibits the translocation function of elongation factor II.
58. Degeneracy of the genetic code implies that
A. a common codon exists for at least two amino acids.
B. the code is not universal throughout the biological species.
C. there is a considerable degree of inaccuracy during transcription.
D. one transfer RNA can recognize more than one codon.
E. the codons may overlap when being translated by the ribosome.
59. The cancer chemotherapeutic agent, methotrexate, acts as a folic
acid antagonist by
A. preventing the absorption of folate from the gut.
B. preventing the transport of folate to the cancer cells.
C. preventing the conversion of dihydrofolate to tetrahydrofolate.
D. blocking the interconversion of single-carbon folate intermediates.
E. blocking the single carbon transfers to homocysteine.
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60. Which of the following statements is TRUE with regard to DNA
synthesis?
A. Chain growth is continuous on both strands of the helix.
B. The process is unidirectional along the axis of the helix.
C. Both ribonucleoside and deoxyribonucleoside triphosphates are
required.
D. Chain growth occurs at the 5' end of new strands.
E. There is an absence of exonuclease activity.
61. During RNA synthesis by DNA-dependent RNA polymerase:
A. inorganic phosphate is cleaved from the precursor nucleotides.
B. only one of the DNA strands in a given chromosome can serve as a
template.
C. nucleosides are added to the 5' end of the growing chain.
D. there are specific sites on DNA for initiating and terminating RNA
synthesis.
E. the polymerase exhibits an active proofreading function.
62. Ultraviolet damage of DNA in skin is associated with which of the
following?
A. DNA ligase detects damaged areas
B. Pyrimidine dimers are formed
C. Both strands are cleaved by an endonuclease
D. Thymine is converted to adenine
E. DNA fragmentation
63. Which of the following statements describing the Watson-Crick
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model for DNA structure is INCORRECT?
A. The double helical structure has two grooves running helically
along its length, one of which is wider than the other.
B. The paired chains have antiparallel directions.
C. The classic Watson-Crick hydrogen bonding between AT and GC
pairs is found in Z- DNA.
D. One turn of the double helix involves approximately 10 nucleotides
and occurs every 34 angstroms.
E. The helical structure is stabilized entirely by hydrogen bonding.
64. Consider a gene for a protein which contains 200 amino acids and
is composed of two exons and one intron. Which of the following
mutations would most likely prevent synthesis of a protein?
A. An insertion mutation in the second exon.
B. A five base deletion from the TATA box region of the gene
promoter.
C. A nonsense mutation in the intron.
D. A nonsense mutation in the second exon.
E. A base substitution mutation in the first intron.
65. Which of the following correctly compares the DNA from
"Pollyanna" virus (22 mole percent cytosine) with DNA from medical
students (32 mole percent thymine).
A. The Tm of medical student DNA will be lower than that of
Pollyanna virus.
B. Medical student DNA has more thymine than adenine.
C. The Tm of medical student DNA will be identical to that of
Pollyanna virus.
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D. Pollyanna virus has more cytosine than guanine.
E. Medical student DNA has a greater molecular weight than
Pollyanna virus.
66. All of the following require GTP during prokaryotic protein
synthesis EXCEPT
A. binding of aminoacyl-tRNA to ribosomes with EF-Tu.
B. polypeptide chain initiation with IF-1, IF-2, and IF-3.
C. peptidyl-tRNA translocation with EF-G.
D. aminoacylation of tRNA by aminoacyl tRNA synthetase.
E. polypeptide chain termination by RF-1, RF-2, and RF-3.
67. Which of the following is TRUE for regulation of eukaryotic gene
expression?
A. Enhancers only work when they are in close proximity to the
promoter.
B. The promoters of actively regulated genes often lack the TATA
box.
C. CG islands near housekeeping genes are heavily methylated.
D. Enhancers may be located downstream of the genes which they
regulate.
E. Enhancers act by inhibiting termination of transcription in
eukaryotic genes.
68. The polymerase chain reaction can detect extremely small
amounts of specific DNA sequences. This analytical tool requires
which one of the following?
A. Primer sequences added in equimolar quantities relative to the
target DNA.
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B. Addition of DNA ligase after each heating cycle.
C. A sequence of heating and cooling cycles.
D. The entire sequence the DNA to be detected must be known.
E. Helicase and primase acting as a primosome.
69. Processing of eukaryotic 45S ribosomal precursor RNA includes:
A. addition of poly A to the 3' end.
B. action of spliceosomes.
C. capping the 5' end with inverted 7-methyl guanosine triphosphate.
D. endonuclease processing to produce 28S, 18S, and 5.8S RNA.
E. production of transfer RNA.
70. Which of the following explains the function of a tumor
promoter?
A. They activate the promoter sites of tumor suppressor genes.
B. They activate mutagens to become carcinogens.
C. They increase the binding of RNA polymerase to oncogene
promoters.
D. They stimulate DNA synthesis.
E. They generally cause retinoblastoma in children.
71. All of the following are true for the reduction of purine
ribonucleotides to purine deoxyribonucleotides EXCEPT
A. It uses reducing equivalents whose ultimate source is NADPH.
B. It involves the same reductase system for both nucleosides.
C. It takes place at the level of the ribonucleoside diphosphate.
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D. It involves cleavage of the glycosidic bond in the sugar nucleotide.
72. Which of the following statements about eukaryotic gene
regulation is TRUE?
A. Single genes can produce multiple proteins by splicing out exons.
B. Membrane-bound and secreted immunoglobulins are encoded by
different structural genes.
C. Genes in active areas of chromatin are protected from DNAase
digestion.
D. Enhancers are responsible for differential splicing and
polyadenylation.
73. The absence of which enzyme involved in the "salvage pathways"
of nucleotide metabolism results in the genetic disease Lesch-Nyhan
Syndrome?
A. Hypoxanthine-guanine phosphoribosyl transferase
B. Aspartate transcarbamoylase
C. Thymidylate kinase
D. Adenylate deaminase
E. Xanthine oxidase
74. The signal peptide found at the amino end of proteins
A. contains a high proportion of hydrophilic amino acids.
B. is cleaved off prior to the translocation of the protein across the cell
membrane.
C. is cleaved off by a protease inside the endoplasmic reticulum.
D. is added on to the polypeptide chain as a post-translational
modification.
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E. is used to anchor the protein to the membrane.
75. What is the pH of a buffer solution containing 0.05 mol/L KH2PO4
and 0.15 mol/L K2HPO4? The pK1 of phosphoric acid is 1.96 and pK2
is 6.8.
A. 4.38
B. 6.35
C. 6.80
D. 7.28
E. 8.76
76. All of the following statements about allosteric enzymes are true
EXCEPT
A. positive cooperativity sensitizes the enzyme to small changes in
substrate concentration.
B. they frequently catalyze the slowest step in a metabolic pathway.
C. the allosteric site can be located on a subunit different from that
containing the catalytic site.
D. the binding of a ligand to the allosteric site induces a
conformational change in the active site.
E. they have substrate saturation curves that frequently show firstorder kinetics.
77. The Michaelis constant, Km, is
A. numerically equal to 1/2 Vm.
B. dependent on the enzyme concentration.
C. independent of pH.
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D. numerically equal to the substrate concentration that gives halfmaximal velocity.
E. increased in the presence of a noncompetitive inhibitor.
78. The affinity of Hb for O2 is increased by
A. the formation of salt bridges in Hb.
B. the cross-linking of the
-chains of Hb.
C. lowering of pH.
D. reduction in 2,3-diphosphoglycerate (DPG) concentration.
E. elevation in the partial pressure of CO2.
79. Topoisomerase enzymes are important in the replication of DNA
because they
A. anneal Okazaki fragments.
B. relax supercoiled DNA.
C. degrade histone proteins.
D. "proofread" newly synthesized DNA.
E. synthesize the RNA primer fragment.
FOR EACH OF THE FOLLOWING QUESTIONS, ONE OR MORE
OF THE ANSWERS OR COMPLETIONS ARE CORRECT.
CHOOSE ANSWER:
A. If only 1, 2, and 3 are correct.
B. If only 1 and 3 are correct.
C. If only 2 and 4 are correct.
D. If only 4 is correct.
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E. If all are correct.
80. The high glucagon:insulin ratio seen in starvation:
1. promotes the mobilization of fatty acids from adipose stores.
2. leads to depletion of liver glycogen stores.
3. leads to the formation of ketone bodies.
4. inhibits fatty acid
oxidation.
81. Which of the following statements about the synthesis of
triglycerides is/are TRUE?
1. Triglycerides are synthesized in the liver.
2. Triglyceride synthesis in the intestine is accomplished by the
addition of two fatty acids to a monoglyceride.
3. Triglyceride synthesis in the adipose tissue starts with glycerol 3phosphate as the glycerol backbone.
4. Triglyceride synthesis uses fatty acids only in the form of the CoA
derivative.
82. Intracellular calcium levels are regulated by
1. calcium dependent ATPase.
2. voltage gated calcium channels.
3. IP3 gated calcium channels.
4. activation of protein kinase C.
83. Changes in oncogenes which have been shown to occur in
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malignancy include
1. amplification of the oncogene.
2. changes in the nucleotide sequence of the oncogene.
3. chromosomal translocation of the oncogene.
4. increased synthesis of oncogene messenger RNA.
84. Which of the following polypeptide hormones is/are formed by
multiple proteolytic cleavages of a single precursor protein?
1. hCG
2. Vasopressin
3. FSH
4. ACTH
85. Mechanisms for the inactivation of neurotransmitters include
1. reuptake at the presynaptic terminal.
2. oxidation by monoamine oxidase.
3. enzymatic hydrolysis.
4. transamination.
86. G proteins that transduce hormone signals
1. are present in the membrane.
2. can bind ATP or ADP.
3. have intrinsic GTPase activity.
4. can activate tyrosine kinase activity.
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87. Biochemical events that have to occur for transmission of sensory
stimulation along the neurons in the nervous system include:
1. passage of ions across the membranes.
2. fusion of neurotransmitter containing vesicles with the postsynaptic
membrane.
3. neurotransmitter binding to the receptor on the postsynaptic
membrane.
4. degradation of the neurotransmitter by the postsynaptic neuron.
88. Transmission of the signal by the atrialnatriuretic factor (ANF) at
the target tissues include a receptor that
1. is an integral membrane protein containing seven transmembrane
domains.
2. has intrinsic guanylate cyclase activity.
3. binds the ligand and generates cAMP as the second messenger.
4. can be desensitized by dephosphorylation.
89. A hormone receptor that functions by activation or inhibition of
adenylate cyclase is most likely to contain:
1. domain(s) to interact with G proteins.
2. domain(s) that pass through the membrane seven times.
3. cytoplasmic domains containing serine and threonine residues that
might be phosphorylated.
4. domain(s) to interact with phospholipase C.
90. The hydroxylation of the steroid nucleus requires
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1. molecular oxygen.
2. NADPH.
3. mixed-function oxygenases.
4. that one oxygen atom is utilized to form water and the other is
incorporated as the hydroxyl group of the steroid metabolite.
91. The insulin receptor
1. consists of two different types of subunits.
2. has intrinsic tyrosine protein kinase activity.
3. is autophosphorylated following insulin binding.
4. is found on the cell surface.
92. Immunoglobin class switching will
1. switch the specific antigen recognition of that unique B-cell to a
different epitope.
2. never permit complement fixation.
3. activate T-helper cells.
4. change immunoglobulin effector functions.
93. Which of the following statements is/are TRUE?
1. The plasma cell is the terminal stage of B-cell differentiation.
2. The plasma cell is the antibody secretion factory.
3. Memory B-cells have an immunoglobulin receptor that recognizes
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cell or a plasma cell.
94. Complement fixation
1. is a consequence of antigen binding by IgD.
2. is an effector function of IgG and IgM, following antigen binding.
3. occurs when IgA binds antigen.
4. results in cell lysis from an enzyme cascade of 11 proteins
interacting with the cell membrane.
95. The humoral immune response is
1. mediated principally through the T-cell antigen receptor.
2. specific because of the paratope recognizing the epitope.
3. requires participation of either one of the class I or class II MHC
proteins.
4. abnormal with production of an autoimmune antibody.
96. Plasma cells
1. are the terminal stage of B-cell differentiation.
2. synthesize H-chains, L-chains, J-chains and the secretory piece.
3. cannot divide to produce many more plasma cells.
4. are memory B-cells.
97. Accessory molecules necessary for signal transduction and for
complete normal immune function is/are
1. T3 in cooperation with the antigen receptor by T-cells.
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2. class I for recognition of antigen by B-cells.
3. alpha and beta polypeptides in cooperation with the antibody by Bcells.
4. CD4 (or T4) for recognition of antigen by cytotoxic T-cells.
98. MHC (major histocompatibility complex) proteins are
1. referred to as class I and class II cell surface proteins.
2. found only on cells of the reticuloendothelial system class II
proteins.
3. transmembrane proteins, each composed of two polypeptide chains
for antigen presentation.
4. found on all cells of the body, except germ line cells and
erythrocytes, for class II proteins.
99. Which of the following statements is/are TRUE?
1. T4 and class I MHC proteins are required for cell lysis.
2. Memory B-cells secrete antibodies.
3. Lymphokines and monokines are not cytokines.
4. Autoimmunity is an immune reaction against self.
100. Regulatory cells can
1. be T-helper cells.
2. produce cytokines.
3. facilitate immunoglobulin class switching.
4. stimulate cell division among various cells of the immune system.
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Answer Key:
1.C
11.B
21.C
31.C
41.D
51.B
61.D
71.D
2.A
12.B
22.A
32.C
42.E
52.D
62.B
72.A
3.B
13.E
23.E
33.A
43.D
53.C
63.E
73.A
4.D
14.B
24.B
34.B
44.D
54.D
64.B
74.C
5.E
15.A
25.D
35.B
45.C
55.E
65.A
75.D
6.A
16.B
26.A
36.C
46.E
56.D
66.D
76.E
7.D
17.A
27.B
37.D
47.B
57.B
67.D
77.D
8.B
18.C
28.E
38.D
48.B
58.D
68.C
78.D
9.A
19.E
29.A
39.C
49.B
59.C
69.D
79.B
10.C
20.B
30.B
40.B
50.E
60.C
70.D
80.A
81.
E
86.
B
91.
E
96.
B
82.
A
87.
B
92.
D
97.
B
83.
E
88.
C
93.
E
98.
E
84.
C
89.
A
94.
C
99.
D
85. A
90. E
95. C
100.
E
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Copyright © 1998 Department of Cell Biology & Biochemistry, TTUHSC
Last revised 11/30/99
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