CELL BIOLOGYExam I

1. In the diagram , Column A could be labeled:a. yeast cellsb. E coli cellsc. mouse cells d. a or ce. a, b, or c

2. E. coli is a good model system for molecular biology studies becausea. it has a small genome.b. it reproduces rapidly.c. mutants can easily be isolated from culture dishes.d. mutations can easily be inducede. all of the above

3. The unique properties of different membranes are primarily a function of their a. glycolipids.b. phospholipids.c. cholesterol molecules.d. proteins.

4. The reaction depicted on theright is a common way that cellsmanage activity of proteins. This reaction is catalyzed bya. Mgb. Fec. phosphatased. kinasee. proteinase

5. Under aerobic conditions, the end product of glycolysis is

a. ethanol. b. lactate.c. phosphoenolpyruvate.d. pyruvate.e. ribose

6. In yeast, the citric acid cycle occurs in thea. cytosol.b. nucleus.c. mitochondriad. lysosomese. endoplasmic reticulum

Characteristic Column A Column B

CELL BIOLOGYExam I

7. During formation of haploid eggs and sperm, one member of each chromosome pair is transmitted to each cell in a type of cell division called

a. mitosis.b. meiosis.c. cytokinesis.d. gametogenesis.

8. Most animal cells area. haploid.b. diploid.c. euploid.d. tetraploid.

9. A codon is aa. region of DNA coding for one protein.b. sequence of three nucleotides on a tRNA that binds to an mRNA.c. sequence of three nucleotides on an mRNA that binds to specific tRNAs.d. sequence of three nucleotides on the coding strand of DNA.

10. Reverse transcriptase is an enzyme that catalyzes _______ synthesis.

a. DNA-dependent RNAb. RNA-dependent DNAc. DNA-dependent DNAd. RNA-dependent RNA

11. Restriction endonucleases are enzymes thata. act only in a single species of bacteria.b. act only on the ends of DNA strands.c. cleave DNA only at specific sequences.d. cleave only nuclear DNA.

12. When introduced into living cells, single-stranded antisense nucleic acids bind to

a. complementary DNA sequences and block RNA synthesis.b. the sense strand of DNA and block RNA synthesis.c. complementary RNA sequences and block protein synthesis.d. Both a and c

13. Annealing or hybridization is a method that can be used to identifya. specific RNAb. specific DNAc. specific genesd. specific chromosomese. all of the above

14. Molecules that capture high energy electrons during the Kreb’s cycle then transport these electrons to the electron transport chain, that molecule which yields the most ATP isa. FADH2b. NADHc. NADd. FADHe. FAD

15. In each cell there would be ______ centromeres.A. 23B. 46C. 69D. 92E. >200

16. In each cell there would be _____ telomeres.A. 23B. 46C. 69D. 92E. >200

17. A gene can be defined as a segment of DNA that codes fora. a protein.b. a functional product.c. messenger RNA.d. messenger RNA or ribosomal RNA.

18. Human mitochondrial DNAA. uses the standard genetic codeB. encodes its own rRNAsC. contains introns like nuclear genesD. is larger than yeast mitochondrial DNAE. has no DNA

19. A transcriptionally active gene compared with a transcriptionally inactive gene would be expected to contain

A. acetylated histonesB. unacetylated histones

20. The sites of spindle fiber attachment to chromosomes during mitosis are proteins called A. nucleosomeB. centromereC. kinetochoreD. telomereE. open-reading frame

CELL BIOLOGYExam I

21. Introns in mRNA-coding genes are the transcribed sequencesA. that code for proteins.B that do not code for proteins.C. that are removed by nucleases.D. between protein-coding sequences.E. at the 3’ end of chromosomes

22. Introns constitute about what percentage of the average human gene?A. 10%B. 40%C. 60%D. 90%E. 30%

23. Synthesis of different isoproteins from the same gene is due toA. intron shuffling.B. exon shuffling.C. alternative splicing.D. exon splicing.E. isomerization

24. Introns are nonfunctional sequences between exons. A. trueB. false

25. Replication of plasmid DNA is independent of a replication origin.A. trueB. false

26. Which of the following statements is true of all known DNA polymerases?A. They synthesize DNA in the 5 to 3 direction, and they require a preformed primer hydrogen-bonded to the template.B. They synthesize DNA in the 5 to 3 direction, and they possess primase activity.C. They require a preformed primer, and they possess helicase activity.D. They synthesize DNA in the 3 to 5 direction, and they possess exonuclease activity.

27. Which of the following statements concerning elongation of DNA at the replication fork is false?A. The leading strand is synthesized continuously in the direction of replication fork movement.B. Each lagging strand Okazaki fragment is synthesized backward from the overall direction of replication.C. The Okazaki fragments are joined by the action of DNA ligase.D. Both strands are synthesized continuously at the replication fork.

28. DNA polymerase requires a primer and cannot initiate synthesis de novo. What serves as a primer for DNA replication?A. Short fragments of DNA complementary to the template strandB. A protein with a free OH groupC. Short fragments of RNA complementary to the template strandD. The DNA forms a loop resulting in the formation of double-stranded hairpins at the end of the DNA molecule and these hairpins serve as primers.

29. DNA polymerases can synthesize DNAA. de novo, by catalyzing the polymerization of free dNTPs.B. by adding dNTPs to complementary dNTPs on a single-stranded DNA.C. by adding dNTPs to a hydroxyl group on the end of a growing polynucleotide chain hydrogen- bonded to a strand of RNA.D. by adding dNTPs to a hydroxyl group on the end of a growing polynucleotide chain hydrogen-bonded to a strand of DNA.

30. The proofreading property of DNA polymerase is due to its _______ activity.A. 3to5exonucleaseB. 5to3exonucleaseC. excision repairD. mismatch repair

31. The most common cause of skin cancer is damage to DNA byA. infrared light.B. ultraviolet light.C. particle radiation.D. chemical exposure.

32. When bidirectional replication forks from adjacent origins meet, a leading strand always runs into a lagging strand.A. trueB. false

33. RNA polymerase differs from DNA polymerase in that itA. synthesizes new strands of RNA from 3 to 5 B. is a monomeric protein.C. can synthesize a complementary strand without the two strands of DNA being separated.D. does not require a primer to initiate synthesis of RNA.

CELL BIOLOGYExam I

34. Which one of the following statements about the newly synthesized strand of a human chromosome is correct?A. It was synthesized from a single origin solely by continuous DNA synthesis.B. It was synthesized from a single origin by a mixture of continuous & discontinuous DNA synthesis C. It was synthesized from multiple origins solely by discontinuous DNA synthesis.D. It was synthesized from multiple origins by a mixture of continuous and discontinuous DNA synthesis.E. It was synthesized from multiple origins by either continuous or discontinuous DNA synthesis, depending on which specific daughter chromosome is being examined.

35. The DNA sequence to which an RNA polymerase binds to initiate transcription of a gene is called a(n)a. enhancer.b. promoter.c. polymerase-binding element.d. origin of transcription.

36. A reporter gene is one thatA. causes other genes to be expressed.B. can produce a product that is easily detected when expressed under the control of a regulatory sequence to which it has been ligated and cloned.C. is always on.D. is turned on by the products of other genes.

37. Activity of enhancers depends on neither their distance nor their orientation with respect to the transcription initiation site (e.g. upstream vs downstream).A. trueB. false

38. Which of the following modifications IS NOT one made to a primary-mRNA molecule in eucaryotic cells to transform the RNA molecule into a mature, functional mRNA.A. CCA addition to one endB. n(AAAAA) addition to one endC. elimination of noncoding regionsD. ligasing of exonsE. there is no exception, all are normal modifications

39. Eukaryotic gene repressor proteins are thought to act by binding toA. DNA sites in competition with activating proteins.B. specific activating proteins, preventing their binding to DNA.C. basal transcription factors, inhibiting transcription.D. All of the above

40. Processing of RNA transcripts occursA. only in eukaryotic cells.B. only with mRNA transcripts.C. only with rRNA and mRNA transcripts.D. with tRNA, rRNA, and mRNA transcripts.

41. The fact that a specific protein leaves a “footprint” on a DNA molecule is indicative ofA. a lack of interaction between the specific protein and DNAB. protection from protease by the specific proteinC. binding of the specific protein to all types of DNAD. binding of the specific protein to a specific sequence of DNAE. B and D

42. The amount of a protein in a cell is regulated by the rate ofA. transcription of its gene.B. translation of its mRNA.C. degradation of the protein.D. All of the above

43. The “wobble” position isA. the 3rd position from the 3’ end of tRNA anticodonB. the 3rd position from the 5’ end of tRNA anticodonC. the 3rd position from the 3’ end of mRNA codonD. the 3rd position from the 5’ end of mRNA codonE. A and C

44. The first amino acid of eukaryotic polypeptides isA. the amino acid encoded by the 5 terminal codon.B. valine.C. N-formylmethionine.D. methionine.E. glutamine

45. Which of the following statements regarding tRNAs is false?A. tRNAS are approximately 70–80 bases long and form a cloverleaf structure.B. All tRNAs have a CCA sequence at their 3 terminus.C. tRNAs differ in sequence only at the anticodon.D. There are several modified bases present in mature tRNAS.

46. In a major protein degradation pathway, a short polypeptide called _______ is attached to a protein to target it for destruction.A. glutathioneB. ubiquinoneC. ubiquitinD. KDEL

CELL BIOLOGYExam I

47. What happens to ubiquitin in proteosomes?A. It is degraded.B. It is released and recycled.C. It is phosphorylated.D. It has an AMP group added.

48. Cells contain 64 tRNAs, with one anticodon for each codon.A. trueB. false

49. The membrane-bounded compartment where steroid hormone synthesis occurs is:a. mitochondiab. lysosomec. Golgid. endoplasmic reticulume. peroxisome

50. The membrane-bounded compartment in eukaryotic cells where newly synthesized proteins are modified is:a. mitochondiab. lysosomec. Golgid. endoplasmic reticulume. c and d

51. The membrane-bounded compartment in eukaryotic cells where breakdown of lipids and toxic molecules occurs is:a. mitochondiab. lysosomec. Golgid. endoplasmic reticulume. peroxisome

52. The nucleolus is the site of ribosomal subunit assembly.a.trueb. false

53. Ribosomes leave the nucleus asa. intact 80S ribosomes.b. intact 70S ribosomes.c. 40S and 60S ribosomal subunits.d. 18S and 28S rRNAse. 40S, 5S and 60S ribosomal subunits

54. Inactive, condensed chromatin is called heterochromatin.a. trueb. false

55. The nuclear localization sequence in a nuclear proteina. is bound by cytoplasmic proteins that direct the

protein to the nuclear pore.b. is a hydrophobic sequence that enables the protein to enter the nuclear membc. aids protein unfolding in order for the protein to thread through nuclear pores.d. prevents the protein diffusing out the nucleus via nuclear pores.e. does not exist

56. Because the large ribosomal RNA complex is too large to pass through the nuclear pores, it is unfolded and bound to chaperones to mediate the process.a. trueb. false

57. All of the following proteins play a role in vesicle formation or vesicle targeting except:a. rab proteinsb. coat proteinsc. v-SNARESd. t-SNARESe. G protein

58. The contractile ring a. is important for cell locomotionb. contains myosinc. is found in adult skeletal muscle cellsd. is a permanent structure in eukaryotic cellse. b and d

59. The intermediate filament disassembly (nuclear laminea) in mitosis is triggered bya. hydrolysis of ATP bound to the subunitsb. filament severing proteinsc. binding of Ca++ to the subunitsd. phosphorylation of the subunitse. dephosphorylation of the subunits

60. Which of the following statements about import of proteins into mitochondria are TRUE?a. The signal sequences on mitochondrial proteins are usually carboxyl terminal.b. The 1st stage of import is across the outer membrane into the intermembrane space.c. Most mitochondrial proteins are not imported from the cytosol but are synthesized inside mitochondria.d. Mitochondrial proteins are translocated across the inner and outer membranes simultaneously.e. Mitochondrial proteins cross the membrane in their native, folded state.

CELL BIOLOGYExam I

61. After isolating the rough endoplasmic reticulum from the rest of the cytoplasm, you purify the RNAs attached to it. Which of the following proteins do you NOT expect the RNA from the rough endoplasmic reticulum to encode?a. Soluble secreted proteinsb. ER membrane proteinsc. Peroxisomal proteinsd. Plasma membrane proteinse. Lysosomal proteins

62. Assembly of the 4 chains of an antibody molecule into a functional antibody occur ina. cytoplasmb. Golgic. nucleusd. ERe. endosome

63. Most small molecules are permeable acrossa. both mitochondrial membranes.

b. the inner, but not the outer, mitochondrial membrane.c. the outer, but not the inner, mitochondrial membrane.d. neither mitochondrial membrane.

64. Mitochondria containa. genes for mitochondrial proteins.b. genes for rRNAs.c. genes for tRNAs.d. all of the abovee. no genes of their own.

65. Which of the following is not based on actin–myosin interactions?a. Cell migration (crawling) over surfacesb. Mitosisc. Cytokinesis of animal cellsd. Phagocytosise. None of the above; all are based on actin–myosin interaction.

66. Tim and Tom area. twin brothers with the same mitochondrial disease.b. chaperones.c. protein translocators in mitochondrial membranes. d. pores in the outer mitochondrial membrane.e. none of the above

67. Microtubules are not the basis fora. movement of chromosomes during mitosis.b. transport of membranous vesicles in the cytoplasm.c. cytokinesis of animal cells.d. movement of cilia and flagella.

68. The major microtubule-organizing center in most animal cells is thea. kinetochore.b. centriole.c. centrosome.d. centromere.

69. What cell components are kinesins able to transport along microtubules?a. Membranous vesicles and mitochondriab. Endoplasmic reticulumc. mRNAsd. All of the above

70. Which of the following IS NOT true about membrane lipids.a. They spontaneously flip-flop from one membrane leaflet to the otherb. they move laterally within one membrane leafletc. they aggregate with membrane proteins to form “lipid rafts”d. they are unequally distributed in the two membrane leaflets or the leaflets are asymmetrical

71. Cholesterol is taken up into most cells by a. phagocytosis.b. receptor-mediated endocytosis.c. simple diffusion.d. active transport.

72. What is the role of tight junctions in the transport of glucose across the intestinal epithelium?

a. Tight junctions open and allow glucose to pass between the epithelial cells.b. Tight junctions keep the Na+-K+ pumps in the apical membrane only.c. Tight junctions keep the Na+-glucose cotransporter in the apical membrane and the glucose-facilitated transporter in the basolateral membrane.

d. Tight junctions hold the epithelial cells together.

73. Coupled transport of glucose and Na+ into the intestinal epithelial cell is an example ofa. facilitated diffusion.b. symport.c. antiport.d. transcytosis.

74. Which of the following describes the relative concentrations of ions in a typical mammalian cell?a. Na+ and Cl– higher inside, K+ higher outsideb. Na+ higher inside, K+ and Cl– higher outsidec. K+ higher inside, Na+ and Cl– higher outsided. K+ and Cl– higher inside, Na+ higher outside

CELL BIOLOGYExam I

75. Channels that open in response to neurotransmitters or other signal molecules are called _______ channels.a. voltage-gatedb. ligand-gatedc. signal-gatedd. ion

76. The glucose-facilitated diffusion transporter can transport glucosea. into the cell only.b. out of the cell only.c. into or out of the cell.d. only in the presence of ATP.

77. Plasma membrane glycolipids are founda. exclusively in the inner leaflet.b. exclusively in the outer leaflet.c. equally distributed between the inner and outer leaflets.d. None of the above

78. Mammalian erythrocytes (red blood cells) are particularly useful for studies of the plasma membrane becausea. they have few peripheral proteins.b. they have no membrane-bound cell organellesc. their plasma membrane is not associated with a cytoskeleton.d. All of the above

79. Integrins area. transmembrane proteins.b. peripheral membrane proteins.c. components of the extracellular matrix.d. components of the desmosome.

80. Ras is a membrane-bound _______ when activated.a. monomeric protein that binds GTPb. dimeric protein that separates into and subunitsc. trimeric protein that separates into and subunitsd. trimeric protein that separates into and subunits

81. Most growth factor receptors area. G protein-linked.b. protein-tyrosine kinases.c. serine-threonine protein kinases.d. intracellular receptors.

82. In an active state of a G proteina. the subunit binds to a target protein and the subunit remains bound to the receptor.b. the and subunits both can bind to target proteins. c. the and subunits both can bind to target proteins.d. the subunit can bind to a target protein and the subunit remains bound to the receptor.

83. In meiosis I, sister chromatidsa. go to opposite poles.b. go to the same poles.c. have kinetochores facing in opposite directions.d. synapse with each other during the zygotene stage.

84. Transcription ceases as chromosome condensation occurs.a. trueb. false

85. Chromosomes are attached to spindle microtubules bya. centromeres.b. kinetochores.c. centrioles.d. centrosomes.

86. Nuclear envelope breakdown occurs at the _______ of _______.a. beginning; prophaseb. end; prophasec. end; prometaphased. end; metaphase

87. Rb is a tumor suppressor gene.a. trueb. false

88. Entry into mitosis occurs becausea. cyclin is destroyed at the beginning of mitosis.b. cyclin is phosphorylated at the beginning of mitosis.c. sufficient cyclin-dependent kinase is synthesized to trigger mitosis.d. cyclin binds to a protein kinase and activates it.

89. The retinoblastoma protein (Rb) binds to and inhibitsa. oncogenes.b. transcription factor E2F.c. cyclin-dependent kinase.d. p53.

CELL BIOLOGYExam I

90. Cell cycles of early embryonic animal cells are unusual because they havea. no G1.b. no G 2.c. a very short S.d. All of the above

91. Skin fibroblasts arrested in G0 are stimulated near a wound to enter G1 by _______ growth factor.a. epidermalb. platelet-derivedc. fibroblastd. keratinocyte

92. The G2 checkpoint prevents entry into _______ if _______.a. G2; DNA synthesis is not completeb. M; DNA synthesis is not completec. M; if DNA is damaged.d. Both b and c

93. Cells are restricted to one round of DNA replication per cycle by origin of replication binding proteins calleda. ATMs.b. Akts.c. Oris.d. MCMs.

94. After development, liver cells stop cycling and stay in G1.a. trueb. false

95. The distinct series of changes that characterizes programmed cell death is calleda. necrosis.b. sepsis.c. apoptosis.d. execution.

96. Which of the following events is not part of apoptosis?a. Fragmenting of chromosomal DNA (maybe)b. Fragmenting of the nucleusc. Fragmenting of the celld. Lysis of cell fragments and release of their contents

97. During development, 50% of neurons die; those that survive are those thata. generated axons.b. received epithelial growth factor.c. made correct connections with their target cells.d. did not receive an extracellular cell death signal.

98. Apoptotic cells produce “eat me” signals, which include _______ of cell surface _______.a. loss; carbohydratesb. loss; phosphatidylserinec. gain; phosphatidylserined. gain; phosphatidylethanolamine

99. Cells that die as the result of acute injury undergoa. lysisb. sepsis.c. apoptosis.d. execution.

100. Members of the Bcl-2 family of proteins area. all caspases.b. all proapoptotic.c. all antiapoptotic.d. either antiapoptotic or proapoptotic.