Biology 340 Name



Biology 340 Name ________________________

Spring 1998

Final Exam Examination Number __________

Multiple Choice. 100 questions

Be sure to put your name and your examination number on the mark-sense sheet.

Put your name on the exam booklet. Both the exam booklet and the mark-sense sheet must be turned in at the end of the period.

You may write in the exam booklet, but only the mark-sense sheet will be graded. No other paper, scratch paper, etc., may be used.

Students must turn in the exam before leaving the room for any reason. A student may not continue working on the exam after having left the room.

Be sure your copy of the examination has 100 questions.

Include both your name and the number of the examination on the scantron sheet. If you do not include the examination number, your exam may not be graded correctly.

If you wish to have your final grade posted, write “Please Post” on your scantron sheet.

1. All virions possess

(a) a capsid and an envelope. (d) DNA.

(b) both DNA and RNA. (e) nucleic acid and a capsid.

(c) RNA.

2. The envelopes of animal viruses are formed

(a) when the virions are released from the host cell by budding.

(b) when the virions are released from the host cell by lysis.

(c) when the viral nucleic acid directs the synthesis of unique viral phospholipids.

(d) when the viral nucleic acid is integrated into the host chromosomes.

(e) when the virion penetrates the host cell plasma membrane.

3. A virion capsid with icosahedral symmetry

(a) resembles a solid geometric shape with 60 triangular faces.

(b) resembles a solid geometric shape with 6 square faces.

(c) resembles a triangle with an extended neck and a polyhedral head.

(d) resembles a stretched-out spiral.

(e) none of the above

4. Which of the following indicates a possible case of tuberculosis?

(a) The presence of gram-negative cocci in the lung secretions of the patient.

(b) The presence of gram-negative rods with bipolar staining in the lung secretions of the patient.

(c) The presence of acid-fast rods in the lung secretions of the patient.

(d) Presence of serum endotoxins.

(e) Skin rash accompanied by high fever.

5. The smallest number of protein subunits that can form an icosahedral capsid is

(a) 3 (d) 60

(b) 9 (e) 180

(c) 20

6. Which of the following best describes a type of complex capsid symmetry?

(a) Protein subunits bound to a nucleic acid molecule in a spiral configuration

(b) Protein subunits arranged to form an icosahedron

(c) A phospholipid bilayer with spike proteins

(d) An icosahedral capsid head attached to a helical capsid tail

(e) A nucleocapsid surrounded by an envelope.

7. New genetic strains of the influenza virus develop due to

(a) the high mutational rate associated with the reverse transcriptase enzyme of the influenza virus.

(b) antigenic variation of the envelope spike proteins (N and H proteins) coupled with genetic exchange of RNA segments.

(c) host immune responses that destroy cells infected with the virus.

(d) onset of neurological symptoms in the late stages of infection.

(e) the effects of aspirin and aspirin-like compounds.

8. The Food Safety and Inspection Service (FSIS) routinely tests meat in packing plants for

a) Camphylobacter and Clostridium

b) Listeria monocytogenes and Staphylococcus aureus

c) Salmonella and E. coli

d) Hantavirus and Influenza

e) Toxoplasma and Streptococcus pyogenes

9. Infections by Corynebacterium diphtheriae are characterized by

(a) pseudomembrane formation in the respiratory tract due to a cytotoxin.

(b) kidney failure due to glomerulonephritis.

(c) destruction of the tissue of the alveoli in the lungs due to tubercle formation.

(d) formation of severe ulcers in the gastrointestinal tract due to an enterotoxin.

(e) flaccid paralysis due to a neurotoxin.

10. The erythrogenic toxin produced by some strains of Streptococcus pyogenes is responsible for

(a) the formation of heart lesions.

(b) the skin rash of scarlet fever.

(c) the kidney damage that complicates streptococcal infections.

(d) ulceration in the gastrointestinal tract.

(e) blockage of nerve impulses at motor neuron end plates.

11. The botulism toxin causes flaccid paralysis by

(a) causing swelling in the meninges.

(b) irritating the lining of the gastrointestinal tract.

(c) inhibiting protein synthesis in neurons.

(d) blocking synaptic transmission at the motor neuron end plates.

(e) causing the formation of gummae in the brain and spinal cord.

12. A major symptom of cholera is

a) severe diarrhea

b) macropapipular rash

c) joint swelling and arthritis-like symptoms

d) fluid buildup in lungs

e) painful urination

13. When the bacterium responsible for tuberculosis spreads from the lungs into other organs and tissues of the body, the resulting condition is known as

(a) primary atypical tuberculosis.

(b) secondary tuberculosis.

(c) aseptic tuberculosis.

(d) miliary tuberculosis.

(e) rickettsial tuberculosis.

14. Approximately what percentage of cases of necrotizing fasciitis are due to Group A streptococcal infections?

a) 100%

b) 75%

c) 50%

d) 25%

e) 0%

15. Hantavirus Pulmonary Syndrome is believed to be transmitted to humans

a) via sexual intercourse

b) via contact with infected rodent saliva and droppings

c) via contaminated food (especially contaminated poultry products)

d) via ticks

e) via human body lice (and occasionally head and crab lice).

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The following choices are used for questions 16 - 20.

(a) streptococcal pharyngitis

(b) glomerulonephritis

(c) rheumatic fever

(d) erisepelas

(e) puerperal sepsis

16. This is a severe sore throat.

17. This is a complication in which the immune response to a Streptococcus pyogenes infection causes damage to the kidney tubules.

18. This is a skin infection caused by Streptococcus pyogenes.

19. This is a complication in which the immune response to a Streptococcus pyogenes infection causes damage to the cardiovascular system and heart valves.

20. This is an infection that can occur in women after childbirth.

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21. The principal mode of transmission for Rocky Mountain Spotted Fever is

(a) blood transfusion

(b) sexual contact

(c) bite of an infected tick

(d) inhalation of bacteria that cause the disease

(e) ingestion of food contaminated with bacterial spores

22. Endemic typhus may be expected to occur in regions where there are

(a) large herds of cattle.

(b) large populations of deer ticks.

(c) large populations of rodents and fleas.

(d) poultry processing plants.

(e) problems with the proper canning of food.

23. AZT, a drug commonly used in the treatment of HIV infections, acts by

a) inhibiting the action of protease enzymes necessary for HIV replication

b) inhibiting the action of host cell ribosomes that bind to the retrovirius RNA

c) increasing the replication of helper T cells

d) inhibiting the replication of DNA by acting as a chain-terminating nucleoside analog

e) blocking the attachment of HIV virions to their host cells.

24. Neisseria meningitidis is a major cause of meningitis in young children. It may be diagnosed by the observation of

(a) acid-fast rods in the spinal fluid.

(b) gram-negative cocci, arranged in pairs, in the spinal fluid.

(c) gram-negative rods in the spinal fluid.

(d) mycoplasmas in the spinal fluid.

(e) gram-positive rods in the spinal fluid.

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The following choices are used for questions 25 - 27.

(a) alpha hemolysis

(b) beta hemolysis

(c) gamma reaction

25. This term refers to a zone of partial hemolysis as evidenced by a green zone surrounding the colony on blood agar.

26. This is the typical hemolytic reaction of Streptococcus pyogenes.

27. This is the typical hemolytic reaction of Streptococcus pneumoniae.

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28. Several months after an infected tick bite, joints can become stiff and swollen with arthritis-like symptoms due to a complication of

(a) Yersinia pestis infections.

(b) Treponema pallidum infections.

(c) Hemophilus influenzae infections.

(d) Borrelia burgdorferi infections.

(e) Bacillus anthracis infections.

29. Erythema chronicum migrans is associated with infections by

(a) Legionella pneumophila (d) Rickettsia rickettsii

(b) Mycoplasma pneumoniae (e) Salmonella typhi

(c) Borrelia burgdorferi

30. Which of the following tests is most useful in the diagnosis of infections by species of the genus Rickettsia?

(a) An acid-fast stain

(b) A Gram stain

(c) A Weil-Felix test

(d) Injecting Rickettsia antigens underneath the skin on the arm of the patient

(e) The hemolytic reaction of the Rickettsia species on blood agar

31. Which of the following organisms is responsible for epidemic typhus?

(a) Salmonella typhi

(b) Rickettsia typhi

(c) Rickettsia prowazekii

(d) Rickettsia rickettsii

(e) Clostridium tetani

32. The formation of lesions called gummae is associated with

(a) chancroid

(b) Lyme disease

(c) tertiary syphilis

(d) tuberculosis

(e) scrofula

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The following choices are used for questions 33 - 36.

(a) Streptococcus agalactiae

(b) Enterococcus faecalis

(c) Streptococcus pyogenes

(d) Streptococcus pneumoniae

33. This species belongs to Lancefield group A.

34. This species belongs to Lancefield group D.

35. This species is characterized by sensitivity to bacitracin.

36. This species is a common intestinal flora.

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37. Outbreaks of epidemic typhus are associated with

(a) areas with large numbers of poultry processing plants.

(b) areas with large numbers of rodents and rodent fleas.

(c) contaminated drinking water.

(d) conditions of poor sanitation where human lice flourish.

(e) the fecal waste of human carriers who harbor the bacteria in their gall bladders.

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The following choices are used for questions 38 - 42.

(a) Mycobacterium tuberculosis

(b) Streptococcus pneumoniae

(c) Neiserria meningitidis

(d) Legionella pneumophila

(e) Mycoplasma pneumoniae

38. Commonly found in aquatic habitats, this organism can contaminate moist aerated surfaces such as building ventilation systems.

39. This organism is responsible for primary atypical pneumonia.

40. Pulmonary lesions surrounded by connective tissue are characteristic of infections by this organism.

41. Cells of this species do not manufacture peptidoglycan.

42. In its natural habitat, this species has been observed to parasitize certain protozoa.

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43. Tetanospasmin

(a) causes severe gastrointestinal irritation and diarrhea.

(b) causes partial breakdown of hemoglobin into bilirubin and biliverdin, resulting the yellow skin discoloration associated with jaundice.

(c) causes flaccid paralysis by blocking synaptic transmission at motor neuron end plates.

(d) causes rigid paralysis by inhibiting protein synthesis in the cells of the joints, causing the cells to die and the joints to fuse.

(e) None of the above.

44. Woolsorter's disease is a form of

(a) anthrax (d) diarrhea

(b) botulism (e) influenza

(c) coryneform infection

45. Which of the following best describes the organism responsible for bubonic plague?

(a) a small, obligately intracellular, gram-negative bacterium

(b) a member of the Herpes virus family

(c) a gram-negative bacterium with bipolar staining

(d) an acid-fast bacterium

(e) a retrovirus

46. A hard chancre is a symptom of infection by

(a) Chlamydia trachomatis (d) Treponema pallidum

(b) Rickettsia typhi (e) Rickettsia prowazekii

(c) Neisseria gonorrhoeae

47. Which of the following is a nonfermentative gram-negative bacterium often associated with respiratory tract infections, infections in burn patients, and nosocomial infections?

(a) Pseudomonas aeruginosa (d) Salmonella enteriditis

(b) Bacillus anthracis (e) Yersinia pestis

(c) Clostridium perfringins

48. All of the following are associated with Staphylococcus aureus EXCEPT

(a) toxic shock syndrome

(b) bacterial food poisoning

(c) impetigo

(d) Rocky Mountain spotted fever

(e) scalded skin syndrome

49. Which of the following is a small, gram-negative bacterium that is an obligately intracellular parasite, similar to Rickettsia, and is associated with urethritis, reproductive tract infections, and eye infections?

(a) Neisseria gonorrhoeae (d) Neisseria menigitidis

(b) Treponema pallidum (e) Chlamydia trachomatis

(c) Herpes simplex

50. Which of the following would be the greatest threat to a person with a wound contaminated with the spores of Clostridium perfringins?

(a) tetanus (d) botulism

(b) anthrax (e) bubonic plague

(c) gas gangrene

51. Mycolic acid

(a) is an unusual lipid found in the plasma membrane of mycoplasmas.

(b) is a waxy component in the cell walls of acid-fast bacteria.

(c) is located in the outer membrane of gram-negative bacteria.

(d) is a polysaccharide component in the cell walls of archaeobacteria.

(e) is an antibacterial agent used in commericial eye-drops.

52. Read each of the following three statements about bacterial colonies.

I. Ideally, an isolated bacterial colony contains cells of only a single species.

II. The morphology of a bacterial colony is a characteristic of the species.

III. Bacterial colonies can be isolated by the streak-plate method using a semisolid medium.

Which statement(s) is (are) true?

(a) I and II only (d) I only

(b) II and III only (e) I, II, and III

(c) I and III only

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The following information pertains to questions 53 - 54.

In each of the following questions, a description of a microorganism is given. Based on the description, determine which of the following choices best describes the microorganism.

(a) The microorganism is prokaryotic.

(b) The microorganism is eukaryotic.

(c) The microorganism is a virus.

(d) Based on the description given, the microorganism could be either prokaryotic or eukaryotic, but not a virus.

(e) Based on the description given, the microorganism could be either prokaryotic, eukaryotic, or a virus.

53. Giardia lamblia is a flagellated protozoan responsible for some cases of chronic gastroenteritis. The pair of nuclei in each pear-shaped cell of this organism gives it the appearance of a cross-eyed face.

54. Rickettsia rickettsii is responsible for the condition known as Rocky Mountain Spotted Fever. Although this organism grows only within an infected host, it has its own DNA and RNA to direct the synthesis of its protein and to control its cell division. Its DNA is found in the nucleoid region of its cytoplasm, but there is no nuclear membrane surrounding the DNA.

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The following information pertains to questions 55 - 57. Thioglycolate broth is a differential medium used to determine the oxygen requirements of bacteria. When a test tube of thioglycolate broth is prepared, an oxygen gradient is established. This means that there is a high concentration of oxygen at the surface of the broth, less oxygen in the middle of the tube, and no oxygen at the bottom of the tube. The following choices are used for questions 55 - 57.

(a) strict aerobe (d) aerotolerant anaerobe

(b) strict anaerobe (e) microaerophile

(c) facultative anaerobe

55. If cells of a bacterial species grow only at the surface of a thioglycolate broth tube, to which group does the species belong?

56. If cells of a bacterial species grow in one narrow band somewhere in the middle of the tube between the surface and the bottom of the tube, to which group does the species belong? (Note: the bacteria do not grow on the surface nor on the bottom, but in a narrow band in the middle.)

57. If cells of a bacterial species grow only at the bottom of a thioglycolate broth tube, to which group does the species belong?

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58. The graph below shows the growth rate of a certain bacterial species at different temperatures. In this graph, a larger growth rate value indicates that the bacteria grew faster at that temperature.

[pic]

Based on the data, which of the following terms best describes the organism?

(a) Extreme thermophile (d) Psychrophile

(b) Moderate thermophile (e) Halophile

(c) Mesophile

59. Porins

(a) are proteins embedded in the outer membrane of gram-negative bacteria.

(b) are the organelles that assemble amino acids into proteins.

(c) are granules of glycogen found in the cytoplasm of certain bacteria.

(d) are regions of the bacterial plasma membrane that are rich in cholesterol.

(e) are plasma membrane folds found in certain bacteria.

60. Which of the following best describes the structure of lipopolysaccharide?

(a) a polymer of glycerol or ribitol linked by phosphate groups

(b) a polymer of alternating glucosamine and ethanolamine units linked by ester bonds

(c) a polymer of -hydroxybutyrate units linked by pentapeptide bridges

(d) a polymer of alternating N-acetylglucosamine and N-acetylmuramic acid units linked by glycosidic bonds

(e) a polymer of O chain polysaccharide and core polysaccharide attached to a Lipid A molecule

61. Adjacent chains of peptidoglycan may be covalently crosslinked by

(a) short chains of 4 or 5 lipopolysaccharide molecules.

(b) tetrapeptide chains that are directly connected to each other.

(c) five units of alternating guanine + cytosine (G+C) molecules.

(d) both (a) and (b)

(e) both (b) and (c)

62. A peptidoglycan layer that is 20 nm to 80 nm thick is commonly seen in

(a) mycoplasmas. (d) archaeobacteria.

(b) gram-positive bacteria. (e) fungi.

(c) gram-negative bacteria.

63. Bacteria that do not have cell walls belong to this group.

(a) mycoplasmas (d) archaeobacteria

(b) gram-positive bacteria (e) acid-fast bacteria

(c) gram-negative bacteria

64. Metachromatic granules are composed of

(a) sulfur (d) polysaccharide

(b) lipid (e) protein

(c) phosphate

65. Which of the following statements best describes the current model of the relationship between the archaeobacteria, the eubacteria, and the eukaryotes?

(a) The eubacteria evolved from the more primitive archaeobacteria about 3 billion years ago. Some time later, the eukaryotes diverged from their eubacterial ancestors.

(b) The ancestors of the present-day archaeobacteria diverged from other organisms first. Later in time, the ancestors of present-day eubacteria and eukaryotes diverged.

(c) Present-day archaeobacteria and eukaryotes share certain important cellular/genetic similarities. This indicates that these two groups are closer phylogenetically to each other than to the eubacteria. It also indicates that the eukaryotes and archaeobacteria shared a common ancestor more recently with each other than with the eubacteria.

(d) The archaeobacteria represent an evolutionary “dead-end” and are destined to be replaced by the far-superior eukaryotic organisms.

66. In negative chemotaxis, as a bacterial cell approaches a repellant

(a) the angle between the flagellar filament and the cell surface increases.

(b) the angle between the flagellar filament and the cell surface decreases.

(c) the lengths of the straight runs increase.

(d) the lengths of the straight runs decrease.

(e) the electrical charge at the cell surface becomes increasingly positive.

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The following choices are used for questions 67 - 68.

(a) organotroph (d) lithotroph

(b) heterotroph (e) phototroph

(c) autotroph

67. This is the best term to describe an organism that uses an inorganic substance as its source of electrons or reduction potential.

68. This is the best term to describe an organism that can utilize CO2 as its sole carbon source.

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69. Which of the following has given taxonomists the greatest insight into phylogenetic relationships between microbial groups?

(a) Biochemical properties

(b) 16S rRNA nucleotide sequences

(c) cytochrome c amino acid sequences

(d) nucleotide sequences of the cytochrome c gene

(e) Cell shape and arrangement

70. The following choices are characteristics or methods used to classify bacterial species. Which choice is NOT based on nucleic acid composition?

(a) DNA hybridization

(b) rRNA sequence analysis

(c) G+C content

(d) Colony morphology

71. A system of classification in which organisms are grouped together to reflect genetic similarity and evolutionary relatedness is a

(a) binomial system (d) parthogenic system

(b) phenetic system (e) phylogenetic system

(c) nomenclature system

72. This kingdom contains the bacteria.

(a) Monera (d) Protista

(b) Fungi (e) Plantae

(c) Animalia

73. This term designates spherical bacterial cells arranged in clusters.

(a) streptococcus (d) diplococcus

(b) staphylococcus (e) tetrad

(c) sarcina

74. With which bacterial group is teichoic acid associated?

(a) gram-positive bacteria (c) archaeobacteria

(b) gram-negative bacteria (d) mycoplasmas

75. Which of the following best describes the function of bacterial spores?

(a) They provide a mechanism for bacterial reproduction.

(b) They mediate the process of spontaneous generation in bacteria.

(c) They induce positive and negative chemotactic responses in bacteria.

(d) They help ensure the survival of the species during conditions of nutrient depletion and waste buildup.

(e) More than one of the above.

76. Certain strains of the bacterium Corynebacterium diphtheriae contain an extra gene that codes for an exotoxin. These strains can cause a severe infection called diphtheria. Other strains that do not have the gene for the exotoxin produce no infection in humans. Which of the following statements best describes the relationship between strains that produce the exotoxin and those that do not?

(a) Strains that produce the toxin are acute, and strains that do not produce the toxin are chronic.

(b) Strains that produce the toxin are primary, and strains that do not produce the toxin are secondary.

(c) Strains that produce the toxin are localized, and strains that do not produce the toxin are systemic.

(d) Strains that produce the toxin are virulent, and strains that do not produce the toxin are nonvirulent.

(e) Strains that produce the toxin are epidemic, and strains that do not produce the toxin are endemic.

77. Which of the following statements is true?

(a) Endotoxins produce varied effects such as neurotoxic or protein inhibition effects, but exotoxins produced generalized irritation and inflammation of epithelial surfaces.

(b) Endotoxins are found attached to the cell wall of certain bacteria, but exotoxins are secreted toxins that may exhibit their effect independently of the presence of the bacteria.

(c) Endotoxins include the neurotoxins of botulism and tetanus, while exotoxins include the enterotoxin of Staphylococcus aureus.

(d) More than one of the above statements are true.

(e) None of the above are true.

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The following choices are used for questions 78 - 79.

(a) coagulase (d) leukocidin

(b) streptokinase (e) hemolysin

(c) hyaluronidase

78. This enzyme breaks down blood clots.

79. This enzyme destroys white blood cells.

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The following choices are used for questions 80 - 81.

(a) Protein A (d) tetanospasmin

(b) Lipid A (e) hemolysin

(c) Protein M

80. Which substance contributes to the adhesion of pathogenic Staphylococcus aureus cells to host tissue?

81. Which substance acts as a neurotoxic bacterial exotoxin?

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82. During respiration, which of the following processes is most directly responsible for the synthesis of the greatest amount of ATP?

(a) the conversion of glucose into pyruvic acid

(b) the conversion of -acetolactic acid into acetylmethylcarbinol

(c) the conversion of pyruvic acid into acetyl CoA and CO2

(d) the tricarboxylic acid cycle

(e) the respiratory electron transport chain

83. Under normal circumstances, the colonization of the human body by normal flora organisms begins

(a) at fertilization, in the Fallopian tube,

(b) at implantation of the embryo in the uterus,

(c) approximately two months before birth (this coincides with the seeding of the thymus gland with thymocytes),

d) during the birthing process (the normal flora develops over the first

e) several months after birth, coinciding with the development of a functional immune system),

84. This reaction represents represents the final step in the anaerobic respiration of certain species of Pseudomonas and Bacillus.

(a) Nitrite (NO2-) Nitrogen (N2)

(b) Water (H2O) Oxygen (O2)

(c) Sulfate (SO42-) Hydrogen sulfide (H2S)

(d) Hydrogen sulfide (H2S) Elemental sulfur (So)

(e) Nitrite (NO2-) Nitrate (NO3-)

85. The Entner-Douderoff pathway of glycolysis is characteristic of

(a) Pseudomonas and related genera

(b) Clostridium acetobutylicum

(c) Bifidobacterium and Leuconostoc

(d) Acetobacter

(e) Nitrobacter and Nitrosomonas

86. This reaction represents the final step in the anaerobic respiration of Desulfovibrio and Desulfotomaculatum.

(a) Nitrite (NO2-) Nitrogen (N2)

(b) Oxygen (O2) Water (H2O)

(c) Sulfate (SO42-) Hydrogen sulfide (H2S)

(d) Hydrogen sulfide (H2S) Elemental sulfur (So)

(e) Nitrite (NO2-) Nitrate (NO3-)

87. The final electron acceptor of the respiratory electron transport chain during aerobic respiration is always

(a) oxygen.

(b) an organic molecule.

(c) NADH.

(d) located in the matrix of the mitochondrion.

(e) responsible for absorbing a photon of light energy.

88. The major purpose of fermentation in bacteria is

(a) the synthesis of organic acids to regulate the pH of the organism’s environment.

(b) to provide a means for bacteria to identify each other by the production of different fermentation end products.

(c) to produce large quantities of ATP from pyruvic acid, since very little ATP is produced during glycolysis.

(d) to oxidize NADH into NAD.

(e) to regenerate ADP for the process of glycolysis.

89. Both staphylococcal food poisoning and salmonellosis can be acquired by eating contaminated food. After eating contaminated food, the time required for the onset of staphylococcal food poisoning is usually shorter than that for salmonellosis because

(a) Staphylococcus aureus grows more rapidly than Salmonella enteritidis serotypes.

(b) cells of Salmonella must reach the bloodstream before symptoms of gastrointestinal irritation are experienced.

(c) foods that contain Salmonella are usually eaten raw.

(d) Staphylococcus aureus grows only under conditions of high salt concentration.

(e) staphylococcal food poisoning is due to the presence of an exotoxin that forms in the food before it is eaten, but salmonellosis requires the colonization and growth of the bacteria in the intestine.

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The following choices are used for questions 90 - 94.

(a) primary infection (d) localized infection

(b) secondary infection (e) systemic infection

(c) subclinical infection

90. The best term to describe an infection that develops in an otherwise healthy individual.

91. The best term to describe an infection that develops in an individual who is already infected with a different organism.

92. The best term to describe an infection in a carrier who shows no symptoms of an infection.

93. The best term to describe an infection that has spread throughout the body.

94. The best term to describe an infection that is limited to a specific region of the body.

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95. A sample of mucous from the trachea of a healthy volunteer was collected by having the volunteer cough up the mucous and spit it into a sterile cup. A colony count revealed the presence of 6500 viable bacterial cells per ml of mucous. A second sample was taken from the same volunteer on the same day, but it was taken by withdrawing it directly from the trachea using a sterile syringe. In the second sample, a colony count revealed that no bacteria were present. Which of the following statements gives the most likely explanation of these results?

(a) A strong immune response destroyed the normal flora of the lower respiratory tract between the time that the first sample was taken and the time that the second sample was taken.

(b) The lower respiratory tract is free of normal flora. Bacteria from the oral cavity were responsible for bacterial contamination in the first sample.

(c) The bacteria in the first sample developed from the process of spontaneous generation.

(d) All of the normal flora of the lower respiratory tract were expelled when the first sample was taken.

96. Which of the following regions of the human body is free of normal flora under normal conditions of health?

(a) upper respiratory tract

(b) meninges

(c) large intestine

(d) more than one of the above

(e) none of the above

97. The ability of a microbial species to cause disease is its

(a) pathogenicity (d) acuteness

(b) infectious index (e) communicability

(c) mutualicity

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The following choices are used for questions 98 - 100.

(a) Light energy is used to remove electrons from a reduced electron donor. The resulting electron transport produces ATP and NADH to be used for carbon fixation.

(b) Pyruvic acid is oxidized to form CO2. Electrons are temporarily stored on NADH, then are transferred to an electron transport chain and a final inorganic electron acceptor. As a result, a lot of ATP is made.

(c) Pyruvic acid is reduced to form a reduced organic acid or alcohol. During this process, NAD is regenerated, but no additional ATP is made.

(d) Glucose is partially oxidized to form pyruvic acid, with a small amount of ATP and NADH made.

(e) A reduced inorganic electron donor is oxidized without the need for light energy. The resulting electron transport produces ATP and NADH to be used for carbon fixation.

98. This statement describes fermentation.

99. This statement describes glycolysis.

100. This statement describes respiration.

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