OPENSTAX MICROBIOLOGY EXAM TESTBANK COMPLETE
ACTUAL EXAM QUESTIONS AND CORRECT DETAILED
SOLUTIONS LATEST 2024-2025
1. It is important to fix bacterial smears on a slide for which of the following
reasons?
A. to attach them to the slide
B. to cause swelling of the cell to make interior structures more visible
C. to enhance the uptake of stains
D. to provide a nutrient medium to sustain the bacteria - CORRECT ANSWER✔✔A.
to attach them to the slide
1. Which of the following is not commonly used for chemical fixation?
A. acetic acid
B. ethanol
C. glutaraldehyde
D. iodine - CORRECT ANSWER✔✔D. iodine
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1. Which of the following is not involved in preparing a bacterial slide for Gram
staining?
A. allowing the sample to dry on the slide
B. fixing the specimen to the slide
C. placing a smear on the slide
D. preparing a wet mount - CORRECT ANSWER✔✔D. preparing a wet mount
1. Which of the following most specifically refers to stains with positively charged
chromophores?
A. acid-fast dyes
B. acidic dyes
C. basic dyes
D. positive dyes - CORRECT ANSWER✔✔C. basic dyes
1. Which of the following most specifically refers to a stain that dyes a specimen
rather than the background?
A. counterstain
B. mordant
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C. negative stain
D. positive stain - CORRECT ANSWER✔✔D. positive stain
1. Which of the following describes the difference between the Ziehl-Neelsen and
Kinyoun acid-fast staining techniques?
A. The Ziehl-Neelsen technique uses a counterstain and the Kinyoun technique
does not.
B. The Ziehl-Neelsen technique uses an acidic dye and the Kinyoun technique does
not.
C. The Ziehl-Neelsen technique uses heat and the Kinyoun technique does not.
D. The Ziehl-Neelsen technique uses two dyes and the Kinyoun technique does
not. - CORRECT ANSWER✔✔C. The Ziehl-Neelsen technique uses heat and the
Kinyoun technique does not.
1. Which of the following described the difference between gram-positive and
gram-negative cells that causes them to stain differently after Gram staining?
A. Gram-positive cells have a mycolic acid layer in their cell walls that holds in
stain, whereas gram-negative cells lack this layer.B. Gram-positive cells have
capsules and gram-negative cells have S layers.
C. Gram-positive cells have thicker cell membranes than gram-negative cells.
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D. Gram-positive cells have thicker peptidoglycan layers in their cell walls than do
gram-negative cells. - CORRECT ANSWER✔✔D. Gram-positive cells have thicker
peptidoglycan layers in their cell walls than do gram-negative cells.
1. Which of the following would not potentially cause a gram-positive cell to
appear gram-negative after Gram staining?
A. counterstaining with crystal violet instead of safranin
B. exposing the cells to ethanol for too long
C. using older bacterial cultures
D. using safranin as a primary stain - CORRECT ANSWER✔✔A. counterstaining with
crystal violet instead of safranin
1. Which of the following does not cause the probe to move up and down above
the specimen in atomic force microscopy?
A. chemical bonding
B. electrostatic forces
C. van der Waals forces
D. variations in current - CORRECT ANSWER✔✔D. variations in current
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