Chapter 3

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Microbiology
Chapter 3
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1

1) Which of the following is NOT equal to 1 mm?

A) 0.001 m

B) 106nm

C) 0.1 cm

D) 100 μm

E) 10-3m

Answer: D

2

2) What structure does light pass through after leaving the condenser in a compound light microscope?

A) ocular lens

B) objective lens

C) specimen

D) illuminator

Answer: C

3

3) Which of the following pairs is mismatched?

A) nigrosin - negative stain

B) methylene blue - simple stain

C) acidic dye - capsule stain

D) basic dye - negative stain

E) crystal violet - simple stain

Answer: D

4

4) Which of the following places the steps of the Gram stain in the correct order?

1-Alcohol-acetone

2-Crystal violet

3-Safranin

4-Iodine

A) 1-2-3-4

B) 2-1-4-3

C) 2-4-1-3

D) 4-3-2-1

E) 1-3-2-4

Answer: C

5

5) Which of the following pairs is mismatched?

A) alcohol-acetone — decolorizer

B) crystal violet — basic dye

C) safranin — acid dye

D) iodine — mordant

E) carbolfuchsin — basic dye

Answer: C

6

6) Which of the following is NOT true regarding the acid-fast stain?

A) It is used to identify members of the genus Mycobacterium.

B) Acid-fast cells retain the primary dye after treatment with acid-alcohol.

C) If cells are acid-fast, they are gram-negative.

D) Acid-fast cells appear red in a completed acid-fast stain.

E) Non-acid-fast microbes appear blue in a completed acid-fast stain.

Answer: C

7

7) The purpose of a mordant in the Gram stain is to

A) remove the simple stain.

B) make the bacterial cells larger.

C) make the flagella visible.

D) prevent the crystal violet from leaving the cells.

E) make gram-negative cells visible.

Answer: D

8

8) Which of the following places the steps in the correct sequence?

1-Staining

2-Making a smear

3-Fixing

A) 1-2-3

B) 3-2-1

C) 2-3-1

D) 1-3-2

E) The order is unimportant.

Answer: C

9

9) The negative stain is used to

A) visualize endospores.

B) determine Gram reaction.

C) determine flagella arrangement.

D) visualize capsules.

E) determine cell size.

Answer: E

10

10) Simple staining is often necessary to improve contrast in which microscope?

A) compound light microscope

B) phase-contrast microscope

C) darkfield microscope

D) fluorescence microscope

E) electron microscope

Answer: A

11

11) Which microscope is used to see internal structures of cells in a natural state?

A) compound light microscope

B) phase-contrast microscope

C) darkfield microscope

D) fluorescence microscope

E) electron microscope

Answer: B

12

12) Which microscope uses visible light?

A) confocal microscope

B) differential interference contrast microscope

C) fluorescence microscope

D) scanning acoustic microscope

E) scanning electron microscope

Answer: B

13

13) Which microscope achieves the highest magnification and greatest resolution?

A) compound light microscope

B) phase-contrast microscope

C) darkfield microscope

D) fluorescence microscope

E) electron microscope

Answer: E

14

14) In using this microscope, the observer does NOT look directly at an image through a lens.

A) compound light microscope

B) phase-contrast microscope

C) darkfield microscope

D) fluorescence microscope

E) electron microscope

Answer: E

15

15) This microscope produces an image of a light cell against a dark background; internal structures are NOT visible.

A) compound light microscope

B) phase-contrast microscope

C) darkfield microscope

D) fluorescence microscope

E) electron microscope

Answer: C

16

16) A virus measures 100 nm in length. What is its length in μm?

A) 10 μm

B) 1 μm

C) 0.1 μm

D) 0.01 μm

E) 0.001 μm

Answer: C

17

17) Which of the following is never useful for observing living cells?

A) phase-contrast microscope

B) darkfield microscope

C) scanning acoustic microscope

D) scanning electron microscope

E) brightfield microscope

Answer: D

18

18) A microorganism measures 5 μm in length. Its length in mm would be

A) 500 mm.

B) 50 mm.

C) 0.5 mm.

D) 0.05 mm.

E) 0.005 mm.

Answer: E

19

19) Which of the following correctly traces the path of light through the compound microscope?

A) light source; condenser; specimen; objective lens; ocular lens

B) condenser; light source; specimen; ocular lens; objective lens

C) light source; specimen; condenser; objective lens; ocular lens

D) condenser; light source; specimen; objective lens; ocular lens

E) light source; condenser; objective lens; specimen; ocular lens

Answer: A

20
card image

In Figure 3.1, line "c" points to the microscope's

A) illuminator.

B) condenser.

C) ocular lens.

D) objective lens.

Answer: B

21

21) Which microscope can be used to visualize DNA or botulinum toxin?

A) compound light microscope

B) phase-contrast microscope

C) scanning tunneling microscope

D) confocal microscope

E) scanning electron microscope

Answer: C

22

22) Which microscope is used to observe a specimen that emits light when illuminated with an ultraviolet light?

A) compound light microscope

B) phase-contrast microscope

C) darkfield microscope

D) fluorescence microscope

E) electron microscope

Answer: D

23

23) Which microscope is most useful for visualizing a biofilm?

A) compound light microscope

B) phase-contrast microscope

C) fluorescence microscope

D) scanning acoustic microscope

E) transmission electron microscope

Answer: D

24

24) Which microscope takes advantage of differences in the refractive indexes of cell structures?

A) compound light microscope

B) phase-contrast microscope

C) darkfield microscope

D) fluorescence microscope

E) electron microscope

Answer: B

25

25) You are performing a Gram stain on gram-positive bacteria and you stop after the addition of the first dye. What is the appearance of the bacteria at this point?

A) purple

B) red

C) colorless

D) brown

Answer: A

26

26) You are performing a Gram stain on gram-negative bacteria and you stop after the addition of the mordant. What is the appearance of the bacteria at this point?

A) purple

B) red

C) colorless

D) brown

Answer: A

27

27) You are performing a Gram stain on gram-negative bacteria and you stop after the decolorizer step. What is the appearance of the bacteria at this point?

A) purple

B) red

C) colorless

D) brown

Answer: C

28

28) You are performing a Gram stain on gram-positive bacteria and you stop after the addition of the counterstain. What is the appearance of the bacteria at this point?

A) purple

B) red

C) colorless

D) brown

Answer: A

29

29) Which type of stain is most useful in helping clinicians to decide which antibiotic to prescribe for a bacterial infection?

A) negative stain

B) simple stain

C) Gram stain

D) endospore stain

E) flagella stain

Answer: C

30

30) Which of the following pairs is mismatched?

A) confocal microscope - produces a three-dimensional image

B) darkfield microscope - uses visible light

C) fluorescence microscope - uses a fluorescent light

D) scanning electron microscope - produces a three-dimensional image

E) scanning tunneling microscope - allows visualization of atoms

Answer: C

31

31) What is the total magnification of a specimen viewed with a 10x ocular lens and a 45x objective lens?

A) 4.5x

B) 10x

C) 45x

D) 100x

E) 450x

Answer: E

32

32) You are studying a cell structure that is approximately 100 nm in size. Which of the following provides the greatest magnification you can use to see this structure?

A) brightfield microscope

B) darkfield microscope

C) transmission electron microscope

D) phase-contrast microscope

E) scanning electron microscope

Answer: E

33

33) Which microscope uses two beams of light to produce a three-dimensional color image?

A) fluorescence microscope

B) phase-contrast microscope

C) darkfield microscope

D) DIC microscope

E) electron microscope

Answer: D

34

34) Which microscope is used to see intracellular detail in a living cell?

A) fluorescence microscope

B) two-photon microscope

C) atomic force microscope

D) transmission electron microscope

E) brightfield microscope

Answer: B

35

35) Which microscope is used to observe viruses and the internal structure of thinly sectioned cells?

A) transmission electron microscope

B) darkfield microscope

C) fluorescence microscope

D) brightfield microscope

E) scanning electron microscope

Answer: A

36

36) Which microscope is used to see detail of a 300-nm virus?
A) fluorescence microscope
B) phase-contrast microscope
C) darkfield microscope
D) DIC microscope
E) electron microscope

Answer: E

37

37) Assume you stain Bacillus by applying malachite green with heat and then counterstaining with safranin. Through the microscope, the green structures are

A) cell walls.

B) capsules.

C) endospores.

D) flagella.

E) The answer cannot be determined.

Answer: C

38

38) Which step in the Gram stain is the critical step in differentiating gram-positive cells from gram-negative cells?

A) safranin

B) alcohol-acetone

C) iodine

D) crystal violet

Answer: B

39

39) You find colorless areas in cells in a Gram-stained smear. What should you apply next?

  1. A) an acid-fast stain
  2. B) a flagella stain
  3. C) a capsule stain
  4. D) an endospore stain
  5. E) a simple stain

Answer: D

40

40) Which microscope is best used for observing the surfaces of intact cells and viruses?

A) phase-contrast microscope

B) darkfield microscope

C) fluorescence microscope

D) brightfield microscope

E) scanning electron microscope

Answer: E

41

41) Bacterial smears are fixed before staining to

A) affix the cells to the slide.

B) make their walls permeable.

C) accept stain.

D) make the cells visible.

Answer: A

42

42) The resolution of a microscope can be improved by changing the

A) condenser.

B) fine adjustment.

C) wavelength of light.

D) diaphragm.

E) coarse adjustment.

Answer: C

43

43) A student is looking at a bacterial specimen using the oil immersion lens, but has forgotten to put immersion oil on the slide. The specimen will appear

  1. A) smaller than it would if immersion oil was used.
  2. B) larger than it would if immersion oil was used.
  3. C) somewhat fuzzy and have poor resolution.
  4. D) the same as it would if the immersion oil was used.
  5. E) to have no color.

Answer: C

44

44) The purpose of the ocular lens is to

A) improve resolution.

B) magnify the image from the objective lens.

C) decrease the refractive index.

D) increase the light.

E) decrease the light.

Answer: B

45

45) In microscopy, the term resolution

A) refers to the ability to distinguish fine structure and detail in a specimen.

B) is the same as the total magnification of a specimen.

C) is improved when longer wavelengths of light are employed.

D) is only observed in stained specimens.

E) refers to magnification when using the electron microscope.

Answer: A