Deck 3: Observing Microorganisms Through a Microscope

Question 1

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

A) Acid-fast cells appear red in a completed acid-fast stain.
B) It is used to identify members of the genus Mycobacterium.
C) Non-acid-fast microbes appear blue in a completed acid-fast stain.
D) Acid-fast cells retain the primary dye after treatment with acid -alcohol.
E) If cells are acid-fast, they are gram-negative.

Answer 1

E

Question 2

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

A) phase-contrast microscope
B) fluorescence microscope
C) darkfield microscope
D) electron microscope
E) compound light microscope

Answer 2

C

Question 3

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

A) fluorescence microscope
B) phase-contrast microscope
C) compound light microscope
D) darkfield microscope
E) electron microscope

Answer 3

C

Question 4

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

A) scanning electron microscope
B) phase-contrast microscope
C) scanning acoustic microscope
D) brightfield microscope
E) darkfield microscope

Question 5

The purpose of a mordant in the Gram stain is to

A) make the bacterial cells larger.
B) make the flagella visible.
C) remove the simple stain.
D) prevent the crystal violet from leaving the cells.
E) make gram-negative cells visible.

Question 6

Which of the following pairs is mismatched?

A) crystal violet  basic dye
B) safranin  acid dye
C) alcohol-acetone  decolorizer
D) carbolfuchsin  basic dye
E) iodine  mordant

Question 7

Which microscope achieves the highest magnification and greatest resolution?

A) darkfield microscope
B) electron microscope
C) compound light microscope
D) phase-contrast microscope
E) fluorescence microscope

Question 8

Figure 3.1 In Figure 3.1, line ʺcʺ points to the microscopeʹs

A) illuminator.
B) ocular lens.
C) objective lens.
D) condenser.

Question 9

Which microscope uses visible light?

A) confocal microscope
B) differential interference contrast microscope
C) scanning acoustic microscope
D) scanning electron microscope
E) fluorescence microscope

Question 10

The negative stain is used to

A) determine cell size.
B) determine Gram reaction.
C) visualize endospores.
D) determine flagella arrangement.
E) visualize capsules.

Question 11

Which of the following pairs is mismatched?

A) methylene blue ‐ simple stain
B) crystal violet ‐ simple stain
C) nigrosin ‐ negative stain
D) basic dye ‐ negative stain
E) acidic dye ‐ capsule stain

Question 12

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) 1-3-2-4
B) 1-2-3-4
C) 2-1-4-3
D) 2-4-1-3
E) 4-3-2-1

Question 13

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

A) fluorescence microscope
B) phase-contrast microscope
C) compound light microscope
D) electron microscope
E) darkfield microscope

Question 14

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

A) illuminator
B) objective lens
C) specimen
D) ocular lens

Question 15

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

A) light source; specimen; condenser; objective lens; ocular lens
B) light source; condenser; specimen; objective lens; ocular lens
C) light source; condenser; objective lens; specimen; ocular lens
D) condenser; light source; specimen; ocular lens; objective lens
E) condenser; light source; specimen; objective lens; ocular lens

Question 16

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

A) 0.1 μm
B) 1 μm
C) 0.001 μm
D) 10 μm
E) 0.01 μm

Question 17

Which of the following is NOT equal to 1 mm?

A) 100 μm
B) 10-3 m
C) 106 nm
D) 0.1 cm
E) 0.001 m

Question 18

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

A) fluorescence microscope
B) phase-contrast microscope
C) compound light microscope
D) darkfield microscope
E) electron microscope

Question 19

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

A) 500 mm.
B) 0.5 mm.
C) 0.005 mm.
D) 0.05 mm.
E) 50 mm.

Question 20

Which of the following places the steps in the correct sequence? 1- Staining
2- Making a smear 3-Fixing

A) 3-2-1
B) 1-2-3
C) 1-3-2
D) 2-3-1
E) The order is unimportant.

Question 21

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

A) 4.5x
B) 45x
C) 100x
D) 10x
E) 450x

Question 22

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

A) compound light microscope
B) phase-contrast microscope
C) electron microscope
D) darkfield microscope
E) fluorescence microscope

Question 23

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

A) negative stain
B) Gram stain
C) endospore stain
D) simple stain
E) flagella stain

Question 24

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

A) darkfield microscope
B) electron microscope
C) phase-contrast microscope
D) compound light microscope
E) fluorescence microscope

Question 25

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

A) compound light microscope
B) phase-contrast microscope
C) scanning tunneling microscope
D) scanning electron microscope
E) confocal microscope

Question 26

Which microscope is used to see detail of a 300 -nm virus?

A) darkfield microscope
B) DIC microscope
C) fluorescence microscope
D) phase-contrast microscope
E) electron microscope

Question 27

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

A) brightfield microscope
B) scanning electron microscope
C) darkfield microscope
D) fluorescence microscope
E) transmission electron microscope

Question 28

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) phase-contrast microscope
C) scanning electron microscope
D) darkfield microscope
E) transmission electron microscope

Question 29

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

A) crystal violet
B) safranin
C) alcohol-acetone
D) iodine

Question 30

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

Question 31

Which of the following pairs is mismatched?

A) confocal microscope ‐ produces a three-dimensional image
B) scanning electron microscope ‐ produces a three-dimensional image
C) fluorescence microscope ‐ uses a fluorescent light
D) darkfield microscope ‐ uses visible light
E) scanning tunneling microscope ‐ allows visualization of atoms

Question 32

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

A) capsules.
B) flagella.
C) endospores.
D) cell walls.
E) The answer cannot be determined.

Question 33

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

A) phase-contrast microscope
B) DIC microscope
C) electron microscope
D) fluorescence microscope
E) darkfield microscope

Question 34

Which microscope is most useful for visualizing a biofilm?

A) phase-contrast microscope
B) scanning acoustic microscope
C) transmission electron microscope
D) fluorescence microscope
E) compound light microscope

Question 35

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

A) an acid-fast stain
B) a flagella stain
C) an endospore stain
D) a capsule stain
E) a simple stain

Question 36

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

Question 37

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

A) fluorescence microscope
B) transmission electron microscope
C) brightfield microscope
D) atomic force microscope
E) two-photon microscope

Question 38

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

A) darkfield microscope
B) phase-contrast microscope
C) scanning electron microscope
D) brightfield microscope
E) fluorescence microscope

Question 39

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

Question 40

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

Question 41

Scanned probe microscopy is used to examine fine detail of molecular complexes, such as blood clots, or molecules, such as DNA.

Question 42

The capsules and flagella of bacteria can be observed in gram -stained smears.

Question 43

If acid-fast bacteria are stained with the Gram stain, they will stain gram-negative.

Question 44

In 1877, Robert Koch thought preparing permanently stained slides would be valuable. Why was his assessment correct?

Question 45

In a completed Gram stain, gram-positive bacteria are purple.

Question 46

In a completed Gram stain, gram-negative bacteria are colorless.

Question 47

You are working in a clinical laboratory and you need to examine an unstained urine sample for the presence of bacteria. What type of light microscope should you use to observe this specimen? Explain your answer.

Question 48

In 1884, Hans Christian Gram described a method of staining bacterial cells while not staining surrounding animal tissues. However, he thought that the staining method he developed was faulty because not all bacteria stained. In a letter to the editor of the journal in which Gram published his findings, write your response to Gramʹs concern.

Question 49

The counterstain used in the Gram stain is a basic dye.

Question 50

Both phase-contrast microscopy and differential interference contrast microscopy are used to view the internal structures of cells without staining.

Question 51

Cells viewed in darkfield microscopy appear similar to those stained with the negative stain.

Question 52

In microscopy, the term resolution

A) refers to the ability to distinguish fine structure and detail in a specimen.
B) refers to magnification when using the electron microscope.
C) is improved when longer wavelengths of light are employed.
D) is only observed in stained specimens.
E) is the same as the total magnification of a specimen.

Question 53

The resolution of a microscope can be improved by changing the

A) condenser.
B) coarse adjustment.
C) diaphragm.
D) wavelength of light.
E) fine adjustment.

Question 54

The greater resolution of the electron microscope compared to the compound microscope is due to the longer wavelengths of the electrons used to examine specimens.

Question 55

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

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

Question 56

Bacterial smears are fixed before staining to

A) accept stain.
B) affix the cells to the slide.
C) make the cells visible.
D) make their walls permeable.

Question 57

The purpose of the ocular lens is to

A) magnify the image from the objective lens.
B) decrease the refractive index.
C) decrease the light.
D) increase the light.
E) improve resolution.

Question 58

The limit of resolution of the compound microscope illuminated with visible light is approximately
0.2 μm.