Deck 3: Observing Microorganisms Through a Microscope

Question 1

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

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

Answer 1

A

Question 2

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

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

Answer 2

B

Question 3

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

Answer 3

E

Question 4

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

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

Question 5

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

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

Question 6

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

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

Question 7

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) colorless
B) purple
C) brown
D) red

Question 8

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

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

Question 9

Which of the following pairs is mismatched?

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

Question 10

The purpose of the ocular lens is to

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

Question 11

The resolution of a microscope can be improved by changing the

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

Question 12

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

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

Question 13

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

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

Question 14

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

Question 15

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

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

Question 16

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) red
B) purple
C) brown
D) colorless

Question 17

The negative stain is used to

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

Question 18

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

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

Question 19

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

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

Question 20

) In microscopy, the term resolution

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

Question 21

The purpose of a mordant in the Gram stain is to

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

Question 22

Which of the following pairs is mismatched?

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

Question 23

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) colorless
B) brown
C) purple
D) red

Question 24

Figure 3.1

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

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

Question 25

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) a capsule stain
D) a simple stain
E) an endospore stain

Question 26

Bacterial smears are fixed before staining to

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

Question 27

Which microscope is most useful for visualizing a biofilm?

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

Question 28

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

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

Question 29

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

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

Question 30

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

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

Question 31

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

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

Question 32

Which of the following is NOT equal to 1 mm?

A) 10 ⁶ nm
B) 100 µm
C) 0.1 cm
D) 10^{- 3} m
E) 0.001 m

Question 33

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) brown
C) colorless
D) red

Question 34

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

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

Question 35

Which microscope achieves the highest magnification and greatest resolution?

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

Question 36

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

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

Question 37

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

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

Question 38

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

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

Question 39

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

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

Question 40

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

Question 41

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

Question 42

Which of the following is NOT useful for observing living cells?

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

Question 43

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

Question 44

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

Question 45

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

Question 46

Which microscope uses visible light?

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

Question 47

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

Question 48

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

Question 49

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

Question 50

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

Question 51

Which of the following pairs is mismatched?

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

Question 52

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

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

Question 53

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 54

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

Question 55

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

Question 56

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 Gram's concern.

Question 57

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