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.

Accepted Answer

Acid-fast cells are not necessarily gram-negative. The acid-fast stain is a separate staining technique used to identify bacteria with waxy cell walls, such as Mycobacterium, which do not stain well with the Gram stain.

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

Accepted Answer

A darkfield microscope produces an image of a light cell against a dark background, and it does not reveal internal structures.

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

Accepted Answer

Simple staining is often used with compound light microscopes to improve contrast by adding color to transparent specimens, making them more visible under the microscope.

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

Accepted Answer

Scanning electron microscopes require a vacuum and sample coating, which makes them unsuitable for observing living cells.

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.

Accepted Answer

A mordant in the Gram stain, such as iodine, is used to form a complex with the crystal violet stain, which helps to fix the dye within the cell walls of gram-positive bacteria, preventing it from being easily washed out.

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

Accepted Answer

Safranin is actually a basic dye, not an acid dye.

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

Accepted Answer

Electron microscopes achieve the highest magnification and greatest resolution by using electron beams instead of light, allowing them to visualize structures at the nanometer scale.

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.

Accepted Answer

The answer of Figure 3.1  In Figure 3.1, line...

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

Accepted Answer

The answer of Which microscope uses visible light?
A) confocal microscope
B)...

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.

Accepted Answer

Negative staining is used to determine cell size because it stains the background, leaving the cells clear and allowing for accurate measurement.

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

Accepted Answer

Basic dyes are used for positive staining, not negative staining. Negative staining typically uses acidic dyes.

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

Accepted Answer

The correct order for Gram staining is: Crystal violet (primary stain), Iodine (mordant), Alcohol-acetone (decolorizer), and Safranin (counterstain).

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

Accepted Answer

The phase-contrast microscope is used to view internal structures of cells in their natural state without staining, by enhancing the contrast of transparent specimens.

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

Accepted Answer

After leaving the condenser, light passes through the specimen in a compound light microscope.

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

Accepted Answer

In a compound microscope, light travels from the light source to the condenser, then through the specimen, followed by the objective lens, and finally through the 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

Accepted Answer

100 nm is equal to 0.1 μm because 1 μm is equal to 1000 nm.

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

Accepted Answer

100 μm is equal to 0.1 mm, not 1 mm.

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

Accepted Answer

An electron microscope uses a beam of electrons instead of light to create an image, and the image is viewed on a screen or photographic plate, not directly through a lens.

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.

Accepted Answer

1 micrometer (μm) is equal to 0.001 millimeters (mm). Therefore, 5 μm is equal to 5 x 0.001 mm, which is 0.005 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.

Accepted Answer

The correct sequence for preparing a slide for microscopic examination is: first, making a smear (2), then fixing the smear (3), and finally staining it (1).

Quiz 3: Observing Microorganisms Through a Microscope

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

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

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

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

The purpose of a mordant in the Gram stain is to

Which of the following pairs is mismatched?

Which microscope achieves the highest magnification and greatest resolution?

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

Which microscope uses visible light?

The negative stain is used to

Which of the following pairs is mismatched?

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

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

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

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

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

Which of the following is NOT equal to 1 mm?

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

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

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