Pearsons Questions Chapter 3

1000×

Which total magnification should be used to observe a 2-µm bacterial cell?

The specimen must be sectioned before viewing.

Which of the following statements is NOT true for both TEM and SEM?

Light source → condenser → specimen → objective lens → ocular lens

Place these structures of the compound light microscope in the order that light passes through them on the way to the observer's eyes: (1) condenser, (2) ocular lens, (3) light source, (4) specimen, (5) objective lens.

Fluorescence

Which of the following types of microscopy can be used to specifically identify pathogens (such as Mycobacterium tuberculosis or rabies virus) in specimens?

• Brightfield microscope

• Fluorescent microscope

• Darkfield microscope

Which of the following are examples of compound microscopes?

0.02-µm ribosome

Which of the following is NOT visible through a compound light microscope?

Micrometer

A(n) __________ is equal to 0.000001 m.

A measure of the light-bending ability of a medium

What does refraction mean?

Immersion oil

__________ acts to decrease refraction of light rays and thus increase resolution.

400

When using a 10× ocular lens and a 40× objective, the total magnification achieved is __________.

1–10 micrometer

Most bacteria are in the __________ size range.

Stage

Holds the microscope slide in position

Ocular Lens

Remagnifies the image by the objective lens

Diaphragm

Controls the amount of light entering the condenser

Condenser

Through which structure would the light pass before it reaches the specimen affixed to the stage?

Resolution

__________ is the quality of the microscope that allows one to distinguish between two points that are very close together.

Scanning acoustic

Which of the following types of microscopy is used to study the structure of the slimy accumulation of bacteria on an IV catheter tip?

Transmission electron microscope

A student is observing an object that displays the internal detail on a virus at great magnification. Which type of microscope is used for this image?

Atomic force

Which type of microscope uses a metal and diamond probe that is gently forced down along the surface of a specimen?

Prevent the loss of resolution due to refraction

Immersion oil is used with the 100 × objective lens of the compound light microscope to __________.

Phase-contrast

Which of the following types of microscopy is most useful for viewing the internal structures of unstained, eukaryotic specimen?

Micrometer

Which of the following is the most appropriate unit for expressing the size of an average bacterial cell?

Scanning electron microscope

A microscopist is studying the surface pores on a bacterial specimen. Which microscope provides the best three-dimensional surface structure image?

Wavelength

Resolution is very good when using an electron microscope because the __________ of the electron beam is much shorter than that of visible light.

Scanning electron microscopy

Which of the following kinds of microscopy would be most appropriate for viewing the shape and arrangement of pili or fimbriae on the surface of a bacterial cell?

Nanometer

What metric unit would be most appropriate for expressing the size of most viruses?

Diaphragm

The __________ is the part of the microscope that controls the amount of light entering the condenser.

Brightfield

Which type of light microscopy is used to visualize stained specimens?

Lowering the stage to increase the distance between the object and the objective lens

A student is observing a Gram stain with the 100 × (oil immersion) lens. The image appears cloudy and dark. Which of the following actions will NOT increase the clarity of the image?

Purple

In the Gram stain, if the decolorizing step is omitted, gram-negative cells will appear __________ at the completion of the staining procedure.

In thick layers of peptidoglycan

In the Gram stain, crystal violet remains in gram-positive cells after treatment with alcohol because crystal violet––iodine (CV––I) complexes are trapped __________.

• Flagella stain

• Negative stain

Which of the following are considered special stains?

Waxy material in their cell walls

Acid-fast Mycobacteria differ from non–acid-fast bacteria by the presence of __________.

The gram-positive organisms would appear purple, and the gram-negative organisms would be colorless.

A student completes a Gram stain on a bacterial smear that has a mix of gram-negative and gram-positive organisms. The student stops the procedure without adding safranin. What would be the outcome of the Gram stain?

Unstained in a colored background

In a negative staining procedure, the bacterial cells would appear __________ when viewed under a microscope.

He didn't properly fix the smear

Your lab partner tells you the bacteria are moving in his Gram-stained smear. You can conclude that __________.

Clear halos

In the capsule stain using India ink, capsules are distinguished as __________ surrounding cells.

Primary stain

In the Gram stain, crystal violet is the __________.

To make gram-negative cells visible

In the Gram stain, what is the purpose of the counterstain?

There are acid-fast bacteria in the specimen

You are viewing a sputum smear that has been stained with an acid-fast stain. On this smear you see 5-micrometer-long red cells. You can conclude that __________.

• Safranin

• Crystal violet

• Malachite green

Which of the following are basic dyes?

To selectively remove stain from cells

In the Gram stain, what is the purpose of the decolorizer?

Gram staining

__________ is important in medical microbiology because the results help physicians select appropriate antibiotics for treatment.

Acid-fast

Bacteria in the genus Mycobacterium can only be stained with which of the following stains?

positive; negative

The __________ charge of a basic dye adheres to the __________ charge of bacterial cell surfaces.

Acid-alcohol is used to remove the primary stain from bacteria that do not have waxy cell walls.

The acid-fast stain differs from the Gram stain procedure in the decolorizing agent used. What is the reagent used in an acid-fast stain, and why is it necessary?

Heat fixation of the smear before staining

Which of the following steps is common to both the Gram stain and the acid-fast stain?

Endospore stain to distinguish dormant structures formed during adverse environmental conditions

Which of the following staining procedures is correctly matched with the principal use for that particular stain?

crystal violet → iodine → decolorizer → safranin

What is the correct order for the Gram stain process?

Fixation differentiates the various cells being observed.

Before cells are stained, the specimen must be fixed. Fixing a specimen accomplishes all of the following EXCEPT which one?