MicroBio Q's TF CH 2

Question 1

The degree to which a substance bends light is known as the

Answer 1

Refractive index

Question 2

When light passes through air to a medium with a great refractive index (i.e., glass), what happens to the light?

Answer 2

The velocity of light decreases and it bends toward the normal

Question 3

Which of the following best describes how a lens works?

Answer 3

Light rays strike the lens and converge onto a focal point

Question 4

A microscope that can remain in focus when the objective lens is changed is described as

Answer 4

Parfocal

Question 5

The total magnification of a bright field microscope with a 10X eyepiece on the high power (100X) objective would be

Answer 5

1000X

Question 6

The ability of a lens to separate or distinguish between small objects that are close together is called

Answer 6

Resolution

Question 7

Which of the following changes would increase the resolution of a specimen observed through a lens?

Answer 7

(A) Decrease the wavelength of light; (B) Increase the refractive index; and ? Increase the numerical aperature

Question 8

Immersion oil is used when observing specimens under high power because

Answer 8

It decreases the refractive index; this increases the numerical aperture

Question 9

The distance between the front surface of the lens and the surface of the cover glass or specimen is called the

Answer 9

Working distance

Question 10

The best resolution achieved by bright field microscopes is approximately

Answer 10

0.2 micrometers

Question 11

A bright field microscope is best for observing which of the following types of specimens?

Answer 11

Fixed, stained bacteria

Question 12

A dark-field microscope is best for observing which of the following types of specimens?

Answer 12

Unpigmented living cells

Question 13

Which of the following microscopes are acceptable for viewing live specimens?

Answer 13

(A) Dark-field microscope; (B) Phase-contrast microscope; and ? Differential interference contrast microscope

Question 14

The _________________ microscope utilizes differences in refractive index and cell density into detectable variations in light intensity.

Answer 14

Phase-contrast

Question 15

Which type of microscope would be best for observing microbial motility and observing endospores?

Answer 15

Phase-contrast

Question 16

The ____________________ microscope allows microbiologists to view three-dimensional live specimens in bright color.

Answer 16

Differential interference contrast (DIC)

Question 17

Fluorescence microscopy takes advantage of which of the following characteristics of objects and light?

Answer 17

Molecules of objects absorb radiant energy and release this trapped energy as light

Question 18

Which type of microscopy exposes a specimen to low wavelength light and forms an image of the object with resulting fluorescent light?

Answer 18

Fluorescence microscopy

Question 19

Fluorescence microscopy is most useful in which of the following?

Answer 19

(A) Observing bacteria tagged with fluorescently labeled antibodies; (B) Visualizing organizms that fluorescence naturally; and ? Observing the localization of specific proteins within a cell

Question 20

The best type of microscopy for observing layered specimens (i.e., biofilms on medical devices) is

Answer 20

Confocal microscopy

Question 21

Fixing cells is advantageous in that it

Answer 21

Toughens cell structures so that they remain during staining

Question 22

Basic dyes work by

Answer 22

Binding to negatively charged molecules on the surface of cells

Question 23

Failure to complete the decolorization step in the Gram stain will result in

Answer 23

All cells will appear purple, or stained with crystal violet

Question 24

Iodine, the mordant in the Gram staining procedure, is used to

Answer 24

Help bind the crystal violet to the target molecule

Question 25

Acid-fast staining is used to stain organisms with

Answer 25

Lipids composed of branched-chain hydroxy fatty acids in their cell walls

Question 26

____________ is required to drive dye into cells to stain for endospores.

Answer 26

Heat

Question 27

Nigrosin, a dye used for negative staining, is used to observe

Answer 27

Capsules

Question 28

The electron microscope is capable of observing organisms at a higher resolution than the bright-field microscope because

Answer 28

The wavelength of the illuminating beam is much shorter than that of visible light

Question 29

Magnification with an electron microscope can be as great as

Answer 29

100,000X

Question 30

Which of the following steps is required to prepare a specimen using transmission electron microscopy (TEM)?

Answer 30

(A) The specimen is sliced into thin layers; (B) The specimen is dehydrated with organic solvents; and ? The specimen is hardened into a plastic block

Question 31

___________________ microscopy can be used to study virus morphology, the structure of flagella, and DNA.

Answer 31

Transmission electron

Question 32

Which type of microscopy works by producing images from electrons released from atoms at an object’s surface?

Answer 32

Scanning electron

Question 33

Ultrastructures of bacterial and archaeal cells, such as the cytoskeleton and inclusion bodies, are usually observed with which type of microscopy?

Answer 33

Electron cryotomography microscopy

Question 34

Which of the following microscopic methods has the greatest magnification and lowest resolution?

Answer 34

Scanning probe microscopy

Question 35

Which of the following microscopic methods can be used to study the interaction of proteins and to visualize membrane proteins?

Answer 35

Atomic force microscopy