Deck 2: Microscopy

Question 1

A light microscope with an objective lens numerical aperture of 0.65 is capable of allowing two objects 400 nm apart to be distinguished when using light with a wavelength of 420 nm.

Answer 1

True

Question 2

Confocal microscopes exhibit improved contrast and resolution by

A)illumination of a large area of the specimen.
B)blocking out stray light with an aperture located above the objective lens.
C)use of light at longer wavelengths.
D)use of ultraviolet light to illuminate the specimen.

Answer 2

B

Question 3

Immersion oil can be used to increase the resolution achieved with some microscope lenses because it increases the __________ between the specimen and the objective lens.

A)optical density
B)refractive index
C)optical density and refractive index
D)neither optical density nor refractive index

Answer 3

B

Question 4

The useful magnification of a light microscope is limited by the ___________ of the light source being utilized.

Question 5

Confocal microscopes,in combination with specialized computer software,can be used to create three-dimensional images of cell structures.

Question 6

A microscope that exposes specimens to ultraviolet,violet,or blue light and forms an image with the light emitted at a different wavelength is called a __________ microscope.

A)phase-contrast
B)dark-field
C)scanning electron
D)fluorescence

Question 7

The special dyes used in fluorescence microscopy that absorb light at one wavelength and emit light at a different wavelength are called __________.

Question 8

A substage condenser is used to focus light onto the specimen,which increases the resolution of a light microscope.

Question 9

Light rays are refracted (bent)when they cross the interface between materials with different refractive indices.

A)differential interference contrast
B)dark field
C)phase-contrast
D)confocal

Question 10

The __________ is the point at which a lens focuses parallel beams of light.

Question 11

A 30 $\times$ objective and a 20 $\times$ ocular produce a total magnification of

A)230 $\times$ .
B)320 $\times$ .
C)50 $\times$ .
D)600 $\times$ .

Question 12

Light rays are refracted (bent)when they cross the interface between materials with different refractive indices.

Question 13

A 45 $\times$ objective and a 10 $\times$ ocular produce a total magnification of

A)900 $\times$ .
B)55 $\times$ .
C)450 $\times$ .
D)145 $\times$ .

Question 14

Immersion oil is used to prevent a specimen from drying out.

Question 15

Immersion oil increases the amount of light passing through a specimen and entering the objective lens.

Question 16

It is possible to build a light microscope capable of 10,000 $\times$ magnification,but the image would not be sharp because resolution is independent of magnification.

Question 17

Resolution decreases when the wavelength of the illuminating light decreases.

Question 18

The __________ is the distance between the center of a lens and the point at which it focuses parallel beams of light.

Question 19

The __________ is the distance between the specimen and the objective lens when the specimen is in focus.

Question 20

In order to view a specimen with a total magnification of 400 $\times$ ,a __________ objective must be used if the ocular is 10 $\times$ .

Question 21

If the decolorizer is left on too long in the Gram-staining procedure,gram-positive organisms will be stained __________ and gram-negative organisms will be stained __________.

A)purple; blue
B)purple; colorless
C)purple; pink
D)pink; pink

Question 22

Prior to staining,smears of microorganisms are heat-fixed in order to

A)allow eventual visualization of internal structures.
B)ensure removal of dust particles from the slide surface.
C)attach it firmly to the slide.
D)create small pores in cells that facilitates binding of stain to cell structures.

Question 23

Negative staining facilitates the visualization of bacterial capsules which are intensely stained by the procedure.

Question 24

Basic dyes such as methylene blue bind to cellular molecules that are

A)hydrophobic.
B)negatively charged.
C)positively charged.
D)aromatic.

Question 25

The instrument that produces a bright image of the specimen against a dark background is called a (n)__________ microscope.

A)phase-contrast
B)electron
C)bright-field
D)dark-field

Question 26

In the Gram-staining procedure,the decolorizer is

A)iodine.
B)safranin.
C)crystal violet.
D)ethanol or acetone.

Question 27

If the decolorizer is not left on long enough in the Gram-staining procedure,gram-positive organisms will be stained __________ and gram-negative organisms will be stained __________.

A)purple; purple
B)purple; colorless
C)purple; pink
D)pink; pink

Question 28

The Schaeffer-Fulton procedure is used to stain

A)flagella.
B)fat deposits.
C)endospores.
D)DNA of chromosomes.

Question 29

In the Gram-staining procedure,the primary stain is

A)iodine.
B)safranin.
C)crystal violet.
D)alcohol.
ASM

Question 30

Gram staining divides bacterial species into roughly two equal groups.

Question 31

In the Gram-staining procedure,the mordant is

A)iodine.
B)safranin.
C)crystal violet.
D)alcohol.

Question 32

After the primary stain has been added but before the decolorizer has been used,gram-positive organisms are stained __________ and gram-negative organisms are stained __________.

A)purple; purple
B)purple; colorless
C)purple; pink
D)pink; pink

Question 33

After the secondary stain has been added,gram-positive organisms are stained __________ and gram-negative organisms are stained __________.

A)purple; purple
B)purple; colorless
C)purple; pink
D)pink; pink

Question 34

If the objective lenses of a microscope can be changed without losing focus on the specimen,they are said to be

A)equifocal.
B)totifocal.
C)parfocal.
D)optifocal.

Question 35

In the Gram-staining procedure,the counterstain is

A)iodine.
B)safranin.
C)crystal violet.
D)alcohol.

Question 36

Acid-fast organisms such as Mycobacterium tuberculosis contain __________ constructed from mycolic acids in their cell walls.

A)proteins
B)carbohydrates
C)lipids
D)peptidoglycan

Question 37

An instrument that magnifies slight differences in the refractive index of cell structures is called a (n)__________ microscope.

A)phase-contrast
B)electron
C)fluorescence
D)densitometric

Question 38

Which of the following is considered to be a differential staining procedure?

A)Gram stain.
B)Acid-fast stain.
C)both Gram stain and Acid-fast stain.
D)Leifson's flagella stain.

Question 39

After the decolorizer has been added,gram-positive organisms are stained __________ and gram-negative organisms are stained __________.

A)purple; purple
B)purple; colorless
C)purple; pink
D)pink; pink

Question 40

As the magnification of a series of objective lenses increases,the working distance

A)increases.
B)decreases.
C)stays the same.
D)cannot be predicted.

Question 41

A procedure that divides organisms into two or more groups depending on their individual reactions to the same staining procedure is referred to as __________ staining.

Question 42

The Gram-staining procedure is an example of:

A)simple staining.
B)negative staining.
C)differential staining.
D)fluorescent staining.

Question 43

Small internal cell structures are best visualized with a

A)light microscope.
B)dark-field microscope.
C)transmission electron microscope.
D)flagellar microscope.

Question 44

The designer of the first transmission electron microscope,_________________,was awarded the 1986 Nobel Prize in physics.

Question 45

It was possible to view viruses only after the invention of the electron microscope because they are too small to be seen with a light microscope.

Question 46

Negative staining with India ink can be used to reveal the presence of capsules that surround bacterial cells.

Question 47

The _________________ microscope is capable of atomic resolution of specimens,even when they are immersed in water.

Question 48

Mordants increase the binding between a stain and specimen.

Question 49

The Gram-staining procedure is widely used because it allows rapid identification of a microorganism with little additional testing.

Question 50

In transmission electron microscopy,spreading a specimen out in a thin film with uranyl acetate,which does not penetrate the specimen,is called

A)freeze-etching.
B)simple staining.
C)shadow staining.
D)negative staining.

Question 51

Because transmission electron microscopy uses electrons rather than light,it is not necessary to stain biological specimens before observing them.

Question 52

__________ breaks frozen specimens along lines of greatest weakness,often down the middle of lipid bilayer membranes so that they may be observed by transmission electron microscopy.

Question 53

Scanning electron microscopy is most often used to reveal

A)surface structures.
B)internal structures.
C)both surface and internal structures simultaneously.
D)either surface or internal structures,but not simultaneously.

Question 54

Thin films of bacteria that have been air-dried onto a glass microscope slide are called __________.

Question 55

An electron microscope uses __________ lenses to focus beams of electrons onto a specimen.

Question 56

Scanning electron microscopes bombard specimens with a stream of electrons; however,the specimen image is produce by electrons that are derived from atoms of the specimen itself rather than by the electrons used to bombard the specimen.

Question 57

The procedure in which a single stain is used to visualize microorganisms is called __________ staining.

Question 58

In order to stain flagella so that they may be readily observed by light microscopy,it is usually necessary to increase their thickness.

Question 59

__________ is the process by which internal and external structures of cells and organisms are preserved and maintained in position.

Question 60

Regions of a specimen with higher electron density scatter ___________ electrons and,therefore,appear __________ in the image projected onto the screen of a transmission electron microscope.

A)more; lighter
B)more; darker
C)fewer; darker
D)fewer; lighter

Question 61

Atomic force microscopes use a scanning probe that maintains a fixed distance from the surface of the specimen.It is useful for specimens that

A)do not conduct electricity well.
B)have extremely uneven surfaces.
C)both do not conduct electricity well and have extremely uneven surfaces are correct.
D)neither do not conduct electricity well nor have extremely uneven surfaces is correct.

Question 62

Scanning tunneling electron microscopes create a three-dimensional image of specimens at atomic level resolution.