Ch2 Test Bank Docx Microscopy

Prescott's Microbiology, 11e (Willey)

Chapter 2 Microscopy

1) The ________ is the point at which a lens focuses parallel beams of light.

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

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

4) 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

5) A 30× objective and a 20× ocular produce a total magnification of ________.

A) 230×

B) 320×

C) 50×

D) 600×

6) A 45× objective and a 10× ocular produce a total magnification of ________.

A) 900×

B) 55×

C) 450×

D) 145×

7) 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

8) 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

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

10) The ________ is the distance between the specimen and the objective lens when the specimen is in focus.

11) The useful magnification of a light microscope is limited by the ________ of the light source being utilized.

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

13) In order to view a specimen with a total magnification of 400×, a ________ objective must be used if the ocular is 10×.

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

15) 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.

16) Resolution improves when the wavelength of the illuminating light decreases.

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

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

19) Immersion oil increases the amount of light entering the objective lens.

20) 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

21) 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

22) 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

23) 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

24) Prior to staining, smears of microorganisms must be heat-fixed in order to ________.

A) allow eventual visualization of internal structures

B) ensure removal of dust particles from the slide surface

C) attach them firmly to the slide

D) create small pores in cells that facilitates binding of stain to cell structures

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

A) proteins

B) carbohydrates

C) lipids

D) peptidoglycan

26) In the Gram-staining procedure, the primary stain is ________.

A) iodine

B) safranin

C) crystal violet

D) alcohol

27) In the Gram-staining procedure, the decolorizer is ________.

A) iodine

B) safranin

C) crystal violet

D) ethanol or acetone

28) In the Gram-staining procedure, the counterstain is ________.

A) iodine

B) safranin

C) crystal violet

D) alcohol

29) In the Gram-staining procedure, the mordant is ________.

A) iodine

B) safranin

C) crystal violet

D) alcohol

30) 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

31) 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

32) After the mordant 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

33) 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

34) 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

35) 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

36) Basic dyes such as methylene blue bind to cellular molecules that are ________.

A) hydrophobic

B) negatively charged

C) positively charged

D) aromatic

37) Gram staining divides bacterial species into two groups based on differences in cell wall structure.

38) Negative staining facilitates the visualization of bacterial capsules that are intensely stained by the procedure.

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

40) Mordants increase the binding between a stain and specimen.

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

42) The procedure in which a single stain is used to visualize microorganisms is called ________ staining.

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

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

45) 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.

46) The Gram-staining procedure is an example of ________.

A) simple staining

B) negative staining

C) differential staining

D) fluorescent staining

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

48) 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

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

50) 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.

51) 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.

52) An electron microscope uses ________ lenses to focus beams of electrons onto a specimen.

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

54) Small internal cell structures are best visualized with a ________.

A) light microscope

B) dark-field microscope

C) transmission electron microscope

D) flagellar microscope

55) 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

56) ________ 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.

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

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

59) 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

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

61) If immersion oil was replaced with water, what would happen?

A) The refractive index would increase, improving resolution.

B) The refractive index of water would be greater than air but less than oil, improving resolution less than oil.

C) The refractive index of water would be less than that of air, decreasing resolution.

D) There would be no difference.

62) As the resolution of a microscope system improves, the size of the smallest object that can be seen clearly ________.

A) is larger.

B) is smaller.

C) is not affected.

63) If you forgot to heat fix a smear before doing a Gram stain, which of the following might occur?

A) The stains would not adhere to the bacteria.

B) The smear may not adhere to the slide.

C) The decolorization step of the Gram stain would not work properly.

D) Gram-positive and Gram-negative bacteria would both stain purple.

64) A specimen has been prepared for viewing with a transmission electron microscope, using uranyl acetate as a negative stain. The area stained by the uranyl acetate will be ________ electron dense compared to specimen itself.

A) more

B) less

C) equally

65) If you forgot the decolorization step while performing a Gram stain, which outcome would you expect?

A) Gram-positive bacteria would stain pink

B) Gram-negative bacteria would stain purple

C) Gram-negative bacteria would be unstained

D) Gram-positive bacteria would be unstained

66) If you forgot to apply the safranin counterstain while performing a Gram stain, which outcome would you expect?

A) Gram-positive bacteria would stain pink.

B) Gram-negative bacteria would stain purple.

C) Gram-negative and Gram-positive bacteria would be unstained.

D) Gram-negative bacteria would be unstained.

67) Which type of microscopy would be preferred for creating a three-dimensional view of the distribution and arrangement of flagella on a bacterial cell surface?

A) Bright-field microscopy

B) Scanning electron microscopy

C) Fluorescence microscopy

D) Transmission electron microscopy

68) Which type of microscopy would be preferred for showing fine internal detail of the eukaryotic organelles?

A) Bright-field microscopy

B) Scanning electron microscopy

C) Fluorescence microscopy

D) Transmission electron microscopy

69) You are researching the structure of a transmembrane protein. Which type of microscopy would provide you the best view of this protein?

A) Bright field microscopy

B) Scanning electron microscopy

C) Transmission electron microscopy

D) Atomic force microscopy

70) If the strength of a lens is the reciprocal of its focal length (1/f ), which of the following lenses will have the greatest strength?

A) A lens with a focal length of 1cm

B) A lens with a focal length of 100 mm

C) A lens with a focal length of 0.1 mm

D) A lens with a focal length of 1 mm

71) Glass has a greater refractive index than air.  This means that ________.

A) the velocity of the light is slowed when it passes through the glass from the air

B) the velocity of the light accelerates when it passes through the glass from the air

C) the velocity of the light is slowed when it passes through the air from the glass

D) the light is bent away from the normal when passing through glass from air