Flashcards in MicroBio Q's TF CH 2 Deck (35):
The degree to which a substance bends light is known as the
When light passes through air to a medium with a great refractive index (i.e., glass), what happens to the light?
The velocity of light decreases and it bends toward the normal
Which of the following best describes how a lens works?
Light rays strike the lens and converge onto a focal point
A microscope that can remain in focus when the objective lens is changed is described as
The total magnification of a bright field microscope with a 10X eyepiece on the high power (100X) objective would be
The ability of a lens to separate or distinguish between small objects that are close together is called
Which of the following changes would increase the resolution of a specimen observed through a lens?
(A) Decrease the wavelength of light; (B) Increase the refractive index; and ? Increase the numerical aperature
Immersion oil is used when observing specimens under high power because
It decreases the refractive index; this increases the numerical aperture
The distance between the front surface of the lens and the surface of the cover glass or specimen is called the
The best resolution achieved by bright field microscopes is approximately
A bright field microscope is best for observing which of the following types of specimens?
Fixed, stained bacteria
A dark-field microscope is best for observing which of the following types of specimens?
Unpigmented living cells
Which of the following microscopes are acceptable for viewing live specimens?
(A) Dark-field microscope; (B) Phase-contrast microscope; and ? Differential interference contrast microscope
The _________________ microscope utilizes differences in refractive index and cell density into detectable variations in light intensity.
Which type of microscope would be best for observing microbial motility and observing endospores?
The ____________________ microscope allows microbiologists to view three-dimensional live specimens in bright color.
Differential interference contrast (DIC)
Fluorescence microscopy takes advantage of which of the following characteristics of objects and light?
Molecules of objects absorb radiant energy and release this trapped energy as light
Which type of microscopy exposes a specimen to low wavelength light and forms an image of the object with resulting fluorescent light?
Fluorescence microscopy is most useful in which of the following?
(A) Observing bacteria tagged with fluorescently labeled antibodies; (B) Visualizing organizms that fluorescence naturally; and ? Observing the localization of specific proteins within a cell
The best type of microscopy for observing layered specimens (i.e., biofilms on medical devices) is
Fixing cells is advantageous in that it
Toughens cell structures so that they remain during staining
Basic dyes work by
Binding to negatively charged molecules on the surface of cells
Failure to complete the decolorization step in the Gram stain will result in
All cells will appear purple, or stained with crystal violet
Iodine, the mordant in the Gram staining procedure, is used to
Help bind the crystal violet to the target molecule
Acid-fast staining is used to stain organisms with
Lipids composed of branched-chain hydroxy fatty acids in their cell walls
____________ is required to drive dye into cells to stain for endospores.
Nigrosin, a dye used for negative staining, is used to observe
The electron microscope is capable of observing organisms at a higher resolution than the bright-field microscope because
The wavelength of the illuminating beam is much shorter than that of visible light
Magnification with an electron microscope can be as great as
Which of the following steps is required to prepare a specimen using transmission electron microscopy (TEM)?
(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
___________________ microscopy can be used to study virus morphology, the structure of flagella, and DNA.
Which type of microscopy works by producing images from electrons released from atoms at an object's surface?
Ultrastructures of bacterial and archaeal cells, such as the cytoskeleton and inclusion bodies, are usually observed with which type of microscopy?
Electron cryotomography microscopy
Which of the following microscopic methods has the greatest magnification and lowest resolution?
Scanning probe microscopy