micro ch 2
What compound is used to stain a specimen that will emit a different wavelength of light than it absorbs?
Fluorochromes
Which term describes the specific location where light rays pass through a lens and gain maximal intensity?
Focal point
The ____ stain was developed by ____ in _____.
Gram; Christian Gram; 1884
Which term describes the measure of how much a substance slows the velocity of light?
Refractive index
Which microscope has the greatest resolving power?
Scanning tunneling microscope
What type of staining involves only one dye?
Simple
The rapid freezing procedure of ________ has provided exciting insights into the structure and function of cells and viruses.
electron cryotomography
This is a picture of a/an ______.
electron microscope
The transmission electron microscope produces an image when the specimen scatters some _______, but those that pass through are used to form an enlarged image of the specimen on a fluorescent screen.
electrons
In preparation for staining, the process by which internal and external structures of specimens are preserved and attached in position on a slide is called
fixation
Visualization of the flagellum requires a differential stain because
flagella are too thin to be seen in a light microscope
An image formed by capturing light emitted by the specimen after it has been excited by ultraviolet light is produced from a _______ microscope.
fluorescent
In fluorescence microscopy, the _____ absorbs light energy from the excitation light and emits colored light.
fluorochrome
Immersion oil is useful in increasing resolution because
it has the same refractive index as glass
The human eye can minimally detect something that is about 0.2 _______ in diameter.
mm
TEM specimens are spread out in a thin film with either phosphotungstic acid or uranyl acetate in ______ staining.
negative
This image of a bacterial virus is a transmission electron micrograph that was prepared by
negative staining
Light entering a prism is bent toward the ______(lines perpendicular to the surface of the prism).
normal
On a microscope, the lens closest to the specimen is the ________ lens.
objective
In a compound light microscope, the ________ forms the magnified image that is further enlarged by one or more additional lenses.
objective lens
The _____ microscope exploits differences in light intensity to provide contrast, thus allowing the viewer to see a clearer, more detailed image of the specimen.
phase-contrast
Capsules are networks composed mostly of _______ that surround many bacteria.
polysaccharide
Green fluorescent gene encodes a _______ that naturally fluoresces green when exposed to light of a certain wavelength.
protein
Which term refers to the ability of an objective lens to separate or distinguish between small objects that are close together?
resolution
Visualization of the capsule on a bacterial cell requires a differential stain because
stains and dyes don't bind to polysaccharides
Focal length is measured as the distance from
the center of the lens to the focal point
As light enters the glass (yellow arrows), it is bent ____ the first normal, and when light leaves the glass and returns to air, it is bent ____ from the second normal.
toward, away
The maximum resolution of a light microscope is dependent on the shortest ______ of light able to be seen.
wavelength
How is lens strength related to focal length?
A lens with short focal length magnifies more than a lens with a longer focal length
When preparing a specimen for microscopy, which two things generally occur during the fixation step?
Cells are killed Cells are attached to slide
Which type of microscope projects a brightly illuminated image on a dark background?
Dark-field
Which type of staining distinguishes organisms based on their staining properties?
Differential
Which three of the following are associated with electron microscopes?
Electromagnets Electron beams Viewing screen
In which process are specimens plunged into an extremely cold liquid?
Electron cryotomography
Which three of the following are associated with light microscopes?
Lamp Eye Glass lenses
Which type of lens magnifies an object more?
Lens with a short focal length
Which of the following are limitations of the light microscope?
Light microscopes have a resolution limit of 0.2 micrometers Light microscopes are not able to show detailed internal cellular structure
Match the microscope with the item at the limit of its resolution: Light microscope Electron microscope Scanning tunneling microscope
Mycoplasma bacteria Amino acid Hydrogen atom
Which statement best describes specimen preparation for TEM?
The specimen is embedded in a matrix and cut into extremely thin slices.
A bright-field microscope forms
a dark image on a lighter background
Match the electron microscope with the correct description: a) Transmission b) Scanning
a) Form image from radiation that has passed through specimen. b) Forms image from electrons released from atoms on an object's surface.
In negative staining of TEM specimens, the _____ appears dark.
background
Prisms _____ light passing through them.
bend
This image shows E. coli stained with crystal violet. Which three of the following can be correctly interpreted from this image?
cell size cell shape cell arrangement
This image was obtained through the use of __ microscopy.
dark-field
The Gram stain is an example of ______ staining, distinguishing Gram negative from Gram positive bacteria.
differential
