Chapter 2: Microscopy

TEM specimens are

Fixed in a plastic-like matrix and cut into thin slices.

Visualization of the flagellum requires a differential stain because

Flagella are too thin to be seen in a light microscope

In this photo, bacterial cells have been treated with a differential stain to highlight the structure called the _____

Flagellum

In fluorescence microscopy, the _____ absorbs light energy from the excitation light and emits colored light.

Fluorochrome

What compound is used to stain a specimen that will emit a different wavelength of light than it absorbs?

Fluorochromes

This image of a bacterial cell is a transmission electron micrograph that was prepared by

Freeze etching

The most widely used differential staining procedure in microbiology is the _______ stain.

Gram strain

The ____ stain was developed by ____ in _____.

Gram; Christian Gram; 1884

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 ________

Heat fixing

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 microscope pictured here uses ______ to visualize specimens.

Electrons

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

Which three of the following are associated with light microscopes? Eye Electron gun Lamp Viewing screen Glass lenses

Eye Glass lenses Lamp

Capsules are networks composed mostly of _______ that surround many bacteria

Polysaccharide

The _______ index is a measure of how much a substance slows the velocity of light.

Refractive

Which term describes the measure of how much a substance slows the velocity of light?

Refractive index

The ability to separate or distinguish between small objects using a microscope is called

Resolution

Forms image from electrons released from atoms on an object's surface.

Scanning

Which microscope allows a view of the atoms on the surface of a solid?

Scanning tunneling microscope

TEM specimens are coated with a thin film of platinum or other heavy metal in the _______ process.

Shadowing

Known for ease of use, _______ staining only uses one dye.

Simple

This image of bacterial cells has been prepared with crystal violet to determine the size, shape, and arrangement of the cells. Crystal violet is considered a(n) _____ stain.

Simple

The microscope component identified by the letter B is the ___

Stage

The microscope component identified by the letter E is the _____.

Stage adjustment knob

Visualization of the capsule on a bacterial cell requires a differential stain because ______.

Stains and dyes don't bind to polysaccharides

Which three of the following are associated with electron microscopes? Viewing screen Light rays Electron beams Glass lenses Electromagnets

Viewing screen Electron beams Electromagnets

The maximum resolution of a light microscope is dependent on the shortest _______ of light able to be seen.

Wavelength

Immersion oil is useful in increasing resolution because

it has the same refractive index as glass

A dark image is formed on a brighter background when using a ______ field microscope.

light

In this image of a gram-stained mixture of cells, the gram-negative cell is indicated by the letter

A

In a confocal microscope, what removes stray light from parts of the specimen that lie above and below the plane of focus?

Aperture

In this image of a gram-stained mixture of cells, the gram-positive cell is indicated by the letter _____

B

In negative staining of TEM specimens, the _____ appears dark.

Background

In this image, bacterial cells have been treated with a differential stain to highlight the structure called the _____.

Capsule

What is the network, usually made of polysaccharide, that surrounds many bacteria and some fungi?

Capsule

This image shows E. coli stained with crystal violet. Which three of the following can be correctly interpreted from this image? cell size cell wall structure cell arrangement presence of flagella presence of a capsule cell shape

Cell shape Cell size Cell arrangement

What usually happens to cells stained for viewing under a bright-field microscope?

Cells are killed

When preparing a specimen for microscopy, which two things generally occur during the fixation step? Cells are killed Cells are attached to slide Cells are distorted Cells are stained

Cells are killed Cells are attached to slide

The microscope component identified by the letter D is the _____

Coarse focus knob

This image was obtained through the use of __ microscopy.

Dark field

Which type of staining distinguishes organisms based on their staining properties?

Differential

As illustrated in the image, the function of immersion oil in microscopy is to

Direct more light rays to the objective lens

In which process are specimens plunged into an extremely cold liquid?

Electron cryotomography

What type of light source is used by a confocal microscope?

Laser

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 the shape and arrangement of bacteria. Light microscopes are not able to show detailed internal cellular structure. Light microscopes have a resolution limit of 2 micrometers.

Light microscopes have a resolution limit of 0.2 micrometers. Light microscopes are not able to show detailed internal cellular structure.

The microscope component identified by the letter F is the ____

Light source

TEM specimens are spread out in a thin film with either phosphotungstic acid or uranyl acetate in _______ staining.

Negative staining

This image of a bacterial virus is a transmission electron micrograph that was prepared by

Negative staining

In a compound light microscope, the ________ lens forms the magnified image that is further enlarged by one or more additional lenses.

Objective

The microscope component identified by the letter C is the _____

Objective lens

The microscope component identified by the letter A is the _____.

Ocular 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

Which part of the specimen scatters more electrons and therefore appears darker?

The most dense region

Which statement best describes specimen preparation for TEM?

The specimen is embedded in a matrix and cut into extremely thin slices.

Specimens prepared for TEM must be cut to extremely ______ slices because electron beams are easily absorbed and scattered by solid matter.

Thin

Which type of electron microscope forms images from radiation that has passed through a specimen?

Transmission

The scanning _______microscope can produce images magnified 100 million times and can even resolve individual atoms on a surface of a solid.

Tunneling

What type of cells are difficult to view in a bright-field microscope?

Unpigmented