Chapter 2 BIOL 3702

Match the electron microscope with the correct description. 1. transmission 2. scanning a. Form image from radiation that has passed through specimen. b. Forms image from electrons released from atoms on an object's surface.

1. a. Form image from radiation that has passed through specimen. 2. b. Forms image from electrons released from atoms on an object's surface.

Match the cellular effects with the correct fixation technique. 1. heat fixation 2. chemical fixation a. inactivates proteins and destroys proteins of sub cellular structures b. inactivates proteins but protects fine cellular structure

1. a. inactivates proteins and destroys proteins of sub cellular structures 2. b. inactivates proteins but protects fine cellular structure

Match negative staining and shadowing in TEM with the correct description. 1. negative staining 2. shadowing a. specimen is spread out in a thin film with either phosphotungstic acid or uranyl acetate b. specimen is coated with a thin film of platinum or other heavy metal

1. a. specimen is spread out in a thin film with either phosphotungstic acid or uranyl acetate 2. b. specimen is coated with a thin film of platinum or other heavy metal

Match the type of fixation with the types of microbes routinely observed using the fixation method. 1. heat fixation 2. chemical fixation a. used to observe bacteria and archaea b. used to observe protists

1. a. used to observe bacteria and archaea 2. b. used to observe protists

Match negative staining and shadowing in TEM with the correct description. 1. negative staining 2. shadowing a. used to study bacterial gas vacuoles b. used to study bacterial flagella and DNA

1. a. used to study bacterial gas vacuoles 2. b. used to study bacterial flagella and DNA

Match the microscope with the item at the the limit of its resolution. 1. light microscope 2. electron microscope 3. scanning tunneling microscope a. amino acid b. Mycoplasma bacteria c. hydrogen atom

1. b. Mycoplasma bacteria 2. a. amino acid 3. c. hydrogen acid

Match the Gram stain step with the state of bacteria after the step. 1. crystal violet 2. iodine 3. alcohol 4. safranin a. Gramm-positive cells remain purple, and gram-negative cells appear red b. gram-positive cells remain purple, and gram-negative cells become colorless c. cells stain purple d. cells remain purple

1. c. cells stain purple 2. d. cells remain purple 3. b. gram-positive cells remain purple, and gram-negative cells become colorless 4. a. Gramm-positive cells remain purple, and gram-negative cells appear red

Correctly list the steps of the Gram stain

1. crystal violet, primary stain 2. iodine, mordant 3. acetone-alcohol, decolorizer 4. safranin, counterstain

In this image of a gram-stained mixture of cells, the gram-negative cell is indicated by the letter B (blue cells) A (pink cells)

A (pink cells)

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

Gram

A bright-field microscope forms a. a dark image on a lighter background b. a black and white image on a bright background c. a lighter image on a dark background

a. a dark image on a lighter background

Which type of dye stains best under low pH conditions? a. acidic b. basic

a. acidic

In negative staining of TEM specimens, the _____ appears dark. a. background b. cell c. nucleus d. cell membranes

a. background

What usually happens to cells stained for viewing under a bright-field microscope? a. cells are killed b. cells remain alive

a. cells are killed

Which of the following must be done to prepare a specimen for SEM? a. dehydrated b. stained c. dried d. metal coated e. fixed

a. dehydrated c. dried d. metal coated e. fixed

Unlike light-based microscopes, ______ microscopes can distinguish points closer than 0.5 nm. a. electron b. dark-field c. confocal d. fluorescent

a. electron

TEM specimens are a. fixed in a plastic-like matrix and cut into thin slices b. chemically treated with silver nitrate prior to exposure to x-rays c. mounted on a metal (typically aluminum) bunt and coated with a metal such as gold d. placed between two thin panes of glass and sealed

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

Which type of microscope forms an image by capturing light emitted by the specimen after it has been excited by ultraviolet light? a. fluorescence b. phase-contrast c. scanning electron d. differential interference

a. fluorescence

In fluorescence microscopy, the _____ absorbs light energy from the excitation light and emits colored light. a. fluorochrome b. glass slide c. cover slip d. antibody

a. fluorochrome

Which process has the advantage of minimizing the presence of artifacts? a. freeze-etching b. negative staining c. shadowing

a. freeze-etching

Which three of the following are associated with light microscopes? a. glass lenses b. electron gun c. eye d. lamp e. viewing screen

a. glass lenses c. eye d. lamp

The staining process to prepare specimens for the TEM ______ the contrast in the material. a. increases b. decreases

a. increases

What type of light source is used by a confocal microscope? a. laser b. fluorescent c. ultraviolet d. incandescent

a. laser

Which of the following are limitations of the light microscope? a. light microscopes are not able to show detailed internal cellular structure b. light microscopes have a resolution limit of 0.2 micrometers c. light microscopes are not able to show the shape and arrangement of bacteria d. light microscopes have a resolution limit of 2 micrometers

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

What is used to coat a specimen in the shadowing process for a TEM? a. platinum b. phosphotungstic acid c. uranyl acetate d. plastic resin

a. platinum

Which three chemicals are used in staining specimens for the TEM? a. uranyl acetate b. osmium tetroxide c. crystal violet d. malachite green e. lead citrate

a. uranyl acetate b. osmium tetroxide e. lead citrate

Which three of the following are associated with electron microscopes? a. viewing screen b. electromagnets c. glass lenses d. light rays e. electron beams

a. viewing screen b. electromagnets e. electron beams

The ____ stain was developed by ____ in _____. a. simple; Frances Jalock; 1772 b. Gram; Christian Gram; 1884 c. acidic fast; John Tubercus; 1902

b. Gram; Christian Gram; 1884

What is the network, usually made of polysaccharide, that surrounds many bacteria and some fungi? a. peptidoglycan b. capsule c. pili d. chitin

b. capsule

Which type of microscope projects a brightly illuminated image on a dark background? a. phase-contrast b. dark-field c. bright-field d. differential interference contrast

b. dark-field

Which type of microscope cannot create a clear image of a living specimen? a. bright-field b. electron c. differential interference contrast d. phase-contrast e. dark-field

b. electron

Which process is used to observe organelles within cells using a TEM? a. shadowing b. freeze-etching c. negative staining

b. freeze-etching

Because the cells are ______ quickly, freeze-etching minimizes the presence of artifacts. a. stained b. frozen c. chemically fixed d. dehydrated

b. frozen

What unique biomolecule is found in acid-fast bacterial cell walls that prevents dyes from binding readily to these cells? a. peptidoglycan b. mycolic acid c. proteins d. cholesterol

b. mycolic acid

Capsules are networks composed mostly of _______ that surround many bacteria. a. lipid b. polysaccharide c. protein d. nucleic acid

b. polysaccharide

Which term refers to the ability of an objective lens to separate or distinguish between small objects that are close together? a. magnification b. resolution c. refraction d. parfocality

b. resolution

Which microscope has the greatest resolving power? a. electron b. scanning tunneling c. light

b. scanning tunneling

Which microscope has the greatest resolving power? a. electron microscope b. scanning tunneling microscope d. light microscope

b. scanning tunneling microscope

Visualization of the capsule on a bacterial cell requires a differential stain because ______. a. the mycolic acid in capsules resist staining by dyes b. stains and dyes don't bind to polysaccharides c. they are found primarily on Gram-positive bacteria d. capsules are too thin to be seen in a light microscope

b. stains and dyes don't bind to polysaccharides

Visualization of the capsule on a bacterial cell requires a differential stain because ______. a. they are found primarily on Gram-positive bacteria b. stains and dyes don't bind to polysaccharides c. capsules are too thin to be seen in a light microscope d. the mycolic acid in capsules resists staining by dyes

b. stains and dyes don't bind to polysaccharides

Which part of the specimen scatters more electrons and therefore appears darker? a. the least dense region b. the most dense region

b. the most dense region

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

b. transmission

What type of cells are difficult to view in a bright-field microscope? a. pigmented b. unpigmented

b. unpigmented

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

bright, light, brightfieqld, or bright-field

Which statement best describes specimen preparation for TEM? a. The specimen is suspended in a semi-viscous medium within a depression-slide for viewing (often a stain is added). b. The specimen is pre-stained with fluorochromatic molecules then fixed onto a slide. c. The specimen is embedded in a matrix and cut into extremely thin slices.

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

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

c. cells are attached to slide d. cells are killed

What compound is used to stain a specimen that will emit a different wavelength of light than it absorbs? a. india ink b. crystal violet c. fluorochromes d. heavy metals

c. fluorochromes

Basic and acidic dyes bind cells by what type of bond? a. covalent b. hydrogen c. ionic

c. ionic

In this image, cells are illustrated as they would appear after each step of the Gram stain procedure. All cells appear the same color after the first step because a. the staining procedure has been done incorrectly b. the first dye, safranin, stains all cells purple c. the first dye, crystal violet, stains all cells purple d. the counterstain has not yet been applied

c. the first dye, crystal violet, stains all cells purple

Electron microscopes have a practical resolution roughly ______ times better than the light microscope. a. 100 b. 1 c. 10 d. 1000

d. 1000

In a confocal microscope, what removes stray light from parts of the specimen that lie above and below the plane of focus? a. coarse adjustment b. objective c. ocular d. aperture

d. aperture

Which type of staining distinguishes organisms based on their staining properties? a. special b. negative c. simple d. differential

d. differential

In which type of staining is the background stained but not the cells? a. simple b. differential c. special d. negative

d. negative

The Gram stain is an example of ______ staining, distinguishing Gram negative from Gram positive bacteria.

differential

TEM specimens are coated with a thin film of platinum or other heavy metal in the _______ process. a. preparation b. coating c. fixation d. staining e. shadowing

e. shadowing

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

An image formed by capturing light emitted by the specimen after it has been excited by ultraviolet light is produced from a ______ microscope.

fluorescence

Dried SEM specimens must be coated with a thin layer of ______ to prevent the buildup of an electrical charge on the surface.

metal

Acid-fast organisms have lipids constructed of _____ acid in their cell walls.

mycolic

India ink and nigrosin are both _____ stains which stain the background and not the cell.

negative

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

negative

In the freeze-etching process, cells are rapidly frozen using liquid ______ which causes the cells to become brittle and break, exposing internal membranes.

nitrogen

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

objective

On a microscope, the lens closest to the specimen is the _____ lens.

objective

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

resolution

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

simple

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

wavelength