Chapter 2 Questions

The lens shape that spreads light waves to magnify an object is a. a parabola. b. a square. c. a circle. d. a triangle.

a. a parabola.

A physician informs you that the pathogen that has been causing your infection is a bacillus. When you look at a magnified image of cells from the infection you see cells of many different shapes and sizes. What shape is the pathogen? a. a rod b. a sphere c. a spiral d. there is no way to determine the shape.

a. a rod

To clearly observe a single bacterium's subcellular structure, the best tool is a. a transmission electron microscope. b. the unaided human eye. c. X-ray crystallography. d. a light microscope.

a. a transmission electron microscope.

Which type of microscopy is particularly useful to study the surfaces of live bacteria? a. atomic force b. SEM c. TEM d. dark-field e. bright-field

a. atomic force

Which technique does not rely on a beam of electrons or light interacting with the specimen? a. atomic force microscopy b. bright-field microscopy c. cyro-electron tomography d. interference microscopy

a. atomic force microscopy

Green fluorescent protein can be fused to other proteins to visualize them via fluorescence microscopy. If the emitted light is green, what color light may have been used as the excitation wavelength? a. blue b. orange c. red d. yellow

a. blue

In ________________, because the frozen sample remains hydrated, the biological molecules retain the same conformation as in solution. a. cryo-EM b. TEM c. SEM d. fluorescence microscopy e. laser confocal microscopy

a. cryo-EM

Eagles can see smaller objects than humans can because a. eagle eyes have lower resolution. b. eagle eyes have higher resolution. c. eagles have compound eyes. d. eagle photoreceptor cells are not as tightly packed in their retina as human photoreceptor cells.

a. eagle eyes have lower resolution.

In fluorescence microscopy, incident light is absorbed by the specimen and re-emitted at a _______________ energy, resulting in a __________________. a. lower; longer wavelength b. lower; shorter wavelength c. higher; longer wavelength d. higher; shorter wavelength e. higher; higher contrast

a. lower; longer wavelength

One __________ is one-thousandth of a millimeter. a. micrometer b. nanometer c. meter d. centi e. kilo

a. micrometer

The ______________ in the Gram stain process binds to the crystal violet, generating a complex that is held more tightly within the cell. a. mordant b. safranin c. alcohol d. bacteria e. slide

a. mordant

A useful application of dark-field optics is the study of bacterial: a. motility b. surfaces c. interiors d. shape e. structure

a. motility

The nosepiece of a compound microscope contains a. objective lenses. b. ocular lenses. c. condenser lenses. d. the diaphragm.

a. objective lenses.

The characteristic of light that allows magnification by a microscope is a. refraction. b. reflection. c. absorption. s. scattering.

a. refraction.

Having fewer photoreceptors per surface area means higher: a. resolution b. magnification c. refraction d. reflection e. wavelength

a. resolution

The best microscope technique for observing the arrangement of different proteins of the surface of bacteria is a. scanning electron microscopy. b. transmission electron microscopy. c. phase-contrast microscopy. d. X-ray crystallography.

a. scanning electron microscopy.

The resolution of the human eye is limited by a. the density of the photoreceptors cells. b. the wavelengths of light that can activate the photoreceptors cells. c. the capillary blood supply to the retina. d. the pupil diameter.

a. the density of the photoreceptors cells.

In microscopy, the term resolution refers to a. the smallest distance by which two objects can be separated and still be distinguished. b. the ability to identify which microbial species is being viewed under the microscope. c. the ability to detect any microbial life forms. d. when a motile protist swims out of the field of view.

a. the smallest distance by which two objects can be separated and still be distinguished.

In bright-field microscopy a. the specimen absorbs light and appears dark. b. the specimen reflects light and appears light. c. there is no contrast between the specimen and the medium. d. any bacterial structure may be observed.

a. the specimen absorbs light and appears dark.

If an object and its surroundings absorb or reflect radiation equally, then the object will be: a. undetectable b. reflected c. refracted d. radiated e. fluoresced

a. undetectable

X-ray diffraction and phase contrast microscopy both involve: a. wave interference b. observation of living specimens c. differential stains d. simple stains e. shadowing.

a. wave interference

A specimen has a diameter of 1.5μm. What is the minimum magnification that will allow a human to resolve this object? a. 10x b. 100x c. 1000x d. 10,000x

b. 100x

The resolution of the human retina is a. 15 nm. b. 150 μm. c. 15 cm. d. 15 m.

b. 150 μm.

In which one of the following types of microscopy is the specimen shadowed with heavy metal? a. atomic force microscopy b. SEM c. TEM d. X-ray diffraction e. dark-field

b. SEM

Which of the following is true of transmission electron microscopy but NOT scanning electron microscopy? a. The specimen is usually fixed and embedded. b. The embedded specimen is cut into thin sections with a microtome. c. The specimen is stained with heavy metal. d. The specimen is viewed as three-dimensional. e. The requirement for a vacuum precludes the viewing of live organisms.

b. The embedded specimen is cut into thin sections with a microtome.

What is the relationship between magnification and depth of field? a. There is a positive relationship, such that is as magnification increases, depth of field increases. b. There is an inverse relationship such that as magnification increases, depth of field decreases. c. There is no relationship between the two; they vary independently. d. There is a fixed relationship, but it depends on the type of microscopy used.

b. There is an inverse relationship such that as magnification increases, depth of field decreases.

A disadvantage of dark-field microscopy is that a. the microbes are seen as dark objects. b. any objects in the specimen will scatter light, leading to increased background noise. c. the microbes to be observed must be killed, fixed, and stained. d. it only reveals the same structures as bright-field microscopy.

b. any objects in the specimen will scatter light, leading to increased background noise.

In which type of microscopy do dust particles interfere the most? a. bright-field microscopy b. dark-field microscopy c. phase-contrast microscopy d. interference microscopy e. fluorescence microscopy

b. dark-field microscopy

Observations of bacterial flagella during motility are best suited to: a. bright-field microscopy b. dark-field microscopy c. SEM d. TEM e. NMR

b. dark-field microscopy

The use of antibodies linked to fluorophores is known as: a. fluorescence b. immunofluorescence c. X-ray diffraction d. atomic force microscopy e. cryo-EM

b. immunofluorescence

In order to resolve spherical bacteria 100 μm in diameter, a. any wavelength of light may be used. b. light of a wavelength less than 100 μm must be used. c. light of a wavelength greater than 100 μm must be used. d. the bacteria must be coated with gold particles.

b. light of a wavelength less than 100 μm must be used

The knife used to cut embedded specimens for observation by TEM is called a: a. crystallographer b. microtome c. grid d. polymer e. scalpel

b. microtome

Resolution is the smallest distance by which two objects can be _____________ and still be _____________. a.magnified; seen b. separated; distinguished c. magnified; separated d. distinguished; separated e. magnified; distinguished

b. separated; distinguished

Empty magnification occurs when a. a microscope without lenses is used. b. the size of an image increases with no increase in resolution. c. the size of an image increases with an increase in resolution. d. the resolution of an image increases while the size of the image decreases.

b. the size of an image increases with no increase in resolution.

A nanometer, nm, is equal to a. 10-2 meters. b. 10-6 meters. c. 10-9 meters. d. 10-12 meters.

c. 10-9 meters

The electron microscope began being used in biology in the a. 1750s b. 1850s c. 1950s d. 2000s

c. 1950s

All electromagnetic radiation travels through a vacuum at what speed? a. 3 x 10^8 mm/sec b. 3 x 10^8 cm/sec c. 3 x 10^8 m/sec d. 3 x 10^8 ft/sec e. 3 x 10^8 mph

c. 3 x 10^8 m/sec

Which of the following is an advantage of electron microscopy? a. Living specimens can be observed. b. The microscope is inexpensive and easy to use. c. Specimens can be observed at high resolution. d. No artifacts are produced.

c. Specimens can be observed at high resolution

Which of the following is a true statement about Gram staining? a. The Gram stain differentiates between the three domains. b. In a Gram-negative cell, the crystal violet-iodide complex is retained by multiple layers of peptidoglycan. c. The outer membrane is disrupted by the decolorizer. d. Human cells appear Gram-positive. e. The mordant is used so that Gram-negative cells may be observed.

c. The outer membrane is disrupted by the decolorizer.

For a molecule to fluoresce, it must first a. reflect light. b. transmit light. c. absorb light. d. scatter light.

c. absorb light.

When energy from light (or other electromagnetic radiation) is acquired by an object, this is called a. refraction. b. reflection. c. absorption. d. scattering.

c. absorption

The typical prokaryotic cell is a. much larger than the typical eukaryotic cell. b. about the same size as the typical eukaryotic cell. c. much smaller than the typical eukaryotic cell. d. more easily resolved under a microscope than a eukaryotic cell.

c. much smaller than the typical eukaryotic cell.

Transmission electron microscopy commonly has a resolution of _______________ times the highest resolution possible for light microscopy. a. ten b. one hundred c. one thousand d. ten thousand e. one million

c. one thousand

Which form of microscopy is based on the difference in refractive index between cell components and the surrounding medium? a. bright-field b. dark-field c. phase contrast d. confocal e. fluorescence

c. phase contrast

Visualization techniques that rely on interference effects are a. bright-field and dark-field microscopy. b. phase-contrast microscopy and dark-field microscopy. c. phase-contrast microscopy and X-ray crystallography. d. X-ray crystallography and scanning electron microscopy.

c. phase-contrast microscopy and X-ray crystallography.

To resolve a bacterium 300 nm in diameter, light shorter than a 300 nm wavelength is required. In practice this will not allow humans to resolve the bacteria because a. bacteria will not absorb or scatter light of this wavelength. b.humans cannot produce light sources that emit this wavelength. c. this wavelength is outside the range of visible light detected by humans. d. light of this wavelength will instantly destroy the bacteria being observed.

c. this wavelength is outside the range of visible light detected by humans.

Atomic force microscopy measures _______________ between a probe and an object to map the three-dimensional topography of a cell. a. hydrogen bonds b. covalent interactions c. van der Waals forces d. pH changes e. magnetic interactions

c. van der Waals forces

Microbial cells can be detected a. never b. only when they are resolved as individual cells. c. when a large population is present (greater than 1 million cells/ml culture). d. only when a microscope is available.

c. when a large population is present (greater than 1 million cells/ml culture).

As lens strength increases, the light cone ____________ and the lens must be ______________ the object. a. narrows; nearer to b. narrows; farther from c. widens; nearer to d. widens; farther from e. widens; touch

c. widens; nearer to

Which objective lens would require the use of immersion oil? a. 4x b. 10x c. 40x d. 100x

d. 100x

The fluorophore acridine orange specifically binds: a. cytoplasm b. cell wall c. protein d. DNA e. RNA

d. DNA

Which of the following staining processes requires crystal violet? a. acid-fast stain b. antibody stain c. negative stain d. Gram stain e. spore stain

d. Gram stain

Which technique requires prior crystallization of the specimen? a. atomic force microscopy b. cyro-electron tomography c. dark-field microscopy d. X-ray diffraction analysis

d. X-ray diffraction analysis

Which technique uses interference patterns from crystallized macromolecules to determine structure at atomic resolution? a. SE b. TEM c. cryo-EM d. X-ray diffraction analysis e. atomic force microscopy

d. X-ray diffraction analysis

Fixatives and heavy atom stains used in EM can introduce _________________ into an image. a. colors b. resolution c. refraction d. artifacts e. fluorescence

d. artifacts

The path of light through a compound microscope is as follows: a. objective lens, specimen, condenser lens, ocular lens b. specimen, condenser lens, objective lens, ocular lens c. specimen, objective lens, ocular lens, condenser lens d. condenser lens, specimen, objective lens, ocular lens

d. condenser lens, specimen, objective lens, ocular lens

A/An ______________ acts to vary the diameter of the light column in a light microscope. a. condenser b. objective c. ocular d. diaphragm e. lens

d. diaphragm

The type of microscope technology used to detect signals in DNA microarrays is a. electron microscopy. b. dark-field microscopy. c. phase-contrast microscopy. d. laser scanning confocal microscopy

d. laser scanning confocal microscopy

When two waves are out of phase by _________________ wavelength, they produce destructive interference, canceling each other's amplitude and resulting in contrast in the image. a. one-tenth b. one-eighth c. one-quarter d. one-half e. one

d. one-half

In humans, resolution is achieved by focusing an image on a retina, packed with light-absorbing: a .rods b. cones c. nerves d. photoreceptor cells e. lenses

d. photoreceptor cells

What is the key property that enables a lens to magnify an image? a. reflection b. resolution c. frequency d. refraction e. wavelength

d. refraction

Which is the most important property that enables a lens to magnify an image? a. absorption b. fluorescence c. reflection d. refraction e. scattering

d. refraction

Increasing the refractive index of the medium between the object and the objective lens increases: a. refraction b. reflection c. magnification d. resolution e. wavelength

d. resolution

Which is the counterstain in the Gram stain procedure? a. crystal violet b. methylene blue c. malachite green d. safranin e. Gram's iodine

d. safranin

Dark-field microscopy depends on which characteristic of light? a. fluorescence b. absorption c. reflection d. scattering

d. scattering

Which of the following occurs when a wave front interacts with an object of smaller dimension than the wavelength? a. absorption b. reflection c. refraction d. scattering

d. scattering

The Gram stain a. stains all prokaryotic and eukaryotic cells. b. stains all prokaryotic cells but not eukaryotic cells. c. stains some bacterial cells based on differences in their DNA structure. d. stains some bacterial cells based on differences in their cell wall.

d. stains some bacterial cells based on differences in their cell wall.

Resolution is not increased by a. increasing the aperture. b. the use of immersion oil. c. the use of a stain on the specimen. d. using a lower-power objective lens.

d. using a lower-power objective lens.

A microscopic structure that is interpreted incorrectly is a/an: a. microtome b. crystal c. shadow d. antibody e. artifact

e. artifact

Which of the following is a negative stain? a. acid-fast stain b. endospore stain c. antibody stain d. simple stain e. capsule stain

e. capsule stain

Which form of microscopy is used with DNA microarrays to observe differences in gene expression? a. light microscopy b. atomic force microscopy c. SEM d. TEM e. confocal fluorescence microscopy

e. confocal fluorescence microscopy

Higher-power lenses require more light and thus an open: a. ocular b. lens c. objective d. condenser e. diaphragm

e. diaphragm

Gram's iodine is the _______________ in the Gram staining procedure. a. primary stain b. counterstain c. decolorizer d. negative stain e. mordant

e. mordant

An image is magnified when light passes through a refractive material shaped so as to __________________ its rays. a. absorb b. block c. concentrate d. condense e. spread

e. spread

Who compared "small animals" from his teeth before and after drinking coffee? a. Hooke b. Fleming c. Gram d. Jenner e. van Leeuwenhoek

e. van Leeuwenhoek