Microbiology Ch 3

The smallest image depicts plasmids from an E. coli cell. These circles of DNA measure about 20 nm (or 0.02 micrometers) in diameter. The next image depicts an adenovirus, measuring about 50 nm (or 0.05 micrometers) in diameter. The third image depicts bacterial cells measuring about 1 micrometer x 5 micrometers. The fourth image is Giardia lamblia, a protozoan parasite measuring approximately 7 micrometers x 20 micrometers. The largest image is a flatworm parasite known as Clonorchis sinensis, measuring approximately 20 mm (or 20,000 micrometers) in length.

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Which of the following types of microscope is used to observe viruses and the internal structure of thinly sectioned cells? A. brightfield microscope B. transmission electron microscope C. scanning electron microscope D. fluorescence microscope E. darkfield microscope

B. transmission electron microscope

You are studying a cell structure that is approximately 100 nm in size. Which of the following provides the lowest magnification you can use to see this structure? A. phase-contrast microscope B. brightfield microscope C. scanning electron microscope D. darkfield microscope E. transmission electron microscope

C. scanning electron microscope

Which of the following is a lens found on electron microscopes but not on light microscopes? A. Condenser lens B. Eyepiece lens C. Objective lens D. Projector lens

D. Projector lens

What does resolution mean? A. the ability of a microscope to distinguish fine details and differentiate between two very close objects B. the ability of a microscope to stay in focus when the objective lenses are moved from low power to high C. the total magnification of the visual image seen D. a measure of the ability of a medium to bend light

A. the ability of a microscope to distinguish fine details and differentiate between two very close objects Resolution is the ability of a microscope to distinguish fine details and differentiate between two very close objects.

What is the total magnification of a specimen viewed with a 10x ocular lens and a 45x objective lens? A. 45x B. 450x C. 4.5x D. 10x E. 100x

B. 450x

What is the role of iodine in the Gram stain process? A. Iodine is a pink dye that acts as the primary stain in the Gram stain technique. B. Iodine is a mordant in the Gram stain technique, which functions to intensify the primary stain. C. Iodine is a basic purple dye, which acts as the primary stain in the Gram stain technique. D. Iodine is the decolorizer removing the primary stain after the first step in the Gram stain technique.

B. Iodine is a mordant in the Gram stain technique, which functions to intensify the primary stain.

You find colorless areas in cells in a Gram-stained smear. What should you apply next? A. a simple stain B. an endospore stain C. a capsule stain D. a flagella stain E. an acid-fast stain

B. an endospore stain

In using this microscope, the observer does NOT look directly at an image through a lens. A. darkfield microscope B. electron microscope C. phase-contrast microscope D. fluorescence microscope E. compound light microscope

B. electron microscope

Which of the following pairs is mismatched? A. scanning electron microscope produces a three-dimensional image B. fluorescence microscope uses a fluorescent light C. confocal microscope produces a three-dimensional image D. scanning tunneling microscope allows visualization of atoms E. darkfield microscope uses visible light

B. fluorescence microscope uses a fluorescent light

Which of the following pairs is mismatched? A. carbolfuchsin basic dye B. safranin acid dye C. crystal violet basic dye D. iodine mordant E. alcohol-acetone decolorizer

B. safranin acid dye

Which type of stain is most useful in helping clinicians to decide which antibiotic to prescribe for a bacterial infection? A. gram stain B. flagella stain C. simple stain D. endospore stain E. negative stain

A. gram stain

Which microscope is most useful for visualizing a biofilm? A. scanning acoustic microscope B. compound light microscope C. phase-contrast microscope D. transmission electron microscope E. fluorescence microscope

A. scanning acoustic microscope

Which of the following is NOT useful for observing living cells? A. scanning electron microscope B. phase-contrast microscope C. scanning acoustic microscope D. brightfield microscope E. darkfield microscope

A. scanning electron microscope

Which of the following types of microscopes is best used for observing the surfaces of intact cells and viruses? A. scanning electron microscope B. fluorescence microscope C. darkfield microscope D. phase-contrast microscope E. brightfield microscope

A. scanning electron microscope

Place the steps of the Gram stain in the correct order. 1-Alcohol-acetone 2-Crystal violet 3-Safranin 4-Iodine A. 1-3-2-4 B. 4-3-2-1 C. 1-2-3-4 D. 2-4-1-3 E. 2-1-4-3

D. 2-4-1-3

When an object is viewed through a light microscope with oculars that magnify 20x and a high-power objective lens that magnifies 100x, what is the total magnification of the object? A. 800x B. 1000x C. 200x D. 2000x

D. 2000x Total magnification is equivalent to the magnification of the ocular times the magnification of the objective lens: 20x times 100x is equivalent to 2000x.

Which step in the Gram stain is the critical step in differentiating gram-positive cells from gram-negative cells? A. iodine B. crystal violet C. safranin D. alcohol-acetone

D. alcohol-acetone

This microscope produces an image of a light cell against a dark background; internal structures are NOT visible. A. fluorescence microscope B. phase-contrast microscope C. electron microscope D. darkfield microscope E. compound light microscope

D. darkfield microscope

Which microscope achieves the highest magnification and greatest resolution? A. darkfield microscope B. phase-contrast microscope C. fluorescence microscope D. electron microscope E. compound light microscope

D. electron microscope

Which microscope is used to observe a specimen that emits light when illuminated with an ultraviolet light? A. darkfield microscope B. compound light microscope C. phase-contrast microscope D. fluorescence microscope E. electron microscope

D. fluorescence microscope

The purpose of the ocular lens is to A. decrease the light. B. improve resolution. C. decrease the refractive index. D. magnify the image from the objective lens. E. increase the light.

D. magnify the image from the objective lens.

What structure does light pass through after leaving the condenser in a compound light microscope? A. ocular lens B. illuminator C. objective lens D. specimen

D. specimen

The resolution of a microscope can be improved by changing the A. condenser. B. coarse adjustment. C. diaphragm. D. wavelength of light. E. fine adjustment.

D. wavelength of light.

Which microscope uses two beams of light to produce a three-dimensional color image? A. electron microscope B. fluorescence microscope C. darkfield microscope D. phase-contrast microscope E. DIC microscope

E. DIC microscope

In a typical brightfield microscope (seen in the animation), at which point does magnification begin? A. The lamp B. The condenser lens C. The ocular lens D. The stage E. The objective lens

E. The objective lens

Simple staining is often necessary to improve contrast in which microscope? A. phase-contrast microscope B. electron microscope C. fluorescence microscope D. darkfield microscope E. compound light microscope

E. compound light microscope

Assume you stain Bacillus by applying malachite green with heat and then counterstaining with safranin. Through the microscope, the green structures are A. undefinable. B. capsules. C. cell walls. D. flagella. E. endospores.

E. endospores.

Which of the following correctly traces the path of light through the compound microscope? A. condenser; light source; specimen; objective lens; ocular lens B. light source; specimen; condenser; objective lens; ocular lens C. condenser; light source; specimen; ocular lens; objective lens D. light source; condenser; objective lens; specimen; ocular lens E. light source; condenser; specimen; objective lens; ocular lens

E. light source; condenser; specimen; objective lens; ocular lens

A paramecium is approximately 150 micrometers in length. What is this measurement expressed in millimeters (mm)? A. 0.15 mm B. 0.015 mm C. 1500 mm D. 1.5 mm E. 15 mm

A. 0.15 mm To obtain the measurement in millimeters, you have divided the measurement in micrometers by 1000.

Place the following steps in the correct sequence. 1-Staining 2-Making a smear 3-Fixing A. 2-3-1 B. 1-2-3 C. 3-2-1 D. The order is unimportant. E. 1-3-2

A. 2-3-1

Chlamydia trachomatis elementary bodies measure approximately 0.25 micrometers in diameter. What is this measurement expressed in nanometers (nm)? A. 250 nm B. 25,000 nm C. 25 nm D. 2500 nm E. 2.5 nm

A. 250 nm To obtain the measurement in nanometers, you have multiplied the measurement in micrometers by 1000.

Consider the following situations, and determine when a simple stain could be used instead of a Gram stain. A. A microbiologist is trying to determine whether a specimen contains bacteria or fungi. B. An unknown species of bacteria is being characterized and identified. C. A specimen is being examined in which the presence of multiple species of bacteria is suspected. D. A wound specimen is being examined.

A. A microbiologist is trying to determine whether a specimen contains bacteria or fungi. A simple stain is used to visualize the entire organism and highlight cellular shapes or structures. In this case, differentiation of bacterial characteristics is not necessary.

A student creates a Gram stain on a bacterial specimen that has a mix of gram-negative and gram-positive organisms but accidentally forgets the decolorizer step. What would the outcome of the Gram stain be? A. All organisms would appear purple (gram-positive). B. All organisms would appear pink (gram-negative). C. All organisms would appear colorless. D. The Gram stain would show pink (gram-negative bacteria) and purple (gram-positive bacteria).

A. All organisms would appear purple (gram-positive). Without the decolorizer step, all the organisms retain the purple stain.

Which of the following statements comparing electron microscopy and light microscopy is FALSE? A. Both the electron microscope and the light microscope use the same wavelengths for illumination. B. Images produced by light microscopes can be in color, whereas electron microscope images are black and white unless they are artificially colored. C. Electron microscopes can allow examination of viruses and internal cell structures, whereas light microscopes are limited to objects that are 0.5 micrometers and larger. D. The electron microscope has greater resolution than the light microscope.

A. Both the electron microscope and the light microscope use the same wavelengths for illumination. The light microscope uses light, and the electron microscope uses electrons.

What would you expect to see if you forgot to perform step 2 of the Gram stain procedure? A. Gram-positive cells would appear pink and Gram-negative cells would appear purple. B. Gram-positive cells would appear purple and Gram-negative cells would appear pink. C. All bacteria would appear pink. D. All bacteria would appear purple.

C. All bacteria would appear pink.

Why is a specimen smaller than 200 nm not visible with a light microscope? A. It is too easy to lose on the stage. B. Visible light is only good at wavelengths below 390 nm. C. Anything smaller than 200 nm cannot interact with visible light. D. The lenses only go to 100 X magnification power.

C. Anything smaller than 200 nm cannot interact with visible light.

Why do electron microscopes have higher resolving power than light microscopes? A. The fluorescent screen adds another magnification step. B. They are capable of producing 3-dimensional images, which light microscopes cannot do. C. Electrons have a smaller wavelength than visible light, leading to higher resolution. D. The copper grid used in electron microscopy provides enhanced resolution.

C. Electrons have a smaller wavelength than visible light, leading to higher resolution.

What happens to the light rays when they hit the specimen? A. They are absorbed by the stage. B. They are focused into a small area towards the objective lens. C. They are reflected, refracted, or absorbed by the specimen. D. They are diverted to the ocular lens.

C. They are reflected, refracted, or absorbed by the specimen.

Which of the following describes the correct path of light in a compound light microscope, from the illumination source to the eye of the observer? A. objective lenses ( specimen ( illuminator( condenser lenses ( body tube ( ocular lens ( eye B. condenser lenses ( illuminator( specimen ( objective lenses ( body tube ( ocular lens ( eye C. illuminator ( condenser lenses ( specimen ( objective lenses ( body tube ( ocular lens ( eye D. illuminator( ocular lens ( body tube ( condenser lens ( specimen ( objective lens ( eye

C. illuminator ( condenser lenses ( specimen ( objective lenses ( body tube ( ocular lens ( eye

You are performing a Gram stain on gram-negative bacteria and you stop after the addition of the mordant. What is the appearance of the bacteria at this point? A. colorless B. red C. purple D. brown

C. purple

You are performing a Gram stain on gram-positive bacteria and you stop after the addition of the counter stain. What is the appearance of the bacteria at this point? A. red B. colorless C. purple D. brown

C. purple

In microscopy, the term resolution A. is improved when longer wavelengths of light are employed. B. is the same as the total magnification of a specimen. C. refers to the ability to distinguish fine structure and detail in a specimen. D. refers to magnification when using the electron microscope. E. is only observed in stained specimens.

C. refers to the ability to distinguish fine structure and detail in a specimen.

A student is looking at a bacterial specimen using the oil immersion lens, but has forgotten to put immersion oil on the slide. The specimen will appear A. the same as it would if the immersion oil was used. B. to have no color. C. somewhat fuzzy and have poor resolution. D. larger than it would if immersion oil was used. E. smaller than it would if immersion oil was used.

C. somewhat fuzzy and have poor resolution.

The purpose of a mordant in the Gram stain is A. to make gram-negative cells visible. B. to make the bacterial cells larger. C. to prevent the crystal violet from leaving the cells. D. to make the flagella visible. E. to remove the simple stain.

C. to prevent the crystal violet from leaving the cells.

The negative stain is used to A. visualize endospores. B. determine flagella arrangement. C. visualize capsules. D. determine cell size. E. determine gram reaction.

C. visualize capsules.

Unaided Eye: -Examining your cat for the presence of fleas Light Microscope: -Examining a clinical specimen, such as a sputum smear, for the presence of bacteria -Examining a blood smear for the presence of malarial parasites

Scanning Electron Microscope: -Viewing the 3D shape of a protozoan and the arrangement and distribution of cilia on its surface -Determining the 3D shape and arrangement of bacterial cells Transmission Electron Microscope: -Viewing ribosomes (20 nm) within a bacterial cell -Viewing a cross section of poliovirus (30 nm) -Viewing the layers of a gram-negative cell wall in a cross section -Confirming the 9 + 2 microtubule arrangement in a eukaryotic flagellum

Which of the following is NOT true regarding the acid-fast stain? A. If cells are acid-fast, they are gram-negative. B. Acid-fast cells retain the primary dye after treatment with acid-alcohol. C. Non-acid-fast microbes appear blue in a completed acid-fast stain. D. It is used to identify members of the genus Mycobacterium. E. Acid-fast cells appear red in a completed acid-fast stain.

A. If cells are acid-fast, they are gram-negative.

What is meant by light rays being divergent? A. It is spreading out B. It is coming together to a focused beam C. It is heading upwards

A. It is spreading out

What is the role of lenses in microscopy? A. Lenses focus either light or electrons to create a magnified image of a specimen. B. Lenses are only used to magnify specimens that are smaller than whole red blood cells. C. Lenses increase the contrast to determine structural differences in stained specimens.

A. Lenses focus either light or electrons to create a magnified image of a specimen.

Which of the following is a characteristic shared by both electron and light microscopes? A. They both employ the use of objective lenses. B. They both utilize white light to magnify the specimen. C. Both microscopes require an internal camera to visualize the specimen. D. Both microscopes have a resolving power of 0.01 nm.

A. They both employ the use of objective lenses.

What is the fate of the electrons that interact with a specimen in an electron microscope? A. They may be absorbed, reflected, or refracted by the specimen. B. They are refracted by the specimen. C. They are absorbed by the specimen. D. They are reflected by the specimen.

A. They may be absorbed, reflected, or refracted by the specimen.

Which of the following staining procedures is matched with the principal use for that stain? A. acid-fast stain for microbes with waxy cell walls B. flagella stain used to distinguish dormant structures formed during adverse environmental conditions C. negative stain used to differentiate cell wall components D. endospore stain to visualize flagella

A. acid-fast stain for microbes with waxy cell walls This stain is very useful in identifying Mycobacterium spp. that exhibit waxy cell walls.

Which of the following pairs is mismatched? A. basic dye negative stain B. nigrosin negative stain C. methylene blue simple stain D. crystal violet simple stain E. acidic dye capsule stain

A. basic dye negative stain

Which microscope is used to see detail of a 300-nm virus? A. electron microscope B. phase-contrast microscope C. darkfield microscope D. fluorescence microscope E. dic microscope

A. electron microscope

A virus measures 100 nm in length. What is its length in μm? A. 10 μm B. 0.01 μm C. 1 μm D. 0.001 μm E. .1 μm

E. .1 μm

What would you anticipate seeing if you accidentally switched crystal violet and safranin while performing a Gram stain? A. Gram-positive bacteria would appear pink and Gram-negative bacteria would appear purple. B. All bacteria would appear purple. C. All bacteria would appear pink. D. Gram-positive bacteria would appear purple and Gram-negative bacteria would appear pink.

B. All bacteria would appear purple.

What is the role of the ocular lens? A. To focus the light to a high intensity in a small area B. To recreate the image in the viewer's eye C. To adjust the wavelength of light D. To do the bulk of the magnification

B. To recreate the image in the viewer's eye

Which structural feature of Gram-positive bacteria enhances their ability to retain the crystal violet dye? A. an outer membrane B. a thick peptidoglycan layer C. a thin peptidoglycan layer D. All of the above contribute to a Gram-positive cell's ability to retain crystal violet.

B. a thick peptidoglycan layer

Bacterial smears are fixed before staining to A. accept stain. B. affix the cells to the slide. C. make the cells visible. D. make their walls permeable.

B. affix the cells to the slide.

Which type of microscope would allow the viewer to see ribosomes inside a cell? A. A light microscope, transmission electron microscope, and scanning electron microscope can all view ribosomes inside a cell. B. A light microscope C. A transmission electron microscope D. A scanning electron microscope

C. A transmission electron microscope

Which of the following measurements is correctly matched with microorganisms of that size? A. bacteria--10 nm B. viruses--10 micrometers C. bacteria--2 micrometers D. viruses--1 cm

C. bacteria--2 micrometers Bacteria are measured in microns or micrometers.

You are performing a Gram stain on gram-negative bacteria and you stop after the decolorizer step. What is the appearance of the bacteria at this point? A. red B. purple C. colorless D. brown

C. colorless

In the figure, line c points to the microscope's A. illuminator. B. ocular lens. C. condenser. D. objective lens.

C. condenser.

Which of the following types of microscopy provides advantages for viewing live images? A. scanning electron microscopy B. fluorescent microscopy C. darkfield microscopy D. transmission electron microscopy

C. darkfield microscopy Darkfield microscopy allows colorless cells to be visualized without applying stains that kill cells.

Which microscope uses visible light? A. fluorescence microscope B. scanning electron microscope C. differential interference contrast D. scanning acoustic microscope E. confocal microscope

C. differential interference contrast

While staining a mixed culture of Gram-positive and Gram-negative bacteria, switching the order of steps 2 and 3 would result in ______________________. A. all bacteria appearing clear B. a change in the Gram reaction; Gram-negative cells would appear purple while Gram-positive cells would appear pink. C. all bacteria appearing purple D. all bacteria appearing pink

D. all bacteria appearing pink

Which microscope takes advantage of differences in the refractive indexes of cell structures? A. compound light microscope B. fluorescence microscope C. electron microscope D. phase-contrast microscope E. darkfield microscope

D. phase-contrast microscope

You are performing a Gram stain on gram-positive bacteria and you stop after the addition of the first dye. What is the appearance of the bacteria at this point? A. colorless B. brown C. red D. purple

D. purple

Which microscope is used to see internal structures of cells in a natural state? A. compound light microscope B. fluorescence microscope C. darkfield microscope D. electron microscope E. phase-contrast microscope

E. phase-contrast microscope

Which microscope can be used to visualize DNA or botulinum toxin? A. phase-contrast microscope B. compound light microscope C. confocal microscope D. scanning electron microscope E. scanning tunneling microscope

E. scanning tunneling microscope

Which microscope is used to see intracellular detail in a living cell? A. atomic force microscope B. transmission electron microscope C. fluorescence microscope D. brightfield microscope E. two-photon microscope

E. two-photon microscope