Chapter 4 - Microscopy, Staining, and Classification Flashcards

What is the role of lenses in microscopy?

1. Lenses increase the contrast to determine structural differences in stained specimens.
2. Lenses are only used to magnify specimens that are smaller than whole red blood cells.
3. Lenses focus either light or electrons to create a magnified image of a specimen.

Why is a specimen smaller than 200 nm not visible with a light microscope?

1. The lenses only go to 100 X magnification power.
2. Visible light is only good at wavelengths below 390 nm.
3. Anything smaller than 200 nm cannot interact with visible light.
4. It is too easy to lose on the stage.

What happens to the light rays when they hit the specimen?

1. They are reflected, refracted, or absorbed by the specimen.
2. They are diverted to the ocular lens.
3. They are absorbed by the stage.
4. They are focused into a small area towards the objective lens.

What is the role of the ocular lens?

1. To adjust the wavelength of light
2. To do the bulk of the magnification
3. To focus the light to a high intensity in a small area
4. To recreate the image in the viewer’s eye

What is meant by light rays being divergent?

1. It is heading upwards
2. It is coming together to a focused beam
3. It is spreading out

In a typical bright-field microscope, at which point does magnification begin?

1. The objective lens
2. The lamp
3. The ocular lens
4. The stage
5. The condenser lens

Which phenomena produces magnification?

1. the wavelength of a radiation source
2. the numerical aperture of a lens
3. the length of an objective lens
4. the refraction of radiation as it passes through a lens
5. the thickness of a microscopic specimen

How are negative stains different from other types of stains?

1. They stain more than one type of specimen.
2. They stain the desired structure or specimen black.
3. They stain the background, leaving the cells colorless.

What is the minimum distinguishable distance that can be seen on a microscope?

Following an endospore stain, how does one distinguish endospores from vegetative cells?

1. Vegetative cells are pink, endospores are green.
2. Vegetative cells are pink, endospores are purple.
3. Vegetative cells are green, endospores are pink.
4. Vegetative cells are purple, endospores are pink.

What is the fundamental purpose of staining in light microscopy?

1. To see the specimen without the aid of a microscope
2. To make the specimen appear larger in the microscope
3. To kill the specimen
4. To increase the contrast and visibility of the specimen

A student from one of the research labs is having trouble preparing a slide for examination and photographing. The bacterial slide that he has brought to you was prepared using a commercially purchased stain. He has asked for your help in determining what he is doing wrong so that he can change the lab protocols and continue on with his project. After examining the slide under oil immersion, you determine that no bacteria are present even though the student is able to show you the culture he used to make that slide that has visible growth in the liquid medium.
Which of the following statements does NOT explain the fact that there are no bacteria present on the student’s slide?

1. By not allowing a glass slide to completely air dry before heat fixation, the flame will cause the surrounding water to boil and this will damage the bacterial cell.
2. Overheating during the fixation step boiled the water within the bacterial cells and resulted in the cells bursting.
3. Insufficient heating of the slide did not drive out the thin layer of water and this resulted in minimal bonding between the bacteria and the glass slide.
4. Rinsing with alcohol during the washing step stripped the bacteria off the glass slide.

You volunteer to help the student with his fixation technique and in choosing a proper stain for the project he is working on. After watching and helping the student correct any problems with his fixation technique, you now need to determine which stains to use. The single criterion for the project is to be able to determine cell shape and size in a pure broth culture after some treatments. No differentiation between cell types is required (i.e., Gram-positive or Gram-negative), so you want to convince the student that a simple stain would be his best option. The charged dyes used in simple staining will penetrate the bacterial cell and will be retained after rinsing the slide with water to remove surplus dye. Which staining procedure would be best to use to stain the slides required for this student’s project? Why?

1. Malachite green and heat will colorize the cell for easier visualization and is a simple process.
2. Using crystal violet followed by a rinse and Gram’s iodine will stain the cells a dark blue with large crystals.
3. The positively charged methylene blue will be attracted to the negatively charged components of the cell wall and will be retained.
4. An acidic stain such as nigrosin will stain the cells a dark black coloration for easier viewing under the microscope.

Put the following descriptions in order for the staining reactions in the cells of a bacterial smear during the Gram staining procedure:

1. Cell wall of Gram-negative cells is broken down; Gram-positive cells remain intact

2. All cells are stained purple

3. Dye molecules are rendered insoluble in presence of mordant; dye is rinsed away

4. Clear cells are stained a red or pink whereas the color of other cells remains unchanged

Nigrosin staining-not safranin staining-of Klebsiella pneumoniae will allow for the visualization of the cell shape and the determination of the presence of a capsule. T/F

Methylene blue can be used to stain DNA because it

1. changes the pH and therefore the structure of DNA.
2. makes DNA electron dense.
3. is an effective fixing agent for nucleic acids.
4. forms ionic bonds with DNA.
5. covalently bonds with DNA.

Viruses are not included in the taxonomic scheme proposed by Carl Woese because they lack _____.

A) proteins.
B) ribosomal RNA.
C) cytoplasm.
D) genetic material.
E) lipid membranes.

Plaques are associated with which of the following methods of laboratory identification of microorganisms?

1. biochemical tests
2. phage typing
3. serological tests
4. nucleic acid analysis

The reagents crystal violet, iodine, and safranin are all associated with which of the following staining procedures?

1. the endospore stain
2. the flagella stain
3. the acid-fast stain
4. the Gram stain

If a microbiologist omitted the decolorizer from a Gram-stained smear, which of the following would happen?

1. All cells in the smear would be purple.
2. Gram-positive cells would be pink and Gram-negative cells would be purple.
3. All cells in the smear would be pink.
4. All cells in the smear would be colorless.

Which of the following is NOT equal to 50 millimeters?

1. 0.05 meters
2. 5,000,000 nanometers
3. 5 centimeters
4. 50,000 micrometers

The Gram stain works because of differences in the ________ of bacteria.

A) antigens
B) capsules
C) cell walls
D) genetic characteristics
E) cell membranes

All of the following are types of light microscopes EXCEPT
A) confocal.
B) bright-field.
C) scanning tunneling.
D) phase-contrast.
E) fluorescent.

Which of the following microscopes produces the highest resolution images?
A) scanning electron
B) fluorescent
C) differential interference
D) atomic force
E) dark-field

A thin film of microbes on a slide is a _______.

A) agglutination.
B) fixation.
C) a Gram reaction.
D) a smear.
E) a biopsy.

The rules of naming organisms are called
A) classification.
B) taxonomy.
C) binomials.
D) nomenclature.
E) identification.

One-thousandth of a meter is a _______.

A) nanometer (nm).
B) yard.
C) millimeter (mm).
D) micrometer (μm).
E) centimeter (cm).

Tannic acid is a mordant (chemical fixative) used in the ________ stain.

A) endospore
B) acid-fast
C) flagellar
D) electron microscopy
E) negative

Species and strains of microbes can be distinguished from one another phenotypically using _______.

A) serological tests.
B) G + C content.
C) electron microscopy.
D) Gram-stain reactions.
E) ribosomal RNA analysis

The ability of a lens to gather light is referred to as its _______.

A) refraction.
B) contrast.
C) magnification.
D) resolution.
E) numerical aperture.

A cell's G + C ratio is associated with which of the following classification methods?

A) physical characteristics
B) biochemical tests
C) analysis of nucleic acids
D) phage typing
E) serological tests

Which of the following is NOT a characteristic of a genus name?

A) It is one of two names used to identify an organism.
B) It is written before the specific epithet.
C) It is always capitalized.
D) It is usually an adjective.
E) It is either underlined or in italics.

The microscope preferred for viewing living specimens is the ________ microscope.

A) scanning tunneling
B) bright-field
C) scanning electron
D) phase-contrast
E) transmission electron

In Gram staining, ethanol-acetone is used as a:

A) mordant.
B) counterstain.
C) drying agent.
D) decolorizing agent.
E) primary stain.

If a microbiology lab student left the safranin out of the Gram stain procedure, what would be the result?

A) All cells would be pink.
B) Gram-positive cells would be pink and Gram-negative cells would be purple.
C) All cells would be purple.
D) Gram-positive cells would be colorless and Gram-negative cells would be pink.
E) Gram-positive cells would be purple and Gram-negative cells would be colorless.

Safranin dye is used as the counterstain in ________ stain(s).

A) the flagellar
B) the acid-fast
C) the Gram
D) the endospore
E) both the Gram and the endospore

Which of the following is NOT associated with an electron microscope?
A) a vacuum
B) a fluorescent screen
C) an electron beam
D) magnetic fields
E) a prism

All of the following are types of light microscopes EXCEPT
A) confocal.
B) bright-field.
C) scanning tunneling.
D) phase-contrast.
E) fluorescent.

Heat is used to drive the stain into cells in the ________ staining procedure(s).

A) capsule stain
B) acid-fast stain
C) Gram stain
D) endospore stain
E) both acid-fast and endospore stains

Which of the following classification methods relies on the morphology of organisms?

A) analysis of nucleic acids
B) physical (phenotypic) characteristics
C) biochemical tests
D) serological tests
E) phage typing

The kingdoms included in the Linnaeus system of classification are _______ and _______.

A) Animalia and Plantae.
B) Fungi and Protista.
C) Prokaryotae and Protista.
D) Animalia and Prokaryotae.
E) Protista and Plantae.

The ________ stain makes use of malachite green.

A) negative
B) acid-fast
C) endospore
D) electron microscopy
E) flagellar

Methylene blue can be used to stain DNA because it

A) changes the pH and therefore the structure of DNA.
B) is an effective fixing agent for nucleic acids.
C) forms ionic bonds with DNA.
D) makes DNA electron dense.
E) covalently bonds with DNA.

The ________ stain is one in which eosin is used.

A) electron microscopy
B) flagellar
C) endospore
D) acid-fast
E) negative

Which of the following is an INCORRECT pairing?
A) magnification; refraction of radiation
B) simple microscope; Leeuwenhoek
C) contrast; staining techniques
D) electron beams; shorter wavelength
E) numerical aperture; curved glass

Bacteria and many other microbes do not ________ and therefore do not fit Linneaus' definition species.

A) have cytoplasmic membranes
B) have nuclei
C) exchange genetic material
D) reproduce sexually
E) reproduce asexually

The primary goal of modern taxonomists is to

A) establish unique identifiers for each species.
B) understand the phylogenetic relationships between organisms.
C) have a complete inventory of all living things.
D) determine what defines a species.
E) There is no consensus among taxonomists regarding their primary goal.

Tungsten is a reagent used in the _______.

A) acid-fast stain.
B) negative stain.
C) electron microscopy stain.
D) flagellar stain.
E) endospore stain.

Which of the following are magnifying lenses?

A) dark-field stops
B) objectives
C) condensers
D) oculars
E) both objectives and the oculars

The most appropriate unit of measurement for intact archaea is the _______.

A) nanometer (nm).
B) centimeter (cm).
C) meter (m).
D) millimeter (mm).
E) micrometer (μm).

A sample is prepared using osmium tetroxide as a stain. This sample has been prepared for a(n) ________ microscope.

A) electron
B) fluorescence
C) differential interference contrast
D) atomic force
E) phase-contrast

Carl Woese proposed the concept of the domain based on differences of which cellular molecule?

A) membrane lipids
B) transfer RNA
C) DNA
D) proteins
E) ribosomal RNA

A structure that appears in a transmission electron micrograph but is NOT actually present in the specimen is known as a(n) _______.

A) artifact.

B) antigen.

C) mordant.

D) biofilm.

E) refraction.

If you were trying to visualize flagella without staining, which microscope would you use?

A) fluorescent
B) phase-contrast
C) confocal
D) bright-field
E) dark-field

A sample from a patient is prepared using the Gomori methenamine silver stain. What type of microbe is suspected of being present?

A) parasitic worm larva
B) virus
C) bacteria
D) protozoal parasite
E) fungus

In the Gram stain procedure, iodine serves as a _______.

A) mordant.
B) primary stain.
C) fixative.
D) counterstain.
E) decolorizing agent.

Why are modern light microscopes better than the ones Leeuwenhoek used?

A) Modern microscopes have lenses with smaller numerical apertures.
B) Modern microscopes are compound and have fivefold better resolution.
C) Modern microscopes have a fivefold better resolution.
D) Modern lenses are made of prisms.
E) Modern microscopes are compound instead of simple.

Viruses are generally measured in _______.

A) millimeters.
B) centimeters.
C) nanometers.
D) micrometers.
E) decimeters.

Why does immersion oil improve resolution?

A) It allows light to travel at a uniform speed on its way to the lens.
B) It decreases the working distance.
C) It increases the angle of refraction of the light.
D) It increases numerical aperture and maintains a uniform light speed.
E) It increases the numerical aperture.

You are shown a micrograph from a light microscope in which the specimens appear bright compared to the background. The micrograph is probably from a(n) ________ microscope.

A) bright-field
B) dark-field
C) Nomarski
D) atomic force
E) phase-contrast

Which of the following statements about transmission electron microscopy is FALSE?

A) The sample is placed in a vacuum.
B) Stains can be applied to improve contrast.
C) Electrons are the source of visualization.
D) Thin segments must be used.
E) Glass lenses are used.

The limits of resolution of atomic force microscopes is in the range of _______.

A) millimeters (mm).
B) centimeters (cm).
C) meters (m).
D) nanometers (nm).
E) micrometers (μm).

Acidic dyes

A) work best in low pH environments.
B) are negatively charged and work best at low pH.
C) are lipid soluble.
D) are used for staining negatively charged molecular structures.
E) are negatively charged.

Which of the following phenomena produces magnification?

A) the refraction of radiation as it passes through a lens
B) the wavelength of a radiation source
C) the numerical aperture of a lens
D) the length of an objective lens
E) the thickness of a microscopic specimen

Carbolfuchsin is the ________ in the acid-fast stain.

A) fixing reagent
B) primary stain
C) counterstain
D) decolorizer
E) mordant

All of the following are common to both the Gram stain and the acid-fast stain EXCEPT

A) primary stain.
B) counterstain.
C) a decolorizing agent and a counterstain.
D) a decolorizing agent.
E) a chemical mordant.

The size of a pork tapeworm is generally described in terms of _______.

A) millimeters (mm.)
B) nanometers (nm).
C) meters (m).
D) micrometers (μm).
E) decimeters (dc).

A virologist wants to observe the surface features of virus particles she is studying. Which of the following microscopes would NOT be useful for her observations?

A) transmission electron
B) scanning electron
C) atomic force
D) differential interference contrast
E) scanning tunneling

In a compound microscope, the lens that directs light through the specimen is the
_______ lens.

A serological test that involves the clumping of antigen and antibody is the
_______ test.

The system of taxonomy used today was originated by _______.

A _______ microscope has a single ocular lens.

A staining procedure that uses a single basic dye is called a _______ stain.

Bacterial viruses, called _______, can be used to help
classify different groups of bacteria.

A primary purpose for the use of stains in microscopy is the increase the
_______ of a specimen.

The process of immobilizing organisms on a glass slide through the application of either
heat or chemicals is _______.

A(n) _______ molecule is one that absorbs invisible radiation and emits visible light.

Carl Woese and his colleagues proposed the _______, a taxon that contains
multiple kingdoms.

Coating a specimen with a heavy metal is a step in preparing it for
_______ microscopy.

A _______ is a substance that binds to a dye and makes it less soluble.

An integral part of serological testing is the use of a solution called
_______ that contains antibodies.

The three domains proposed by Carl Woese are the Archaea, the Eukarya, and the Protista. T/F

Light rays that are in phase reinforce each other and produce a brighter image. T/F

The endospore stain reveals internal structures within cells of the genera Bacillus and Clostridium. T/F

Scanning tunneling microscopes map the topography of a specimen by detecting the deflection of the probe tip. T/F

Gram staining of bacteria provides all the physical characterization necessary to identify bacterial species. T/F

Light rays that pass through the edge of a curved lens will be refracted more than those that pass through the center. T/F

Three-dimensional images of specimens can be obtained using scanning electron microscopes. T/F

The Gram stain can be used to distinguish bacteria based on the structure of their cell walls. T/F

Acid-fast cells such as Mycobacterium lose the color of the primary stain in the presence of hydrochloric acid. T/F

A resolution of 1μm would be better than a resolution of 0.5 μm. T/F

What refracts light?

List and explain five types of techniques that can be used to identify unknown microorganisms.

A unit of measurement is typically _______ than the object being measured.

_______ refers to the use of light or electrons to magnify objects.

The microscope used to view ultra-structure of the cell is called _______.

Electron microscopes use _______ lenses to control focus and magnification.

The color of the basic dyes is in the _______ ion.

In Gram staining, the Gram negative bacteria appear _______ in color.

Acid fast staining is an example of _______ staining.

Scanning electron microscopes are used to view _______ structures.

The microscope that uses UV sources of illumination are called _______ microscopes.

In fluorescent microscopy, the background appears _______.

The three domains proposed by Carl Woese are _______, _______, and _______.

Which of the following pairs are mismatched?

1. Gram-negative bacteria; negative stain
2. iodine; mordant
3. alcohol; decolorizer
4. methylene blue; simple stain

The purpose of mordant in Gram staining is:

1. to remove the simple stain
2. to make the bacterial cell larger
3. to make the flagella visible
4. to prevent the crystal violet from leaving the cell
5. none of the above

Place the following steps in the correct sequence: 1. staining 2. making a smear 3. fixing

1. 1-2-3
2. 3-2-1
3. 2-3-1
4. 2-1-3
5. 1-3-2

This microscope is used to observe a specien that emits light when illuminated with a UV light.

1. compound light microscope
2. phase contrast microscope
3. dark field microscope
4. fluorescence microscope
5. electron microscope

The appearance of Gram positive bacteria after adding the counter stain in the Gram stain:

1. violet
2. red
3. colorless
4. brown
5. none of the above

The appearance of Gram negative bacteria after completing the Gram stain is:

1. purple
2. red
3. colorless
4. brown
5. blue

Cells are differentiated after which step in Gram staining?

1. crystal violet
2. safranin
3. alcohol decolization
4. iodine
5. none of the above

The microscope that is used to see internal ultra-structures is the transmission electron microscope. T/F

Bacterial smears are heat fixed before staining to make their cell wall more permeable. T/F

Acid fast bacteria have mycolic acid in their cell wall that makes them more permeable to stains and chemicals. T/F

In acid fast staining the acid fast bacteria appear red while non-acid fast bacteria appear blue. T/F

In negative staining the negatively charged dye molecules bind to the negatively charged part of the bacteria. T/F

What is the name of the use of light or electrons to magnify objects?

What are the 4 principles of microscopy?

What is the distance between two corresponding parts of a wave called?

What refracts light?

What refracts electron beams?

What is it called if a scientist were to use multiple lens to magnify an image millions of time, but the image is blurry and faint?

What are the two properties that determine the clarity of an image?

What is another name for resolution?

What is the minimum distinguishable distance that can be seen on a microscope?

What is the numerical aperture of a lens?

What refers to differences in intensity between two objects or between an object and its background?

What is one way to increase contrast?

What kind of microscope has the background illuminated?

What kind of microscope has the specimen appear light against a dark background?

What are the 2 types of bright field microscopes?

What is a simple microscope?

What is a photograph taken by means of a microscope called?

What are dark field microscopes useful for?

What are phase microscopes used for?

Which microscope is particularly useful in studying cilia and flagella?

Molecules that absorb energy from invisible radiation (such as ultraviolet light) and then radiate the energy back as a longer, visible wavelength are said to be _______.

Which kind of microscope uses an UV light source to fluoresce objects?

The resolving power of _______ microscopes is much greater than that of light microscopes.

What are the two types of electron microscope?

Which electron microscope generates a beam of electrons that produce an image on a fluorescent screen?

Can transmission electron microscopes be used to examine living things?

Which microscopes use a magnetic field within a vacuum tube to manipulate a beam of electrons called primary electrons?

Which microscope rapidly focuses the electrons back and forth across a specimen’s surface, which has previously been coated with a metal such as platinum or gold?

Which microscopes utilize minuscule, pointed electron probes?

What are the 2 types of probe microscope?

Dyes used as stains for light microscopy are usually made of _______.

A salt is composed of a positively charged _______ and a negatively charged _______.

What is the colored portion of a dye called?

Which dyes stain alkaline structures and work best in acidic environments?

Which dyes combine with and stain acidic structures and work best under basic conditions?

Which dyes are used most commonly in microbiology, and why?

What kind of dyes are used in negative staining, and why?

Name 3 simple stains?

What are differential stains?

What are some examples of differential stains?

In the Gram stain, what color do Gram positive cells stain?

Why must air be evacuated from the column of an electron microscope?

Which of the following is NOT a characteristic of a genus name?

A) It is one of two names used to identify an organism.
B) It is written before the specific epithet.
C) It is always capitalized.
D) It is usually an adjective.
E) It is either underlined or in italics.

Endospores cannot be stained by normal staining procedures because their cell walls are practically impermeable to all chemicals. T/F

Gomori methenamine silver stain is used to screen for the presence of fungi and the location of carbohydrates in tissues. T/F

Hematoxylin and eosin are used to detect the presence of cancer cells. T/F

The fluorescent stain is used to reveal the presence of negatively charged capsules. T/F

The stains used for electron microscopes include pararosaniline and carbolfuchsin. T/F

A bacteriophage is a virus that inserts its DNA into a bacterium. T/F

Biologists classify organisms for the following reasons EXCEPT

1. to bring a sense of order and organization to the variety and diversity of living things
2. to enhance communication
3. to further the field of microbiology
4. to make predictions about the structure and function of similar organisms
5. to uncover and understand potential evolutionary connections.

The organization of organisms on the basis of mutual similarities into non-overlapping groups is called taxa. T/F

Taxonomy is the science of classifying and naming organisms. T/F

A group of organisms that interbreed to produce viable offspring are called a species. T/F

Which of the following is smallest?

a. decimeter

b. millimeter

c. nanometer

d. micrometer

A nanometer is __________________ than a micrometer.

a. 10 times larger

b. 10 times smaller

c. 1000 times larger

d. 1000 times smaller

Resolution is best described as the __________________.

a. ability to view something that is small

b. ability to magnify a specimen

c. ability to distinguish between two adjacent objects

d. difference between two waves of electromagnetic radiation

Curved glass lenses __________________ light.

a. refract

b. bend

c. magnify

d. both a and b

Which of the following factors is important in making an image appear larger?

a. thickness of the lens

b. curvature of the lens

c. speed of the light passing through the lens

d. all of the above

Which of the following is different between light microscopy and transmission electron microscopy?

a. magnification

b. resolution

c. wavelengths

d. all of the above

Which of the following types of microscopes produces a three-dimensional image with a shadowed appearance?

a. simple microscope

b. differential interference contrast microscope

c. fluorescence microscope

d. transmission electron microscope

Which of the following microscopes combines the greatest magnification with the best resolution?

a. confocal microscope

b. phase-contrast microscope

c. dark-field microscope

d. bright-field microscope

Negative stains such as eosin are also called __________________.

a. capsule stains

b. endospore stains

c. simple stains

d. acid-fast stains

In the binomial system of nomenclature, which term is always written in lowercase letters?

a. kingdom

b. domain

c. genus

d. specific epithet

The type of fixation developed by Koch for bacteria is __________________.

Immersion oil __________________ (increases/decreases) the numerical aperture, which __________________ (increases/ decreases) resolution because __________________ (more/fewer) light rays are involved.

__________________ refers to differences in intensity between two objects.

Cationic chromophores such as methylene blue ionically bond to __________________ charged chemicals such as DNA and proteins.

Which of the following is NOT a characteristic of viruses?

1. They are acellular.
2. They are composed of genetic material and protein.
3. They are visible with a light microscope.
4. They are smaller than prokaryotic cells.
5. They are obligatory parasites.