Deck 18: Techniques in Cell and Molecular Biology

Question 1

What is the name of the special device used to section a frozen block of tissue?

A)microtome
B)ultramicrotome
C)cryomicrotome
D)ultratome
E)microslicer

Answer 1

C

Question 2

The 3-D computerized reconstruction of a cell generated by cryoelectron tomography is called a(n)________.

A)tomatogram
B)chromatogram
C)tomogram
D)telegram
E)tonogram

Answer 2

C

Question 3

The electron beam strikes the specimen in an area where there is a high concentration of heavy metal atoms.What does the spot on the phosphorescent screen of the electron microscope just below this part of the specimen look like?

A)It is dark.
B)It is bright.
C)It is speckled.
D)It is invisible.
E)It is purple.

Answer 3

A

Question 4

What part of a microscope is responsible for altering the relative distance between the specimen and the objective,thus focusing the final image precisely on the plane of the retina?

A)condenser lens
B)objective lens
C)ocular lens
D)the iris
E)focusing knob

Question 5

How do you prepare tissue for electron microscopy without using fixatives?

A)Freeze it gradually over a few hours.
B)Freeze it rapidly.
C)Subject it to a vacuum rapidly.
D)Heat it to dry it rapidly.
E)Coat it quickly in heavy metal.

Question 6

In freeze-fracture methodology,the metal-carbon coating of the freeze-fracture specimen is viewed in the electron microscope after the tissue template has been thawed,removed and discarded.What is the name of the metal-carbon construct that is viewed in the scope?

A)a model
B)a repeat
C)a replica
D)an object
E)a metallica

Question 7

Of what is the electron source of an electron microscope,the cathode,composed?

A)a tungsten wire filament
B)an iron wire filament
C)a titanium wire filament
D)an iron spike filament
E)a tungsten spike filament

Question 8

Which part of a microscope uses the real,enlarged image formed by the objective lens in the column of the microscope and forms from it an enlarged,virtual image?

A)condenser lens
B)the numerical aperture
C)ocular lens
D)iris
E)focusing knob

Question 9

Good fixatives are chemicals that _______ and ________ cellular macromolecules without producing artifacts.

A)precipitate,degrade
B)degrade,denature
C)denature,precipitate
D)denature,polarize
E)polarize,precipitate

Question 10

The magnification of a microscope is equal to __________.

A)the product of magnification produced individually by the ocular and the N.A.
B)the product of magnification produced individually by the ocular and objective lenses
C)the magnification power of the objective lens divided by the N.A.
D)the magnification power of the ocular lens divided by the N.A.
E)the magnification power of the objective lens divided by that of the ocular lens.

Question 11

Why does the fracture plane usually pass through the center of cell membranes?

A)Fracture planes are naturally attracted to lipids.
B)Fracture planes take the path of least resistance through the block and the center of the membrane is such a path.
C)Fracture planes are repelled by the cytoplasm and pushed toward the membrane.
D)Fracture planes take the path of highest resistance through the block and the center of the membrane is such a path.
E)Fracture planes are attracted to phospholipids tails,especially their ends,by their hydrophobicity.

Question 12

Which part of a microscope is responsible for gathering diffuse rays from the microscope light source and illuminating the specimen with a small cone of bright light?

A)condenser lens
B)objective lens
C)ocular lens
D)iris
E)focusing knob

Question 13

Which electron microscope technique below is used to view the surfaces of objects ranging in size from a virus to an animal's head and generates a three-dimensional image?

A)positive staining
B)negative staining
C)scanning electron microscopy
D)shadow casting
E)freeze-fracture freeze-etch

Question 14

A(n)_________ is responsible for collecting light rays previously focused on the specimen.

A)condenser lens
B)objective lens
C)ocular lens
D)iris
E)focusing knob

Question 15

What advantage do images produced by freeze-fracturing and freeze-etching have over images generated with freeze-fracturing alone?

A)The images with freeze-fracture-freeze-etch are three-dimensional.
B)The images with freeze-fracture-freeze-etch are in color.
C)The images with freeze-fracture-freeze-etch reveal both the external and the internal surfaces of the cell membrane.
D)The images with freeze-fracture-freeze-etch reveal only the external surface of the cell membrane.
E)The images with freeze-fracture-freeze-etch reveal only the internal surface of the cell membrane.

Question 16

Why must a specimen that is to be viewed in the SEM have no water in it?

A)Water causes the specimen to swell.
B)Water distorts the image.
C)The specimen will be observed in a vacuum,which will cause the water to freeze.
D)The specimen will be observed in a vacuum,which will cause the water to evaporate rapidly and damage the specimen,altering its surface structure.
E)Water attracts electrons.

Question 17

The fractured surface of the specimen is coated with a heavy metal layer with the metal being deposited at an angle.A uniform carbon layer is deposited on top of the metal layer from directly overhead to cement the patches of metal into a solid layer.What is the name for this process?

A)freeze-fracture
B)replication
C)entrapment
D)metallification
E)freeze-etch

Question 18

What word or phrase describes what you get if the magnification power of the microscope exceeds the ability of the scope to resolve?

A)empty resolution
B)waste
C)empty magnification
D)refractibility
E)birefringence

Question 19

With what molecules in a cell does osmium tetroxide primarily react?

A)DNA
B)RNA
C)fatty acids
D)proteins
E)carbohydrates

Question 20

Why is a uniform layer of carbon applied to a replica after the metal has coated the specimen at an angle?

A)to make the replica smooth
B)to cement the patches of metal into a solid surface
C)to make the replica rough
D)to make the replica transparent to electrons
E)to make the replica opaque to electrons

Question 21

Which technique for detecting radioactivity is the best one for quantifying the amount of radioactivity in a specimen?

A)autoradiography
B)an NMR machine
C)liquid scintillation spectrometry
D)mass spectrometry
E)AFM

Question 22

Which form of radiation is emitted by the most commonly used isotopes and by most biologically important isotopes?

A)an alpha particle
B)a delta particle
C)a beta particle
D)gamma radiation
E)an omega particle

Question 23

A(n)________ is a substance that reveals its presence in one way or another and thus can be localized or monitored during an experiment.

A)trancer
B)tracer
C)phosphor
D)fluor
E)trancept

Question 24

When specimens are air-dried,what causes the damage that the tissues suffer?

A)shrinkage
B)swelling
C)surface tension at air-water interfaces
D)hydrostatic pressure
E)air pressure

Question 25

With what is the solvent in an SEM specimen's cells usually replaced?

A)water
B)glycerol
C)a liquid transitional fluid,usually CO2,that has been vaporized under pressure
D)serum
E)hydrochloric acid

Question 26

________ are atoms with the same number of protons and varying number of neutrons.

A)Isomers
B)Isosceles
C)Isotopes
D)Epitopes
E)Haplotypes

Question 27

A ________ is a culture in which the cells have undergone genetic modifications that allow them to grow indefinitely.

A)cell establishment
B)cell line
C)cell kultur
D)monolayer
E)suspension culture

Question 28

In which technique is radioactivity detected by mixing the sample in a vial with a special fluid that contains compounds that emit light if struck by a beta particle? The amount of light emitted in the fluid is a measure of the amount of radioactivity in sample.

A)autoradiography
B)an NMR machine
C)liquid scintillation spectrometry
D)mass spectrometry
E)AFM

Question 29

What happens if a photographic emulsion is brought into close contact with radioactive source in a specimen?

A)The emulsion is degraded in places close to a radioactive atom.
B)The particles emitted by the source leave tiny,black silver grains in the emulsion after photographic development.
C)The particles emitted by the source leave tiny,black potassium grains in the emulsion after photographic development.
D)The particles emitted by the source leave tiny,silver carbon grains in the emulsion after photographic development.
E)The particles emitted by the source leave tiny,gold atoms in the emulsion after photographic development.

Question 30

If the photographic emulsion used in the autoradiography procedure is left in contact with the isotope for a longer period of time,what happens?

A)There are more exposed silver grains.
B)There are fewer exposed silver grains.
C)There is no change in the number of exposed silver grains.
D)The entire specimen will be uniformly covered with exposed silver grains.
E)There will be very few exposed silver grains.

Question 31

Which form of radiation is composed of electromagnetic radiation or photons?

A)an alpha particle
B)a delta particle
C)a beta particle
D)gamma radiation
E)omega radiation

Question 32

What determines the identity and chemical properties of an atom?

A)the number of protons in its nucleus
B)the number of neutrons in its nucleus
C)the number of electrons in its nucleus
D)the number of protons in the atom's electron shells
E)the number of neutrons in the atom's electron shells

Question 33

How do enzymes like trypsin release cells from tissues to create preparations of single cells?

A)The enzymes digest extracellular domains of proteins that mediate cell adhesion.
B)The enzymes digest intracellular domains of proteins that mediate cell adhesion.
C)The enzymes digest intracellular domains of proteins that mediate cytoskeletal function.
D)The enzymes digest extracellular domains of proteins that mediate cytoskeletal function.
E)The enzymes digest extracellular domains of proteins that mediate endocytosis.

Question 34

__________ are established with cells that have been obtained directly from the organism;most of these cultures produced from animal cells are obtained from ________.

A)Primary cultures,embryos
B)Secondary cultures,adult organisms
C)Primary cultures,adult organisms
D)Secondary cultures,embryos
E)Secondary cultures,primary cultures

Question 35

_________ are established with cells that have been frozen in liquid nitrogen,thawed and then placed in a waiting culture medium.They are usually previously cultured cells that were frozen for storage.

A)Primary cultures
B)Secondary cultures
C)Tertiary cultures
D)Supernatant cultures
E)Penultimate cultures

Question 36

What is a chelator?

A)a substance that precipitates cells
B)a substance that degrades the proteins that hold cells together
C)a substance that binds to or chelates calcium ions to remove them from solution
D)a substance that precipitates calcium ions
E)a substance that adds calcium ions to a solution

Question 37

Which of the following words is a correct description of image formation in the scanning electron microscope?

A)direct
B)explosive
C)indirect
D)flexible
E)inflexible

Question 38

Which form of radiation is equivalent to a helium atom nucleus?

A)an alpha particle
B)a delta particle
C)a beta particle
D)gamma radiation
E)an omega particle

Question 39

What method is typically used to dry specimens for scanning electron microscopy?

A)air drying
B)critical-point drying
C)forced air drying
D)vacuum drying
E)dehydrational drying

Question 40

Which form of radiation is equivalent to an electron?

A)an alpha particle
B)a delta particle
C)a beta particle
D)gamma radiation
E)an omega particle

Question 41

What is required in order to study a protein's fine structure or function?

A)It must be isolated in a relatively pure state.
B)It must be observed in a light microscope.
C)It must be denatured.
D)It must be enzymatically degraded.
E)It must be fixed.

Question 42

A culture system in which cells are grown in a three-dimensional matrix consisting of synthetic and/or natural extracellular materials is called a ______.

A)three-dimensional culture system
B)two-dimensional culture system
C)matrix culture system
D)secondary culture system
E)organic culture system

Question 43

Most proteins have an isoelectric point ________ 7.

A)equal to
B)above
C)below
D)far above
E)at or above

Question 44

What is the term for a variety of techniques in which a mixture of dissolved components is fractionated as it moves through a porous matrix?

A)electrophoresis
B)isoelectric focusing
C)chromatography
D)selective precipitation
E)sucrose density centrifugation

Question 45

What typically happens if the cells of a cell line are injected into susceptible lab animals?

A)They become a normal part of the appropriate tissue in the lab animal.
B)They soon die.
C)They typically grow into malignant tumors.
D)They typically grow into the appropriate organ.
E)They become part of organs

Question 46

What property of proteins is used to purify them by selective precipitation?

A)binding specificity
B)solubility differences
C)molecular weight
D)molecular shape
E)isoelectric point

Question 47

After plant cells have been separated and grown in culture,they can grow into an undifferentiated clump of cells called a(n)__________.

A)callus
B)callous
C)blastema
D)tumor
E)blastula

Question 48

For each protein,there is a pH at which negative and positive charges are equal.This pH is referred to as the ___________.

A)pH point
B)neutralization point
C)isometric point
D)isoelectric point
E)isotonic point

Question 49

Protein solubility in a given solution is based on ____________.

A)the relative balance between protein-solvent and protein-protein interactions
B)the relative balance between protein-solvent and protein-salt interactions
C)the relative balance between protein-sucrose and protein-protein interactions
D)the relative balance between protein-solvent and protein-lipid interactions
E)the relative balance between protein-solvent and protein-polynucleotide interactions

Question 50

A plant cell that lacks a cell wall is called a(n)_________.

A)celluplast
B)protoblast
C)protoplast
D)spheroplast
E)epiblast

Question 51

As solvent passes through a column,it is collected as it drips out of the bottom of the column into a series of tubes;each of these tubes is called a(n)____________.

A)elutant
B)fractal
C)diluent
D)fraction
E)comutant

Question 52

__________ is the ratio of the amount of the protein of interest to the total amount of total protein present in the sample.

A)Radioactivity
B)Special activity
C)Specific activity
D)Magnetic activity
E)Proteinaceous activity

Question 53

Which of the following is a technique used to isolate a particular organelle in bulk so that its function can be studied or so that an enzyme can be isolated from it?

A)differential interference contrast microscopy
B)differential centrifugation
C)affinity chromatography
D)selective precipitation
E)autoradiography

Question 54

Under what set of circumstances will organelles move to the bottom of a centrifuge tube in a centrifugal field?

A)if the organelle is smaller than ribosomes
B)if the organelle has too much fat content
C)if the organelle is less dense than the surrounding medium
D)if the organelle is more dense than the surrounding medium
E)if the organelle has less fat content than the surrounding medium

Question 55

Why does ion exchange chromatography depend on the pH of the medium?

A)The charge of each amino acid R group depends on the medium's pH.
B)The charge of each nucleic acid R group depends on the medium's pH.
C)The charge of each fatty acid R group depends on the medium's pH.
D)The charge of each terminal amino acid depends on the medium's pH.
E)The shape of each protein depends on the medium's pH.

Question 56

What salt is most often used in selective precipitation experiments?

A)sodium chloride
B)sodium carbonate
C)ammonium sulfate
D)ammonium chloride
E)sodium thiocyanate

Question 57

What technique distributes the contents of a homogenate into various layers according to the components' densities?

A)sucrose density gradient centrifugation
B)sucrose density chromatography
C)isoelectric density focusing
D)liquid scintillation spectrometry
E)autoradiography

Question 58

In which chromatographic method are the charges of the proteins in question the basis of their purification?

A)affinity chromatography
B)gel filtration
C)HPLC
D)ion exchange chromatography
E)polyvalent chromatography

Question 59

When a cell is growing on a culture dish,what is the word that refers to the lower surface of the cell facing toward the substratum?

A)anterior
B)dorsal
C)posterior
D)ventral
E)caudal

Question 60

What is the significance of the varying porosity of gel filtration media?

A)It allows water to restrict solubility.
B)It allows proteins or nucleic acids to diffuse in and out of the beads differentially.
C)It causes the proteins or nucleic acids to denature.
D)It causes the proteins or nucleotides to precipitate.
E)It causes the proteins or nucleic acids to solubilize.

Question 61

Under what circumstances will a component in a solution or a suspension sediment through a centrifugal field?

A)if it has a greater density than the surrounding medium
B)if it has a lower density than the surrounding medium
C)if it is wet
D)if the surrounding medium is denser than the component
E)if the component and the surrounding medium have equal density

Question 62

Where is RNA found after the ethanol precipitation step in the DNA isolation procedure?

A)at the interface between the aqueous and phenol phases
B)in the aqueous phase
C)in the phenol phase
D)at the ethanol/saline interface
E)settled in a flocculant precipitate at the bottom of the vessel

Question 63

What is the name of the procedure in which proteins separated on a polyacrylamide gel are transferred with the application of a current to a nitrocellulose filter placed against the gel and subsequently identified by their interaction with specific antibodies?

A)a Southern blot
B)a Northern blot
C)an Eastern blot
D)a Western blot
E)an East Northeastern blot

Question 64

How are fragments already in a mass spectrometer further fragmented if this becomes necessary?

A)injection of pepsin
B)injection of more trypsin
C)collision of peptides with an inert gas
D)collision of peptides with nitrogen gas
E)collision of peptides with oxygen

Question 65

What happens to the solution viscosity after DNA has been released into it by treating nuclei with a buffered saline solution containing SDS?

A)It increases markedly.
B)It decreases markedly.
C)There is no change.
D)There is an increase followed by a rapid decrease.
E)There is a decrease followed by fluctuating increases.

Question 66

To what are the reflection positions and intensities on the photographic plate of an X-ray crystallography experiment related?

A)proton densities of proteins
B)neutron densities of proteins
C)electron densities of proteins
D)proton densities of nucleic acids
E)neutron densities of lipids

Question 67

How sensitive is gel electrophoresis when it is used to separate DNA?

A)It can separate fragments of DNA that differ grossly in size.
B)It can separate really big DNAs from very small DNAs.
C)It can separate DNAs that differ by hundreds of nucleotides.
D)It can separate DNA molecules that vary in length by only a single nucleotide.
E)It can separate DNA molecules that vary in length by five or more nucleotides.

Question 68

Which technique could be used for molecular weight (mass)determinations in proteins?

A)X- ray diffraction
B)chromatofocusing
C)diethylaminoethyl (DEAE)cellulose chromatography
D)affinity chromatography
E)SDS-PAGE

Question 69

Electron cryomicroscopy can be used to cause membrane proteins to become closely packed at very low temperatures into two-dimensional crystalline arrays within the plane of a membrane.The structures of such proteins are then determined from combined,high-resolution electron microscope images of many different protein molecules taken at various angles.This process is called __________.

A)cryopreservation
B)electron crystallography
C)cryohistology
D)electron cryocrystallography
E)proton microscopy

Question 70

The amount of light passing through a solution unabsorbed or _________ is measured by ________ on the other side of the cuvette.

A)transmitted light,thermocouplers
B)absorbed light,thermocouplers
C)transmitted light,photocells
D)absorbed light,photocells
E)transmitted light,charged coupling devices

Question 71

What does the change in field direction in pulsed field electrophoresis accomplish?

A)It makes the DNA molecules move faster.
B)It causes the DNA molecules to reorient themselves during their migration.
C)It causes the DNA molecules to denature.
D)It causes the DNA molecules to renature.
E)It causes the stain to adhere better to the DNA molecules.

Question 72

Pulsed-field electrophoresis is typically used to separate what molecules?

A)small DNA molecules
B)very small DNA molecules
C)proteins larger than 25,000 daltons
D)DNA molecules greater than about 25 kb
E)DNA molecules smaller than about 25 kb

Question 73

Non-denaturing gel electrophoresis (PAGE)has the disadvantage that it ____________.

A)separates solely on the basis of charge
B)allows the detection of proteins in a gel by their biological activity
C)separates on the basis of more than one property thus to some degree confusing the results
D)separates solely on the basis of molecular weight
E)separates on the basis of molecular weight and frictional coefficient

Question 74

After exposing a DNA extract to phenol or a mixture of phenol and chloroform and centrifuging the solution,where are the proteins located?

A)in the upper aqueous phase
B)in the lower phenol phase
C)in the upper phenol phase
D)in the lower aqueous phase
E)precipitated at the boundary between the aqueous and phenol phases

Question 75

In what electrophoresis medium are small RNAs or DNAs of a few hundred nucleotides typically separated?

A)agarose
B)polyacrylamide
C)cellulose
D)paper
E)dextran

Question 76

What is usually the first step in the purification of DNA?

A)homogenization of cells and isolation of nuclei
B)fixation of the cells
C)isolation of mitochondria and chloroplasts
D)crystallization of DNA
E)removal of deoxyribonucleases

Question 77

Which of the following is most likely to elute first from a gel filtration column if each of them is essentially globular?

A)a 250 kilodalton protein
B)a 120 kilodalton protein
C)a chromate ion
D)a 12 kilodalton protein
E)an 80 kilodalton protein

Question 78

When making a measurement in a spectrophotometer if you are illuminating a specimen with ultraviolet light,into what kind of container should it be placed?

A)in a basinette
B)in a special,flat-sided quartz container
C)in a borosilicate glass tube
D)in a special,flat-sided glass container
E)in a special,flat-sided plastic container

Question 79

Why do phenol and buffered saline separate into two phases when one centrifuges the mixture during the DNA extraction procedure?

A)They are soluble.
B)They are miscible.
C)They are immiscible.
D)One freezes and the other does not.
E)They are both hydrophobic.

Question 80

How can a researcher visualize all of the DNA fragments present in an electrophoresis gel?

A)using a labeled probe with a sequence complementary to the desired DNA fragment
B)staining with ethidium bromide
C)staining with potassium chloride
D)using labeled antibodies
E)staining with Coomassie Blue