Deck 9: The Cytoskeleton and Cell Motility

Question 1

Which element of the cytoskeleton is found in the cytoplasm and the nucleus?

A)microfilaments
B)microtubules
C)intermediate filaments
D)macrofilaments
E)indeterminate filaments

Answer 1

C

Question 2

The splitting of the cytoplasm of a parent cell into two daughter cells is called ______.

A)diakinesis
B)cytokinesis
C)mitosis
D)meiosis
E)cytomegaly

Answer 2

B

Question 3

In a growing plant cell,cellulose microfibrils are oriented _______ the direction of cell growth.

A)identically to
B)perpendicular to
C)parallel to
D)diagonal to
E)horizontal to

Answer 3

B

Question 4

Which type of cytoskeletal element is described as tough,ropelike fibers composed of a variety of related proteins like keratin?

A)microfilaments
B)microtubules
C)intermediate filaments
D)macrofilaments
E)indeterminate filaments

Question 5

An abnormally high level of _______ of the MAP protein tau is implicated in the development of strange,tangled filaments called _________ that have been seen in the brains of patients suffering from several fatal neurodegenerative diseases like Alzheimer's disease.

A)phosphorylation,neurofibrillary tangles
B)phosphorylation,neurofibrillary anastomoses
C)dephosphorylation,neurofibrillary tangles
D)dephosphorylation,neurofibrillary anastomoses
E)amination,neurofibrillary tangles

Question 6

Which element of the cytoskeleton is found in the cytoplasm and the nucleus?

A)microfilaments
B)microtubules
C)intermediate filaments
D)macrofilaments
E)indeterminate filaments

Question 7

What kinds of forces are thought to hold microtubular structure together?

A)strong interactions
B)noncovalent interactions
C)covalent interactions
D)magnetism
E)strong interactions and covalent interactions

Question 8

The microtubule wall is composed of globular proteins arranged in longitudinal rows called _________.

A)microfilaments
B)protofilaments
C)prototubules
D)prototubulins
E)microtubular units

Question 9

In what form are proteins and neurotransmitters usually transported down the axon of a nerve cell?

A)individually by diffusion
B)in groups of ten
C)inside transport vesicles
D)inside the Golgi complex
E)tied individually to microtubules

Question 10

Fluorescence microscopy allows investigators to view things _________ of regular light microscopes.

A)above the limits of resolution
B)above the limits of magnification
C)below the limits of resolution
D)below the limits of magnification
E)at the limits of magnification

Question 11

Which of the following could be a method used to label microtubules with a fluorescent dye?

A)injecting tubulin with a fluorescent dye
B)attaching a fluorescently-labeled antibody to tubulin
C)attaching a fluorescently-labeled antibody to actin
D)inducing a cell to express the gene for tubulin that has been fused to the gene for GFP
E)attaching a fluorescently-labeled antibody to tubulin and inducing a cell to express the gene for tubulin that has been fused to the gene for GFP

Question 12

Which type of cytoskeletal element is characterized as a hollow,rigid cylindrical tube with walls composed of tubulin subunits?

A)microfilaments
B)microtubules
C)intermediate filaments
D)all of these choices
E)minitubules

Question 13

Given that axons growing out of a neuron require the growth outward of microtubules to support the lengthening axon,what would be likely to happen to axons growing out from a neuron when they are exposed to colchicine or nocodazole?

A)Axons would grow more rapidly.
B)Axonal outgrowth would cease.
C)Axons would branch more often.
D)Axonal outgrowth would change direction more frequently.
E)There would be no change in axonal outgrowth.

Question 14

How are microtubules thought to affect cell shape in plants?

A)Microtubules of the plant cell cortex are thought to affect the movement of cellulose-synthesizing enzymes in the cell membrane,which,in turn,affect cell wall growth and shape.
B)Microtubules of the plant cell vacuole are thought to affect the movement of cellulose-synthesizing enzymes in the cell membrane,which,in turn,affect cell wall growth and shape.
C)Microtubules of the plant cell cortex are thought to affect the movement of lipid-synthesizing enzymes in the cell membrane,which,in turn,affect cell wall growth and shape.
D)Microtubules of the plant cell wall are thought to affect the movement of cellulose-synthesizing enzymes in the cell membrane,which,in turn,affect cell wall growth and shape.
E)Microtubules of the plant cell nucleus are thought to affect the movement of cellulose-synthesizing enzymes in the cell membrane,which,in turn,affect cell wall growth and shape.

Question 15

In cell biology and with respect to microtubules,intermediate filaments,and microfilaments,the word "dynamic" means ________.

A)impressive
B)constant
C)ever-changing
D)energetic
E)forceful

Question 16

Which cytoskeletal element is found could be described as solid,thinner structures that are often organized into a branching network?

A)microfilaments
B)microtubules
C)intermediate filaments
D)macrotubules
E)minifilaments

Question 17

Which of the following appears to be the most extensible?

A)intermediate filaments
B)microtubules
C)microfilaments
D)spindle fibers
E)microtubules and spindle fibers

Question 18

You use an ionic detergent to extract materials from a cell.When you do,much of the mRNA stays behind with the cytoskeleton,which is not solubilized by this treatment.What do these results mean?

A)The cytoskeleton denatures in ionic detergents.
B)The mRNA is solubilized by the ionic detergents.
C)The mRNA is anchored to the cytoskeleton.
D)The cytoplasm is anchored to the mRNA.
E)The cytoskeleton is destabilized by the ionic detergent.

Question 19

In a normal microtubule,how many protofilaments make up its cylindrical wall?

A)13
B)15
C)11
D)9
E)17

Question 20

Which of the following is a function performed by the cytoskeleton?

A)provides structural support that determines cell shape and resists deforming forces
B)positions various organelles within the cell interior
C)provides a network of tracks over which materials like mRNA and organelles move within cells
D)serves as a force-generating apparatus that moves cells from one place to another
E)all of these choices

Question 21

Which MTOC gives rise to cilia and flagella?

A)a centrosome
B)basal bodies
C)centriole
D)PCM
E)the plus end

Question 22

A small zone of fluorescent microtubules in a cell is photobleached so that their fluorescent label gives off no light.Some time later fluorescence returns to the bleached zone in the cell.Which of the following is a possible explanation for the recovery of fluorescence in the region of the cell previously bleached?

A)the dynamics of the microtubules turning over in that bleached zone of the cell
B)the growth of new microtubules into the bleached zone
C)movement of microtubules through the bleached zone
D)all of these choices
E)the dynamics of the microtubules turning over in that bleached zone of the cell and the growth of new microtubules into the bleached zone

Question 23

The movement of endocytic vesicles formed in the neuron terminals from the synapse to the cell body is said to be in a(n)________ direction.

A)retrograde
B)anterograde
C)astronomical
D)radial
E)intergrade

Question 24

What end of a microtubule is associated with the centrosome?

A)the plus end
B)the minus end
C)the 5'-end
D)the 3'-end
E)the 0-end

Question 25

What is the direct source of energy that powers molecular motors?

A)hydrolysis of GTP
B)hydrolysis of ATP
C)a proton gradient
D)a H⁺ gradient
E)condensation of ATP

Question 26

Which of the following molecular motors is associated with microfilaments?

A)kinesins
B)dyneins
C)kinesins and myosins
C)myosins
D)kinesins and dyneins

Question 27

Kinesin movement along a microtubule is said to be highly ________ meaning that it can move considerable distances along an individual microtubule without falling off.

A)excessive
B)processive
C)depressive
D)progressive
E)egressive

Question 28

The simplest and the original assumption about step size for molecular motors was that as the motor protein walked along the actin or microtubule polymer it would step__________.

A)10 nm for every ATP that was hydrolyzed whether it was traveling along actin or tubulin
B)the distance of one tubulin dimer or actin subunit for every 2 ATPs that were hydrolyzed
C)the distance of three tubulin dimers or actin subunits for every ATP that was hydrolyzed
D)random distances along the cytoskeletal polymer for every ATP that was hydrolyzed
E)the distance of one tubulin dimer or actin subunit for every ATP that was hydrolyzed

Question 29

The current model for the nucleation of microtubules is that a helical array of $\gamma$ -tubulin subunits forms an open,lock-washer-like ring-shaped template upon which the first row of $\alpha$$\beta$ -tubulin dimers assembles.How does this model account for the polarity of microtubules?

A)Only the $\alpha$ -tubulin of a heterodimer can bind to the ring of $\gamma$ -subunits.
B)Only the $\beta$ -tubulin of a heterodimer can bind to the ring of $\gamma$ -subunits.
C)The ring structure straightens out the microtubule.
D)The ring structure interacts with a homodimer instead of a heterodimer.
E)Only the $\alpha$ -tubulin of a heterodimer can bind to the ring of $\gamma$ -subunits and the ring structure straightens out the microtubule.

Question 30

Motor proteins are able to generate force by ___________.

A)undergoing a series of conformational changes
B)breaking bonds
C)making bonds
D)adding amino acids to the end of the molecular motor
E)making bonds AND adding amino acids to the end of the molecular motor

Question 31

In order to measure the step size of kinesin,a group of investigators attached a small silica bead to the tail of a kinesin molecule.What advantage(s)did the attached silica bead provide?

A)The bead made kinesin activity visible.
B)The bead helped to denature kinesin making its properties easier to measure.
C)The bead provided a handle for manipulating and holding the motor using an optical trap.
D)The bead absorbed laser light in a manner proportional to the distance the motor moved.
E)The bead made kinesin activity visible AND provided a handle for manipulating and holding the motor using an optical trap.

Question 32

Which of the following molecular motors is known to travel in a retrograde direction along microtubules?

A)kinesins
B)dyneins
C)myosins
D)kinesins and myosins
E)kinesins and dyneins

Question 33

Structures that move from the cell body of a neuron down the axon toward the neuron terminals are said to move in a(n)_________ direction.

A)retrograde
B)anterograde
C)astronomical
D)radial
E)intergrade

Question 34

Which of the following molecular motors is known to travel in an anterograde direction along microtubules?

A)kinesins
B)dyneins
C)myosins
D)kinesins and dyneins
E)kinesins and myosins

Question 35

The first direct measurement of a motor taking single steps was an analysis of _______ stepping using _________.

A)myosin,optical trap technology
B)dynein,ion exchange chromatography
C)kinesin,optical trap technology
D)kinesin,ion exchange chromatography
E)dynein,polyacrylamide gel electrophoresis

Question 36

Nucleation of microtubules takes place rapidly inside a cell,where it occurs in association with a variety of specialized structures called _____________.

A)MTOCs
B)the centrosome
C)basal bodies
D)microtubule-organizing centers
E)All of the other answers

Question 37

What part of the molecular motor kinesin is responsible for binding to the cargo to be hauled?

A)the motor domain
B)the neck
C)the rod-like stalk
D)the fan-shaped tail
E)the motor domain and the neck

Question 38

Which of the following treatments does not disassemble microtubules in living cells?

A)slightly elevated temperature
B)hydrostatic pressure
C)elevated Ca²⁺ ion concentration
D)colchicine or vinblastine treatment
E)all of these choices disassemble microtubules in living cells

Question 39

The sperm basal body becomes ______________.

A)a basal body of the fertilized egg
B)pericentriolar material
C)five microtubules
D)a flagellum of the later embryo
E)a centriole during the first mitotic division of the fertilized egg

Question 40

What is the minimum number of kinesin heads in contact with a microtubule at all times?

A)0
B)1
C)2
D)3
E)4

Question 41

Treatment of isolated sperm axonemes with 0.6 M NaCl has been shown to remove selectively the outer arms from the A microtubules of the axoneme,leaving the inner arms in place.What would be the most likely effect on the NaCl-treated axoneme when ATP was added to the medium?

A)The axoneme would fall apart completely.
B)The axonemes would beat at about half the rate of the intact axoneme.
C)The central microtubules would disassemble leaving the rest of the axoneme intact.
D)The axoneme would be solubilized.
E)Every element of the axoneme would be permanently cross-linked.

Question 42

For a long time,it was thought that cilia were unimportant or _________,despite their presence on almost all cells.This idea arose because the cilia on most cells are non‐motile,and it was assumed that motility was the key function of cilia.

A)flagellar
B)execrable
C)ciliopathic
D)vestigial
E)vestibular

Question 43

___________ are recently discovered diseases that result from organelle dysfunction.Specifically,each of these diseases is a set of seemingly unrelated disease symptoms that all result from defects in cilia.

A)Flagellopathies
B)Cilioflagellar diseases
C)Ciliopathies
D)Ciliary diseases
E)Pathophysicilias

Question 44

What protein is responsible for intraflagellar transport of IFT trains back toward the cell body?

A)kinesin-II
B)myosin
C)cytoplasmic dynein
D)kinesin
E)cytoplasmic kinesin

Question 45

The _______ link is an elastic protein-based linkage that connects tubulin doublets in cilia and flagellae.The resultant bridges play an important role in ciliary and flagellar movement by limiting the extent that adjacent doublets can slide over one another.The resistance to sliding provided by these bridges causes the axoneme to bend.

A)plectin
B)filamentin
C)nexin
D)vimentin
E)myosin

Question 46

The core of a cilium is called the ________.

A)troponeme
B)dynomeme
C)cilioneme
D)axoneme
E)flagelloneme

Question 47

The peripheral doublets of the axoneme are connected to one another by a(n)________ composed of an elastic protein-based linkage called the _______.

A)intersheath bridge,nexin link
B)peridoublet sheath,dynein link
C)interdoublet bridge,nexin link
D)interdoublet sheath,dynein link
E)peridoublet sheath,nexin link

Question 48

Which of the following treatments did not help microtubules to polymerize when homogenates prepared from brain tissue received it?

A)Mg²⁺ ions
B)GTP
C)EGTA
D)a temperature of 37°C
E)a temperature of 4°C

Question 49

Which of the following is normally associated with the cilia of organisms from protists to mammals?

A)a 9 + 0 pattern
B)a 9 + 1 pattern
C)a 9 + 2 pattern
D)microtubules
E)none of these choices

Question 50

Bardet‐Biedl syndrome (BBS)is caused by mutations in any one of a number of genes that affect protein trafficking into cilia.Persons afflicted with BBS exhibit a remarkable range of abnormalities,like polydactyly,obesity,kidney disease,etc.These disparate symptoms are thought to reflect the function of cilia ________________.

A)as sensors for a magnetic field
B)as locomotory organelles
C)as sources of flagella
D)as binding sites for actin
E)as antennas to receive signals that regulate development and physiology

Question 51

From what structure do cilia and flagella emerge?

A)centromeres
B)basal bodies
C)centrioles
D)spindle
E)MTOC

Question 52

PC1 and PC2 form a complex in which PC2 serves as a(n)____________.

A)sensor for fluid flow in the kidney tubules
B)associated Ca²⁺ ion channel
C)water channel
D)associated Ca²⁺ ion pump
E)associated K⁺ channel

Question 53

One surprising symptom of that occurs in roughly half of patients who have non-motile cilia is a complete reversal of the left-right asymmetry of the internal organs.This condition is called _________.

A)misplaced organs
B)situs reversus
C)ambiorganismus
D)sinus inversus
E)situs inversus

Question 54

To which end of microtubules are tubulin subunits primarily added in vitro?

A)the minus end
B)the N-terminal end
C)the plus end
D)the C-terminal end
E)the 5'-end

Question 55

If there is no flow of extraembryonic fluid over a mouse embryo,___________.

A)most of the embryos die early in development
B)the majority of embryos still orient correctly
C)the left-right asymmetry decision for the embryo is made at random
D)the majority of embryos exhibit situs inversus
E)the embryos exhibit no asymmetrical arrangement of organs

Question 56

EDTA is a chemical that binds to and removes (chelates)divalent cations from solution.Treatment of isolated axonemes with EDTA leads to the removal of the inner and outer arms extending from the A microtubules of the axoneme.Which of the following statements wouls appear to be true based on this information?

A)Potassium ions are required for dynein to bind to the A tubules of the axoneme.
B)Chlorine ions are required for dynein to bind to the A tubules of the axoneme.
C)Magnesium ions are required for dynein to bind to the A tubules of the axoneme.
D)Magnesium ions are required for tubulin to bind to the A tubules of the axoneme.
E)Sodium ions are required for tubulin to bind to the A tubules of the axoneme.

Question 57

Of what protein are the arms attached to the A microtubule of the axoneme composed?

A)tubulin
B)actin
C)dynein
D)keratin
E)myosin

Question 58

Why are taxol,vinblastine and other drugs like them used as chemotherapy agents?

A)They preferentially kill tumor cells.
B)They preferentially stabilize tumor cells.
C)They disrupt tumor cell membranes.
D)They prevent the entry of cells into the first stage of meiosis.
E)They inhibit mitochondria.

Question 59

Which of the following is NOT a function of a cilium?

A)moving the cell from place to place
B)moving fluid and particulate material past the cell
C)a role in sensory function in monitoring the properties of extracellular fluids
D)moving vesicles down the nerve cell axon
E)All of these choices are functions of a cilium.

Question 60

Which of the following is a plausible explanation for the fact that the chemical EGTA blocks microtubule disassembly?

A)EGTA binds to Ca²⁺ ions,which are known to induce microtubule depolymerization.
B)EGTA binds to Mg²⁺ ions,which are known to induce microtubule depolymerization.
C)EGTA binds to Ca²⁺ ions,which are known to induce microtubule polymerization.
D)EGTA destroys Ca²⁺ ions,which are known to inhibit microtubule polymerization.
E)EGTA destroys Mg²⁺ ions,which are known to inhibit microtubule polymerization.

Question 61

Researchers worked with mouse embryos that had non‐motile cilia and used a pump to drive an artificially created flow over their surface.When the flow was leftward directed,the mice developed _____________.

A)normal organ positions
B)situs inversus
C)randomly placed organ positions
D)the embryos die fairly early in development
E)the embryos develop into identical twin embryos

Question 62

Along which structure do membranous vesicles and organelles typically engage in local movement in the cell periphery of an animal cell?

A)mitochondria
B)microtubules
C)microfilaments
D)intermediate filaments
E)lysosomes

Question 63

The cilia-driven flow in human and mouse embryos is detected by ___________.

A)renin
B)the Na⁺-K⁺ pump
C)polycystins
D)polyphenylin
E)cysteine

Question 64

Why is myosin V able to take very large steps along a microfilament?

A)Its neck is twisted.
B)Its neck is relatively long.
C)Its neck is relatively short.
D)Its tail is very long.
E)Its tail is bipolar.

Question 65

What chemical below is known to bind to free actin monomers and block their incorporation into the polymer?

A)cytochalasins
B)nocodazole
C)phalloidin
D)latrunculin
E)phalloidin and latrunculin

Question 66

What motor is associated with microfilaments?

A)myoglobin
B)kinesin
C)myosin
D)dynein
E)myometrium

Question 67

You inject labeled keratin subunits into cultured skin cells.What happens a few minutes later?

A)The keratin subunits remain in the cytoplasmic keratin subunit pool.
B)Filaments become labeled at sites scattered throughout their length,rather than at their ends.
C)Filaments become labeled at both ends simultaneously.
D)Filaments become labeled at one end exclusively.
E)The entire intermediate filament network is quickly labeled.

Question 68

Which protein below is often a component of intermediate filaments?

A)alpha-tubulin
B)beta-tubulin
C)actin
D)keratin
E)myosin

Question 69

What kind of cells seems to rely mostly on microfilaments for long-distance transport of cytoplasmic vesicles and organelles,probably due to the restricted microtubule distribution in these cells?

A)red blood cells
B)white blood cells
C)plant cells
D)neurons
E)muscle cells

Question 70

Along which structure do membranous vesicles and organelles typically move long distances in an animal cell?

A)mitochondria
B)microtubules
C)microfilaments
D)intermediate filaments
E)lysosomes

Question 71

What seems to control the assembly and disassembly of intermediate filaments?

A)denaturation
B)sulfation
C)phosphorylation and dephosphorylation
D)hydrolysis
E)hydroxylation

Question 72

With which of the following structures are intermediate filaments associated?

A)the nuclear envelope in the center of the cell
B)hemidesmosomes
C)desmosomes
D)the neurofilaments of neuron axons
E)all of these choices

Question 73

Which of the following words best describes the structure of an actin filament?

A)single actin strand
B)triple helix
C)hyperpolar filament
D)double helix
E)supercoil

Question 74

Which of the following does not describe the types of microfilament organization normally seen in cells?

A)ordered arrays
B)highly branched networks
C)tightly anchored bundles
D)cylindrical conglomerations
E)all of these choices describe types of microfilament organization

Question 75

The myosin filament is characterized as a(n)_________ filament.

A)bipolar
B)unipolar
C)tripolar
D)parallel
E)orthogonal

Question 76

From where does the energy to run myosin motors come?

A)GTP
B)ATP
C)proton gradient
D)CTP
E)creatine phosphate

Question 77

A culture of Dictyostelium slime mold is prepared in which the myosin II gene is deleted.In which activity or activities below are these cells unable to participate?

A)separation of chromosomes during mitosis
B)cell elongation
C)cytokinesis
D)separation of chromosomes during mitosis and cell elongation
E)separation of chromosomes during mitosis and cytokinesis

Question 78

The cross-bridges that hold intermediate filaments together are composed of _______.

A)filamentin
B)plectin
C)ascriptin
D)dynein
E)myosin

Question 79

The central,rod-shaped domain of an intermediate filament is flanked on each side by globular domains of variable size and sequence.What structure forms the core of the central,rod-shaped domain?

A)alpha-helix
B)beta-pleated sheet
C)double helix
D)quaternary coil
E)coiled coil

Question 80

Which property below is most characteristic of intermediate filaments?

A)elastic
B)highly resistant to shrinkage
C)springy
D)ability to absorb mechanical stresses applied by the extracellular environment
E)hyperflexible