Deck 9: The Cytoskeleton and Cell Motility

Question 1

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/depolymerized 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.

Answer 1

C

Question 2

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

A)in the same direction as
B)perpendicular to
C)parallel to
D)diagonally to
E)horizontal to

Answer 2

B

Question 3

Left or right handed spiral growth in Arabidopsis has been linked to all of the following proteins EXCEPT:

A)α tubulin
B)β tubulin
C)plant specific MAPs
D)actin
E)all of these proteins have been linked to spiral growth

Answer 3

D

Question 4

Which of the following describes functions 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)providesa networkof tracks overwhich materialslike mRNAand organelles move within cells
D)serves as a force-generating apparatus that moves cells from one place to another
E)all of these choices are correct

Question 5

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

Question 6

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 7

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

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

Question 8

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

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

Question 9

Which of the following is most extensible?

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

Question 10

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

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

Question 11

Given that axons growing out of a neuron require the outward growth of microtubules to support the lengtheningaxon, 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 12

Which of the following would be the most direct method 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 13

How 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 14

When the MAP protein tau has abnormally high levels of __________, it is associated with 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 15

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

A)actin filaments
B)protofilaments
C)prototubules
D)prototubulins
E)microtubular units

Question 16

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)minitubules

Question 17

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

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

Question 18

What kinds of forces hold microtubular structure together?

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

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

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

Question 21

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

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

Question 22

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)varying 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 23

Point mutations in α or β tubulin which are associated with spiral growth in Arabidopsis plants are often located at

A)sites of lipid-protein interaction
B)sites of sugar-protein interaction
C)sites of nucleic acid-protein interaction
D)sites of protein-protein interaction

Question 24

Which MTOC gives rise to cilia and flagella?

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

Question 25

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

Question 26

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 27

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

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

Question 28

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 29

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 30

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 31

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

A)hydrolysis of GTP
B)hydrolysis of ATP
C)aproton gradient
D)an H⁺ gradient
E)condensation of ATP

Question 32

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

Question 33

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 terms are correct

Question 34

Which of the following molecular motors are associated with actin filaments?

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

Question 35

Which of the following treatments do/does NOT disassemble microtubules in living cells?

A)slightly elevated temperature
B)hydrostatic pressure
C)elevatedCa²⁺ion concentration
D)colchicine or vinblastine treatment
E)all of these choices disassemble microtubules in living cells

Question 36

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

Question 37

The enzyme whose activity is altered when microtubule arrangements are misaligned, leading to spiral Arabidopsis growth is:

A)SPIRAL1
B)cellulose synthetase
C)plant specific MAP
D)SPIRAL2
E)microfibril synthetase

Question 38

Motor proteins are able to generate force by ___________.

A)undergoing a series of conformational changes
B)polymerization of protofilaments
C)deploymerization of protofilaments
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 39

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 40

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

A)They preferentially affect actively dividing cells, like tumor cells.
B)They 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 41

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)inflexible

Question 42

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 43

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

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

Question 44

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

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

Question 45

Which of the following is NOT a function of cilia?

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

Question 46

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 47

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)a 9 + 3 pattern
E)none of these choices

Question 48

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

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

Question 49

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 50

The _______ link is an elastic protein-based linkage that connects tubulin doublets in cilia and flagella. 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 51

The core of a cilium is called the ________.

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

Question 52

Which protein below is often a component of intermediate filaments?

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

Question 53

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 would 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 54

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 55

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 disparatesymptoms are thought to reflect the function of cilia ________________.

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

Question 56

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 57

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

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

Question 58

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 59

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

A)normal organ positions
B)situsinversus
C)randomly placed organ positions
D)abnormally; embryos died fairly early in development
E)into identical twin embryos

Question 60

Treatment of isolated spermaxonemes with 0.6 M NaClhas been shown to selectively remove 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 61

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)theneurofilaments of neuronal axons
E)all of these choices are correct

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)actin filaments
D)intermediate filaments
E)lysosomes

Question 63

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 64

What accounts for the decrease in the length of an entire muscle?

A)the combined decrease in sarcomere length
B)the combined shortening of actin filaments
C)the combined shortening myosin filaments
D)the combined shortening of thin filaments
E)the combined decrease in sarcomere length and the combined shortening of actin filaments

Question 65

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

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

Question 66

How do muscle cells become multinucleate?

A)They become multinucleate as they undergo fission.
B)They become multinucleate via the embryonic fusion of large numbers of mononucleate myoblasts.
C)They become multinucleate via the embryonic fusion of large numbers of multinucleate myoblasts.
D)They become multinucleate via mitosis in myoblasts without cytokinesis.
E)They become multinucleate via the embryonic fusion of mononucleaateneuroblasts.

Question 67

What is the name of the densely staining area between the lightly staining areas at the outer edges of a sarcomere?

A)A bands
B)H zones
C)I bands
D)Z lines
E)M lines

Question 68

Myofibrils in a muscle cell are made up of a repeating linear array of contractile units called ________.

A)sarcocytes
B)blastomeres
C)myomeres
D)sarcomeres
E)myotubules

Question 69

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 70

What motor is associated with microfilaments?

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

Question 71

What protein is thought to act like a "molecular ruler" by regulating the number of actin monomers that are allowed to assemble into a thin filament?

A)troponin
B)myosin
C)nebulin
D)titin
E)tropomyosin

Question 72

A culture of Dictyostelium slime mold is prepared in which the myosin II gene is deleted. In which of the activity/ activities described 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 73

Which region of the sarcomere represents the region of overlap between the two types of filaments in the sarcomere?

A)A bands
B)the part of the A band on either side of the H zone
C)I bands
D)Z lines
E)the part of the H zone on either side of the A band

Question 74

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 75

What is the name of the lightly staining areas at the outer edges of a sarcomere?

A)A bands
B)H zones
C)I bands
D)Z lines
E)M lines

Question 76

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 77

What happens to the Z line positioning after contraction of the sarcomere?

A)The distance between the Z lines does not change.
B)The distance between the Z lines decreases.
C)The distance between the Z lines increases.
D)The Z lines disappear.
E)The Z lines become curved.

Question 78

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

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

Question 79

Which region of the sarcomere contains only actin thin filaments or actin filaments?

A)A bands
B)H zones
C)I bands
D)Z lines
E)M lines

Question 80

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

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