Deck 14: Cellular Movement: Motility and Contractility

Question 1

Biochemical evidence supporting the sliding filament model of muscle contraction includes the observation that

A)myosin light chains can be phosphorylated.
B)titin connects each end of a thick filament to a Z line.
C)TnC binds Ca2⁺.
D)actin has polymerization ATPase activity.
E)myosin has an ATP-dependent crossbridge cycle.

Answer 1

E

Question 2

All of the following are actin-dependent nonmuscle motilities except

A)extension of the ER.
B)cleavage furrow constriction in cytokinesis.
C)chemotaxis.
D)cyclosis or cytoplasmic streaming.
E)amoeboid movement.

Answer 2

A

Question 3

Each of the following diseases is classified as a primary cilia dysplasia (also known as a ciliopathy)except

A)Kartagener's syndrome.
B)situs inversus totalis.
C)heterotaxia.
D)Griscelli's disease.
E)All are primary cilia dysplasias.

Answer 3

D

Question 4

Which of the following is incorrect about stimulation of striated muscle contraction by the neuromuscular junction?

A)Acetylcholine is stored in vesicles in the axon terminal.
B)Acetylcholine is secreted in response to a nerve action potential.
C)Acetylcholine binds to soluble receptors in the extracellular environment.
D)Acetylcholine binding stimulates sodium ions to enter the muscle cell.
E)T tubules carry action potentials into the muscle cell.

Question 5

In the axoneme,dynein sidearms are anchored on

A)B tubules.
B)A tubules.
C)central pair tubules.
D)radial spokes.
E)interdoublet nexin.

Question 6

Which of the following characteristics is not associated with cardiac muscle?

A)intercalated discs
B)electrical coupling by gap junctions
C)involuntary nervous control
D)fusion of cardiomyocytes into large multinucleated myofibers
E)striations

Question 7

Cytological examination of resting and contracted muscle provides important support for the sliding filaments model for how skeletal muscle contracts.This evidence includes the observation that during contraction the

A)Z lines move farther apart.
B)lengths of the thick filaments shorten significantly.
C)lengths of the thin filaments shorten significantly.
D)I bands get longer.
E)H zone becomes narrower.

Question 8

Motility may involve

A)movement of a cell/organism through its environment.
B)movement of the environment past a cell.
C)movement of components within a cell.
D)shortening of a cell.
E)All of the above are correct.

Question 9

Striated muscle has light and dark bands.The light bands are called ________,whereas the dark bands are called ________.

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

Question 10

Which of the following statements is correct with respect to flagella and cilia?

A)The flagellum is usually at the leading end of a swimming sperm cell.
B)Cilia generate a force parallel to the cell surface.
C)There usually are fewer cilia than flagella.
D)Cilia generally are longer than flagella.
E)Cilia often have a helical pattern of movement.

Question 11

Which of the following lists of structures is in the correct order from inside to outside of the cell?

A)axoneme,transition zone,basal body
B)transition zone,basal body,axoneme
C)axoneme,basal body,transition zone
D)basal body,transition zone,axoneme
E)basal body,axoneme,transition zone

Question 12

The axonemal "9 + 2" pattern of microtubules is nine ________ surrounding a(n)________.

A)outer doublets; central pair
B)basal bodies; inner two
C)central tubules; double pair
D)B tubule structures; middle two
E)triplet microtubules; basal bodies

Question 13

The "9 + 0" pattern of microtubules is associated with

A)bacterial locomotion.
B)cyanobacterial locomotion.
C)respiratory tract cilia.
D)sperm tail flagella.
E)primary (sensory)cilia.

Question 14

Motor proteins convert

A)mechanical energy to chemical energy.
B)heat energy to mechanical energy.
C)kinetic energy to mechanical energy.
D)chemical energy to mechanical energy.
E)chemical energy to heat energy.

Question 15

Which of the following major protein components of skeletal muscle is incorrectly matched with its function?

A)titin-links thick filaments to Z line
B)nebulin-links thin filaments to Z line
C)myomesin-links myosin bipolar filaments at M line
D)troponin-binds along the length of the thin filaments and blocks myosin binding sites
E)actin-major component of thin filaments

Question 16

Ca2⁺-calmodulin stimulates phosphorylation of myosin by

A)Ca2⁺-ATPase.
B)focal adhesion kinase.
C)myosin light chain kinase.
D)ryanodine receptor.
E)titin.

Question 17

In relaxed muscle,Ca2⁺ is found in highest concentration in the

A)sarcoplasm.
B)T tubules.
C)sarcoplasmic reticulum.
D)sarcolemma.
E)neuromuscular junction.

Question 18

Which of the following changes take place as the muscle contracts?

A)The Z lines get closer together.
B)The H zones get smaller.
C)The I band gets smaller.
D)The A band gets smaller.
E)A,B,and C are correct.

Question 19

Which of the following features is not shared by microtubule and microfilament molecular motors?

A)coupling ATP hydrolysis to change shape and attachment of the motor to its associated cytoskeletal filament
B)retention of bound ADP and Pi products immediately after ATP hydrolysis
C)cycles of ATP hydrolysis,release of ADP and Pi,and binding of new ATP as they undergo a crossbridge cycle of force production on a filament
D)similar structural features that transduce changes in the motor protein shape into movement
E)The motors share all these features.

Question 20

________ links the thick filaments to the Z line.

A)Troponin
B)Tropomyosin
C)Titin
D)Nebulin
E)Myomesin

Question 21

Which of the following would you use to inhibit the contraction of muscle in vitro as a control for an experiment you are conducting?

A)a drug that increases sarcoplasm Ca2⁺ concentration
B)a motor protein ATPase inhibitor
C)a Ca2⁺-ATPase inhibitor
D)a drug that increases T-tubule depolarization
E)All would inhibit muscle contraction.

Question 22

Addition of ATP to isolated axonemes causes localized bending.What can be done to the isolated axonemes to cause the outer doublets to slide past each other unrestrained,lengthening the overall structure instead of causing bending?

A)add gelsolin
B)remove the interdoublet nexin links
C)add nocodazole
D)remove the ATP
E)inhibit tektin activity with a drug

Question 23

In striated muscle contraction,the Ca2⁺-ATPase pump

A)releases Ca2⁺ from the T tubule.
B)secretes Ca2⁺ from the axon terminal.
C)is voltage-gated.
D)decreases Ca2⁺ in the sarcoplasm.
E)increases Ca2⁺ binding to TnC.

Question 24

A Ca2⁺-binding protein that activates many enzymes,including myosin light-chain kinase,is

A)Ca2⁺-ATPase.
B)gelsolin.
C)calmodulin.
D)myosin light-chain phosphatase.
E)TnC.

Question 25

In the axoneme,nexin

A)transports tubulin to the axoneme tip for assembly.
B)generates force for outer doublets sliding past each other.
C)projects inward from each doublet toward the central pair microtubules.
D)links adjacent outer doublets to limit sliding.
E)connects each outer doublet to the plasma membrane.

Question 26

During the sliding process in microtubules in cilia and flagella,the stalks of an axonemal dynein attach to,produce force on,and detach from a(n)________ in a cyclic manner.

A)A tubule
B)B tubule
C)radial spoke
D)interdoublet nexin connections
E)central pair

Question 27

Which of the following proteins attaches a crawling cell to the substrate in a focal adhesion?

A)actin
B)myosins
C)α-actinin
D)integrin
E)titin

Question 28

In the axoneme,sidearms

A)are 10 protofilament incomplete microtubules attached to 13 protofilament microtubules.
B)generate force to slide microtubules past one another.
C)project toward the central pair from each outer doublet.
D)link adjacent doublet microtubules to limit sliding.
E)are complete 13 protofilament microtubules.

Question 29

Primary cilia have a(n)________ function and typically display a ________ structure.

A)axonal; 9+2
B)motile; 9+0
C)motile; 9+2
D)sensory; 9+0
E)filopodial; 9+4

Question 30

Which of the following is responsible for retrograde axonal transport?

A)cytoplasmic dynein
B)kinesin 5
C)kinesin 13
D)myosin V
E)kinesin 1

Question 31

Which of the following would you expect to observe in an in vitro experimental mixture containing microtubules anchored by their minus ends to centrosomes,polystyrene beads with kinesin or dynein motors attached,and ATP?

A)movement of kinesin-attached beads along microtubules away from centrosomes
B)movement of dynein-attached beads along microtubules toward from centrosomes
C)movement of beads in either direction along a single microtubule
D)removal of ATP stopping all bead movement along microtubules
E)All would be expected.

Question 32

Kinesin 1 and myosin II share each of the following features except

A)two heads.
B)dimers formed by heavy chain tails coiled around each other.
C)formation of bipolar filaments.
D)plus end directed motor activity.
E)ATPase activity.

Question 33

Which of the following is the correct order of events in a crawling cell?

A)protrusion at the cell's leading edge,attachment of protrusion,pulling the cell forward,release and retraction of trailing edge
B)attachment of protrusion,pulling the cell forward,protrusion at the cell's leading edge,release and retraction of trailing edge
C)release and retraction of protrusion,protrusion at the cell's leading edge,attachment of trailing edge,pulling the cell forward
D)attachment of protrusion,protrusion at the cell's leading edge,pulling the cell forward,release and retraction of trailing edge
E)pulling the cell forward,release and retraction of protrusion,protrusion at the cell's leading edge,attachment of trailing edge

Question 34

Axonemal dyneins are

A)associated with organelle movement.
B)associated with cilia and flagella.
C)monomeric myosin-like proteins.
D)responsible for axonal anterograde transport.
E)All of the above are correct.

Question 35

Where would you expect to find the Ca2⁺-activated form of gelsolin in cells crawling by amoeboid movement?

A)in and around focal adhesions
B)at a pseudopodium tip where endoplasm is converting to ectoplasm
C)at a pseudopodium base where ectoplasm is converting to endoplasm
D)in the primary cilium
E)at the cell trailing edge where force is produced to drive endoplasm forward streaming

Question 36

Arp2/3-dependent actin polymerization directly drives which of the following activities at the leading edge of crawling cells?

A)filament rearward translocation
B)lamellipodia protrusion
C)new adhesion formation
D)generation of tension
E)focal adhesion detachment

Question 37

Kinesin 1 is highly processive motor,taking more than 100 steps (covering 1 μm along a microtubule)before dissociating,primarily because

A)it hydrolyzes ATP more rapidly than other motors.
B)one of its two heads is always attached in it hand-over-hand mechanism.
C)light chains at its nonmotor end attach to cargo vesicles.
D)its efficiency of converting ATP hydrolysis energy to useful work is 60-70%.
E)All are required for processivity.

Question 38

In the sliding filament model of muscle contraction,I bands contain

A)thick filaments.
B)thin filaments.
C)myosin II.
D)myomesin.
E)both thick and thin filaments.

Question 39

Each of the following is an example of microfilament-based motility and contractility except

A)ciliary motility.
B)pseudopodia formation.
C)cytoplasmic streaming.
D)cytokinesis.
E)trailing edge retraction in a moving cell.

Question 40

Which of the following sequences is in the correct order for the cyclic process by which a myosin head generates force on an actin filament for muscle contraction?

A)power stroke,crossbridge formation,crossbridge dissociation,cocking of myosin head
B)crossbridge formation,power stroke,crossbridge dissociation,cocking of myosin head
C)crossbridge formation,cocking of myosin head,power stroke,crossbridge dissociation
D)crossbridge formation,crossbridge dissociation,cocking of myosin head,power stroke
E)crossbridge formation,power stroke,crossbridge dissociation,power stroke,cocking of myosin head

Question 41

Cyclosis (cytoplasmic streaming)is driven by ________ that interact with ________ that are anchored to chloroplasts near an algal cell wall.

Question 42

In the T-tubule triad structure seen in electron micrographs of striated muscle,the T tubule is flanked by two terminal cisternae of the ________.This association facilitates opening terminal cisternae ryanodine receptors,which ________ to initiate sarcomere contraction.

Question 43

Eukaryotic motile cilia and flagella have similar structures but vary in number,length,and function.For each of the following,compare/contrast cilia and flagella.
a.number present per cell
b.length of appendage
c.direction of force generated relative to the direction of the appendage
d.function in unicellular and multicellular eukaryotes
e.motion analogy

Question 44

________ is the process that moves tubulin subunits to the flagellar tip where they assemble onto axonemal microtubules.

Question 45

Crawling cells produce broad,thin protrusions known as ________ and pointed structures called ________ at the leading edge of the cell.

Question 46

Name each of the three polypeptides of troponin chains and identify what each binds to.
________ binds to ________
________ binds to ________
________ binds to ________

Question 47

You identify a protein that may play a role in microtubule-based transport.Propose a series of experiments that would aid you in confirming your assessment that this protein has a role in microtubule-based transport.

Question 48

________ is a directional movement in response to a graded chemical stimulus.

Question 49

The ________ element of the sarcoplasmic reticulum is where ________ function to decrease sarcoplasmic Ca2⁺ concentration for muscle relaxation.

Question 50

The contractile ________ are aligned in ________ and ________ striated muscles but not in ________ muscles.

Question 51

Striated muscle myofibrils are end-to-end associations of the fundamental contractile units of the muscle cell known as ________.

Question 52

When migrating cells move toward a greater concentration of a diffusible chemical,the chemical is called a ________.

Question 53

Mutations in myosin V cause a human disorder known as ________,involving partial albinism and neurological defects.

Question 54

Rigor mortis after death is caused by myosin crossbridges that fail to dissociate from the actin thin filaments because of lack of ________.

Question 55

The structural organization of muscle fibers makes it possible to produce contractile force.
a.What is the fundamental contractile unit of skeletal muscle?
b.What are the names of the bands,lines and zone of the contractile unit of skeletal muscle?
c.Each of the contractile unit region names in (b)contains a letter.What does each of these letters stand for?
d.What changes occur in the contractile unit regions during contraction?

Question 56

Consider the observations that a label on one head of a myosin V dimer moves in steps of 72 nm,but a label much nearer the myosin tail moves in steps of 36 nm.Discuss how these observations support a hand-over-hand mechanism rather than an inchworm mechanism of myosin V motility on an actin filament.

Question 57

The ________ protein complex facilitates the interaction between cytoplasmic dynein,a cargo vesicle,and a microtubule.

Question 58

The tetanus toxin tetanospasmin blocks release of the neurotransmitter (GABA)that inhibits motor neurons and decreases muscle contraction.This causes persistence of the signal to contract and the resulting violent muscle contraction known as tetanic spasm.Compare the sustained contraction of muscle cells in rigor mortis with muscle contraction caused by the action of tetanospasmin on motor neurons.

Question 59

Myosin II is ideally suited for muscle contraction because it forms ________ filaments.

Question 60

Microtubule motors ________ move vesicles toward the minus end of a microtubule.

Question 61

Explain why sarcomere tension increases as the sarcomere length shortens from an extended length of 3.5 μm to 2 μm but then decreases if the sarcomere contracts to a length of 1.5 μm.

Question 62

Explain why myosin II in a sarcomere can produced force only for that sarcomere contraction and not for that sarcomere extension.