chapter 16

Mutations in myosin VII result in an autosomal recessive disorder called ________ , which is characterized by congenital profound hearing loss, problems in the vestibular system, and retinitis pigmentosum.

Usher's syndrome

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

chemoattractant

myosin

major component of thick filaments

titin

major component of thin filament

Ca2+ ATPase

major protein of sarcoplasmic reticulum

troponin

mediates calcium regulation of contraction

sidearms

slide mircotubules past one another

myosin II, filament

slides along actin in sarcomere

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.

Although answers will vary, some possibilities include: deleting the gene from cells and looking for a disruption of microtubule-based transport; treatment of cells with potential inhibitors and the restoration of activity with the removal of the inhibitor; or the association of the gene deficiency with a genetic disease.

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

Chemotaxis

Compare the sustained contraction of muscle cells in rigor mortis with that which results from the action of tetanospasmin (tetanus toxin) on motor neurons.

In the case of rigor mortis, the ATP supply is readily depleted because the cells are in various stages of dying. Low levels of ATP are associated with the inability of the cross-bridges to disassociate. The cells accumulate cross-bridges over time until ATP is depleted from the cell. In the case of tetanospasmin, the release of inhibitory neurotransmitters is prevented. As a result, the signal to contract is persistent. The continuous stimulation of contraction does not allow sufficient numbers of calcium ions to be moved back into the sarcoplasmic reticulum. As a result, the consistent levels of calcium in cytosol keep the muscle cells in a chronic state of contraction.

________ muscle is nonstriated, whereas ________ and ________ muscle is striated.

Smooth; cardiac; skeletal

Discuss how stereocilia work in the organ of Corti and how some chemotherapeutic agents and aminoglycoside antibiotics result in deafness.

Stereocilia are actin-rich structures that aid in sensing movements of fluid within in the inner ear. These are important in the transduction of auditory and vestibular signals. Stereocilia are especially sensitive to chemotherapeutic drugs (such as cisplatin) and aminoglycoside antibiotics. The destruction of the stereocilia results in hearing loss because the signals associated with auditory and vestibular senses are lost in proportion to the numbers of stereocilia destroyed. In some instances the hearing loss is permanent.

Troponin is a complex of three polypeptide chains called ________, ________, and ________.

TnT; TnC; TnI

Cilia and flagella in eukaryotes are similar in structure but vary in number, length, and function. For each of the following, 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

a. One or few flagella may be present, while cilia are present in large numbers. b. Flagella are generally longer than cilia. c. Flagella generate a force parallel to the axis of the appendage, while cilia generate a force perpendicular to the axis. d. The function of flagella in both multicellular and unicellular eukaryotes is the movement of the cell. This is also the case for unicellular cells with cilia, while multicellular organisms use cilia to move the environment rather than the cell. e. The motion of flagella is symmetrical and undulatory. The student may suggest that the motion is like a propeller or like an outboard motor. Cilia display an oarlike pattern of beating.

Movement of animals is dependent on skeletal muscle. The ability of muscle to contract is dependent on the structural organization of muscle fibers. a. What is the fundamental contractile unit of skeletal muscle, which is composed of bands, lines, and a zone? b. What are the letters that describe the bands, lines, and the zone? c. What do these letters represent? d. During contraction, the length of the muscle shortens due to changes within the contractile unit. What are the changes that take place with respect to the bands, lines, and the zone?

a. The sarcomere is the fundamental contractile unit of the muscle cells. b. A and I bands, M and Z lines, H zone c. A-anisotropic, I-isotropic, M-myomesin, Z-zwischen, H-hell d. The A band and M line are unchanged, but the I band and H zone get smaller or disappear. The distance between Z lines gets smaller.

Which of the following is associated with retrograde movement? A) dynein B) actin C) tubulin D) myosin E) kinesin

a. dynein

Cells that undergo amoeboid movement have an outer layer of thick, gelatinous cytoplasm called the ________ and an inner layer of more fluid cytoplasm called the ________. A) ectoplasm; endoplasm B) lamellipodium; pseudopodium C) gelation layer; solation zone D) protoplasm; proplasm E) outer jelly; inner soup

a. ectoplasm; endoplasm

In addition to microtubule motor proteins, ________ are also involved in vesicular transport. A) nonmuscle myosins B) actin C) tubulin D) leptin E) dyesins

a. nonmuscle myosins

The "9 + 2" pattern of the axoneme is nine ________ of microtubules and two additional microtubules in the center called the ________. A) outer doublets; central pair B) basal bodies; inner two C) central tubules; double pair D) circular structures; middle two E) triplet groups; basal bodies

a. outer doublets; central pair

The crawling displayed by many embryonic cells in animals involves distinct events. Which of the following sequences places these events in correct order? 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

a. protrusion at the cell's leading edge, attachment of protrusion, pulling the cell forward, release and retraction of trailing edge

Calcium-calmodulin complexes ultimately mediate the phosphorylation of myosin in which of the following cells? A) smooth muscle B) cardiac muscle C) neurons D) pacemaker E) skeletal muscle

a. smooth muscle

All of the following are actin-dependent nonmuscle motility except A) translocation of multienzyme complexes. B) pinching off of the cleavage furrow in cytokinesis. C) chemotaxis. D) cyclosis or cytoplasmic streaming. E) amoeboid movement.

a. translocation of multienzyme complexes.

myomesin

actin

axonemal dynein

activation of sliding in flagellar microtubule

Cytoplasmic streaming depends on the protein ________.

actomyosin

CapZ

attaches actin filaments to Z line

α-actinin

attaches actin to Z line

Cilia and flagella are comprised of a(n) ________ connected to a(n) ________.

axoneme; basal body

Sidearms are attached to ________. A) B tubules B) A tubules C) central pairs D) radial spokes E) interdoublet nexin

b. A tubules

You wish to inhibit the contraction of muscle in vitro as a control for an experiment you are conducting. To do this, which of the following would you use? A) dyneinase B) ATPase inhibitors C) mysoinase II D) contractionase E) serotonin

b. ATPase inhibitors

During the sliding process in microtubules, the stalks of the dynein attach to and detach from the ________ in a cyclic manner. A) A tubule B) B tubule C) radial spoke D) interdoublet nexin connections E) central pair

b. B tubule

Which of the following statements is correct with respect to flagella and cilia? A) Flagella display an oarlike pattern of beating. B) Cilia generate a force parallel to the cell surface. C) There are usually fewer cilia than flagella. D) Cilia are generally longer than flagella. E) Cilia often have a helical pattern of movement.

b. Cilia generate a force parallel to the cell surface.

Which of the following sequences of skeletal muscle proteins is correctly listed from smallest to largest? A) actin, titin, nebulin, myosin B) actin, myosin, nebulin, titin C) titin, nebulin, actin, myosin D) myomesin, myosin, titin, nebulin E) actin, myosin, titin, troponin

b. actin, myosin, nebulin, titin

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

b. associated with cilia and flagella.

To carry out their function, kinesin family proteins must attach to their respective A) dynein. B) cargo. C) adaptor proteins. D) only choices B and C E) choices A, B, and C

b. cargo.

Muscle contraction occurs in a cyclic process. Which of the following sequences is in the correct order? A) power stroke, cross bridge formation, cross bridge dissociation, cocking of myosin B) cross bridge formation, power stroke, cross bridge dissociation, cocking of myosin C) cross bridge formation, cocking of myosin, power stroke, cross bridge dissociation D) cross bridge formation, cross bridge dissociation, cocking of myosin, power stroke E) cross bridge formation, power stroke, cross bridge dissociation, power stroke, cocking of myosin

b. cross bridge formation, power stroke, cross bridge dissociation, cocking of myosin

Which of the following steps in cell crawling is accompanied by Arp2/3-dependent actin polymerization at the leading edge? A) initiation B) protrusion C) attachment D) contractile activities E) both choices A and D

b. protrusion

In the axoneme, sidearms A) are incomplete microtubules. B) slide microtubules past one another. C) project inward at each doublet. D) link adjacent doublets. E) are complete microtubules.

b. slide microtubules past one another.

Axonemal dynesin is characterized by A) motion along actin filaments. B) sliding in flagellar microtubules. C) motion toward the "minus" end of the microtubule. D) activation of sliding along actin in sarcomere. E) motion toward the "plus" end of the microtubule.

b. sliding in flagellar microtubules.

In the sliding filament model of muscle contraction, I bands contain A) thick filaments. B) thin filaments. C) myosin. D) sacrcomeres. E) both thick and thin filaments.

b. thin filaments.

tropomyosin

binds along the length of thin filaments

myosin V, dimer

binds to membranes

The neuromuscular junction is incorrectly described in which of the following statements? A) Neurotransmitters are stored in vesicles in the axon terminal. B) The sarcolemma is the plasma membrane of a muscle cell. C) Acetylcholine binds receptors in the synaptic cleft. D) T tubules carry action potentials into the muscle cell. E) Acetylcholine binding allows sodium ions to enter the muscle cell.

c. Acetylcholine binds receptors in the synaptic cleft.

________ links the thick filaments to the Z line. A) Troponin B) Tropomyosin C) Titin D) Nebulin E) Myosin

c. Titin

A calcium-binding protein that aids in the activation of many enzymes, including myosin light-chain kinase, is A) calcium phosphorylase. B) activase. C) calmodulin. D) myosin light-chain phosphatase. E) junctional complex.

c. calmodulin.

Kinesin is a motor molecule that is characterized by A) activation of sliding in flagellar microtubules. B) sliding along actin in sarcomere. C) motion toward the "plus" end of the microtubule. D) motion along actin filaments. E) motion toward the "minus" end of the microtubule.

c. motion toward the "plus" end of the microtubule.

In relaxed muscle, calcium is found in high concentration in the A) myofibril. B) T tubules. C) sacroplasmic reticulum. D) sarcolemma. E) neuromuscular junction.

c. sacroplasmic reticulum.

Specialized hair cells that contain special actin-rich sensory structures called __________ are located within the organ of Corti in the cochlea of the ear. A) connecting cilia B) primary cilia C) stereocilia D) undulipodia E) respiratory cilia

c. stereocilia

A tubule

complete microtubule

The microtubule-associated protein ________ provides motion toward the minus end of the microtubule.

cytoplasmic dynein

Primary cilia have a ________ structure and are observed in ________ structures. A) 9 + 2; neural B) 9 + 0; neural C) 9 + 2; sensory D) 9 + 0; sensory E) 9 + 4; developmental

d. 9 + 0; sensory

All of the following diseases are classified as ciliopathies except A) Kartagener's triad. B) BardetBieldl syndrome. C) MeckelGruber syndrome. D) Griscelli's disease. E) polycystic kidney disease.

d. Griscelli's disease.

Which of the following terms is incorrectly matched with the word from which it was derived? A) Z line-zwischen B) M line-myomesin C) H zone-hell D) I band-irregular E) A band-anisotropic

d. I band-irregular

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

d. I bands; A bands

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

d. basal body, transition zone, axoneme

During cell crawling, the cell must attach to the substrate upon which it is crawling. One group of attachment proteins is the ________. A) actins B) actomyosins C) creatines D) integrins E) titins

d. integrins

In the axoneme, nexin A) is an incomplete microtubule. B) slides microtubules past one another. C) projects inward at each doublet. D) links adjacent doublets. E) is a complete microtubule.

d. links adjacent doublets.

Biochemical evidence supporting our current model of muscle contraction includes the observation that A) myosin binds calcium. B) titin binds calcium. C) actin has ATPase activity. D) myosin has ATPase activity. E) actin and myosin have the same molecular weight.

d. myosin has ATPase activity.

Which of the following characteristics is not associated with cardiac muscle? A) intercalated discs B) contracts spontaneously C) involuntary D) pointed ends E) striations

d. pointed ends

The calcium pump or calcium ATPase A) is responsible for removing calcium from the T tubule. B) increases the level of calcium in the axon terminal. C) is a passive process. D) removes calcium from the sarcoplasm. E) increases bone density.

d. removes calcium from the sarcoplasm.

Which of the following major protein components of skeletal muscle is incorrectly matched with its function? A) titin-links thick filaments at Z line B) nebulin-links thin filaments at Z line C) myomesin-myosin binding protein present at M line D) troponin-binds along the length of the thin filaments and covers myosin binding sites E) actin-major component of thin filaments

d. troponin-binds along the length of the thin filaments and covers myosin binding sites

The protein complex ________ facilitates the interaction between cytoplasmic dynein and the target.

dynactin

Cytological examination of resting and contracted muscle provides important support for our current 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 and thin filaments change significantly. C) microtubules disassemble. D) muscle fibers change color. E) H zone becomes smaller.

e. H zone becomes smaller.

The "9 + 0" cilia arrangement is associated with A) eubacteria. B) cyanobacteria. C) cilia lining the respiratory tract. D) flagella on sperm cells. E) animal embryonic development.

e. animal embryonic development.

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) choices A, B, and C

e. choices A, B, and C

B tubule

incomplete microtubule

Tubulin subunits are added to growing cilia or flagella by ________.

intraflagellar transport

In order for a cell to crawl, it must produce a protrusion at the front of the cell (leading edge). One type of protrusion is a thin sheet called a(n) ________; another is a pointed structure called a(n) ________.

lamellipodium; filopodium

nexin

links adjacent doublets

actin

links thick filaments to Z line

nebulin

links thin filament to Z line

All of the following are examples of nonmuscle motility and contractility except A) microsome formation. B) pseudopodia formation. C) cytoplasmic streaming. D) actin polymerization of Listeria. E) phagocytosis.

microsome formation.

The ________ account for 1015% of microtubules.

microtubule-associated proteins

cytoplasmic dynein

motion toward "minus" end of microtubule

kinesin

motion toward "plus" end of microtubule

radial spokes

project inward at each doublet

After death, the lack of ATP stops the dissociation of cross-bridges, and the muscle is locked in a stiff, rigid state called ________.

rigor mortis

Myofibrils are subdivided along their length by repeating units called ________, which are the fundamental contractile units of the muscle cell.

sarcomeres

In electron micrographs, the appearance of the T tubule with the terminal cisternae on either side appears as three circles called a(n) ________.

triad