Cell Bio Chapter 17 Quiz

Kinesin and dynein motor proteins each use the energy of ____ to power their movements _______ along microtubules. a) ATP hydrolysis, in a single direction b) ATP hydrolysis, in both directions c) GTP hydrolysis, in a single direction d) GTP hydrolysis, in both directions

ATP hydrolysis, in a single direction

Which one of the following statements about the cytoskeleton is true? a) All eucaryotic cells have actin, microtubules, and intermediate filaments in their cytoplasm. b) The cytoskeleton provides a rigid and unchangeable structure important for the shape of the cell. c) The three cytoskeletal filaments perform distinct tasks in the cell and act completely independently of one another. d) Actin filaments and microtubules have an inherent polarity, with a plus end that grows more quickly than the minus end.

Actin filaments and microtubules have an inherent polarity, with a plus end that grows more quickly than the minus end.

Which of the following statements is false? a) Cytochalasins prevent actin polymerization. b) Actin filaments are usually excluded from the cell cortex. c) Integrins are transmembrane proteins that can bind to the extracellular matrix. d) ARPs can promote the formation of branched actin filaments.

Actin filaments are usually excluded from the cell cortex.

You are examining a cell line in which activation of the Rho family member Rac promotes lamellipodia formation. Which of the following statements is most likely to be true? a) Cells carrying a Rac mutation that makes Rac act as if it is always bound to GTP will polymerize more unbranched actin filaments than normal cells. b) Cells carrying a Rac mutation that makes Rac unable to exchange GDP for GTP will polymerize more unbranched actin filaments than normal cells. c) Cells carrying a Rac mutation that makes Rac act as if it is always bound to GTP will polymerize more branched actin filaments than normal cells. d) Cells carrying a Rac mutation that makes Rac unable to exchange GDP for GTP will polymerize more branched actin filaments than normal cells.

Cells carrying a Rac mutation that makes Rac act as if it is always bound to GTP will polymerize more branched actin filaments than normal cells.

Which one of the statements below about intermediate filaments is false? a) They can stay intact in cells treated with concentrated salt solutions. b) They can be found in the cytoplasm and the nucleus. c) They can be anchored to the plasma membrane at cell-cell junction. d) Each filament is about 10 μm in diameter.

Each filament is about 10 μm in diameter.

True or False? Minus end-directed microtubule motors (like dyneins) deliver their cargo to the periphery of the cell, whereas plus end-directed microtubule motors (like kinesins) deliver their cargo to the interior of the cell. a) True b) False

False

Dynamic instability in microtubules stems from the intrinsic capacity of tubulin molecules to hydrolyze: a) peptide bonds b) tubulin dimers c) GTP d) ATP

GTP

The end of a growing microtubules is rich in which type of tubulin molecule? a) GTP-associated tubulin molecules b) GDP-associated tubulin molecules

GTP-associated tubulin molecules

Which is the toughest and most durable of the three types of cytoskeletal filaments? a) Intermediate filaments b) microtubules c) actin filaments

Intermediate filaments

Which of the following describes the structure of an actin filament? a) It is a hollow cylinder made up of actin molecules. b) It is a twisted chain of actin molecules. c) It is a structure with a long tail and two globular heads.

It is a twisted chain of actin molecules.

What is the name of the thin sheetlike structures that a fibroblast regularly extends during cell crawling? a) Pseudopods b) Filopodia c) Lamellipodia d) Phagosomes

Lamellipodia

Keratins, neurofilaments, and vimentins are all categories of intermediate filaments. Which of the following properties below is not true of these types of intermediate filaments? a) They strengthen cells against mechanical stress. b) Dimers associate by noncovalent bonding to form a tetramer. c) They are found in the cytoplasm. d) Phosphorylation causes disassembly during every mitotic cycle.

Phosphorylation causes disassembly during every mitotic cycle.

Which one of the following statements about microtubules is true? a) Motor proteins move in a directional fashion along microtubules by using the inherent structural polarity of a protofilament. b) The centromere nucleates the microtubules of the mitotic spindle. c) Because microtubules are subject to dynamic instability, they are used only for transient structures in a cell. d) ATP hydrolysis by a tubulin heterodimer is important for controlling the growth of a microtubule.

Motor proteins move in a directional fashion along microtubules by using the inherent structural polarity of a protofilament.

Which of the following types of intermediate filaments are found in all animal cells? a) Keratins b) Vimentin and vimentin-related filaments c) Nuclear lamins d) Neurofilaments

Nuclear lamins

Which of the following statements about organellar movement in the cell is false? a) Organelles undergo saltatory movement in the cell. b) Only the microtubule cytoskeleton is involved in organellar movement. c) Motor proteins involved in organellar movement use ATP hydrolysis for energy. d) Organelles are attached to the tail domain of motor proteins.

Only the microtubule cytoskeleton is involved in organellar movement.

Which one of the following statements about the cytoskeleton is false? a) The cytoskeleton is made up of three types of protein filament. b) The bacterial cytoskeleton is important for cell division and DNA segregation. c) Protein monomers that are held together with covalent bonds form cytoskeletal filaments. d) The cytoskeleton of a cell can change in response to the environment.

Protein monomers that are held together with covalent bonds form cytoskeletal filaments.

Cell movement involves the coordination of many events in the cell. Which of the following phenomena are not required for cell motility? a) Myosin-mediated contraction at the rear of the moving cell b) Integrin association with the extracellular environment. c) Nucleation of new actin filaments. d) Release of Ca2+ from the sarcoplasmic reticulum.

Release of Ca2+ from the sarcoplasmic reticulum.

Which of the following statements about skeletal muscle contraction is false? a) When a muscle cell receives a signal from the nervous system, voltage-gated channels open in the T-tubule membrane. b) The changes in voltage across the plasma membrane that occur when a muscle cell receives a signal from the nervous system cause an influx of Ca2+ into the sarcoplasmic reticulum, triggering a muscle contraction. c) A change in the conformation of troponin leads to changes in tropomyosin such that it no longer blocks the binding of myosin heads to the actin filament. d) During muscle contraction, the Z discs move closer together as the myosin heads walk toward the plus ends of the actin filaments.

The changes in voltage across the plasma membrane that occur when a muscle cell receives a signal from the nervous system cause an influx of Ca2+ into the sarcoplasmic reticulum, triggering a muscle contraction.

If GTP hydrolysis occurs on a tubulin molecule at the plus end of a microtubule protofilament before another tubulin molecule is added, what typically happens to the microtubule? a) The microtubule polymerizes. b) The microtubule depolymerizes. c) The microtubule remains the same size.

The microtubule depolymerizes.

Which end of a microtubule is embedded in the centrosome? a) The plus end b) The minus end

The minus end

The concentration of actin monomers is high in the cytosol. What keeps these monomers from polymerizing totally into filaments? a) The concentration is high, but not high enough for polymerization to occur. b) The monomers are bound by proteins that prevent their polymerization. c) Not enough of the monomers are bound to ATP.

The monomers are bound by proteins that prevent their polymerization.

Which of the following statements regarding dynamic instability is false? a) Each microtubule filament grows and shrinks independently of its neighbors. b) The GTP cap helps protect a growing microtubule from depolymerization. c) GTP hydrolysis by the tubulin dimer promotes microtubule shrinking. d) The newly freed tubulin dimers from a shrinking microtubule can be immediately captured by growing microtubules and added to their plus end.

The newly freed tubulin dimers from a shrinking microtubule can be immediately captured by growing microtubules and added to their plus end.

Which of the following is the main function of intermediate filaments? a) To provide tracks for guiding intracellular transport b) To enable cells to crawl c) To enable cells to withstand the mechanical stress that occurs when cells are stretched

To enable cells to withstand the mechanical stress that occurs when cells are stretched

In eucaryotic cells, the cell cortex is made of: a) In eucaryotic cells, the cell cortex is made of: b) a network of microtubules. c) a network of actin filaments.

a network of actin filaments.

Which of the following conditions below is likely to decrease the likelihood of skeletal muscle contraction? a) partial depolarization of the T-tubule membrane, such that the resting potential is closer to zero b) addition of a drug that blocks Ca2+ binding to troponin c) an increase in the amount of ATP in the cell d) a mutation in tropomyosin that decreases its affinity for the actin filament

addition of a drug that blocks Ca2+ binding to troponin

Which of the situations below will enhance microtubule shrinkage? a) addition of a drug that inhibits GTP exchange on free tubulin dimers b) addition of a drug that inhibits GTP hydrolysis of tubulin dimers c) addition of a drug that increases the affinity of tubulin molecules carrying GDP for other tubulin molecules d) addition of a drug that blocks the ability of a tubulin dimer to bind to γ-tubulin

addition of a drug that inhibits GTP exchange on free tubulin dimers

You are interested in understanding the regulation of nuclear lamina assembly. To create an in vitro system for studying this process you start with partly purified nuclear lamina subunits to which you will add back purified cellular components to drive nuclear lamina assembly. Before you start doing experiments, your instructor suggests that you consider what type of conditions would be most amenable to the assembly of nuclear lamina from its individual subunits in vitro. Which of the following conditions do you predict would be most likely to enhance the assembly of the nuclear lamina? a) addition of phosphatase inhibitors b) addition of ATP c) addition of a concentrated salt solution that is 10 times the concentration normally found in the nucleoplasm d) addition of protein kinase inhibitors

addition of protein kinase inhibitors

The hydrolysis of GTP to GDP carried out by tubulin molecules ________________. a) provides the energy needed for tubulin to polymerize b) occurs because the pool of free GDP has run out c) tips the balance in favor of microtubule assembly d) allows the behavior of microtubules called dynamic instability

allows the behavior of microtubules called dynamic instability

Keratins are NOT found in: a) hair b) reathers c) the tongue d) bones

bones

The drug taxol binds tightly to microtubules and prevents them from depolymerizing. The drug colchicine binds tightly to free tubulin and prevents its polymerization into microtubules. Which of these drugs arrests dividing cells in mitosis? a) taxol b) colchicine c) both

both

The following statement is consistent with which type(s) of microtubule? "It uses dynein motors." a) cilliary (or flagellar) microtubule b) mitotic spindle microtubule c) both a and b d) none of the above

both a and b

Which of the following structures shorten during muscle contraction? a) myosin filaments b) flagella c) sarcomeres d) actin filaments

carcomeres

The following statement is consistent with which type(s) of microtubule? "It is arranged in a "9 + 2" array." a) cilliary (or flagellar) microtubule b) mitotic spindle microtubule c) both a and b d) none of the above

cilliary (or flagellar) microtubule

The following statement is consistent with which type(s) of microtubule? "It is involved in moving fluid over the surface of cells." a) cilliary (or flagellar) microtubule b) mitotic spindle microtubule c) both a and b d) none of the above

cilliary (or flagellar) microtubule

The following statement is consistent with which type(s) of microtubule? "It is involved in sperm motility." a) cilliary (or flagellar) microtubule b) mitotic spindle microtubule c) both a and b d) none of the above

cilliary (or flagellar) microtubule

The following statement is consistent with which type(s) of microtubule? "The basal body is the organizing center." a) cilliary (or flagellar) microtubule b) mitotic spindle microtubule c) both a and b d) none of the above

cilliary (or flagellar) microtubule

Match the type of intermediate filament with its appropriate location. vimentins

connective tissue

The following proteins are important for cell movement. Match the following proteins with their function. myosin II

contracting the rear of the cell

The hydrolysis of bound ATP to ADP in an actin filament _____ the strength of binding between monomers in the filament. a) increases b) decreases c) has no effect

decreases

Intermediate filaments are found in what structure? a) the mitotic spindle b) centrosomes c) desosomes d) cilia

desosomes

Match the type of intermediate filament with its appropriate location. keratins

epithelia

__________ support and strengthen the nuclear envelope. a) microfilamnets b) microtubules c) intermediate filaments

intermediate filaments

In a centrosome, which structures serve as nucleation sites for the formation of microtubules? a) Tubulin protofilaments b) αβ-tubulin dimers c) α- and β-tubulin monomers d) gamma-tubulin rings

gamma-tubulin rings

Microtubules are: a) rope-like strands. b) mesh-like networks. c) hollow tubes. d) interlocking chains.

hollow tubes.

__________ can be connected through desmosomes. a) microfilaments b) microtubules c) intermediate filaments

intermediate filaments

__________ include keratin and neurofilaments. a) microfilaments b) microtubules c) intermediate filaments

intermediate filaments

Rank the following cytoskeletal filaments from smallest to largest in diameter (1 = smallest in diameter, 4 = largest) intermediate filaments ____ microtubules ___ actin filament ___ myofibril ___

intermediate filaments 2 microtubules 3 actin filament 1 myofibril 4

The following proteins are important for cell movement. Match the following proteins with their function. integrins

involvement in focal contacts

__________ are composed of a monomer that binds ATP. a) microfilaments b) microtubules c) intermediate filaments

microfilaments

__________ are important for formation of the contractile ring during cytokinesis. a) microfilaments b) microtubules c) intermediate filaments

microfilaments

___________ are abundant in filopodia. a) microfilaments b) microtubules c) intermediate filaments

microfilaments

___________ are directly involved in muscle contraction. a) microfilaments b) microtubules c) intermediate filaments

microfilaments

The stability of __________ involves a GTP cap. a) microfilaments b) microtubules c) intermediate filaments

microtubules

Which of the following cytoskeletal structures grows out from a centrosome toward the cell periphery? a) intermediate filaments b) microtubules c) actin filaments

microtubules

Which of the following cytoskeletal structures makes up the mitotic spindle? a) intermediate filaments b) microtubules c) actin filaments

microtubules

Which of the following cytoskeletal structures provides tracks for guiding intracellular transport? a) intermediate filaments b) microtubules c) actin filaments

microtubules

___________ are components of the mitotic spindle. a) microfilaments b) microtubules c) intermediate filaments

microtubules

___________ are used in the eucaryotic flagellum a) microfilaments b) microtubules c) intermediate filaments

microtubules

The following statement is consistent with which type(s) of microtubule? "It is nucleated at the centrosome." a) cilliary (or flagellar) microtubule b) mitotic spindle microtubule c) both a and b d) none of the above

mitotic spindle microtubule

Your friend works in a biotech company that has just discovered a drug that seems to promote lamellipodia formation in cells. Which of the following molecules below is unlikely to be involved in the pathway that this drug affects? a) Rac b) ARP c) actin d) myosin

myosin

Match the type of intermediate filament with its appropriate location. neurofilaments

nerve cells

The following statement is consistent with which type(s) of microtubule? "The monomer is sequestered by profilin" a) cilliary (or flagellar) microtubule b) mitotic spindle microtubule c) both a and b d) none of the above

none of the above

The following proteins are important for cell movement. Match the following proteins with their function. ARP proteins

nucleation of new actin filaments

Match the type of intermediate filament with its appropriate location. lamins

nucleus

Which one of the following statements is correct? Kinesins and dyneins ____________________. a) have tails that bind to the filaments b) move along both microtubules and actin filaments c) often move in opposite directions to each other d) derive their energy from GTP hydrolysis

often move in opposite directions to each other

Place the following in order of size, from the smallest to the largest. (1 = smallest, 5 = largest) protofilament ___ microtubule ___ alpha-tubulin ___ tubulin dimer ___ mitotic spindle ___

protofilament 3 microtubule 4 alpha-tubulin 1 tubulin dimer 2 mitotic spindle 5

The following proteins are important for cell movement. Match the following proteins with their function. profilin

regulation of the availability of actin monomers

Intermediate filaments are: a) tubelike structures b) springlike structures. c) ropelike structures. d) meshlike structures.

ropelike structures.

Which of the following items below are not important for flagellar movement? a) sarcoplasmic reticulum b) ATP c) dynein d) microtubules

sarcoplasmic reticulum

The microtubules in a cell form a structural framework that can have all the following functions except which of the following? a) holding internal organelles such as the Golgi apparatus in particular positions in the cell. b) creating long thin cytoplasmic extensions that protrude from one side of the cell. c) strengthening the plasma membrane. d) moving materials from one place to another inside a cell.

strengthening the plasma membrane.

In eucaryotic flagellum, the bending of microtubules is driven by: a) the basal body. b) the motor protein ciliary dynein. c) the fluid that surrounds the flagellum. d) actin and myosin

the motor protein ciliary dynein.

The centrosome relies on microtubule assembly and disassembly to locate chromosomes in the cytoplasm. a) false b) true

true