Question 1

Which of the following items is not important for flagellar movement?

Accepted Answer

A) sarcoplasmic reticulum 
B) ATP 
C) dynein 
D) microtubules 
A) sarcoplasmic reticulum 
B) ATP 
C) dynein 
D) microtubules

Question 2

The graph in Figure 17-10 shows the time course of the polymerization of pure tubulin in vitro.You can assume that the starting concentration of free tubulin is much higher than it is in cells.   
Figure 17-10
A.Explain the reason for the initial lag in the rate of microtubule formation.
B.Why does the curve level out after point C?

Accepted Answer

A.Before they can polymerize to form mic

Question 3

The graph in Figure 17-18 shows the time course of the polymerization of pure tubulin in vitro.Assume that the starting concentration of free tubulin is higher than it is in cells.   Figure 17-18
Three parts of the curve are labeled above it as A, B, and C.You conduct a similar in vitro tubulin-polymerization experiment, only this time you include purified centrosomes in your preparation.When you plot your data, which part of your graph should be most dissimilar to the curve shown in Figure 17-18?

Accepted Answer

A) A 
B) B 
C) C 
D) None.The shape of my graph should be identical to the graph produced when tubulin is polymerized in the absence of purified centrosomes. 
A) A 
B) B 
C) C 
D) None.The shape of my graph should be identical to the graph produced when tubulin is polymerized in the absence of purified centrosomes.

Question 4

Indicate whether each of the following statements refers to a ciliary microtubule, a microtubule of the mitotic spindle, both types of microtubule, or neither type of microtubule.
A.The basal body is the organizing center.
B.The monomer is sequestered by profilin.
C.It is arranged in a "9 + 2" array.
D.It is nucleated at the centrosome.
E.It uses dynein motors.
F.It is involved in sperm motility.
G.It is involved in moving fluid over the surface of cells.

Accepted Answer

A.ciliary microtubules
B.neith

Question 5

Phosphorylation of nuclear lamins regulates their assembly and disassembly during mitosis.You add a drug to cells undergoing mitosis that inhibits the activity of an enzyme that dephosphorylates nuclear lamins.What do you predict will happen to these cells? Why?

Accepted Answer

Cells should become arrested in mitosis.

Question 6

Which of the following statements about the movement of materials in a nerve axon is TRUE?

Accepted Answer

A) Movement along microtubules in the axon is slower than free diffusion, but necessary due to the importance of directional transport. 
B) The small jerky steps seen when vesicles move along microtubules are due to the shrinkage of microtubules that occurs when axonal microtubules undergo dynamic instability. 
C) Microtubules within an axon are arranged such that all microtubules point in the same direction with their minus ends toward the nerve cell body. 
D) Microtubules within the axon support the unidirectional motion of materials from the nerve cell body to the axon terminal, while materials transported back from the axon terminal to the cell body move along intermediate filaments. 
A) Movement along microtubules in the axon is slower than free diffusion, but necessary due to the importance of directional transport. 
B) The small jerky steps seen when vesicles move along microtubules are due to the shrinkage of microtubules that occurs when axonal microtubules undergo dynamic instability. 
C) Microtubules within an axon are arranged such that all microtubules point in the same direction with their minus ends toward the nerve cell body. 
D) Microtubules within the axon support the unidirectional motion of materials from the nerve cell body to the axon terminal, while materials transported back from the axon terminal to the cell body move along intermediate filaments.

Question 7

Which of the following statements about the cytoskeleton is TRUE?

Accepted Answer

A) All eukaryotic 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. 
A) All eukaryotic 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.

Question 8

Which of the following statements about the cytoskeleton is FALSE?

Accepted Answer

A) The cytoskeleton is made up of three types of protein filaments. 
B) The cytoskeleton controls the location of organelles in eukaryotic cells. 
C) Covalent bonds between protein monomers hold together cytoskeletal filaments. 
D) The cytoskeleton of a cell can change in response to the environment. 
A) The cytoskeleton is made up of three types of protein filaments. 
B) The cytoskeleton controls the location of organelles in eukaryotic cells. 
C) Covalent bonds between protein monomers hold together cytoskeletal filaments. 
D) The cytoskeleton of a cell can change in response to the environment.

Question 9

Compared to the normal situation, in which actin monomers carry ATP, what do you predict would happen if actin monomers that bind a nonhydrolyzable form of ATP were incorporated into actin filaments?

Accepted Answer

A) Actin filaments would grow longer. 
B) Actin filaments would grow shorter because depolymerization would be enhanced. 
C) Actin filaments would grow shorter because new monomers could not be added to the filaments. 
D) No change, as the addition of monomers binding nonhydrolyzable ATP would not affect actin filament length. 
A) Actin filaments would grow longer. 
B) Actin filaments would grow shorter because depolymerization would be enhanced. 
C) Actin filaments would grow shorter because new monomers could not be added to the filaments. 
D) No change, as the addition of monomers binding nonhydrolyzable ATP would not affect actin filament length.

Question 10

Cell movement involves the coordination of many events in the cell.Which of the following phenomena is not required for cell motility?

Accepted Answer

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 
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

Question 11

Which of the following statements about skeletal muscle contraction is FALSE?

Accepted Answer

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. 
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.

Question 12

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?

Accepted Answer

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. 
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.

Question 13

Your friend discovers a protein that she names EBP.EBP binds to microtubule plus ends, and she hypothesizes a role for EBP in increasing dynamic instability.To determine the function of EBP, she examines its effect on microtubules.She polymerizes microtubules from purified centrosomes in a Petri plate and determines the number of shrinking microtubules over a three-minute time interval for different concentrations of EBP.The data she obtained are shown in Figure 17-8. (A)

(B)

(C)

Figure 17-8
Is this result consistent with her hypothesis? Explain.

Accepted Answer

No, the data graphed in Figure 17-8 are

Question 14

You are curious about the dynamic instability of microtubules and decide to join a lab that works on microtubule polymerization.The people in the lab help you grow some microtubules in culture using conditions that allow you to watch individual microtubules under a microscope.You can see the microtubules growing and shrinking, as you expect.The professor who runs the lab gets in a new piece of equipment, a very fine laser beam that can be used to sever microtubules.She is very excited and wants to sever growing microtubules at their middle, using the laser beam.
A.Do you predict that the newly exposed microtubule plus ends will grow or shrink? Explain your answer.
B.What do you expect would happen to the newly exposed plus ends if you were to grow the microtubules in the presence of an analog of GTP that cannot be hydrolyzed, and you then severed the microtubules in the middle with a laser beam?

Accepted Answer

A.The newly exposed microtubule plus end

Question 15

Do you agree or disagree with this statement? Explain your answer.
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.

Accepted Answer

Disagree.The plus ends of microtubules u

Question 16

Figure 17-21 shows two isolated outer-doublet microtubules from a eukaryotic flagellum with their associated dynein molecules.   
Figure 17-21
A.Sketch what will happen to this structure if it is supplied with ATP.
B.Sketch what will happen to this structure if the linking proteins are removed and it is supplied with ATP.
C.In a complete flagellum, what would happen if all the dynein molecules were active at the same time?

Accepted Answer

A.See Figure A17-21A.
B.See Figure A17-2

Question 17

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below.Not all words or phrases will be used; use each word or phrase only once.
$\begin{array}{lll}
\text { antiparallel } & \text { four } & \text { tail } \
\beta \text { barrel } & \text { globular } & \text { ten } \
\text { coiled-coil } & \text { head } & \text { trimeric } \
\text { covalent } & \text { rod } & \text { twenty-five } \
\text { eight } & \text { seven } & \text { two }
\end{array}$

Intermediate filaments are elongated fibrous proteins with an N-terminal globular __________ region and a C-terminal globular __________ region; these regions flank the elongated rod domain.The α-helical region of the rod interacts with the α-helical region of another monomer in a __________ configuration to form a dimer.__________ dimers will line up to form a staggered tetramer.__________ strands of tetramers come together and twist together to form the __________ nm filament.The __________ domains are exposed on the surface of the intermediate filament, allowing for interaction with cytoplasmic components.

Accepted Answer

Intermediate filaments are elongated fib

Question 18

You discover a protein, MtA, and find that it binds to the plus ends of microtubules in cells.The hypothesis that best explains this localization is that MtA

Accepted Answer

A) is involved in stabilizing microtubules. 
B) binds to GTP-bound tubulin on microtubules. 
C) is important for the interaction of microtubules with the centrosome. 
D) will not bind to purified microtubules in a test tube. 
A) is involved in stabilizing microtubules. 
B) binds to GTP-bound tubulin on microtubules. 
C) is important for the interaction of microtubules with the centrosome. 
D) will not bind to purified microtubules in a test tube.

Question 19

Kinesins were purified by adding the nonhydrolyzable analog AMP-PNP to cytoplasmic extracts containing microtubules, purifying the microtubules, and then releasing the kinesin proteins, which were still attached to the microtubules, by adding ATP.Would this trick have worked to purify myosin motors attached to actin filaments? Explain.

Accepted Answer

No, addition of a nonhydrolyzable form o

Question 20

Which of the statements below about intermediate filaments is FALSE?

Accepted Answer

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 a cell-cell junction. 
D) Each filament is about 10 μm in diameter. 
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 a cell-cell junction. 
D) Each filament is about 10 μm in diameter.

Which of the following items is not important for flagellar movement?

Phosphorylation of nuclear lamins regulates their assembly and disassembly during mitosis.You add a drug to cells undergoing mitosis that inhibits the activity of an enzyme that dephosphorylates nuclear lamins.What do you predict will happen to these cells? Why?

Which of the following statements about the movement of materials in a nerve axon is TRUE?

Which of the following statements about the cytoskeleton is TRUE?

Which of the following statements about the cytoskeleton is FALSE?

Compared to the normal situation, in which actin monomers carry ATP, what do you predict would happen if actin monomers that bind a nonhydrolyzable form of ATP were incorporated into actin filaments?

Cell movement involves the coordination of many events in the cell.Which of the following phenomena is not required for cell motility?

Which of the following statements about skeletal muscle contraction is FALSE?

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?

Do you agree or disagree with this statement? Explain your answer. 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.

You discover a protein, MtA, and find that it binds to the plus ends of microtubules in cells.The hypothesis that best explains this localization is that MtA

Which of the statements below about intermediate filaments is FALSE?

Cells: The Fundamental Units of Life

Chemical Components of Cells

Energy, Catalysis, and Biosynthesis

Protein Structure and Function

DNA and Chromosomes

DNA Replication and Repair

From DNA to Protein

Control of Gene Expression

How Genes and Genomes Evolve

Analyzing the Structure and Function of Genes

Membrane Structure

Transport Across Cell Membranes

How Cells Obtain Energy From Food

Energy Generation in Mitochondria and Chloroplasts

Intracellular Compartments and Protein Transport

Cell Signaling

The Cell-Division Cycle

Sexual Reproduction and the Power of Genetics

Cell Communities: Tissues, Stem Cells, and Cancer

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Exam 17: Cytoskeleton

Which of the following items is not important for flagellar movement?

Phosphorylation of nuclear lamins regulates their assembly and disassembly during mitosis.You add a drug to cells undergoing mitosis that inhibits the activity of an enzyme that dephosphorylates nuclear lamins.What do you predict will happen to these cells? Why?

Which of the following statements about the movement of materials in a nerve axon is TRUE?

Which of the following statements about the cytoskeleton is TRUE?

Which of the following statements about the cytoskeleton is FALSE?

Compared to the normal situation, in which actin monomers carry ATP, what do you predict would happen if actin monomers that bind a nonhydrolyzable form of ATP were incorporated into actin filaments?

Cell movement involves the coordination of many events in the cell.Which of the following phenomena is not required for cell motility?

Which of the following statements about skeletal muscle contraction is FALSE?

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?

Do you agree or disagree with this statement? Explain your answer. 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.

You discover a protein, MtA, and find that it binds to the plus ends of microtubules in cells.The hypothesis that best explains this localization is that MtA

Which of the statements below about intermediate filaments is FALSE?

Cells: The Fundamental Units of Life

Chemical Components of Cells

Energy, Catalysis, and Biosynthesis

Protein Structure and Function

DNA and Chromosomes

DNA Replication and Repair

From DNA to Protein

Control of Gene Expression

How Genes and Genomes Evolve

Analyzing the Structure and Function of Genes

Membrane Structure

Transport Across Cell Membranes

How Cells Obtain Energy From Food

Energy Generation in Mitochondria and Chloroplasts

Intracellular Compartments and Protein Transport

Cell Signaling

The Cell-Division Cycle

Sexual Reproduction and the Power of Genetics

Cell Communities: Tissues, Stem Cells, and Cancer

Filters