Question 1

Which of the following is a G-actin sequestering protein that allows cells to maintain a relatively high G-actin concentration in cells?

Accepted Answer

A) thymosin β₄ 
B) FH2 domain of formin 
C) profilin 
D) cofilin 
A) thymosin β₄ 
B) FH2 domain of formin 
C) profilin 
D) cofilin

Question 2

In the operational model for movement of myosin along an actin filament,the power stroke occurs during:

Accepted Answer

A) binding of ATP. 
B) hydrolysis of ATP. 
C) release of phosphate (Pi). 
D) release of ADP. 
A) binding of ATP. 
B) hydrolysis of ATP. 
C) release of phosphate (Pi). 
D) release of ADP.

Question 3

The two proteins that play the most important role in actin microfilament elongation are:

Accepted Answer

A) thymosin β4 and cofilin. 
B) cofilin and profilin. 
C) profilin and thymosin β4. 
D) CapZ and cofilin. 
A) thymosin β4 and cofilin. 
B) cofilin and profilin. 
C) profilin and thymosin β4. 
D) CapZ and cofilin.

Question 4

Cofilin:

Accepted Answer

A) cleaves actin by binding the ATP-actin in the filament. 
B) cleaves actin by twisting adjacent F-actin monomers in the filament. 
C) recruits G-actin monomers to the elongating F-actin microfilament. 
D) promotes exchange of ADP for ATP on G actin. 
A) cleaves actin by binding the ATP-actin in the filament. 
B) cleaves actin by twisting adjacent F-actin monomers in the filament. 
C) recruits G-actin monomers to the elongating F-actin microfilament. 
D) promotes exchange of ADP for ATP on G actin.

Question 5

Multinucleated cells may result from a defect in:

Accepted Answer

A) myosin V. 
B) myosin I. 
C) stress fiber formation. 
D) myosin II. 
A) myosin V. 
B) myosin I. 
C) stress fiber formation. 
D) myosin II.

Question 6

Which of the following properties is not shared by all myosins?

Accepted Answer

A) the ability to bind ATP 
B) the ability to form dimers 
C) the ability to bind actin 
D) the presence of a head domain 
A) the ability to bind ATP 
B) the ability to form dimers 
C) the ability to bind actin 
D) the presence of a head domain

Question 7

In a scratch wound assay,cells are treated with inhibitors of Rho kinase.What would be observed?

Accepted Answer

A) The cells completely close the scratch,and only lamellipodia and filapodia are seen with actin staining. 
B) The distance the cells migrate into the scratch is small,and actin staining reveals stress fibers,lamellipodia,and filapodia. 
C) The cells are stimulated to undergo mitosis. 
D) The cells migrate into the scratch,but no stress fibers can be observed with actin staining. 
A) The cells completely close the scratch,and only lamellipodia and filapodia are seen with actin staining. 
B) The distance the cells migrate into the scratch is small,and actin staining reveals stress fibers,lamellipodia,and filapodia. 
C) The cells are stimulated to undergo mitosis. 
D) The cells migrate into the scratch,but no stress fibers can be observed with actin staining.

Question 8

Decoration of actin filaments with myosin S1 is commonly used to:

Accepted Answer

A) attach actin filaments to cell membranes. 
B) disassemble actin filaments. 
C) reveal the polarity of actin filaments. 
D) reveal the polarity of myosin filaments. 
A) attach actin filaments to cell membranes. 
B) disassemble actin filaments. 
C) reveal the polarity of actin filaments. 
D) reveal the polarity of myosin filaments.

Question 9

What are the functions of the myosin head domain and tail domain,respectively?

Accepted Answer

The myosin head domain is the portion of

Question 10

Small G proteins,including Rho,Rac,and Cdc42,contribute to the coordinated movement and overall polarity of a migrating cell.Assuming that the cell is migrating in a left-to-right fashion,which of the following is correct?

Accepted Answer

A) active Cdc42 at the leading edge of the cell and active Rho at the back of the cell 
B) active Rac at the back of the cell and active Cdc42 at the front of the cell 
C) active Cdc42 at the back of the cell and active Rac at the leading edge of the cell 
D) active Rac at the leading edge of the cell and active Rho at the back of the cell 
A) active Cdc42 at the leading edge of the cell and active Rho at the back of the cell 
B) active Rac at the back of the cell and active Cdc42 at the front of the cell 
C) active Cdc42 at the back of the cell and active Rac at the leading edge of the cell 
D) active Rac at the leading edge of the cell and active Rho at the back of the cell

Question 11

Describe the functional properties of the head,neck,and tail domains of myosin.

Accepted Answer

The head domain of myosin is a specializ

Question 12

Lamellipodia are located:

Accepted Answer

A) at a moving cell's trailing edge. 
B) at a moving cell's leading edge. 
C) around the entire periphery of a nonmotile cell. 
D) throughout the cytosol of a moving cell. 
A) at a moving cell's trailing edge. 
B) at a moving cell's leading edge. 
C) around the entire periphery of a nonmotile cell. 
D) throughout the cytosol of a moving cell.

Question 13

Which of the following is NOT a function of myosin-powered movements?

Accepted Answer

A) skeletal muscle contraction 
B) cytoplasmic streaming 
C) cytokinesis 
D) flagellum-mediated cell motility 
A) skeletal muscle contraction 
B) cytoplasmic streaming 
C) cytokinesis 
D) flagellum-mediated cell motility

Question 14

During treadmilling,actin subunits add:

Accepted Answer

A) predominantly to filament (+)ends. 
B) predominantly to filament (−)ends. 
C) equally to both filament ends. 
D) along the length of filaments. 
A) predominantly to filament (+)ends. 
B) predominantly to filament (−)ends. 
C) equally to both filament ends. 
D) along the length of filaments.

Question 15

How do actin filaments appear when viewed by negative stain electron microscopy?

Accepted Answer

When viewed by negative stain

Question 16

Three major groups of filament systems comprising the cytoskeleton are all composed of polymers of assembled subunits,which vary in thickness when assembled.Which is the correct order,from smallest to largest,of the filament systems?

Accepted Answer

A) microtubules,microfilaments,intermediate filaments 
B) intermediate filaments,microtubules,microfilaments, 
C) microfilaments,microtubules,intermediate filaments 
D) none of the above 
A) microtubules,microfilaments,intermediate filaments 
B) intermediate filaments,microtubules,microfilaments, 
C) microfilaments,microtubules,intermediate filaments 
D) none of the above

Question 17

All myosins move toward the (+)end of actin filaments EXCEPT:

Accepted Answer

A) myosin I. 
B) myosin II. 
C) myosin V. 
D) myosin VI. 
A) myosin I. 
B) myosin II. 
C) myosin V. 
D) myosin VI.

Question 18

Which region of myosin interacts with actin filaments?

Accepted Answer

A) the head domain 
B) the rod domain 
C) the light chains 
D) the tail domain 
A) the head domain 
B) the rod domain 
C) the light chains 
D) the tail domain

Question 19

How are actin-binding proteins involved in gel-sol transitions?

Accepted Answer

The transformation between sol and gel s

Question 20

Which of the following proteins promotes actin assembly and is involved in signaling pathways controlling actin assembly at the plasma membrane?

Accepted Answer

A) myosin 
B) profilin 
C) thymosin β₄ 
D) filamin 
A) myosin 
B) profilin 
C) thymosin β₄ 
D) filamin

Exam 16: Cell Organization and Movement I: Microfilaments

Which of the following is a G-actin sequestering protein that allows cells to maintain a relatively high G-actin concentration in cells?

In the operational model for movement of myosin along an actin filament,the power stroke occurs during:

The two proteins that play the most important role in actin microfilament elongation are:

Cofilin:

Multinucleated cells may result from a defect in:

Which of the following properties is not shared by all myosins?

In a scratch wound assay,cells are treated with inhibitors of Rho kinase.What would be observed?

Decoration of actin filaments with myosin S1 is commonly used to:

What are the functions of the myosin head domain and tail domain,respectively?

Small G proteins,including Rho,Rac,and Cdc42,contribute to the coordinated movement and overall polarity of a migrating cell.Assuming that the cell is migrating in a left-to-right fashion,which of the following is correct?

Describe the functional properties of the head,neck,and tail domains of myosin.

Lamellipodia are located:

Which of the following is NOT a function of myosin-powered movements?

During treadmilling,actin subunits add:

How do actin filaments appear when viewed by negative stain electron microscopy?

Three major groups of filament systems comprising the cytoskeleton are all composed of polymers of assembled subunits,which vary in thickness when assembled.Which is the correct order,from smallest to largest,of the filament systems?

All myosins move toward the (+)end of actin filaments EXCEPT:

Which region of myosin interacts with actin filaments?

How are actin-binding proteins involved in gel-sol transitions?

Which of the following proteins promotes actin assembly and is involved in signaling pathways controlling actin assembly at the plasma membrane?

Chemical Foundations

Molecular Genetic Techniques

Protein Structure and Function

Culturing and Visualizing Cells

Fundamental Molecular Genetic Mechanisms

Bio-membrane Structure

Genes Genomics and Chromosomes

Transcriptional Control of Gene Expression

Post-Transcriptional Gene Control

Transmembrane Transport of Ions and Small Molecules

Cellular Energetics

Moving Proteins Into Membranes and Organelles

Vesicular Traffic, Secretion, and Endocytosis

Signal Transduction and G-Protein Coupled Receptors

Signaling Pathways That Control Gene Activity

Cell Organization and Movement II: Microtubules and Intermediate Filaments

Regulating the Eukaryotic Cell Cycle

Integrating Cells Into Tissues

Cell Birth, Lineage, and Death

Nerve Cells

Immunology

Cancer

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