Question 1

The critical concentration for tubulin polymerization is the concentration of

Accepted Answer

A) tubulin dimers at which all dimers assemble into microtubules. 
B) unassembled tubulin dimers when assembly is balanced with disassembly. 
C) tubulin dimers at which dimers assemble onto microtubule minus ends but disassemble from plus ends. 
D) unassembled tubulin dimers when there is net disassembly of dimers from both microtubule ends. 
E) tubulin dimers in most cells. 
A) tubulin dimers at which all dimers assemble into microtubules. 
B) unassembled tubulin dimers when assembly is balanced with disassembly. 
C) tubulin dimers at which dimers assemble onto microtubule minus ends but disassemble from plus ends. 
D) unassembled tubulin dimers when there is net disassembly of dimers from both microtubule ends. 
E) tubulin dimers in most cells.

Question 2

What is the importance of proteins that precisely control when and where cytoskeletal elements polymerize and depolymerize? Make sure to give examples in your explanations.

Accepted Answer

Their precise control of filament existe

Question 3

Tubulin may assemble onto one end while disassembling from the other end of the same microtubule simultaneously in a process known as

Accepted Answer

A) dynamic instability. 
B) treadmilling. 
C) nucleation. 
D) oligomerization. 
E) catastrophe-rescue. 
A) dynamic instability. 
B) treadmilling. 
C) nucleation. 
D) oligomerization. 
E) catastrophe-rescue.

Question 4

________ proteins promote depolymerization of existing microtubules at the ends.

Accepted Answer

The answer of ________ proteins promote depolymerization of existing microtubules...

Question 5

The ________ is a complex network of interconnected filaments and tubules that extends throughout the cytosol from the nucleus to the inner surface of the plasma membrane.

Accepted Answer

A) cytoskeleton 
B) microtubule apparatus 
C) axoneme 
D) desmin sheath 
E) microfilament array 
A) cytoskeleton 
B) microtubule apparatus 
C) axoneme 
D) desmin sheath 
E) microfilament array

Question 6

Profilin does all of the following except

Accepted Answer

A) competes with thymosin β4 for binding to actin monomers. 
B) sequesters actin monomers to prevent any polymerization. 
C) binds to formin in order to "stage" actin monomers for addition to a growing filament. 
D) promotes actin monomer addition to a filament plus end. 
E) Profilin does all of the above. 
A) competes with thymosin β4 for binding to actin monomers. 
B) sequesters actin monomers to prevent any polymerization. 
C) binds to formin in order to "stage" actin monomers for addition to a growing filament. 
D) promotes actin monomer addition to a filament plus end. 
E) Profilin does all of the above.

Question 7

Activation of the ________ G-protein results in the extension of lamellipodia.

Accepted Answer

The answer of Activation of the ________ G-protein results in...

Question 8

Activation of which of the following is associated with the formation of focal adhesions and stress fibers?

Accepted Answer

A) Cdc42 
B) plectin 
C) Rho 
D) Rac 
E) γ-tubulin 
A) Cdc42 
B) plectin 
C) Rho 
D) Rac 
E) γ-tubulin

Question 9

The two main types of eukaryotic microtubules are the ________ and ________ microtubules.

Accepted Answer

cytoplasmi

Question 10

Which technique would best be used to visualize movement of unlabeled vesicles along microtubules?

Accepted Answer

A) immunofluorescence microscopy of fixed material 
B) live cell fluorescence microscopy 
C) computer-enhanced digital video microscopy 
D) deep-etch electron microscopy 
E) A,B,C,or D would be equally useful. 
A) immunofluorescence microscopy of fixed material 
B) live cell fluorescence microscopy 
C) computer-enhanced digital video microscopy 
D) deep-etch electron microscopy 
E) A,B,C,or D would be equally useful.

Question 11

Based on composition similarities,actin can be divided into two major groups: the muscle-specific actins (________-actin)and nonmuscle actins (________- and ________-actin).

Accepted Answer

The answer of Based on composition similarities,actin can be divided...

Question 12

Which of the following cytoskeletal proteins would be expected to be involved in binary fission of a bacterium into two bacteria?

Accepted Answer

A) FtsZ 
B) MreB 
C) plectin 
D) crescentin 
E) tubulin 
A) FtsZ 
B) MreB 
C) plectin 
D) crescentin 
E) tubulin

Question 13

Describe an additional experimental approach used to study the cytoskeleton in which the activity of cytoskeletal elements is affected in ways similar to those resulting from drug treatment.

Accepted Answer

Using organisms or cell lines

Question 14

Which of the following is not a function of the cytoskeleton?

Accepted Answer

A) cell locomotion 
B) cell division 
C) organelle movement 
D) establishing cell shape 
E) passive transport 
A) cell locomotion 
B) cell division 
C) organelle movement 
D) establishing cell shape 
E) passive transport

Question 15

Which of the following is false about lamellipodia?

Accepted Answer

A) Their formation is stimulated by activation of Rac. 
B) They may have associated filopodia. 
C) They contain bundles of microtubules that push the plasma membrane forward. 
D) They extend at the leading edge of crawling cells. 
E) They contain branched networks of actin filaments. 
A) Their formation is stimulated by activation of Rac. 
B) They may have associated filopodia. 
C) They contain bundles of microtubules that push the plasma membrane forward. 
D) They extend at the leading edge of crawling cells. 
E) They contain branched networks of actin filaments.

Question 16

Which of the following proteins would be a good drug target for interfering with microfilament network breakdown?

Accepted Answer

A) profilin 
B) CapZ 
C) gelsolin 
D) tropomodulin 
E) calmodulin 
A) profilin 
B) CapZ 
C) gelsolin 
D) tropomodulin 
E) calmodulin

Question 17

Microtubules and microfilaments are similar with respect to each of the following except

Accepted Answer

A) inherent polarity of the structure. 
B) localization similar to that of intermediate filaments in cells. 
C) association with motor proteins. 
D) plus and minus ends for polymerization. 
E) both are polymers of subunits. 
A) inherent polarity of the structure. 
B) localization similar to that of intermediate filaments in cells. 
C) association with motor proteins. 
D) plus and minus ends for polymerization. 
E) both are polymers of subunits.

Question 18

Which phase of microtubule polymerization in vitro would be affected most by adding short microtubules to unpolymerized GTP-tubulin?

Accepted Answer

A) lag phase 
B) elongation phase 
C) addition of tubulin dimers to microtubule (+)ends at the plateau phase 
D) addition of tubulin dimers to microtubule (−)ends at the plateau phase 
E) treadmilling 
A) lag phase 
B) elongation phase 
C) addition of tubulin dimers to microtubule (+)ends at the plateau phase 
D) addition of tubulin dimers to microtubule (−)ends at the plateau phase 
E) treadmilling

Question 19

What is the effect of cofilin on an actin microfilament?

Accepted Answer

A) caps the microfilament plus end 
B) caps the microfilament minus end 
C) increases turnover of ATP-actin at the microfilament plus end 
D) increases turnover of ADP-actin at the microfilament plus end 
E) increases turnover of ADP-actin at the microfilament minus end 
A) caps the microfilament plus end 
B) caps the microfilament minus end 
C) increases turnover of ATP-actin at the microfilament plus end 
D) increases turnover of ADP-actin at the microfilament plus end 
E) increases turnover of ADP-actin at the microfilament minus end

Question 20

Intermediate filaments

Accepted Answer

A) are 7 nm in diameter. 
B) can be composed of the protein vimentin. 
C) are abundant in plant cells. 
D) are the only cytoskeletal filament responsible for animal cell shape. 
E) A,B,C,and D. 
A) are 7 nm in diameter. 
B) can be composed of the protein vimentin. 
C) are abundant in plant cells. 
D) are the only cytoskeletal filament responsible for animal cell shape. 
E) A,B,C,and D.

Exam 13: Cytoskeletal Systems

The critical concentration for tubulin polymerization is the concentration of

What is the importance of proteins that precisely control when and where cytoskeletal elements polymerize and depolymerize? Make sure to give examples in your explanations.

Tubulin may assemble onto one end while disassembling from the other end of the same microtubule simultaneously in a process known as

________ proteins promote depolymerization of existing microtubules at the ends.

The ________ is a complex network of interconnected filaments and tubules that extends throughout the cytosol from the nucleus to the inner surface of the plasma membrane.

Profilin does all of the following except

Activation of the ________ G-protein results in the extension of lamellipodia.

Activation of which of the following is associated with the formation of focal adhesions and stress fibers?

The two main types of eukaryotic microtubules are the ________ and ________ microtubules.

Which technique would best be used to visualize movement of unlabeled vesicles along microtubules?

Based on composition similarities,actin can be divided into two major groups: the muscle-specific actins (________-actin)and nonmuscle actins (________- and ________-actin).

Which of the following cytoskeletal proteins would be expected to be involved in binary fission of a bacterium into two bacteria?

Describe an additional experimental approach used to study the cytoskeleton in which the activity of cytoskeletal elements is affected in ways similar to those resulting from drug treatment.

Which of the following is not a function of the cytoskeleton?

Which of the following is false about lamellipodia?

Which of the following proteins would be a good drug target for interfering with microfilament network breakdown?

Microtubules and microfilaments are similar with respect to each of the following except

Which phase of microtubule polymerization in vitro would be affected most by adding short microtubules to unpolymerized GTP-tubulin?

What is the effect of cofilin on an actin microfilament?

Intermediate filaments

A Preview of Cell Biology

The Chemistry of the Cell

The Macromolecules of the Cell

Cells and Organelles

Bioenergetics: the Flow of Energy in the Cell

Enzymes: the Catalysts of Life

Membranes: Their Structure,function,and Chemistry

Transport Across Membranes: Overcoming the Permeability Barrier

Chemotrophic Energy Metabolism: Glycolysis and Fermentation

Chemotrophic Energy Metabolism: Aerobic Respiration

Phototrophic Energy Metabolism: Photosynthesis

The Endomembrane System

Cellular Movement: Motility and Contractility

Beyond the Cell: Cell Adhesions, cell Junctions, and Extracellular Structures

The Structural Basis of Cellular Information: Dna, chromosomes, and the Nucleus

DNA Replication, repair, and Recombination

Gene Expression: Ithe Genetic Code and Transcription

Gene Expression: Iiprotein Synthesis and Sorting

The Regulation of Gene Expression

Molecular Biology Techniques for Cell Biology

Signal Transduction Mechanisms: Ielectrical and Synaptic Signaling in Neurons

Signal Transduction Mechanisms: Iimessengers and Receptors

The Cell Cycle and Mitosis

Sexual Reproduction,meiosis,and Genetic Recombination

Filters

The two main types of eukaryotic microtubules are the and microtubules.

Based on composition similarities,actin can be divided into two major groups: the muscle-specific actins (-actin)and nonmuscle actins (- and -actin).