Deck 15: Cytoskeletal Systems

Question 1

Actin bundles give shape and support to the _ found in cells of the small intestine.

A)lamellipodia
B)centrosomes
C)microvilli
D)nuclei
E)microtubules

Answer 1

C

Question 2

In binary fission, one would expect the involvement of which of the following cytoskeletal proteins?

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

Answer 2

A

Question 3

F- actin filaments

A)are oriented similar to DNA, with strands helical and antiparallel to one another.
B)are composed of G- actin dimers.
C)are composed of polymerized G- actin monomers wound around each other in a helix.
D)polymerize at the same rate in both directions from both ends of the filament.
E)are composed of four linear strands.

Answer 3

C

Question 4

Which stage of microtubule assembly is the stage in which nucleation occurs?

A)elongation
B)sheets of protofilaments
C)dimers
D)closing of microtubules
E)oligomers

Question 5

Capping proteins such as CapZ

A)cause microtubules branching.
B)stabilize microtubules.
C)destabilize microtubules.
D)connect microtubules to microfilaments.
E)cause microtubules to lengthen.

Question 6

Intermediate filaments

A)are grouped into five classes based on the cell types in which they are found.
B)are smooth and sticky.
C)have molecular masses averaging 500 kDa.
D)were first discovered in muscle cells.
E)assemble from nonfibrous filaments.

Question 7

According to the current model, which of the following is the correct sequence of microtubule assembly?

A)protofilaments, sheets of protofilaments, closing of microtubule, elongating microtubule, dimers, oligomers
B)dimers, oligomers, protofilaments, elongating microtubule, sheets of protofilaments, closing of microtubule
C)dimers, oligomers, protofilaments, sheets of protofilaments, closing of microtubule, elongating microtubule
D)dimers, sheets of protofilaments, closing of microtubule, oligomers, protofilaments, elongating microtubule
E)dimers, oligomers, sheets of protofilaments, protofilaments, closing of microtubule, elongating microtubule

Question 8

Of the following microtubule interacting proteins, which might you potentially investigate as a mechanism for disrupting cell division in actively replicating tumor cells?

A)FtsZ
B)catastrophins
C)G- actin
D)tau
E)+- tip proteins

Question 9

One of the following drugs blocks cell division because it stabilizes the microtubules. What is this drug, and for what is it used?

A)benzimidazole; colchicine
B)vincristine; bacterial infections
C)vinblastine; antimitotic therapy
D)nocodazole; allergies
E)taxol; breast cancer

Question 10

All of the following are moved by molecular motors EXCEPT

A)cytoskeletal filaments.
B)glucose.
C)chloroplasts.
D)secretory vesicles.
E)Golgi complex.

Question 11

causes microtubules to form tight bundles in nerve cells.

A)Tau
B)Tubulin
C)Kinesis
D)Dynein
E)Actin

Question 12

Lamellipodia

A)contain microtubules.
B)do not involve actin or tubulin.
C)add structural rigidity to cells.
D)are found in the basal lamina.
E)are thin sheets of cytoplasm use for cell movement.

Question 13

Intermediate filaments

A)are 70 nm in diameter.
B)can be composed of the protein vimentin.
C)are solely responsible for animal cell shape.
D)are composed of alpha and beta tubulin.
E)both A and D

Question 14

Microtubules have an inner diameter of and an outer diameter of .

A)25 nm; 30 nm
B)8 nm; 12 nm
C)15 nm; 25 nm
D)7 mm; 14 mm
E)15 mm; 25 mm

Question 15

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

A)cell movement
B)positioning of enzymes
C)moving of organelles
D)passive transport
E)cell division

Question 16

Ring- shaped complexes in the centrosome contain _ in combination with _ .

A)gamma tubulin; tubulin GTP
B)alpha tubulin; gamma tubulin
C)gamma tubulin; pericentrin
D)beta tubulin; tubulin GTP
E)alpha tubulin; cilium

Question 17

Which of the following is NOT a function associated with the cytoskeleton?

A)signal transducer
B)scaffold for support and maintenance of cell shape
C)anchoring site for mRNA during transcription
D)organizes the organelles within the cytoplasm
E)cell division

Question 18

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.

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

Question 19

Tubulin may assemble and disassemble simultaneously in a process known as

A)MAP motoring.
B)treadmilling.
C)actin- regulated assembly.
D)microtubule organizing.
E)dynamic instability.

Question 20

A high- resolution video camera is used in which of the following microscopic techniques?

A)transmission electron microscopy
B)fluorescent staining of cytoskeleton proteins
C)scanning electron microscopy
D)computer- enhanced digital video microscopy
E)immunofluorescence microscopy

Question 21

are proteins that promote depolymerization of extant microtubules at the ends.

Question 22

The model is used to describe the simultaneous polymerization and depolymerization of microtubules.

Question 23

Critical concentration is

A)the concentration of G- actin in most muscle cells.
B)the concentration of tubulin dimers at which assembly is balanced with disassembly.
C)required before nucleation can occur.
D)the concentration of tubulin dimers at which assembly occurs primarily.
E)both A and D

Question 24

The is a dense network of microfilaments just beneath the plasma membrane.

Question 25

Microtubules and microfilaments differ with respect to each of the following EXCEPT

A)occurrence.
B)size.
C)associated motor proteins.
D)subunits.
E)a state of dynamic instability.

Question 26

Axonemal microtubules

A)are highly disorganized, but very stable.
B)are required to maintain axons.
C)are organized around a central shaft or axoneme.
D)may be loosely associated with basal bodies.
E)did not become clearly recognized until better fixation techniques became available in the 1960s.

Question 27

Which of the following is NOT true of the main structural forms of actin?

A)Actin filaments form filament bundles.
B)Actin filaments may form a filament network (gel).
C)Actin filaments are severed to form filament bundles.
D)Actin monomers may form actin filaments or G- actin protein complexes.
E)Capped filaments are made from actin filaments.

Question 28

Microfilaments function in

A)maintenance of cellular shape in animal cells.
B)cell division.
C)cytoplasmic streaming.
D)muscle contraction.
E)all of the above

Question 29

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

Question 30

Which of the following intermediate filament proteins is incorrectly matched with the tissue in which it is found?

A)cytokeratins- epithelial
B)GFA protein- nervous
C)nestin- connective
D)vimentin- mesenchymal
E)desmin- smooth muscle

Question 31

A variety of proteins link actin to membranes. A protein is used to link actin to the membrane.

A)spectrin; ER
B)linker; plasma
C)band 4.1; mucous
D)band 4.1; basal
E)ankyrin; lysosome

Question 32

The microtubule- organizing center (MTOC)

A)acts as an anchor for both ends of the microtubule.
B)is associated with two centrioles in plant cells.
C)is positioned near the cell membrane.
D)is called a centrosome during interphase.
E)serves as a site for microtubule and microfilament assembly.

Question 33

resist tensile forces and contain keratin to form the protective barrier of the skin.

A)Actin filaments
B)Intermediate filaments
C)Microtubules
D)Microfilaments
E)Keratin- associated filaments

Question 34

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

Question 35

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

A)intermediate filaments
B)y- tubulin
C)Rho
D)Ras
E)Cdk- 42

Question 36

All of the following are components associated with the bacterial cytoskeleton EXCEPT

A)MreB.
B)plaktin.
C)crescentin.
D)FtsZ.
E)both B and C

Question 37

Elongation of the microtubule occurs by the

A)addition of G- actin subunits to the (+)end.
B)addition of tubulin subunits to the (+)end.
C)addition of tubulin subunits to each end.
D)deletion of G- actin subunits from the (+)end.
E)addition of the tubulin subunits to the (+)end, but removal from the (- )end.

Question 38

The model was proposed by Mitchison and Kirschner to explain how polymerization and depolymerization of microtubules occur simultaneously.