Cytoskeleton I, II

Question 1

Which is a correct match of cytoskeleton organization and function?

A. Intestinal epithelial cells are non polarized and posses microvilli that function to minimize surface area on the luminal face to promote absorption.

B. Sperm have a unique cytoskeleton and streamlined shape that allows travel.

C. Skeletal muscle cells are specialized to exert a weak contractile force along multiple vectors.

Answer 1

B

Question 2

Actin is nucleated by which two specific molecules?

A. Arp2/3 complex and fimbrin

B. Alpha Actinin and fimbrin

C. Formins and fimbrin

D. Arp2/3 complex and formins

E. Alpha Actinin and formins

Answer 2

D

Question 3

Actin filament growth is controlled by __________ that bind the plus end of actin.

A. formins

B. myostin motors

C. capping proteins

D. poly-A 5’ cap (#tbt LOL jk)

Answer 3

C

Question 4

Actin is bundled by which two specific molecules?

A. Arp2/3 complex and fimbrin

B. Alpha Actinin and fimbrin

C. Formins and fimbrin

D. Arp2/3 complex and formins

E. Alpha Actinin and formins

Answer 4

B

Question 5

_________ catalyzes ADP to ATP on actin monomers to “recharge” them.

A. Fimbrin

B. Cofilin

C. Profilin

D. Villin

E. None of these

Answer 5

C

Question 6

Actin filaments are severed by ______.

A. Fimbrin

B. Cofilin

C. Profilin

D. Villin

E. None of these

Answer 6

B

Question 7

In the sarcomere, actin filaments are linked at the _________ by alpha-actinin and CapZ.

A. M-Line

B. I-band

C. A-band

D. Z-line

Answer 7

D

Question 8

Which class of myosin is most associated with (skeletal muscle) contraction?

A. Myosin I

B. Myosin II

C. Myosin III

D. Myosin IV

E. Myosin V

Answer 8

B

Question 9

Which class of myosin is most associated with organelle transport?

A. Myosin I

B. Myosin II

C. Myosin III

D. Myosin IV

E. Myosin V

Answer 9

E

Question 10

What two components are required for the Z-disk to be pulled closer together (i.e. the sarcomere to change from relaxed to contracted)?

Answer 10

ATP, Ca²⁺

Question 11

F-actin length is controlled by _________.

A. Fimbrin

B. Cofilin

C. Profilin

D. Villin

E. None of these

Answer 11

E - The F-actin (or thin filament) length is controlled by nebulin.

Question 12

Myosin length is controlled by _________.

A. Titin

B. Nebulin

C. Profilin

D. Villin

E. None of these

Answer 12

A

Question 13

Microtubules:

A. are assembled from subunits, though they are built from heterodimers rather than single monomers

B. are polar in nature, and have a plus and minus end

C. have a - end that grows at twice the rate of the + end

D. are the most robust of the cytoskeletal proteins

Answer 13

B

Question 14

The polymerization energy source of microtubule growth is _____.

Answer 14

GTP

Question 15

Dynamic instability:

A. is an alteration between growth and rapid disassembly

B. is a hallmark of actin

C. describes the depolymerization of microtubules, which is 100x faster from an end containing GTP tubulin than GDP tubulin

D. All of the above

Answer 15

A

Question 16

Which moves towards the plus end during the movement of various organelles throughout the cell?

A. Dynein

B. Nexin

C. Tektin

D. Kinesin

Answer 16

D

Question 17

Which drives toward the minus end during the movement of various organelles throughout the cell?

A. Dynein

B. Nexin

C. Tektin

D. Kinesin

Answer 17

A

Question 18

Intermediate filaments are like actin and tubulin because they:

A. differ according to cell type

B. are present in all cells

C. are formed from monomers to make a filamentous structure

D. are extremely stable

Answer 18

C

Question 19

In the dendritic nucleation model for actin assembly, which protein or protein complex is required for nucleating branched actin filaments?

A. Arp2/3

B. Cofilin

C. Myosin

D. Profilin

Answer 19

A

Question 20

Which scenario best describes the addition of G-actin to an actin filament?

A. addition occurs only to the + end

B. addition occurs only to the - end

C. addition occurs to both the + and - ends, though preferentially to the + end

D. addition occurs equally to both the + and - ends

Answer 20

C

Question 21

Microtubules:

A. are found within microvilli

B. utilize GTP as a polymeriation energy source

C. generally grow towards the centrioles in nucleated cells

D. have a + end that depolymerizes at a slower rate than the - end

E. have a + end that grows more slowly than the - end

Answer 21

B

Question 22

The mitotic spindle is made up of:

A. F-actin

B. G-actin

C. tropomyosin

D. myosin motors

E. microtubules

Answer 22

E

Question 23

All three classes of cytoskeletal proteins form polymers. Choose the rank order that best represents the relative stability of these polymers, in the order from most stable to least stable.

A. Intermediate filaments: tubulin: actin

B. Tubulin: actin: intermediate filaments

C. Intermediate filaments: actin: tubulin

D. Actin: tubulin: intermediate filaments

Answer 23

C

Question 24

Active kinesin motors:

A. generally adopt a folded conformation in the presence of cargo and microtubules

B. detach from a microtubule with each step

C. are utilized for the plus-end directed (i.e. anterograde) movement of membrane vesicles

D. are utilized in the nucleus-directed (i.e. retrograde) trafficking of organelles

Answer 24

C