Cytoskeleton

Question 1

Principle protein of microfilaments and microtubules

Answer 1

actin and tubulin respectively

Question 2

Microfilaments are typically located as:

Answer 2

filament netwrok under plasma membrane, contractile bundle, and parallel bundles (stress fiber and cores for microvilli and stereocillia)

Question 3

Microfilament structure

Answer 3

double helical arrangement of actin molecules

Question 4

G-actin

Answer 4

unpolymerized

Question 5

f-actin

Answer 5

polimerized, polar

Question 6

Actin Polymerization

Answer 6

requires ATP and depends on local concentration of G-actin and other actin binding proteins… done as necessary for cell fxn

Question 7

G/F actin ratio

Answer 7

always in equilibrium

Question 8

“Treadmilling”

Answer 8

New molecules add preferentially to (+) end filament, others lost at (-) end = continuous flow actin from (+) end
to (-) end

Question 9

How is actin arranged in the cell?

Answer 9

As a loose meshwork of crosslinked filaments typically found immediatelyunder and attached to the
plasma membrane. As bundles of parallel
filaments crosslinked by proteins such as fimbrin or villin

Question 10

What is the crosslinking protein often associated with actin filaments specificlly in lood meshwork of crosslinked filaments

Answer 10

filamin

Question 11

Microvilli

Answer 11

Microvilli are finger-like projections of the surface of some cells such as intestinal epithelial cells & have a core composed of a bundle of parallel
microfilaments

Question 12

Cytochalasins B and D

Answer 12

These drugs bind (+) end of microfilament &

block addition of new actin molecules

Question 13

Phalloidin

Answer 13

This drug stabilizes microfilament structure &
prevents depolymerization. Thus blocks cell activities requiring
reversible polymerization & depolymerization

Question 14

Composition of microtubules

Answer 14

composed of tubulin a and B dimers, bind microtubule associated proteins

Question 15

What molecule begins polymerization in microtubules

Answer 15

y-tubulin

Question 16

Cytoplasmic vs. motor microtubules

Answer 16

cytoplasmic is more liable, has single tubules, and

Question 17

microfilaments vs. microtubules source of energy for polymerization

Answer 17

microfilaments: ATP and microtubules: GTP

Question 18

How are microtubules aligned in cells?

Answer 18

Because they have polarity, - end in the center associated with centrioles and + end in edges

Question 19

Kinesin

Answer 19

moves along microtubule from - end to + end

Question 20

Dynein

Answer 20

moves along microtubule from + end to - end

Question 21

Colchicine

Answer 21

binds tubulin dimers & blocks their addition to tubule end
causing rapid depolymerization of the microtubules. Is used for treatment of gout.

Question 22

Taxol

Answer 22

binds to tubulin in the intact microtubule & stabilizes the
microtubule. Is used in therapy for breast cancer.

Question 23

Vinblastin and Vincristine

Answer 23

bind microtubule and are used as anti-

mitotic and anti-proliferative drugs in cancer therapy

Question 24

Intermediate Filamens

Answer 24

cytoskeletal fxn, no large pools of monomers in equilibrium with filaments, chemically ressistant and stable

Question 25

What control polymerization in intermediate filaments?

Answer 25

phosphorylation

Question 26

What are the 6 major classes of intermediate filament proteins?

Answer 26

keratin, vimentin and vimentin like proteins, neurofilament protein, lamins, and beaded filaments

Question 27

Filaggrin

Answer 27

binds keratin filaments into bundles

Question 28

plectin family of proteins

Answer 28

bind microfilaments, microtubules, and | intermediate filaments into 3-D networks

Question 29

Plakins

Answer 29

involved in binding of intermediate filaments to hemidesmosomes, & actin filaments to neurofilaments of sensory neurons. Includes desmoplakins, desmoplakin-like proteins, and plakoglobulins

Question 30

Lamins in intermediate filaments

Answer 30

strengthen the nuclear envelope

Question 31

Where are intermediate filaments located in the cell

Answer 31

concntrated in a dense ring around nucleus and radiate to periphery

Question 32

Where do intermediate filaments attach in epithilia?

Answer 32

attach to desmosome and hemidesmosome cell junctions as tonofilaments and strengthen layer

Question 33

Fxns of microfilaments

Answer 33

anchorage and movement of membrane proteins, structural core of microvilli, locomotion of cels, extension of cell processes (filopodia and lamellopodia), cytoplasmic streaming, cytokinesis, and morphogenetic movements of tissues during embriology

Question 34

Fxns of microtubules

Answer 34

intracellular vesicular transport and organelle movement, movement of cilia and flagella, chromosome movement, maintenance of cell shape, and maintenance of position of ER and intermediate filaments