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Histology Exam 1 > Lecture 6: Cytoskeleton > Flashcards

Lecture 6: Cytoskeleton Flashcards

1
Q

components of cytoskeleton

A

microfilaments
intermediate filaments
microtubules

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2
Q

compare size of cytoskeleton components

A 
microfilaments = actin = 7nm
intermediate = tonofilaments = 8-10nm
microtubules = 25nm
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3
Q

actin binds to specific transmembrane proteins

A

cadherins

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4
Q

monomer of actin

A

G-actin (globules)

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5
Q

polymer/long chain of actin

A

F-actin (filamentous)

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6
Q

varieties of actin

A

3
alpha
beta
gamma

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7
Q

G-actin readily binds with ___ .

A

ATP

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8
Q

G-actin can bind with __ # of other monomers.

A

2 others

one on each side

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9
Q

actin filaments display _____ .

A

polarity

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10
Q

overall structure of microfilaments

A

double helix of G-actin subunits

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11
Q

F-actin polymerization requires ___ .

A

ATP

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12
Q

polymerization of actin is a _____ situation, meaning……..?

A

dynamic situation

meaning it is reversible and constantly in flux

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13
Q

ATP-actin is added at the _______ end.

A

growing end
barbed end
plus end

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14
Q

ADP-actin is found at the ______ end.

A

slow end
pointed end
minus end

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15
Q

which end of an actin filament is faster in polymerization?

A

plus end is 5-10x faster

minus end is more prone to depolymerization

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16
Q

low [G-actin]

A

depolymerization

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17
Q

mild [G-actin]

A

dynamic equilibrium

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18
Q

high [G-actin]

A

net addition
polymerization at both ends
***remember barbed is faster than pointed end

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19
Q

a dynamic equilibrium between adding to the barbed end and removal from the pointed end

A

treadmilling
associated with mild [G]
results in zero net growth

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20
Q

drugs that effect actin polymerization

A

Cytochalasins
phalloidin
latrunculins

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21
Q

Cytochalasins

A

bind to barbed ends

inhibiting growth

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22
Q

phalloidin

A

bind to actin filaments

prevent depolymerization

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23
Q

latrunculins

A

bind to g-actin

induce depolymerization of f-actin

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24
Q

molecules that can control treadmilling

A

cofilin
Arp2/3
phalloidin
latrunculins

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25
Q

spectrin

A

found RBCs - help maintain their cell shape

binds to cortical cytoskeleton plasma membrane

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26
Q

dystrophin

A

binds to cortical cytoskeleton to plasma membrane

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27
Q

villin and fimbrin

A

cross link actin filaments in microvilli

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28
Q

calmodulin and myosin I

A

cross link actin to plasma membrane in microvilli

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29
Q

alpha actin

A

cross link stress fibers

connect actin to protein plasma membrane complex

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30
Q

filamin

A

cross link actin at wide angles to form screen like gels

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31
Q

thymosin

A

holds G-actin in a reserve pool

preventing polymerization

32
Q

profilin

A

binds to G-actin catalyzing ADP into ATP
promotes transfer from thymosin to barbed end
promoting polymerization

33
Q

Arp2/3

A

initiates growth of F-action from sides of pre-existing filament

34
Q

cofilin

A

depolymerization factor

stimulates removal of ADP G-actin at the pointed end

35
Q

gelsolin

A

cuts filaments into pieces and caps barbed end

preventing loss or addition of monomers

36
Q

gelsolin in Ca presence

A

fragments F-actin and remains bound to plus end

37
Q

thin filament width

A

7nm

38
Q

intermediate filament width

A

8-10nm

39
Q

thick filament width

A

25nm

40
Q

intermediate filaments are abundant in cells that are subject to _______ stressors. and provide ____ strength

A

mechanical stress

tensile strength

41
Q

intermediate assembly

2 polypeptides form a ….?

A

coiled dimer

staggered antiparallel arrangement

42
Q

which is more stable between intermediate and thin filaments

A

intermediate filaments

43
Q

intermediate assembly

coiled dimers…..?

A

dimers arrange in staggered antiparallel to form

—–tetramers

44
Q

intermediate assembly

tetramers…..?

A

tetramers assemble end to end forming

—–protofilaments

45
Q

an intermediate fiber is equal to = ?

A

8 protofilaments

46
Q

2 monomers =
2 dimers =
8 tetramer bundles =

A

parallel dimer
tetramer
protofilament

47
Q

protofilaments arrange in a rod to form…..?

A

intermediate filament

48
Q

diameters of microtubules

A 
outer = 25nm
inner = 14nm
49
Q

microtubules are composed of…..

A

tubulin dimers

alpha+beta subunits

50
Q

a slice or single row of tubulin dimers

A

protofilament

51
Q

a microtubule is equal to =

A

13 protofilaments

which are arranged in a circle to form a cylinder with a hollow center

52
Q

distinguish between the ends of a microtubule

A

plus=fast growing end

minus = slow growing end

53
Q

plus end of microtubule

A

fast growing end
beta subunit bound to GTP
grows rapidly in low [Ca]

54
Q

tubulin is less stable after ________ because ….?

A

after polymerization

because GTP has been hydrolyzed to GDP

55
Q

growth pattern of microtubule

A

capable of growth and shortening at plus end

56
Q

high [tubulin–GTP]

A

dimers will add more rapidly than GTP hydrolysis

result = growth of microtubule

57
Q

low [tubulin–GTP]

A

GTP at plus end is hydrolyzed to GDP

result = dimers are lost – shortening of microtubule

58
Q

tubulin is less stable….

A

when GTP is hydrolyzed to GDP

or called depolymerization

59
Q

factors that inhibit microtubule polymerization

A

Colchicines
Colcemid
vincristine & vinblastine

60
Q

factor that can stop mitosis at metaphase and bind to tubulin dimers (what does this prevent)

A

colchicines

prevent microtubule polymerization

61
Q

anticancer drugs that effect microtubule polymerization

A

vincristine and vinblastine

62
Q

drug that can stabilize microtubules

A

taxol
anticancer drug
binds to microtubules – preventing depolymerization

63
Q

taxol can prevent microtubule ________ , how does this prevent cancer?

A

prevent depolymerization

does not allow that depolymerization of mitotic spindles which is required for cell separation

64
Q

how can stabilizing and destabilizing microtubule drugs both fight cancer?

A

anything that interferes with microtubules, interferes with mitosis

thus not allowing cells to reproduce

65
Q

functions of the cytoskeleton

A

cell mvt
cell support, strength, shapes
cell adherence
microtubule monorail system

66
Q

microtubule roles in mitosis

A

kinetochore microtubules
mitotic spindles
cytokinesis

67
Q

microtubules act as a monorail system for moving _____, but how do we attach these to the microtubules?

A

for vesicle transport

must utilize motor proteins for attachment
kinesin and dynein

68
Q

vesicle transport from minus to plus end of a microtubule

A

kinesin

carries full vesicles to destination

69
Q

vesicle transport from plus to minus end of a microtubule

A

dynein

carries empty vesicles back to source

70
Q

why do microtubule’s require 2 different motor proteins

A

in vesicle transport each protein only travels one way, it is then carried by the other motor protein back to it’s original starting point

71
Q

if kinesin and dynein only travel one way, how do they get back to their starting point?

A

they carry each other

72
Q

myosin I

A

1 head
tail binds to cell membrane
head binds to actin
direction of head motion toward the barbed end

73
Q

myosin II

A

2 heads
tail binds to myosin II
head binds to actin
direction of head motion toward the plus end

74
Q

kinesin

A

2 heads
tail binds to vesicle
head binds to microtubules
direction of head motion toward the plus end

75
Q

cytoplasmic dynein

A

2 heads
tail binds to vesicle
head binds to microtubules
direction of head motion toward the minus end (pointed)

76
Q

inactive myosin II tails

A

have their light chain tails folded back in loops

close to their heads

77
Q

active myosin II tails

A

have their tails stretched straight out

Histology Exam 1 (8 decks)

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