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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
spectrin
found RBCs - help maintain their cell shape | binds to cortical cytoskeleton plasma membrane
26
dystrophin
binds to cortical cytoskeleton to plasma membrane
27
villin and fimbrin
cross link actin filaments in microvilli
28
calmodulin and myosin I
cross link actin to plasma membrane in microvilli
29
alpha actin
cross link stress fibers | connect actin to protein plasma membrane complex
30
filamin
cross link actin at wide angles to form screen like gels
31
thymosin
holds G-actin in a reserve pool | preventing polymerization
32
profilin
binds to G-actin catalyzing ADP into ATP promotes transfer from thymosin to barbed end promoting polymerization
33
Arp2/3
initiates growth of F-action from sides of pre-existing filament
34
cofilin
depolymerization factor | stimulates removal of ADP G-actin at the pointed end
35
gelsolin
cuts filaments into pieces and caps barbed end | preventing loss or addition of monomers
36
gelsolin in Ca presence
fragments F-actin and remains bound to plus end
37
thin filament width
7nm
38
intermediate filament width
8-10nm
39
thick filament width
25nm
40
intermediate filaments are abundant in cells that are subject to _______ stressors. and provide ____ strength
mechanical stress | tensile strength
41
intermediate assembly | 2 polypeptides form a ….?
coiled dimer | staggered antiparallel arrangement
42
which is more stable between intermediate and thin filaments
intermediate filaments
43
intermediate assembly | coiled dimers.....?
dimers arrange in staggered antiparallel to form | -----tetramers
44
intermediate assembly | tetramers.....?
tetramers assemble end to end forming | -----protofilaments
45
an intermediate fiber is equal to = ?
8 protofilaments
46
2 monomers = 2 dimers = 8 tetramer bundles =
parallel dimer tetramer protofilament
47
protofilaments arrange in a rod to form.....?
intermediate filament
48
diameters of microtubules
``` outer = 25nm inner = 14nm ```
49
microtubules are composed of.....
tubulin dimers | alpha+beta subunits
50
a slice or single row of tubulin dimers
protofilament
51
a microtubule is equal to =
13 protofilaments | which are arranged in a circle to form a cylinder with a hollow center
52
distinguish between the ends of a microtubule
plus=fast growing end minus = slow growing end
53
plus end of microtubule
fast growing end beta subunit bound to GTP grows rapidly in low [Ca]
54
tubulin is less stable after ________ because ….?
after polymerization | because GTP has been hydrolyzed to GDP
55
growth pattern of microtubule
capable of growth and shortening at plus end
56
high [tubulin--GTP]
dimers will add more rapidly than GTP hydrolysis result = growth of microtubule
57
low [tubulin--GTP]
GTP at plus end is hydrolyzed to GDP result = dimers are lost -- shortening of microtubule
58
tubulin is less stable....
when GTP is hydrolyzed to GDP | or called depolymerization
59
factors that inhibit microtubule polymerization
Colchicines Colcemid vincristine & vinblastine
60
factor that can stop mitosis at metaphase and bind to tubulin dimers (what does this prevent)
colchicines | prevent microtubule polymerization
61
anticancer drugs that effect microtubule polymerization
vincristine and vinblastine
62
drug that can stabilize microtubules
taxol anticancer drug binds to microtubules -- preventing depolymerization
63
taxol can prevent microtubule ________ , how does this prevent cancer?
prevent depolymerization does not allow that depolymerization of mitotic spindles which is required for cell separation
64
how can stabilizing and destabilizing microtubule drugs both fight cancer?
anything that interferes with microtubules, interferes with mitosis thus not allowing cells to reproduce
65
functions of the cytoskeleton
cell mvt cell support, strength, shapes cell adherence microtubule monorail system
66
microtubule roles in mitosis
kinetochore microtubules mitotic spindles cytokinesis
67
microtubules act as a monorail system for moving _____, but how do we attach these to the microtubules?
for vesicle transport must utilize motor proteins for attachment kinesin and dynein
68
vesicle transport from minus to plus end of a microtubule
kinesin | carries full vesicles to destination
69
vesicle transport from plus to minus end of a microtubule
dynein | carries empty vesicles back to source
70
why do microtubule's require 2 different motor proteins
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
if kinesin and dynein only travel one way, how do they get back to their starting point?
they carry each other
72
myosin I
1 head tail binds to cell membrane head binds to actin direction of head motion toward the barbed end
73
myosin II
2 heads tail binds to myosin II head binds to actin direction of head motion toward the plus end
74
kinesin
2 heads tail binds to vesicle head binds to microtubules direction of head motion toward the plus end
75
cytoplasmic dynein
2 heads tail binds to vesicle head binds to microtubules direction of head motion toward the minus end (pointed)
76
inactive myosin II tails
have their light chain tails folded back in loops | close to their heads
77
active myosin II tails
have their tails stretched straight out

Histology Exam 1 (8 decks)

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