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Med 103 > Cytoskeleton > Flashcards

Cytoskeleton Flashcards

1
Q

what colors do microtubules, microfilaments and intermediate filaments show on fluorescent staining

A

microtubules- green
microfilament/actin - red
intermediate filaments - blue

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2
Q

which is the largest

a) actin filaments
b) microtubules
c) intermediate filaments

A

microtubules

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3
Q

is the cytoskeleton larger in prokaryotes or eukaryotes

A

eukaryotes

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4
Q

is the cytoskeleton static or dynamic

A

dynamic

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5
Q

what are intermediate filaments composed of

A

fibrous protein

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6
Q

which cytoskeleton structure is a rope-like fiber

A

intermediate filament

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7
Q

which cytoskeleton structure forms a meshwork structure

A

intermediate filaments

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8
Q

what is a desmosome

A

cell structure specialized for cell-to-cell adhesion

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9
Q

what are the intermediate filaments in the nucleus

A

nuclear lamins

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10
Q

what are the intermediate filaments in epithelial cells

A

keratin filaments

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11
Q

what are the intermediate filaments in the connective tissue, muscle cells, and glial cells

A

vimentin and vimentin related filaments

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12
Q

nuclear lamins are only located in a few animal cells. true or false

A

false. they are located in all animal cells

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13
Q

what intermediate filaments are in nerve cells

A

neurofilaments

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14
Q

what is Epidermolysis bullosa simple

A

A genetic disease, keratin gene mutation. A mutant form of keratin makes skin more prone to blistering

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15
Q

what aids in the bundling of intermediate filaments and links these filaments to other cytoskeletal protein networks

A

plectin

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16
Q

what does plectin mutation cause

A

a combination of; Epidermolysis bullosa simple muscular dsytrophy and neurodegenaration

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17
Q

what happened to mice lacking plectin gene

A

died within a few days due to abnormal heart muscles

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18
Q

what do defects in nuclear lamins cause

A

cause a rare class of premature aging disorders called progeria i.e. the nucleus loses its shape

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19
Q

what is the major microtubule organizing centre in animal cells

A

the centrosome

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20
Q

what drives the dynamic instability of microtubules

A

GTP hydrolysis

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21
Q

drugs cannot modify dynamic instability of microtubules true or false.

A

false. they can

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22
Q

what do microtubules help motor proteins do

A

drive intracellular transport

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23
Q

what does dynein do

A

They convert the chemical energy stored in ATP to mechanical work. Dynein transports various cellular cargos, provides forces and displacements important in mitosis, and drives the beat of eukaryotic cilia and flagella

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24
Q

where do microtubules grow from at their plus ends

A

gamma tubulin

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25
Q

microtubules grow independently of their neighbors. true or false

A

true

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26
Q

what is selective stabilization of microtubules

A

where the length of some microtubules are maintained and others arent

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27
Q

what do capping proteins do

A

control access to the free barbed ends of actin filaments and is therefore a major factor affecting actin filament elongation

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28
Q

what does selective stabilization do to a cell

A

polarize it

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29
Q

how does GTP hydrolysis control stabilization

A

by GTP binding to tubulin dimer causing more addition of GTP-tubulin

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30
Q

what causes shrinking of the microtubule

A

GDP binding to the tubulin dimer

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31
Q

what drug binds and stabilizes microtubules

A

taxol (treat breast and ovarian cancers)

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32
Q

what is the effect of colchicine and colcemid

A

binds tubulin dimers and prevents their polymerization

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33
Q

what drugs have the same effect as colchicine, colcemid

A

vinblastine and vincristine (childhood hematologic malignancies)

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34
Q

what drug prevents cell division during mitosis

A

colchicine (for gout)

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35
Q

most differentiated cells are polarized. what does this mean

A

one end of the cell is structurally and functionally different from the other

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36
Q

true or false, organelles travel slower by diffusion than by microtubules

A

false. it can take years for their diffusion whereas in microtubules it takes seconds

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37
Q

what are the two families of motor proteins

A

dynein and kinesin

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38
Q

what do motor proteins do

A

move vesicles along microtubules

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39
Q

how do dynein and kinesin move along the microtubules

A

using their globular heads

40
Q

what directions do dynein and kinesin move

A

dynein moves towards the minus end and kinesin moves towards the plus end

41
Q

what determines the cargo type when moving along the microtubule

A

depends on the tail of the dynein or kinesin

42
Q

what are the repetitive movements cilia makes

A

power stroke and recovery stroke

43
Q

how are microtubules in cilium and flagella arranged

A

9+2

44
Q

what causes the flagella with dynein to bend

A

linking protein

45
Q

what does dynein do in an isolated doublet microtubule

A

producing microtubule sliding with help of ATP

46
Q

what does cell crawling depend on

A

cortical actin

47
Q

what decreases stability of the actin filament

A

ATP hydrolysis

48
Q

how do actin filaments regulate filament length

A

Treadmilling

49
Q

what does phalloidin (drug) do

A

binds and stabilizes filaments

50
Q

which drug caps plus end and prevents polymerization in actin filaments

A

cytochalasin

51
Q

what does latrunculin (drug) do

A

binds actin monomers and prevents polymerization

52
Q

what are types of actin binding proteins (name 6)

A 
myosin motor protein 
side-binding protein 
cross linking protein (cortex)
severing protein 
nucleating protein
bundling protein (filopodia)
53
Q

what proteins regulate filament formation

A

thymosine and profilin (prevent their polymerization)

54
Q

what protein promote polymerization of actin filaments

A

formin

55
Q

what help move a cell forward

A

Forces generated in the actin-filament-rich cortex

56
Q

which direction does myosin I move across the microtubule

A

from negative to positive ends

57
Q

what has a dramatic effect on the organization of actin

filaments in fibroblasts

A

Activation of Rho family GTPases

58
Q

name two regulators in actin dynamics

A

Rac and cdc42

59
Q

what triggers muscle contraction

A

Ca ion increase

60
Q

what is the bare region

A

where the heads and tails of myosin meet (confirm this)

61
Q

what defines the boundaries of the sarcomere

A

Z-disc

62
Q

what surrounds the myofibrils

A

T tubules and the sarcoplasmic reticulum

63
Q

what controls skeletal muscle contraction

A

troponin and tropomyosin (blocks myosin binding sites) complexes

64
Q

what does Ca do in muscle contraction

A

exposes myosin binding site

65
Q

what is an example of a capping protein

A

gelsolin, which prevent polymerization of the filament

66
Q

what are the three classes of actin

A

α-actin of muscle, β-actin, and γ-actin of non-muscle cells.

67
Q

what proteins other than myosin bind to actin to perform essential cellular functions

A

α-actinin, spectrin, fimbrin, filamin, gelsolin, and talin

68
Q

what are the three types of association in actin filaments

A

Contractile bundles
Gel-like networks
Parallel bundles

69
Q

what types of association in actin usually has myosin

A

Contractile bundles

70
Q

what structure maintains focal contacts of the cell with extracellular matrix

A

actin filaments

71
Q

what is the relationship between integrin, talin, vinculin, fibronectin and the actin filaments

A

integrin (a transmembrane protein) binding to fibronectin and talin, which contacts both vinculin and the actin filament

72
Q

what is the function of gel-like connection

A

provide the structural foundation of much of the cell cortex

73
Q

what provides stiffness in gel-like networks

A

protein filamin

74
Q

what are fimbrin and villin responsible for

A

forming actin filaments into closely packed parallel bundles that form the core of microspikes and microvilli, respectively

75
Q

what does spectrin do

A

assists in structural integrity of cortex

76
Q

where are bundles of actin filaments anchored

A

terminal web

77
Q

what structures anchor the nucleus

A

intermediate filaments

78
Q

how many tetramers form an intermediate filament

A

8

79
Q

what is the head and the tail of each monomer called

A

N-terminus (head) and C-terminus (tail)

80
Q

what is the central domain composed of

A

elongated alpha helix

81
Q

what type of isoforms are keratin fibers

A

family of acidic and basic isoforms

82
Q

what is Epidermolysis bullosa simplex (EBS) characterized by

A

skin blisters after minor trauma (keratin 5 and 14 mutant genes)

83
Q

what conditions leads to excessive keratinization of the epidermis

A

Epidermolytic hyperkeratosis (EH) ((mutations of keratin 1 and 10 genes)

84
Q

fragmentation of the epidermis of the palms and soles is caused by what disease

A

Epidermolytic plantopalmar keratoderma (EPPK) (keratin 9 mutation)

85
Q

what is most common intermediate filament protein

A

vimentin

86
Q

what is vimentin derived from

A

mesenchyme

87
Q

what binds keratin filaments into bundles

A

flaggrin

88
Q

what do Synemin and plectin bind

A

desmin and vimentin, respectively

89
Q

what do plakins assist in

A

assist the maintenance of contact between the keratin intermediate filaments and hemidesmosomes of epithelial cells as well as actin filaments with neurofilaments of sensory neurons

90
Q

describe centriole structure

A

composed of nine highly organized microtubule triplets.

91
Q

which of the following do microtubules not do

a) axoplasmic transport in neurons
b) melanin transport in pigment cells
c) movement of RNA along the nucleus
d) vesicle movements among different cell compartments

A

c

92
Q

what are the main side effects of taxol

A

neurotoxicity and suppression of hematopoiesis (production of all of the cellular components of blood and blood plasma)

93
Q

what is Kartagener’s syndrome

A

autosomal recessive ciliary dyskinesia frequently associated with bronchiectasis and sterility in men

94
Q

what is Kartagener’s syndrome a result of

A

structural abnormalities in the axoneme (defective or absent dynein) that prevent mucociliary clearance in the airways (leading to persistent infections) and reduce sperm motility and ovarium transport in the oviduct (leading to sterility)

95
Q

where are the microtubules not dynamic

A

axonemes

96
Q

what are the monomeric proteins in intermediate filaments

A

alpha helical rod like protein

97
Q

what is the overall structure of intermediate filaments

A

cable of 4 intertwined protofibrils, each consisting of bundled tetramers associated end to end

Med 103 (13 decks)

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