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MCP > flashcards_mcpcytoskeleton > Flashcards

flashcards_mcpcytoskeleton

1
Q

3 types of filaments in eukaryotes that organize internal cells tructure, segregate organelles at cell division, maintian cell shape, generate force

A

microfilaments, itnermediate filaments, microtubules

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2
Q

each of the three filament systems have different

A

physicial properties (stiffness strength and flexibility) intracellular distributions, biochemical properties

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3
Q

microfilaments are made of monomers of the protein actin which is a

A

42 KDA globular protein

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4
Q

actin is what type of binding protein

A

atp and magenisum

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5
Q

what cofactors are required for filament assembly for actin

A

atp and magensium

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6
Q

after actin is ___ after joining with atp, it can then hydrolysize to adp

A

polymerized

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7
Q

in mammals, ___ actin genes all encode very simila rporteins but they are 6 different cell specific regions fo actin expression

A

six

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8
Q

actin which are encoded by alpha actin genes

A

skeletal muscle, cardiac muscle, vascualr smooth muscle, digestive smooth muscle

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9
Q

actin which are encoded by beta and gamma actin genes

A

two non muscle actins

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10
Q

microfilaments are formed by self assembly of actin monomers into two stranded 5-7nm ___ fibers of varying length

A

helical

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11
Q

the unfirom orientation of monormmers results in the ____ of actin filaments

A

structural polarity

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12
Q

one the end of each actin filament is a minus/pointed end or a

A

plus or barbed end

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13
Q

the plus or barbed end of an actin filament assemblys much

A

fadster than minus or pointed end

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14
Q

structural polarity of actin is determined by

A

grwoth rate and electron microscoping appearene after binding of myosin s1 fragments

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15
Q

treadmilling of actin filaments is caused by

A

hydrolysis of atp to adp, actin with bound adp actin disassembling

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16
Q

free subunits of actin exchange

A

nucleotides

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17
Q

what does actin have to be attached to be assembled into a filament

A

atp

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18
Q

assembled subunits of actin hydrolyze

A

atp

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19
Q

___ actin are individual actin

A

g actin

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20
Q

___ acitn are actin filaments

A

f actin

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21
Q

assembly of actin begins with the ___ of three monomers of actin

A

nulceation

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22
Q

growth of f actin is faster at the ____ end

A

barbed

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23
Q

treadmilling is due to the ____ of the barbed end and net loss of pointed end

A

net loss

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24
Q

zone of adp bound actin monomers is towards the

A

pointed end of filament

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25
Q

in vivo actin assembly is regulated by actin monomer proteins called

A

thymosisn and profilins

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26
Q

what actin binding proteins affect

A

actin assembly, length, number, organization and in vivo function of microfilaments

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27
Q

actin binding proteint hat affects force

A

myosin

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28
Q

actin binding rptoein that affects motlity

A

troponin

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29
Q

actin binding protein that crosslink

A

filamin

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30
Q

actin proitejn that bundles

A

alpha actinin and fimbrina

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31
Q

actin protein that cap filaments

A

alpha beta capping proteinz

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32
Q

actin protein that anchor filaments to other structures like the plasma membrane

A

talin

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33
Q

microfilaments may be crosslinked to form bundles for

A

strength

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34
Q

micofilaments may form a scaffold for

A

mobility

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35
Q

the combination fo a the plasma membrane with a mesh of crosslinked actin is called the

A

cell cortex

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36
Q

membrane assocaited microfilaments can be involved in contraction, extension, or in stabilization of the

A

plasma membrane

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37
Q

membrane associated micorfilament scan be involved in the extension fo plasma membrane to form

A

filopodia and lamellipodia

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38
Q

stress fibers are antiparralel contractile bundles of actin that terminate on th e plasma membrane at

A

focal contacts

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39
Q

membrane associated microfilaments can be involved in the stabilization of a particular membrane shape such as in

A

microvilli, stress fibers, lamellipodia, contractile ring

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40
Q

the actin related protein complex mediates assembly of ___ array of actin filaments at leading edge of cell membrane

A

branched

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41
Q

assembly of actin filament near membrane is esstential for

A

pushing out the thin lamellar edge of cell

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42
Q

phalloidin is from the mushroom

A

amnita phalloides

43
Q

phalloidoin stabilizes actin filamenrs by binding along fragment while ____ block actin filament assembly at plus end

A

cytochalasins

44
Q

two drugs which disrupt cell motility and cytokinesis

A

phalloidin and cytochalasins

45
Q

Through interactions with ___, microfilaments generate many varieties of motility such as muscle contraction, amoeboid movement, cytokinesis, ruffling, and some forms of intracellular vesicle movement.

A

myosin ATPases

46
Q

all myosins are ___ directed

A

plus end

47
Q

what are similar in all myosins

A

globular catlytic head sequence

48
Q

what are different in all myosins

A

carboxyl terminal tails

49
Q

the ___ tails of myosin II proteins mediate the assembly of two headed dimers via a coiled coil interaction

A

c terminal

50
Q

the dimers fo moysin II can assembly in a tail to tail configuation to give

A

bipolar thick filaments

51
Q

what non muscle myosins dont form filaments \n

A

single headed myosins like moysin 1

52
Q

to create movemrent moysoin II interacts with two

A

overlapping sets of actin filaments polarized in opposite directions

53
Q

myosin II has heads facining in

A

two different directions

54
Q

Actin-myosin complexes mediate several kinds of ____ in many types of eukaryotic cells.

A

motility

55
Q

Actin-myosin force production is regulated by phosphorylation of myosin-associated proteins called

A

myosin light chains.

56
Q

coordinaion of myosin motiility and actin assembly/disassembly powers

A

cell motility

57
Q

____ assembly extends the lamellipodiun

A

actin

58
Q

attachment to the substrate and ___ of microfilament bundles pulls the cell forward

A

contraction

59
Q

detachment oif actin on the ____ of the cell and further contraction brings the cell forward

A

back end

60
Q

Actin-myosin force production is regulated by phosphorylation of myosin-associated proteins called

A

myosin light chains

61
Q

in nonmuscle cells, Ca++ concentration changes cause phosphorylation of light chains by activating

A

myosin light chain kinase

62
Q

This regulation of non-muscle contraction is therefore said to be myosin-based or

A

thick filament-based regulation.

63
Q

inactive state of myosin II

A

light chains are not phopshorylated

64
Q

protein kinases that phopshylate myosin light chains in nonmuscle cells are activated indirectly by

A

increase in calcium ion concentration

65
Q

myofibirl is

A

actin and myosin fragments

66
Q

skeletal muscle fibers are ____ nucleared synncytial cells

A

multi

67
Q

myofibrils are mad eup of short repeating units called

A

sarcomeres

68
Q

sarcomere is made up of

A

2 actin fibers and a bipolar myosin in between

69
Q

myofibrials are arrounded by the

A

sdacroplasmic reituclum

70
Q

muscular dystrophy is caused not be weakness in contractile muscle but rather weakness in the ____ fibers which causes a weakness in the integreting of the membrane

A

support

71
Q

plus ends of actin filaments attach to

A

z discs

72
Q

___ reduces affinity of actin binding to myosin

A

atp

73
Q

Minus ends of actin filaments extend away from Z discs but do not ___ in the center of sarcomeres

A

overlap

74
Q

____ a huge protein, associates with the actin filaments and determines the length of the microfilaments in the sarcomere

A

nebulin

75
Q

what protein is 71 times the size of actin

A

titin

76
Q

___ protein extends from the z disc to the thick mysosin filaments and acts ion the center myosin filaments

A

titin

77
Q

Myofibrils are bound to each other by ____ intermediate filaments.

A

desmin

78
Q

the entire myofibril is anchored to the plasmam membrane by ____ which is defectuve in people with Becker/Duchenne form of muscualr dystroiphy

A

dystrophin

79
Q

each myofibril is separated from its neighbor by the

A

sacroplasmic reitium

80
Q

the ____ functions to store and release clacium ions

A

sarcoplasmic reticumum

81
Q

in the state of Rigor-The myosin head is tightly bound to the actin filament and

A

nucleotide-free.

82
Q

in the state of muscle release ____ binding to the myosin head lowers the affinity of myosin for actin resulting in release.

A

atp

83
Q

cocked muscle orientaiton involves ____ causes a 5nm translocation of the head to cock it in preparation for the power stroke.

A

ATP hydrolysis

84
Q

the cocked confirmation has a weak affinity for the

A

actin filament

85
Q

Dissociation of the inorganic _____ increases the affinity of the myosin head for the actin filament and activates the power stroke.

A

phosphate

86
Q

Dissociation of ___ is stimulated by translocation of the myosin head back to its original configuration.

A

ADP

87
Q

when all myosins in a sacromere are actived, heads facing opposite directions on each filament walk along actin and pull towards

A

z discs

88
Q

when all the myosins in a sacromere are activated, the sacromere

A

shortens

89
Q

Simultaneous shortening of all the sarcomeres in a muscle cell results in shortening of the muscle, which pulls on ____ that attach to bone

A

tendons

90
Q

3 polypepties of troponin

A

troponin t, tropinin I, and troponin C

91
Q

troponin T binds to _____ thereby positioning the complex on the actin filament,

A

tropomyosin

92
Q

troponin I binds to actin filaments and affects ____ on the actin filament

A

tropomyosin positioning

93
Q

actin of thin filament based regulation is mediated by the ___ complex

A

troponin

94
Q

conformaitonal change of calcium bidning to troponin c induces movement fo

A

troponin i and troponin T

95
Q

troponin ___ moves tropomyosin away from multiple myosin vinding sites

A

t

96
Q

troponin on actin prevent it from acting on myosin unless ___ is around

A

calcium

97
Q

for muscle contractio calcuum release channels open in the

A

sacroplasmic reiticulum

98
Q

depolarize cell letting in calcium from outside which activates sacroplastic reticiulm membrane which releases a ton of

A

calcium

99
Q

causes of rigor mortis

A

calcium can’t be pumped back into sarcoplastic reiticulum keeping muscles contracted, and atp can’t attach to myosin preventing myosin from beign released from actin

100
Q

binding of calcium to troponin c allows troponin 1 to release its hold on actin, allowing ___ to move away from myosin binding site

A

troomyosin

101
Q

A voltage gated Ca++ channel imbedded in the _____ senses the action potential and in response sarcoplasmic reticulum membrane Ca++ release channels open to spill Ca++ ions into the cytosol surrounding the myofibrils.

A

transverse tubule

102
Q

____ pumps in the sarcoplasmic reticulum membrane pump the Ca++ back out of the cytosol, and myosin is prevented from interacting with actin.

A

CaATPase

103
Q

tropomyosin prevents mysoin from interacting with actin unless ___ is around

A

calcium

104
Q

____ protein limits the length of growing filaments

A

limits

MCP (3 decks)

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