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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
in vivo actin assembly is regulated by actin monomer proteins called
thymosisn and profilins
26
what actin binding proteins affect
actin assembly, length, number, organization and in vivo function of microfilaments
27
actin binding proteint hat affects force
myosin
28
actin binding rptoein that affects motlity
troponin
29
actin binding protein that crosslink
filamin
30
actin proitejn that bundles
alpha actinin and fimbrina
31
actin protein that cap filaments
alpha beta capping proteinz
32
actin protein that anchor filaments to other structures like the plasma membrane
talin
33
microfilaments may be crosslinked to form bundles for
strength
34
micofilaments may form a scaffold for
mobility
35
the combination fo a the plasma membrane with a mesh of crosslinked actin is called the
cell cortex
36
membrane assocaited microfilaments can be involved in contraction, extension, or in stabilization of the
plasma membrane
37
membrane associated micorfilament scan be involved in the extension fo plasma membrane to form
filopodia and lamellipodia
38
stress fibers are antiparralel contractile bundles of actin that terminate on th e plasma membrane at
focal contacts
39
membrane associated microfilaments can be involved in the stabilization of a particular membrane shape such as in
microvilli, stress fibers, lamellipodia, contractile ring
40
the actin related protein complex mediates assembly of ___ array of actin filaments at leading edge of cell membrane
branched
41
assembly of actin filament near membrane is esstential for
pushing out the thin lamellar edge of cell
42
phalloidin is from the mushroom
amnita phalloides
43
phalloidoin stabilizes actin filamenrs by binding along fragment while ____ block actin filament assembly at plus end
cytochalasins
44
two drugs which disrupt cell motility and cytokinesis
phalloidin and cytochalasins
45
Through interactions with ___, microfilaments generate many varieties of motility such as muscle contraction, amoeboid movement, cytokinesis, ruffling, and some forms of intracellular vesicle movement.
myosin ATPases
46
all myosins are ___ directed
plus end
47
what are similar in all myosins
globular catlytic head sequence
48
what are different in all myosins
carboxyl terminal tails
49
the ___ tails of myosin II proteins mediate the assembly of two headed dimers via a coiled coil interaction
c terminal
50
the dimers fo moysin II can assembly in a tail to tail configuation to give
bipolar thick filaments
51
what non muscle myosins dont form filaments \n
single headed myosins like moysin 1
52
to create movemrent moysoin II interacts with two
overlapping sets of actin filaments polarized in opposite directions
53
myosin II has heads facining in
two different directions
54
Actin-myosin complexes mediate several kinds of ____ in many types of eukaryotic cells.
motility
55
Actin-myosin force production is regulated by phosphorylation of myosin-associated proteins called
myosin light chains.
56
coordinaion of myosin motiility and actin assembly/disassembly powers
cell motility
57
____ assembly extends the lamellipodiun
actin
58
attachment to the substrate and ___ of microfilament bundles pulls the cell forward
contraction
59
detachment oif actin on the ____ of the cell and further contraction brings the cell forward
back end
60
Actin-myosin force production is regulated by phosphorylation of myosin-associated proteins called
myosin light chains
61
in nonmuscle cells, Ca++ concentration changes cause phosphorylation of light chains by activating
myosin light chain kinase
62
This regulation of non-muscle contraction is therefore said to be myosin-based or
thick filament-based regulation.
63
inactive state of myosin II
light chains are not phopshorylated
64
protein kinases that phopshylate myosin light chains in nonmuscle cells are activated indirectly by
increase in calcium ion concentration
65
myofibirl is
actin and myosin fragments
66
skeletal muscle fibers are ____ nucleared synncytial cells
multi
67
myofibrils are mad eup of short repeating units called
sarcomeres
68
sarcomere is made up of
2 actin fibers and a bipolar myosin in between
69
myofibrials are arrounded by the
sdacroplasmic reituclum
70
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
support
71
plus ends of actin filaments attach to
z discs
72
___ reduces affinity of actin binding to myosin
atp
73
Minus ends of actin filaments extend away from Z discs but do not ___ in the center of sarcomeres
overlap
74
____ a huge protein, associates with the actin filaments and determines the length of the microfilaments in the sarcomere
nebulin
75
what protein is 71 times the size of actin
titin
76
___ protein extends from the z disc to the thick mysosin filaments and acts ion the center myosin filaments
titin
77
Myofibrils are bound to each other by ____ intermediate filaments.
desmin
78
the entire myofibril is anchored to the plasmam membrane by ____ which is defectuve in people with Becker/Duchenne form of muscualr dystroiphy
dystrophin
79
each myofibril is separated from its neighbor by the
sacroplasmic reitium
80
the ____ functions to store and release clacium ions
sarcoplasmic reticumum
81
in the state of Rigor-The myosin head is tightly bound to the actin filament and
nucleotide-free.
82
in the state of muscle release ____ binding to the myosin head lowers the affinity of myosin for actin resulting in release.
atp
83
cocked muscle orientaiton involves ____ causes a 5nm translocation of the head to cock it in preparation for the power stroke.
ATP hydrolysis
84
the cocked confirmation has a weak affinity for the
actin filament
85
Dissociation of the inorganic _____ increases the affinity of the myosin head for the actin filament and activates the power stroke.
phosphate
86
Dissociation of ___ is stimulated by translocation of the myosin head back to its original configuration.
ADP
87
when all myosins in a sacromere are actived, heads facing opposite directions on each filament walk along actin and pull towards
z discs
88
when all the myosins in a sacromere are activated, the sacromere
shortens
89
Simultaneous shortening of all the sarcomeres in a muscle cell results in shortening of the muscle, which pulls on ____ that attach to bone
tendons
90
3 polypepties of troponin
troponin t, tropinin I, and troponin C
91
troponin T binds to _____ thereby positioning the complex on the actin filament,
tropomyosin
92
troponin I binds to actin filaments and affects ____ on the actin filament
tropomyosin positioning
93
actin of thin filament based regulation is mediated by the ___ complex
troponin
94
conformaitonal change of calcium bidning to troponin c induces movement fo
troponin i and troponin T
95
troponin ___ moves tropomyosin away from multiple myosin vinding sites
t
96
troponin on actin prevent it from acting on myosin unless ___ is around
calcium
97
for muscle contractio calcuum release channels open in the
sacroplasmic reiticulum
98
depolarize cell letting in calcium from outside which activates sacroplastic reticiulm membrane which releases a ton of
calcium
99
causes of rigor mortis
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
binding of calcium to troponin c allows troponin 1 to release its hold on actin, allowing ___ to move away from myosin binding site
troomyosin
101
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.
transverse tubule
102
____ pumps in the sarcoplasmic reticulum membrane pump the Ca++ back out of the cytosol, and myosin is prevented from interacting with actin.
CaATPase
103
tropomyosin prevents mysoin from interacting with actin unless ___ is around
calcium
104
____ protein limits the length of growing filaments
limits

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