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Molecular Exam 2 > The Cytoskeleton 2: Organization and Behavior > Flashcards

The Cytoskeleton 2: Organization and Behavior Flashcards

1
Q

What is listeria?

A

pathogenic bacteria that invade your intestinal cells

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2
Q

Where is listeria found?

A

unwashed lettuce, animal products, dairy + meats

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3
Q

What are the symptoms of listeria?

A 
headache
stiff neck
confusion
lost of balance
convulsions
fever and muscle aches
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4
Q

What does listeria cause?

A

Food poisoning, especially if you are immunologically deficient or immunocompromised

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5
Q

Pregnant women are _____ time likely to get a listeria infection

A

10

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6
Q

What could be the results of listeria infection during pregnancy?

A

miscarriage
stillbirth
newborn death

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7
Q

What is the treatment of listeria?

A

IV antibiotics

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8
Q

Listeria attaches to ________ on enterocytes

A

receptors

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9
Q

What is the unusual behavior of listeria based on

A

actin cytoskeleton and accessory proteins

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10
Q

What makes up the comet tails of listeria?

A

actin filaments

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11
Q

What are the three types of actin filament accessory proteins?

A

affect actin subunits
affects actin filaments
affects filament bundling, cross linking and attachment to membranes

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12
Q

What are the accessory proteins that affect actin subunits?

A

ARP complex
Formin
Thymosin
Profilin

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13
Q

Describe the ARP complex

A

nucleates assembly to form weblike, highly branch chains and remains associated with minus end

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14
Q

Describe formin

A

nucleates assembly of long, unbranched chains and remains associated with growing plus end

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15
Q

Describe thymosin

A

binds actin subunits, prevents assembly

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16
Q

Describe profilin

A

binds actin subunits, speeds elongation

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17
Q

What are the two types of ARP proteins? How identical are they to actin?

A

Arp2 and Arp3

45% identical

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18
Q

The ARP complex nucleates actin filament growth from the _______ end, allowing elongation at the ____ end

A

minus; plus

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19
Q

ARP complex requires what?

A

activating factor

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20
Q

In absence of the activating factor, Arp 2 and Arp3 are masked by other proteins to prevent them from _______

A

nucleating a new actin filament

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21
Q

When the ARP complexes bind to the activating factor, it includes a _________. Which mimics the ______ of actin filament.

A

conformational change; plus end

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22
Q

Arp complex binding bypasses the _____ step of filament nucleation

A

rate limiting step

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23
Q

Bacteria surface causes local ______ of actin filaments

A

nucleation

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24
Q

Listeria presents a surface protein called what?

A

ActA

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25
Q

What does ActA do?

A

activates Arp 2/3 complex causes local nucleation of actin filaments which are cross linked

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26
Q

What are the driving force to push cell through cytoplasm?

A

growing filaments

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27
Q

When does the ARP complex work the most efficiently?

A

When bound to the side of the preexisting actin filament filaments cross linked.

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28
Q

Filament branches grow at a _______ angle relative to the original filament

A

70 degree

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29
Q

What are force pushes?

A

addition of actin branched filament pushes the batter along

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30
Q

The actin filaments in cell cortex determine the _____ and ______ of the cell surface

A

shape; movement

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31
Q

What are lamellipdia?

A

flat protrusive veils

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32
Q

What are filopodia or microvilli?

A

spiky bundles

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33
Q

What do formins nucleate the growth of?

A

straight and unbranched actin filaments

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34
Q

Where does formin come from?

A

dimeric proteins

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35
Q

Each formin subunit having a _______ for an actin monomer

A

binding site

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36
Q

How do formin dimers nucleate actin filament polymerization?

A

capturing two monomers at the plus end or growing end of an actin filament

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37
Q

What does thymosin do?

A

regulation of availability of actin monomers for actin polymerization

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38
Q

Thymosin keeps actin monomers ______ so they are readily available for generating ______

A

soluble, filaments

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39
Q

Actin monomers bound to thymosin are in a what state?

A

a locked state

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40
Q

What does profilin do?

A

recruits actin monomers to the actin filament for polymerization

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41
Q

When profilin binds to the actin monomer what happens?

A

it exposes the site of actin that binds to the plus end of the actin filament

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42
Q

Addition of an actin monomer to the filament induces conformational change in the actin that ______ its affinity for proflin

A

reduces

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43
Q

When profilin falls off, what is the result?

A

actin filament is one subunit longer

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44
Q

What accessory proteins affect actin filaments and stabilize?

A

tropomodulin
tropomyosin
capping protein

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45
Q

What accessory proteins affect actin filaments and dissemble?

A

cofilin

gelsolin

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46
Q

Describe tropomodulin

A

prevents assembly and disassembly at minus end-stabilizes actin filament- for long lived filament stabilization

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47
Q

Describe tropomyosin

A

stabilizes filament- prevents binding with the proteins

48
Q

Describe capping protein

A

prevents assembly and disassembly at plus end

49
Q

Describe cofilin

A

binds ADP actin filaments, accelerates disassembly

50
Q

Describe gelsolin

A

severs actin filaments and binds to plus end

51
Q

Where is tropomodulin present?

52
Q

Actin filaments are stabilized by the binding of ______

A

tropomyosin

53
Q

What happens when actin filaments bind with tropomyosin?

A

prevents the actin filament interaction with other proteins

54
Q

What do capping proteins bind to?

A

actin filaments

55
Q

What does the capping protein reduce the rate of?

A

polymerization and depolymerization

56
Q

What is another name for cofilin?

A

actin depolymerizing factor

57
Q

Cofilin binds to both ______ filament and ____ ______ subunits

A

actin; free actin

58
Q

When bound to cofilin why does the filament twist more tightly?

A

weakens the contacts between actin subunits making the filament brittle and more easy to cut

59
Q

The smaller filaments gelsolin makes are available for what?

A

elongation or disassembly

60
Q

What accessory proteins contribute to filament bundling, cross linking and attachment to membranes

A 
a- actinin
fimbrin 
filamin 
spectrin 
ERM family
61
Q

a-actinin and fimbrin are what types of proteins?

A

bundling proteins

62
Q

What is a bundling protein?

A

cross links actin filaments into a parallel array

63
Q

filamin is what type of protein?

A

gel-forming

64
Q

What is a gel forming protein?

A

holds two actin filaments together at a large angle to each other to create a looser meshwork

65
Q

a-actinin cross links acting filaments into _____ bundles, allowing myosin II to enter to make actin filaments______

A

loose; contractile

66
Q

fimbrin cross links actin filaments into ____ bundles, excluding myosin II

67
Q

Filamin promotes the formation of loose, highly viscous Gell like networks by clamping together 2 ________

A

actin filaments

68
Q

Why do cells require actin gel?

A

to extend membrane projections and helps cells to crawl across a solid surface

69
Q

Where does spectrin attach?

A

to the membrane

70
Q

If spectrin is defective, what is the result?

A

fragile red blood cells–hemolytic anemia that can lead to hereditary spherocytosis

71
Q

What is included in the ERM family?

A

Ezrin, radixin, and moesin

72
Q

What does ERM do?

A

mediate the attachments between actin and plasma membrane

73
Q

How many binding sites does the ERM family have? and what does each one of them do?

A

two binding sites
one bind to actin filament
one bind on transmembrane protein

74
Q

What are the three major groups of microtubule accessory proteins?

A

tublin dimers
microtubules
filament cross linking

75
Q

What are the three types of tubulin dimers?

A

stathmin
TIPS
y-TuRC

76
Q

What does stathmin do?

A

binds subunits, prevents assembly

77
Q

What does TIPS do?

A

(the plus end tracking proteins) remains associated with the growing plus ends and can link them to structures such as membranes

78
Q

What does y-TuRC do?

A

nucleates assembly and remains associated with minus end

79
Q

__________ are the regular subunits for microtubules

A

alpha and beta tubulin

80
Q

y- tubulin is involved in what?

A

nucleation of microtubule growth

81
Q

Where are microtubules nucleated from?

A

microtubule organizing center (MTOC)

82
Q

Microtubules grow ______ from the MTOC from the _____ end

A

outward; plus

83
Q

What is the y-tubulin ring complex (y-TuRC) responsible for?

A

nucleation of microtubule growth

84
Q

The major MTOC of animal cells is the ________

A

centrosome

85
Q

Microtubule are nucleated at the centrosome at their ______ end, with plus ends pointing outward and now toward the cell _______

A

minus, periphery

86
Q

What are the different kinds of microtubule accessory proteins?

A

katanin
MAPs
XMAP215
Kinesin 13

87
Q

What does katanin do?

A

servers microtubules

88
Q

What do MAPs do?

A

(microtubule associated proteins)

stabilize tubules by binding along sides

89
Q

What does XMAP215 do?

A

a microtubule associated protein that stabilizes plus ends and accelerates assembly

90
Q

What does Kinesin 13 do?

A

enhances catastrophic disassembly at plus end

91
Q

What microtubule accessory protein alters the filaments stability and mechanical properties?

92
Q

MAPs stabilize microtubules against _______

A

disassembly

93
Q

How many domains do MAPs have? What do each do?

A

two domains
one for binding to microtubule
one projects outward

94
Q

MAPs stabilizes free ends of microtubule and _____ the switch from a growing to a shrinking state

95
Q

XMAP215 stabilizes free ends of microtubule and ____ the switch from a growing to a shrinking state

96
Q

Kinesin 13 ______ the rate at which microtubule switches from a growing to a shrinking state

97
Q

How does Kinesin 13 bind to microtubule ends and pry protofilaments apart?

A

by lowering the activation energy barrier that prevents a microtubule from springing apart

98
Q

What are the types of filament cross linking microtubule accessory proteins?

A

plectin

tau, MAP2

99
Q

What does pectin do?

A

cross linking protein, links microtubules to intermediate filaments

100
Q

What does Tau and MAP2 do?

A

both cause bundling of microtubules

101
Q

MAP2 has a longer _____ than tau

A

projecting domain

102
Q

Tau binds to the microtubule where?

A

N and C termini

103
Q

Where do cytoskeletal motor proteins bind?

A

polarized cytoskeletal filaments

104
Q

Cytoskeletal motor proteins slide against each other generating force that drives ________

A

muscle contraction or cell division

105
Q

What are the two major groups of cytoskeleton motor proteins?

A

kinesins and dyneins

106
Q

What is kinesin?

A

Protein that uses ATP to walk along microtubule track to move vesicles

107
Q

Which way does kinesin walk?

A

toward plus end of microtubule

108
Q

Where does kinesin carry its binding site and what for?

A

carried in tail for a membrane enclosed organelle

109
Q

Which direction does dynein move?

A

toward minus end

110
Q

What is function of cytoplasmic dynein?

A

vesicle trafficking, localization of the Golgi apparatus

111
Q

What is the function of axonemal dynein?

A

specialized for rapid and efficient sliding movements of microtubule that drive the beating of cilia and flagella

112
Q

What are two examples of short term cytoskeletal structures?

A

mitotic spindle

those assisting with crawling across a solid surface: cell migration

113
Q

Cells must produce ________

114
Q

What is chemotaxis?

A

cell movement in a direction controlled by a gradient of a diffusible chemical

115
Q

Where do neutrophils move?

A

move toward a source of bacterial infection by detecting peptides that are derived form of bacteria proteins

116
Q 
Which of the following items nucleates actin filament growth from the minus end allowing growth at the plus end with repeated rounds of branching nucleation resulting in a highly branched web of actin filaments (as seen in Listeria infections of enterocytes)?
A. Profilin
B. Gelsolin
C. ARP 2/3 Complex 
D. Formin
E. g-TURC
A

C. ARP 2/3 Complex

Molecular Exam 2 (13 decks)

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