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Cell Biology > Chapter 14: The Cytoskeleton & Cell Movement > Flashcards

Chapter 14: The Cytoskeleton & Cell Movement Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

the cytoskeleton provides a

A

structural framework for the cell

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2
Q

the cytoskeleton serves as a scaffold that determines

A
  • cell shape
  • general organization
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3
Q

the cytoskeleton is responsible for

A

movement & cell locomotion

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4
Q

the cytoskeleton transports

A

organelles & other cell structures through the cell

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5
Q

the cytoskeleton can be described as a

A

dynamic structure w/ changing architecture

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6
Q

the cytoskeleton localizes the ________ at the center

A

nucleus

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7
Q

what are the 3 principle types of protein filaments that compose the cytoskeleton?

A
  1. actin filaments (microfilament)
  2. intermediate filaments
  3. microtubules
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8
Q

actin filaments are aka

A

microfilaments

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9
Q

what is known as the primary cytoskeleton protein?

A

actin filaments

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10
Q

actin filaments are helical polymers of

A

actin protein

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11
Q

actin filaments are organized into a variety of

A

linear bundles

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12
Q

actin filaments are ___________ throughout the cell, but most concentrated beneath the

A
  • dispersed
  • plasma membrane
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13
Q

actin filaments are the smallest filaments that participate in

A

cell adhesion

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14
Q

actin filaments are not a double helix but instead a

A

single strand

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15
Q

describe the steps in actin filament assembly

A
  • G actin form dimers
  • dimers form trimers
  • multiple trimers form F actin filament
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16
Q

the G actin is composed of a

A

barbed(+) and pointed(-) end

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17
Q

what are the group of proteins involved in the polymerization of actin filaments?

A

formin

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18
Q

define nucleation

A

the formation of dimers and trimers

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19
Q

actin monomers bind _____ -> hydrolyzed to _____ following filament assembly

A
  • ATP
  • ADP
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20
Q

what is NOT required for polymerization of actin filaments?

A

ATP

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21
Q

what polymerize more readily than ADP-bound monomers?

A

ATP-bound actin

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22
Q

define steady state

A

rate of + end addition = rate of loss from the - end

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23
Q

what is meant by treadmilling?

A

the net length of the polymer does not change as individual monomers are transferred from one end to the other

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24
Q

what describes the lengthening of actin filaments

A

increased [] of bound ATP

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25
Q

what describes the shortening of actin filaments

A

increased [] of bound ADP

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26
Q

actin-binding proteins regulate the

A

assembly & disassembly of actin

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27
Q

profilin promotes

A

monomer binding by exchanging ADP for ATP

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28
Q

what acts as a nucleation site to initiate branching of new filaments?

A

Arp2/3

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29
Q

Arp2/3 is an example of an

A

actin binding protein

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30
Q

what stabilize actin filaments?

A

tropomyosin & capping proteins

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31
Q

what cleaves actin filaments

A

cofilin

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32
Q

cofilin cleaves filaments making new ends for filaments to

A

polymerize or depolymerize

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33
Q

actin-binding proteins also serve to

A

organize/stabilize actin filaments

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34
Q

what is the name for the filaments that cross-link actin filaments?

A

filamen

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35
Q

what form bundles of tightly packed parallel arrays?

A

fimbrin & α-actinin

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36
Q

actin bundles form what anatomical structure

A

microvilli

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37
Q

what are known as specialized regions of the plasma membrane that form contacts with adjacent cells or to a surface?

A

adherens junctions

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38
Q

adherens junction require

A

actin

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39
Q

what are known as attachment sites for large bundles of actin filaments called stress fibers?

A

focal adhesions

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40
Q

stress fibers are bundles of

A

actin filaments linked by α-actin

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41
Q

focal adhesions detach to act as

A

signal sequences

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42
Q

what links actin to transmembrane proteins of the muscle cell plasma membrane?

A

dystrophin

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43
Q

what medical condition results from the absence of dystrophin?

A

Duchenne’s

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44
Q

what medical condition results from abnormal dystrophin?

A

Becker’s

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45
Q

Duchenne’s and Becker’s syndrome is the progressive degeneration of…and it is ___ linked

A

skeletal muscle

x

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46
Q

microvilli are

A

actin bundles in intestinal epithelium

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47
Q

stereocilia are

A

actin bundles of the inner ear

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48
Q

actin filaments are also involved in

A

locomotion

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49
Q

give some examples of cell locomotion

A
  • spread of cancer cells
  • embryonic cells during development
  • WBCs to fight infection
  • wound healing
  • phagocytosis
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50
Q

define cell crawling

A

cell locomotion across a surface

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51
Q

list the 3 steps in locomotion

A
  1. extension from leading edge
  2. attachment
  3. dissociation & retraction
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52
Q

myosin V are

A

‘two headed’

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53
Q

myosin V transport

A

organelles & intermediate filaments cargo toward barbed ends of actin filaments

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54
Q

what are known as a large heterogeneous family of proteins?

A

intermediate filaments

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55
Q

what makes up the nuclear lamina?

A

intermediate filaments

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56
Q

intermediate filaments span the cytoplasm between

A

cell junctions

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57
Q

intermediate filaments between cell junctions give ____________ __________ to the cell

A

mechanical strength

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58
Q

intermediate filaments are NOT

A

dynamic structures

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59
Q

intermediate filaments give the skin

A

strength & elasticity

60
Q

intermediate filaments integrates the components of the

A

cytoskeleton

61
Q

intermediate filaments organize the

A

internal structure of the cell

62
Q

what is known as the elaborate network in cytoplasm?

A

intermediate filaments

63
Q

intermediate filaments extend from a

A

ring around the nucleus to the plasma membrane

64
Q

intermediate filaments position

A

nucleus to the center of the cell

65
Q

intermediate filaments are NOT involved in

A

cell movement

66
Q

intermediate filaments are typically regulated by

A

phosphorylation

67
Q

actin filaments are polar but intermediate filaments are

A

non-polar

68
Q

intermediate filament dimers are central domains of

A

2 chains forming coiled-coils

69
Q

tetramers in intermediate filaments are formed when dimers associate in a

A

staggered anti-parallel fashion

70
Q

in order to form protofilaments tetramers assemble

A

end to end

71
Q

the final structure of intermediate filaments is composed of

A

8 protofilaments

72
Q

intermediate proteins are involved in

A

NS and epithelium

73
Q

name the 2 specialized cell contacts that epithelial cells have

A
  • desmosomes
  • hemidesmosomes
74
Q

desmosomes are

A

junction between cells (cell—–cell)

75
Q

hemidesmosomes are junctions between

A

epithelial cells and underlying connective tissue (cell——substrate)

76
Q

desmosome attachments are mediated by

A

plakins

77
Q

what link adjoining cells?

A

cadherins

78
Q

examples of hemidesmosomes are

A

keratin filaments and integrins linked to ECM

79
Q

Lou Gehrig’s Disease is aka

A

amyotrophic lateral sclerosis (ALS)

80
Q

ALS are abnormalities in

A

neurofilaments

81
Q

ALS leads to the

A

progressive loss of motor neurons

82
Q

ALS results in

A

muscle atrophy & paralysis

83
Q

epidermolysis bullosa simplex is the mutation in a

A

Keratin gene

84
Q

epidermolysis bullosa simplex causes the development of

A

skin blisters resulting from cell lysis after minor trauma

85
Q

what are known as large hollow cylinders of tubulin protein

A

microtubules

86
Q

microtubules are more rigid than

A

actin or intermediate filaments

87
Q

microtubules are long straight and originate at one end to a single microtubule organizing center known as a

A

centrosome

88
Q

microtubule polymerization and depolymerization are involved in

A

G-protein signaling and vesicle transport

89
Q

are microtubules dynamic?

A

YES

90
Q

microtubules consist of a single type of globular protein known as

A

tubulin

91
Q

microtubules determine…

A

cell shape

92
Q

microtubules are involved in cell

A

locomotion

93
Q

microtubules are also involved in

A

chromosome segregation

94
Q

microtubules are hollow cylinders enclosing a

A

lumen

95
Q

the wall of a microtubule consists of ____ protofilaments which causes the…

A

13

closing of microtubule

96
Q

define a microtubule protofilament

A

linear polymer of tubulin dimers consisting of 2 polypeptides

97
Q

what are the 2 polypeptides that compose a microtubule protofilament?

A
  1. α-tubulin
  2. β-tubulin
98
Q

All ___________ in protofilaments have the same ____________.

A

heterodimers

orientation

99
Q

protofilaments associating in the same orientation assigns _______________ to the microtubule

A

polarity

100
Q

explain the process of microtubule assembly

A

tubulin dimers -> oligomers -> protofilament -> sheets of protofilaments -> closing microtubule -> elongating microtubule

101
Q

similar to actin microtubules can also undergo

A

treadmilling

102
Q

microtubule dimers are high in affinity when

A

bound to GTP

103
Q

microtubule dimers have a low affinity when

A

bound to GDP

104
Q

what end of the microtubule grows away from the centrosome

A

+ end

105
Q

when tubulin [] is high tubulin GTP is added to the microtubule tip…

this results in a

A

faster than the incorporated GTP can be hydrolyzed

GTP cap

106
Q

the GTP cap helps stabilize….& promote…

A

stabilize: the microtubule tip
promote: further growth

107
Q

what occurs at lower tubulin []

A
  • rate of growth decreases
  • GTP hydrolysis catches up
108
Q

no GTP cap being present favors

A

microtubule polymerization

109
Q

what regulates the dynamic nature of MT?

A

microtubule-associated proteins

110
Q

microtubule-associated proteins track the growth of MT to the

A

plasma membrane

111
Q

polymerase microtubule-associated proteins

A

accelerate growth

112
Q

depolymerase microtubule-associated proteins

A

dissociate GTP-tubulin

113
Q

depolymerase microtubule-associated proteins lead to

A

catastrophe

114
Q

what proteins help rescue MT from catastrophe

A

CLASP proteins

115
Q

CLASP proteins keep what microtubule-associated protein inactive?

A

depolymerase

116
Q

what is known as the MT organizing center?

A

centrosome

117
Q

what initiates the polymerization at centrioles

A

γ-tubulin

118
Q

what is the direction of MT in dendrites of neurons?

A

in both directions

119
Q

what is the direction of MT in axons of microtubules?

A

in one direction, positive away from nucleus

120
Q

how can MT grow in both directions in dendrites?

A

b/c dendrites have ample supply of γ-tubulin

121
Q

what is the direction of growth of kinesin?

A

plus end (away from centrosome)

122
Q

what is the direction of growth of dynein?

A

minus end (toward centrosome)

123
Q

kinesin is composed of

A

2 heavy chains + 2 light chains

124
Q

dynein is composed of

A

2-3 heavy chains + multiple light chains

125
Q

what part of motor proteins bind MTs and ATP?

A

globular head

126
Q

how does a motor protein remain inactive until it has cargo to transport?

A

light chain bends and is on head domain preventing ATP binding & hydrolysis

127
Q

who demonstrated the motor lock?

A

Kozielski’s

128
Q

Kinesin pulls what along the MTs toward the plus end?

A

ER

129
Q

kinesin localizes __________ away from the center

A

lysosomes

130
Q

dynein helps to position ______________ toward the center

A

Golgi stacks

131
Q

what occurs when MTs are depolymerized?

A

the ER retracts to the center of the cell

132
Q

microtubules also make what important structures needed for cell movement?

A

cilia & flagella

133
Q

MTs extend outward from a

A

microtubule-organizing center (centrosome)

134
Q

what occurs before the dissociation of the nuclear envelope?

A

duplication of centrosomes

135
Q

MTs aid in the even distribution of

A

sister chromatids

136
Q

how is MT organization completely reorganized in mitotic cells?

A

by rapidly disasembling

137
Q

kinetochore microtubules

A

bind to kinetochore

138
Q

interpolar microtubules aid in

A

elongating the cell

139
Q

chromosomal microtubules aid in the

A

accurate separation of sister chromosomes

140
Q

astral microtubules aid in

A

shortening & taking centrosomes apart

141
Q

what are the 2 distinct mechanisms which chromosome movement occurs?

A

anaphase a & b

142
Q

explain anaphase A

A
  • kinetochore MTs shorten
  • chromosomes toward spindle poles
  • minus end-directed motor protein is involved
143
Q

explain anaphase B

A
  • elongation of interpolar MTs causes the separation of spindle poles
  • overlapping interpolar MTs push poles apart
  • astral MTs shorten by motor proteins anchored in the cell mem.
144
Q

what are critical for cell division?

A

microtubules

145
Q

what drugs bind tubulin & inhibit polymerization?

A

colchicine & colcemid

146
Q

what drugs inhibit rapidly dividing cells?

A

vincristine & vinblastine

147
Q

what drug stabilizes rather than inhibits MT assembly?

A

taxol

Cell Biology (12 decks)

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