Chapter 14: The Cytoskeleton & Cell Movement Flashcards
1
Q
the cytoskeleton provides a
A
structural framework for the cell
2
Q
the cytoskeleton serves as a scaffold that determines
A
- cell shape
- general organization
3
Q
the cytoskeleton is responsible for
A
movement & cell locomotion
4
Q
the cytoskeleton transports
A
organelles & other cell structures through the cell
5
Q
the cytoskeleton can be described as a
A
dynamic structure w/ changing architecture
6
Q
the cytoskeleton localizes the ________ at the center
A
nucleus
7
Q
what are the 3 principle types of protein filaments that compose the cytoskeleton?
A
- actin filaments (microfilament)
- intermediate filaments
- microtubules
8
Q
actin filaments are aka
A
microfilaments
9
Q
what is known as the primary cytoskeleton protein?
A
actin filaments
10
Q
actin filaments are helical polymers of
A
actin protein
11
Q
actin filaments are organized into a variety of
A
linear bundles
12
Q
actin filaments are ___________ throughout the cell, but most concentrated beneath the
A
- dispersed
- plasma membrane
13
Q
actin filaments are the smallest filaments that participate in
A
cell adhesion
14
Q
actin filaments are not a double helix but instead a
A
single strand
15
Q
describe the steps in actin filament assembly
A
- G actin form dimers
- dimers form trimers
- multiple trimers form F actin filament
16
Q
the G actin is composed of a
A
barbed(+) and pointed(-) end
17
Q
what are the group of proteins involved in the polymerization of actin filaments?
A
formin
18
Q
define nucleation
A
the formation of dimers and trimers
19
Q
actin monomers bind _____ -> hydrolyzed to _____ following filament assembly
A
- ATP
- ADP
20
Q
what is NOT required for polymerization of actin filaments?
A
ATP
21
Q
what polymerize more readily than ADP-bound monomers?
A
ATP-bound actin
22
Q
define steady state
A
rate of + end addition = rate of loss from the - end
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
24
Q
what describes the lengthening of actin filaments
A
increased [] of bound ATP
25
what describes the shortening of actin filaments
increased [] of bound ADP
26
actin-binding proteins regulate the
assembly & disassembly of actin
27
profilin promotes
monomer binding by exchanging ADP for ATP
28
what acts as a nucleation site to initiate branching of new filaments?
Arp2/3
29
Arp2/3 is an example of an
actin binding protein
30
what stabilize actin filaments?
tropomyosin & capping proteins
31
what cleaves actin filaments
cofilin
32
cofilin cleaves filaments making new ends for filaments to
polymerize or depolymerize
33
actin-binding proteins also serve to
organize/stabilize actin filaments
34
what is the name for the filaments that cross-link actin filaments?
filamen
35
what form bundles of tightly packed parallel arrays?
fimbrin & α-actinin
36
actin bundles form what anatomical structure
microvilli
37
what are known as specialized regions of the plasma membrane that form contacts with adjacent cells or to a surface?
adherens junctions
38
adherens junction require
actin
39
what are known as attachment sites for large bundles of actin filaments called stress fibers?
focal adhesions
40
stress fibers are bundles of
actin filaments linked by α-actin
41
focal adhesions detach to act as
signal sequences
42
what links actin to transmembrane proteins of the muscle cell plasma membrane?
dystrophin
43
what medical condition results from the absence of dystrophin?
Duchenne's
44
what medical condition results from abnormal dystrophin?
Becker's
45
Duchenne's and Becker's syndrome is the progressive degeneration of...and it is ___ linked
skeletal muscle
x
46
microvilli are
actin bundles in intestinal epithelium
47
stereocilia are
actin bundles of the inner ear
48
actin filaments are also involved in
locomotion
49
give some examples of cell locomotion
- spread of cancer cells
- embryonic cells during development
- WBCs to fight infection
- wound healing
- phagocytosis
50
define cell crawling
cell locomotion across a surface
51
list the 3 steps in locomotion
1. extension from leading edge
2. attachment
3. dissociation & retraction
52
myosin V are
'two headed'
53
myosin V transport
organelles & intermediate filaments cargo toward barbed ends of actin filaments
54
what are known as a large heterogeneous family of proteins?
intermediate filaments
55
what makes up the nuclear lamina?
intermediate filaments
56
intermediate filaments span the cytoplasm between
cell junctions
57
intermediate filaments between cell junctions give ____________ __________ to the cell
mechanical strength
58
intermediate filaments are NOT
dynamic structures
59
intermediate filaments give the skin
strength & elasticity
60
intermediate filaments integrates the components of the
cytoskeleton
61
intermediate filaments organize the
internal structure of the cell
62
what is known as the elaborate network in cytoplasm?
intermediate filaments
63
intermediate filaments extend from a
ring around the nucleus to the plasma membrane
64
intermediate filaments position
nucleus to the center of the cell
65
intermediate filaments are NOT involved in
cell movement
66
intermediate filaments are typically regulated by
phosphorylation
67
actin filaments are polar but intermediate filaments are
non-polar
68
intermediate filament dimers are central domains of
2 chains forming coiled-coils
69
tetramers in intermediate filaments are formed when dimers associate in a
staggered anti-parallel fashion
70
in order to form protofilaments tetramers assemble
end to end
71
the final structure of intermediate filaments is composed of
8 protofilaments
72
intermediate proteins are involved in
NS and epithelium
73
name the 2 specialized cell contacts that epithelial cells have
- desmosomes
- hemidesmosomes
74
desmosomes are
junction between cells (cell-----cell)
75
hemidesmosomes are junctions between
epithelial cells and underlying connective tissue (cell------substrate)
76
desmosome attachments are mediated by
plakins
77
what link adjoining cells?
cadherins
78
examples of hemidesmosomes are
keratin filaments and integrins linked to ECM
79
Lou Gehrig's Disease is aka
amyotrophic lateral sclerosis (ALS)
80
ALS are abnormalities in
neurofilaments
81
ALS leads to the
progressive loss of motor neurons
82
ALS results in
muscle atrophy & paralysis
83
epidermolysis bullosa simplex is the mutation in a
Keratin gene
84
epidermolysis bullosa simplex causes the development of
skin blisters resulting from cell lysis after minor trauma
85
what are known as large hollow cylinders of tubulin protein
microtubules
86
microtubules are more rigid than
actin or intermediate filaments
87
microtubules are long straight and originate at one end to a single microtubule organizing center known as a
centrosome
88
microtubule polymerization and depolymerization are involved in
G-protein signaling and vesicle transport
89
are microtubules dynamic?
YES
90
microtubules consist of a single type of globular protein known as
tubulin
91
microtubules determine...
cell shape
92
microtubules are involved in cell
locomotion
93
microtubules are also involved in
chromosome segregation
94
microtubules are hollow cylinders enclosing a
lumen
95
the wall of a microtubule consists of ____ protofilaments which causes the...
13
closing of microtubule
96
define a microtubule protofilament
linear polymer of tubulin dimers consisting of 2 polypeptides
97
what are the 2 polypeptides that compose a microtubule protofilament?
1. α-tubulin
2. β-tubulin
98
All ___________ in protofilaments have the same ____________.
heterodimers
orientation
99
protofilaments associating in the same orientation assigns _______________ to the microtubule
polarity
100
explain the process of microtubule assembly
tubulin dimers -> oligomers -> protofilament -> sheets of protofilaments -> closing microtubule -> elongating microtubule
101
similar to actin microtubules can also undergo
treadmilling
102
microtubule dimers are high in affinity when
bound to GTP
103
microtubule dimers have a low affinity when
bound to GDP
104
what end of the microtubule grows away from the centrosome
+ end
105
when tubulin [] is high tubulin GTP is added to the microtubule tip...
this results in a
faster than the incorporated GTP can be hydrolyzed
GTP cap
106
the GTP cap helps stabilize....& promote...
stabilize: the microtubule tip
promote: further growth
107
what occurs at lower tubulin []
- rate of growth decreases
- GTP hydrolysis catches up
108
no GTP cap being present favors
microtubule polymerization
109
what regulates the dynamic nature of MT?
microtubule-associated proteins
110
microtubule-associated proteins track the growth of MT to the
plasma membrane
111
polymerase microtubule-associated proteins
accelerate growth
112
depolymerase microtubule-associated proteins
dissociate GTP-tubulin
113
depolymerase microtubule-associated proteins lead to
catastrophe
114
what proteins help rescue MT from catastrophe
CLASP proteins
115
CLASP proteins keep what microtubule-associated protein inactive?
depolymerase
116
what is known as the MT organizing center?
centrosome
117
what initiates the polymerization at centrioles
γ-tubulin
118
what is the direction of MT in dendrites of neurons?
in both directions
119
what is the direction of MT in axons of microtubules?
in one direction, positive away from nucleus
120
how can MT grow in both directions in dendrites?
b/c dendrites have ample supply of γ-tubulin
121
what is the direction of growth of kinesin?
plus end (away from centrosome)
122
what is the direction of growth of dynein?
minus end (toward centrosome)
123
kinesin is composed of
2 heavy chains + 2 light chains
124
dynein is composed of
2-3 heavy chains + multiple light chains
125
what part of motor proteins bind MTs and ATP?
globular head
126
how does a motor protein remain inactive until it has cargo to transport?
light chain bends and is on head domain preventing ATP binding & hydrolysis
127
who demonstrated the motor lock?
Kozielski's
128
Kinesin pulls what along the MTs toward the plus end?
ER
129
kinesin localizes __________ away from the center
lysosomes
130
dynein helps to position ______________ toward the center
Golgi stacks
131
what occurs when MTs are depolymerized?
the ER retracts to the center of the cell
132
microtubules also make what important structures needed for cell movement?
cilia & flagella
133
MTs extend outward from a
microtubule-organizing center (centrosome)
134
what occurs before the dissociation of the nuclear envelope?
duplication of centrosomes
135
MTs aid in the even distribution of
sister chromatids
136
how is MT organization completely reorganized in mitotic cells?
by rapidly disasembling
137
kinetochore microtubules
bind to kinetochore
138
interpolar microtubules aid in
elongating the cell
139
chromosomal microtubules aid in the
accurate separation of sister chromosomes
140
astral microtubules aid in
shortening & taking centrosomes apart
141
what are the 2 distinct mechanisms which chromosome movement occurs?
anaphase a & b
142
explain anaphase A
- kinetochore MTs shorten
- chromosomes toward spindle poles
- minus end-directed motor protein is involved
143
explain anaphase B
- 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
what are critical for cell division?
microtubules
145
what drugs bind tubulin & inhibit polymerization?
colchicine & colcemid
146
what drugs inhibit rapidly dividing cells?
vincristine & vinblastine
147
what drug stabilizes rather than inhibits MT assembly?
taxol
