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BIO107 - CELL AND MOLECULAR BIOLOGY > Cytoskeleton (1-3) > Flashcards

Cytoskeleton (1-3) Flashcards

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1
Q

Families of protein filaments

A

-actin filaments
-microtubules
-intermediate filaments

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2
Q

for cells to function properly, they must organize themselves in space and interact mechanically with each other and with their environment.

A

cytoskeleton

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3
Q
A
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4
Q

shape of the cell’s surface; whole-cell locomotion; pinching of one cell into two.

A

Actin filaments

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5
Q

positions of membrane-enclosed organelles; direct intracellular transport; from the mitotic spindle.

A

Microtubules

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6
Q

mechanical strength

A

intermediate filaments

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7
Q

-are dynamic and adaptable
-can change or persist, according to need
-a structural rearrangement in a cell requires extra energy when conditions change.

A

Cytoskeletal systems

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8
Q

-underlie the plasma membrane of animal cells.
-strength and shape to its thin lipid bilayer.

A

Actin filaments

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9
Q

cell-surface projections

A

lamellipodia and filopodia

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10
Q

on the surface of hair cells in the inner ear contain stable bundles of actin filaments that tilt as rigid rods in response to sound.

A

stereocilia

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11
Q

on the surface of intestinal epithelial cells vastly increase the apical cell-surface area to enhance nutrient absorption.

A

microvilli

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12
Q

In _______, actin filaments drive rapid streaming of the cytoplasm inside cells.

A

plants

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13
Q

-found in cytoplasmic array that extends to cell periphery.
-form a bipolar mitotic spindle during cell division.

A

Microtubules

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14
Q

-function as motile whips or sensory devices on the surface of the cell.
-tightly aligned bundles that serve as tracks for the transport of materials down along neuronal axons.

A

cilia

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15
Q

In _______, organized arrays of microtubules help to direct the pattern of cell wall synthesis.

A

plant cells

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16
Q

in many _______, microtubules form framework upon the entire cell is built.

A

protozoans

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17
Q

-line the inner face of the nuclear envelope, forming a protective cage for the cell’s DNA.

A

intermediate filaments

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18
Q

in the ________, intermediate filaments twisted into strong cables that can hold epithelial cells sheet together or help nerve cells to extend long and robust axons, and allow to form tough appendages such as hair and fingernails.

A

cytosol

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19
Q

rapid reorganization of cytoskeleton

A

cell division

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20
Q

After the chromosomes have replicated, the ________ _______ array that spreads throughout the cytoplasm is reconfigured into the bipolar _______ _______.

A

interphase microtubule, mitotic spindle

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21
Q

enable the fibroblast to crawl across the surface of the dish rearrange so that the cell stops moving and assume a more spherical shape.

A

specialized actin structures

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22
Q

after replication: form a belt around the middle of the cell

A

actin and motor protein

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23
Q

constricts like a tiny muscle to pinch the cell into two.

A

contractile ring

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24
Q

advance by extending a protrusive structure filled with newly polymerized actin filaments

A

neutrophils

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25
Q

produce stable, large-scale structures for cellular organization.

A

mature neurons or epithelial cells

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26
Q

specialized epithelial cells in the intestines and lungs

A

microvilli and cilia

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27
Q

able to maintain a constant location, length, and diameter over the entire lifetime of the cell.

A

microvilli and cilia

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28
Q

for the actin bundles at the cores of microvilli on intestinal epithelial cells, is only a ____ days.

A

few

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29
Q

stereocilia on the hair cells

A

lifetime

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30
Q

Cytoskeleton is also responsible for large-scale ______ _____, enabling cells to tell the difference between top and bottom or front and back.

A

cellular polarity

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31
Q

use organized arrays of microtubules, actin filaments, and intermediate filaments to maintain the critical differences between the apical surface and the basolateral surface.

A

polarized epithelial cells

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32
Q

also must maintain strong adhesive contacts with one another to enable this single layer of cells to serve as an effective physical barrier.

A

polarized epithelial cells

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33
Q

How does cells builds filaments?

A

by assembling large numbers of the small subunits, like building a skyscraper out of bricks.

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34
Q

can diffuse rapidly in the cytosol, whereas the assembled filaments cannot.

A

small subunits

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35
Q

subunits for actin filaments

A

actin subunits

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36
Q

subunits for microtubules

A

tubulin

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37
Q

subunits of intermediate filaments

A

subunits that are elongated and fibrous

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38
Q

form as polymeric assemblies of subunits that self-associate, using a combination of end-to-end and side-to-side protein contacts.

A

the three major types of cytoskeletal filaments

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39
Q

The subunits of actin filaments and microtubules are asymmetrical and bind to one another head-to-tail so that they all point in one direction.

A

Polarity

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40
Q

-are symmetrical and thus do not form polarized filaments with two different ends.
-also do not catalyze the hydrolysis of ATP or GTP.

A

Intermediate filament subunits

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41
Q

Microtubules are built of ___ protofilaments

A

13

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42
Q

linear strings of subunits joined end-to-end that associate with one another laterally to form a _______ ________.

A

hollow cylinder

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43
Q

the greater energy required to break multiple noncovalent bonds simultaneously allows microtubules to resist ______ _______.

A

thermal breakage

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44
Q

-determines the spatial distribution and the dynamic behavior of the filaments.
- bind to the filaments or their subunits to determine the sites of assembly of new filaments.
- bring cytoskeletal structure under control of extracellular and intracellular signals.
- maintain a highly organized but flexible internal structure.

A

accessory proteins

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45
Q

among the most fascinating proteins that associate with the cytoskeleton are the ______ ________.

A

motor proteins

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46
Q

Where does the motor protein bind?

A

polarized cytoskeletal filament.

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47
Q

uses the energy derived from repeated cycle of ATP hydrolysis to move along it.

A

motor proteins

48
Q

what many motor proteins carry

A

membrane-enclosed organelles

49
Q

What are the organelles that the motor proteins carry?

A

mitochondria, Golgi stacks or secretory vesicles to their appropriate location in the cell.

50
Q

Other motor proteins cause _____ ______ to exert tension or to slide against each other, generating the force that drives such phenomena as muscle contraction, ciliary beating, and cell division.

A

cytoskeletal filaments

51
Q

Bacteria has ______ of all eukaryotic cytoskeletal filaments.

A

homologs

52
Q

-tubulin homolog –>forms Z-ring (septum during cell division)
-generate a bending force that drives the membrane invagination and site for localization of enzymes.

A

FtsZ

53
Q

-actin homolog
-scaffold to direct the synthesis of the peptidoglycan cell wall

A

MreB and Mbl

54
Q

abnormalities in cell shape and defects in chromosomes segregation

A

mutations

55
Q

bacterial actin homolog; encoded by a gene on certain bacterial plasmids that also carry genes responsible for antibiotic resistance.

A

ParM

56
Q

ParM assembles into filaments that associate at each end with a copy of the plasmid, and growth of the ParM filament pushes the ______ ______ ______ apart

A

replicated plasmid copies

57
Q

-influences the crescent shape of Caulobacter crescentus
-homolog of intermediate filaments

A

Crescentin

58
Q

actin subunit

A

globular or G-actin

59
Q

How many amino acid polypeptide carrying a tightly associated molecule of ATP or ADP does the actin subunit globular or G-actin have?

A

375

60
Q

three isoforms of actin

A

alpha (a), beta (B) and gamma (y) actin

61
Q

isoform of actin that is expressed in muscle cells

A

a-Actin

62
Q

isoforms of actin that are found together in almost all non-muscle cells.

A

B- and y-Actin

63
Q

Assembly of actin subunits

A

head-to-tail–> tight, right-handed helix

64
Q

Actin subunits assemble head-to-tail to form a tight, right-handed helix, forming a structure about * nm wide called ______ or ________.

A

Filamentous or F-actin

65
Q

filaments are polar and have structurally different ends: a slower growing minus end or _____ ___

A

pointed end

66
Q

filaments are polar and have structurally different ends: a faster-growing plus end or ______ ___.

A

barbed end

67
Q

nucleotide-binding cleft directed toward the ______ ___.

A

minus end

68
Q

the minimum length at which random thermal fluctuations are likely to cause it to bend.

A

persistence length

69
Q

The regulation of actin filament formation is an important mechanism by which cells control their _____ and _______.

A

shape and movement

70
Q

subunits assemble into an initial aggregate, or nucleus, that is stabilized by multiple subunit-subunit contacts and can then elongate rapidly by addition of more subunits.

A

nucleation

71
Q

is rate limiting and is additionally inhibited by actin-binding proteins

A

formation of small actin oligomers

72
Q

In vitro polymerization of G-actin proceeds in three sequential phases, what are these?

A

-nucleation
-elongation
-steady-state

73
Q

lag period; G-actin aggregates into short, unstable oligomers; when oligomers reaches a certain length, it can act as a stable seed or nucleus.

A

Nucleation

74
Q

rapidly increases in length by the addition of actin monomers to both of its ends.

A

elongation

75
Q

as F-actin filament grows, the concentration of G-actin monomers ______.

A

decreases

76
Q

G-actin monomers exchange with subunits at the filament ends, but there is no net change in the total mass of filaments.

A

steady-state

77
Q

when steady-state phase has been reached, the concentration of the pool of unassembled subunits is called ______ ______, __

A

critical concentration, Cc

78
Q

the ratio of the “on” and “off” rate constant

A

dissociation constant

79
Q

measures the concentration of G-actin where the addition of subunits is balanced by the dissociation of subunits

A

dissociation constant

80
Q

actin filaments grow faster at ____ ___ than at _____ ___.

A

plus end, minus end

81
Q

manifested by the different rates at which G-actin adds to the two ends

A

polarity of F-actin

82
Q

nucleate the polymerization of G-actin

A

myosin-decorated actin filaments

83
Q

newly polymerized (undecorated) actin is ______ times as long at the (+) end as at the (-) end of the filaments.

A

5-10

84
Q

difference in elongation rates at the opposite ends of an actin filament is caused by

A

a difference in Cc values at the two ends

85
Q

the plus end of an actin filament is ______, it can elongate only from its minus end

A

capped

86
Q

elongation takes place only at the plus end when the minus end of a filament is ______.

A

blocked

87
Q

Cc is about ____ _____ lower for polymerization at the (+) end than for addition at the (-) end

A

six times

88
Q

G-actin concentration below Cc+, there is __ ________ ______.

A

no filament growth

89
Q

G-actin concentrations between Cc+ and Cc-

A

growth is only at the (+) end

90
Q

G-actin concentration above

A

no growth at both ends

91
Q

G-actin concentrations intermediate between the Cc values for the plus end the minus ends, subunits continue to be added at the end and lost from the minus end

A

steady-state phase

92
Q

newly added subunits travelling through the filament, as if on a ______, until they reach the plus end, where they dissociate

A

treadmill

93
Q

effect on filaments: Latrunculin

A

depolymerizes

94
Q

effect on filaments: Cytochalasin B

A

Depolymerizes

95
Q

effect on filaments: Phalloidin

A

stabilizes

96
Q
A
97
Q

Chemical inhibitors of actin

A

-Latrunculin
-cytochalasin B
-Phalloidin

98
Q

chemical inhibitors of Microtubules

A

-Taxol (paclitaxel)
-Nocodazole
-Colchicine

99
Q

effect on filaments: Taxol

A

stabilizes

100
Q

effects on filaments: Nocodazole

A

Depolymerizes

101
Q

effects on filaments: Colchicine

A

depolymerizes

102
Q

Binds actin subunits

A

Latrunculin

103
Q

Caps filament plus ends

A

Cytochalasin B

104
Q

Binds along filaments

A

Phalloidin

105
Q

Binds along filaments: Microtubules

A

Taxol

106
Q

Binds tubulin subunits

A

Nocodazole

107
Q

Caps filament ends

A

Colchicine

108
Q

polymerization of actin is controlled by

A

its concentration, pH, and conc. of salts and ATP

109
Q

actin behavior is regulated by _________ ________ that bind actin monomers or filaments

A

accessory proteins

110
Q

a measure of how long an individual actin monomer spends in a filament as it treadmills.

A

filament half-life

111
Q

____ of the actin is in filament and ____ is
soluble monomer

A

50%, 50%

112
Q

cell contains proteins that bind to the actin
monomers and make polymerization much

A

less favorable

113
Q

inhibition of actin polymerization;
they cannot associated with either the plus
or minus ends; neither hydrolyze nor
exchange their bound nucleotide

A

thymosin

114
Q

binds to the face of the actin
monomer opposite the ATP-binding cleft,
blocking the side of the monomer that would
normally associate with the filament minus
end, while leaving exposed the site on the
monomer that binds to the plus end

A
115
Q

binds to the face of the actin
monomer opposite the ATP-binding cleft,
blocking the side of the monomer that would
normally associate with the filament minus end, while leaving exposed the site on the monomer that binds to the plus end

A

profilin

BIO107 - CELL AND MOLECULAR BIOLOGY (8 decks)

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