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Histology > Cytoskeleton (Exam 1) > Flashcards

Cytoskeleton (Exam 1) Flashcards

1
Q

What are the 3 specific kinds of protein structures that make up the cytoskeleton

A

Microfilaments (actin) (7nm thick)
Intermediate filaments (8-10 nm thick)
Microtubules (25nm in diameter)

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2
Q

Actin filaments are highly _______ among eukaryotes

A

conserved

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3
Q

how tick are actin filaments

A

7nm thck

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4
Q

how long may actin filaments be

A

may be up to 7 micrometers long

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5
Q

actin filaments are organized into ______ and _____ networks

A

Bundles, 3-D

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6
Q

Actin filaments bind to specific transmembrane proteins either ____ or ____

A

directly, indirectly

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7
Q

Actin filaments exist in what two forms

A

Monomers (G-actin) and long chains (F-actin)

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8
Q

What are the three major varieties of actin filaments

A 
alpha actin (found in muscle tissue)
Beta actin (non-muscle actin)
Gamma actin (non-muscle actin)
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9
Q

each actin monomer (G actin) has a binding site for ____, which binds tightly to G-actin

A

ATP

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10
Q

Each actin monomer can bind tightly with two other actin monomers to form what

A

Filamentous actin (F-actin)

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11
Q

Actin monomers are oriented in the same direction and thus display

A

Polarity

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12
Q

Actin _______ is reversible

A

Polymerization

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13
Q

The rate at which actin monomers are aded to the growing filament is proportional to what

A

cytosolic concentration of actin filaments

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14
Q

what type of actin dissociates more readily from filaments than ATP-actin

A

ADP-actin

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15
Q

what is the first step in actin polymerization

A

Nucleation: a trimer is formed

additional actin monomers can be added to either end

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16
Q

ATP -actin associates with which end of actin

A

The growing (plus or barbed) ends

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17
Q

The ATP is hydrolyzed to _____ following polymerization

A

ADP

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18
Q

The barbed end grows how much faster than the pointed end

A

5-10 times faster

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19
Q

Very low concentration of G-actin favor the ____ of actin filaments

A

disassembly

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20
Q

Intermediate concentrations of G-actin favor

A

Treadmilling

  • dynamic equilibrium between the minus end and the plus end
  • results in zero net growth
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21
Q

Actin microfilaments consist of a ____ _______ chain of G-actin subunits

A

Double helical

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22
Q

name two drugs that affect actin polymerization

A

cytochalasin and Phalloidin

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23
Q

Cytochalasin role in actin polymerization

A

drug that inhibits elongation
can inhibit movements (cell division)
Binds to the barbed ends of actin

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24
Q

What is Phalloidin’s role in actin polymerization

A

Binds to actin filaments and prevents dissociation
can be labeled with fluorescent dyes to allow visualization of actin filaments
prevents depolymerization by binding to actin filaments

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25
what determines the different functions of actin
Actin-binding proteins and not actin itself
26
Spectrin
is an actin binding protein found in RBCs binds cortical cytoskeleton to the plasma membrane
27
Dystrophin
Actin binding protein binds cortical cytoskeleton to the plasma membrane (defects can lead to muscular dystrophy)
28
Villain and Fimbrin
Actin binding proteins | cross-link actin filaments in microvilli
29
Calmodulin and Myosin I
Actin binding proteins | Cross-links actin to plasma membrane in microvilli
30
alpha actin
actin binding protein | cross-links stress fibers and connects actin to protein-plasma membrane complexes
31
Filamin
Actin binding protein | Cross-links actin at wide angles to form screen-like gels
32
Thymosin
Actin binding protein that controls treadmilling | captures actin monomers and prevents actin monomers from being polymerized
33
Profilin
Actin binding protein that controls treadmilling binds to actin monomers facilitates exchange of bound ADP for ATP- which favors polymerization increases actin growth
34
Gelsolin
Actin binding protein that controls treadmilling Destabilizes F-actin and caps actin filaments, preventing loss and addition of G-actin in presence of calcium ion, fragments actin filaments and remains bound to plus end
35
Cofilin
Actin binding protein that controls treadmilling | Triggers depolymerization of ADP- bound Actin at the minus end
36
Arp 2/3
Actin binding protein that controls treadmilling | initiates growth of F-actin from sides of existing filament- causes branching
37
Latrunculins
Actin binding protein that controls treadmilling | binds to G-Actin and induces F-actin depolymerization
38
how thick are intermediate filaments
8-10nm
39
where are intermediate filaments most abundant
in cells that are subject to mechanical stress
40
What is the function of intermediate filaments
Provide tensile strength in cells such as neurons and muscle strengthen epithelial cells as desmosomes and hemidesmosomes form a cytoplasmic network in most cells associate with other cytoskeletal elements to form a scaffolding that organizes the internal structure of the cell
41
What structural component do all intermediate filaments have
A common monomer consisting of a central alpha-helical rod flanked by head and tail domains
42
what determines the specific functions of intermediate filaments
Head and tail domains
43
Describe intermediate filament structure
Central rod of two polypeptides form a cold dimer - Rods are aligned tail-to-tail and head-to-head -dimers associated in a staggered antiparallel fashion to form tetramers tetramers assemble end to end to form protofilaments pairs of protofilaments associate laterally to form a protofibril 4 protofibrils are wound together to form filaments (8 protofilaments)
44
Which are more stable actin filaments or intermediate filaments
intermediate filaments | because dimers align in antiparallel fashion, polymerized filaments do not have distinct ends (no treadmilling)
45
Type I Intermediate filaments
Acidic Keratins
46
Type II intermediate filaments
Neutral to basic keratins
47
Type III intermediate filaments
Vimentin Desmin Glial fibrillary acidic protein Peripherin
48
Type IV Intermediate filaments
Neurofilaments
49
Type V intermediate filaments
Nuclear lamins (associated with nuclear membrane and assembly of nuclear membrane)
50
Type VI intermediate filaments
Nestin
51
How large is the diameter of microtubules
25 micrometers
52
What is a structural characteristic across microtubules
alpha and beta tubulin
53
Microtubules consist of how many protofilaments
13
54
how are the 13 protofilaments arranged
parallel to form a cylinder with a hollow core
55
How are microtubules similar to actin
they have a + and - end (display polarity)
56
What tubule dimers with GTP bound associate with the growing end of a microtubule
Beta tubulin
57
The plus end of a microtubule grows more rapidly in the presence of what
low calcium ion concentration
58
what destabilizes a microtubule
hydrolysis of GTP to GDP
59
which Tubulin subunit faces the plus end
The beta tubulin
60
Factors that inhibit microtubule polymerization
Colchicines (originally used to arrest mitotic cells, would arrest in metaphase) Colcemid Vincristine (anticancer drug) Vinblastin (anticancer drug used to treat Hodgkin's lymphoma) Nocodazole
61
Factors that stabilize microtubules
Taxol (anticancer drug- used to treat ovarian cancer) | blocks mitotic division by not allowing formation of mitotic spindle
62
Functions of the cytoskeleton
``` cell movement support and strength for the cell phagocytosis Mitotic spindle formation Cytokinesis Cell-to-Cell and cell-to-extracellular matrix adherence changes in cell shape ```
63
Anterograde
Transports cargo along microtubule | mediated by Kinesin (toward the plus end)
64
Retrograde transport
Dynein | runs toward minus end or back to axon hillock
65
what does myosin I bind to
Actin and cell membrane
66
how many heads does myosin I have
one
67
What does the tail of myosin I bind to
Vesicles
68
How many heads does Myosin V have
Two heads
69
What does the heads of myosin V bind to
Actin
70
What do the tails of myosin V bind to
Vesicles
71
How many heads does myosin II have
Two heads
72
what does the tails of myosin II bind to
Myosin
73
What do the heads of myosin II bind to
Actin

Histology (10 decks)

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