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Lecture 18 Flashcards

1
Q

What are the three major components of the cytoskeleton?

A

microfilaments, microtubules, intermediate filaments

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2
Q

What gives cells direction?

A

cytoskeleton

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3
Q

How does the cytoskeleton give cells polarity?

A

by having a top (apical) and bottom (basal)

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4
Q

What are the subunits of microfilaments?

A

actin

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5
Q

what are microtubules made out of?

A

ab-tubulin dimer

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6
Q

what regulates the rearrangement or movement of cytoskeleton?

A

signal transduction pathway

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7
Q

which binds to actin? (ATP or GTP)

A

ATP

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8
Q

which binds to a/b-tubulin? (ATP or GTP)

A

GTP

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9
Q

which cytoskeletal components are highly dynamic?

A

microtubules and microfilaments

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10
Q

which cytoskeletal components are less dynamic?

A

intermediate filaments

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11
Q

which cytoskeletal components are polarized?

A

microfilaments and microtubules

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12
Q

which cytoskeletal components are unpolarized?

A

intermediate filaments

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13
Q

what are the motor proteins for microfilaments?

A

myosins

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14
Q

what are the motor proteins for microtubules?

A

kinesin and dynein

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15
Q

what are the motor proteins for intermediate filaments?

A

no motor proteins

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16
Q

function of microfilaments

A

contractile machinery and network at the cell cortex

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17
Q

function of microtubules

A

organization and long-range transport of organelles

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18
Q

function of intermediate filaments

A

cell and tissue integrity

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19
Q

what is actin made out of?

A

G-actin

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20
Q

what is G-actin?

A

globular actin protein with an ATP-binding cleft

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21
Q

what is F-actin?

A

filament actin, polymerization of G-actin into a filament

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22
Q

what is the ATP binding cleft

A

on G-actin that creates polarity = points towards the (-) end

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23
Q

what are the three phases of actin polymerization

A

nucleation, elongation, steady state

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24
Q

what is nucleation?

A

slow/lag phase, binding of 3 G-actin units = nucleus/seed

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25
what is elongation
fast phase, monomers being added to initial seed
26
what is the steady state
the addition and removal of monomers at each end happens at the same rate
27
directionality actin is preferably grown/added to?
(+) end
28
what is treadmilling?
how G-actin moves through the filament, add (+) and subtract (-) end
29
what is profilin
protein that assists in assembly of actin (works at + end)
30
what is cofilin
protein that assists in disassembly of actin (works at – end)
31
what are capping proteins
prevent G-actin monomers from being added
32
what is Cap Z
capping protein for (+) end, restricts assembly/disassembly to (–) end
33
what is tropomodulin?
capping protein for (–) end, restricts assembly/disassembly to (+) end
34
what polymerizes unbranched filaments of microfilaments?
formins
35
what are formins made out of?
2 FH2 domains (dimer)
36
function of FH1 in formin?
to recruit profilin ATP-actin to feed into FH2
37
how does FH2 polymerize F-actin?
in a alternative shifting pattern
38
what is responsible for the different sections in the microfilament?
the hydrolysis of ATP towards the (-) end
39
what polymerizes branched microfilament segments?
the Arp2/3 complex
40
what are the components of Arp 2/3?
2 ATP binding sites
41
what are associated proteins in the Arp 2/3 complex?
WCA and WASp
42
what is WASp?
nucleation promoting factor that includes a WCA domain
43
function of WCA in WASp?
makes the nucleus/seed
44
what angle are branched filaments always at with respect to the original filament?
70º
45
how is the function of Arp 2/3 and branched filament polymerization initiated?
signal transduction pathway
46
how is listeria able to use our microfilament machinery?
it contains cell-surface proteins that act as actin binding sites
47
with the use of our microfilament machinery, how does listeria move into a neighboring cell?
via actin polymerization, the disassembly/assembly of F-actin will push it into next cell
48
what is the advantage of listeria by using the microfilament polymerization process?
can hide from immune system
49
branched microfilaments in endocytosis
branched microfilaments facilitate transport of endocytic vesicles to its target location
50
myosins
motor proteins associated with microfilaments
51
what are the three distinct domains of myosins?
head that contains the actin binding site, neck and tail
52
where is myosins present in?
skeletal muscles
53
what are the three common classes of myosins?
I, II, V
54
functions of class I myosins
membrane association, endocytosis
55
functions of class II myosins
contraction in skeletal muscles
56
functions of class V myosins
organelle transport, has proteins at the end that will interact with organelles and vesicles
57
what is the directionality of myosins?
moves toward (+) end of microfilaments (used as myosin tracks)
58
what are muscle cells divided into?
sarcomeres
59
what outlines sarcomeres
Z-disks
60
what ends of the microfilaments are anchored to Z-disks
(+) ends
61
how can myosins move towards the Z-disks in contraction of muscles?
adding ATP and Ca2+
62
what relaxes muscles?
removing calcium
63
what is nebulin
protein that helps stabilize filament
64
what is titin?
elastic protein that prevents overstretching
65
function of tropomyosin
blocks sites that myosin would bind to
66
function of troponin
binds and causes conformational change and shifts tropomyosin to expose myosin binding sites of actin monomers
67
what class of myosin forms contractile rings
class II
68
why must light-chains of myosins be phosphorylated for smooth muscle contraction?
myosin usually in folded inactive state without calcium present = calcium present = contraction can happen
69
what phosphorylates myosin light chains?
myosin light chain kinase
70
in smooth muscle, what happens when there are low levels of calcium?
MLC kinase = inactive, MLC phosphatase = active, myosin reverts to folded state

Cell Molec (16 decks)

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