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Cell Molec > Lecture 18 > Flashcards

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
Q

what is elongation

A

fast phase, monomers being added to initial seed

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26
Q

what is the steady state

A

the addition and removal of monomers at each end happens at the same rate

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27
Q

directionality actin is preferably grown/added to?

A

(+) end

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28
Q

what is treadmilling?

A

how G-actin moves through the filament, add (+) and subtract (-) end

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29
Q

what is profilin

A

protein that assists in assembly of actin (works at + end)

30
Q

what is cofilin

A

protein that assists in disassembly of actin (works at – end)

31
Q

what are capping proteins

A

prevent G-actin monomers from being added

32
Q

what is Cap Z

A

capping protein for (+) end, restricts assembly/disassembly to (–) end

33
Q

what is tropomodulin?

A

capping protein for (–) end, restricts assembly/disassembly to (+) end

34
Q

what polymerizes unbranched filaments of microfilaments?

A

formins

35
Q

what are formins made out of?

A

2 FH2 domains (dimer)

36
Q

function of FH1 in formin?

A

to recruit profilin ATP-actin to feed into FH2

37
Q

how does FH2 polymerize F-actin?

A

in a alternative shifting pattern

38
Q

what is responsible for the different sections in the microfilament?

A

the hydrolysis of ATP towards the (-) end

39
Q

what polymerizes branched microfilament segments?

A

the Arp2/3 complex

40
Q

what are the components of Arp 2/3?

A

2 ATP binding sites

41
Q

what are associated proteins in the Arp 2/3 complex?

A

WCA and WASp

42
Q

what is WASp?

A

nucleation promoting factor that includes a WCA domain

43
Q

function of WCA in WASp?

A

makes the nucleus/seed

44
Q

what angle are branched filaments always at with respect to the original filament?

A

70º

45
Q

how is the function of Arp 2/3 and branched filament polymerization initiated?

A

signal transduction pathway

46
Q

how is listeria able to use our microfilament machinery?

A

it contains cell-surface proteins that act as actin binding sites

47
Q

with the use of our microfilament machinery, how does listeria move into a neighboring cell?

A

via actin polymerization, the disassembly/assembly of F-actin will push it into next cell

48
Q

what is the advantage of listeria by using the microfilament polymerization process?

A

can hide from immune system

49
Q

branched microfilaments in endocytosis

A

branched microfilaments facilitate transport of endocytic vesicles to its target location

50
Q

myosins

A

motor proteins associated with microfilaments

51
Q

what are the three distinct domains of myosins?

A

head that contains the actin binding site, neck and tail

52
Q

where is myosins present in?

A

skeletal muscles

53
Q

what are the three common classes of myosins?

A

I, II, V

54
Q

functions of class I myosins

A

membrane association, endocytosis

55
Q

functions of class II myosins

A

contraction in skeletal muscles

56
Q

functions of class V myosins

A

organelle transport, has proteins at the end that will interact with organelles and vesicles

57
Q

what is the directionality of myosins?

A

moves toward (+) end of microfilaments (used as myosin tracks)

58
Q

what are muscle cells divided into?

A

sarcomeres

59
Q

what outlines sarcomeres

A

Z-disks

60
Q

what ends of the microfilaments are anchored to Z-disks

A

(+) ends

61
Q

how can myosins move towards the Z-disks in contraction of muscles?

A

adding ATP and Ca2+

62
Q

what relaxes muscles?

A

removing calcium

63
Q

what is nebulin

A

protein that helps stabilize filament

64
Q

what is titin?

A

elastic protein that prevents overstretching

65
Q

function of tropomyosin

A

blocks sites that myosin would bind to

66
Q

function of troponin

A

binds and causes conformational change and shifts tropomyosin to expose myosin binding sites of actin monomers

67
Q

what class of myosin forms contractile rings

A

class II

68
Q

why must light-chains of myosins be phosphorylated for smooth muscle contraction?

A

myosin usually in folded inactive state without calcium present = calcium present = contraction can happen

69
Q

what phosphorylates myosin light chains?

A

myosin light chain kinase

70
Q

in smooth muscle, what happens when there are low levels of calcium?

A

MLC kinase = inactive, MLC phosphatase = active, myosin reverts to folded state

Cell Molec (16 decks)

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