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BIOL1025 - Fundamentals of cell biology and physiology > Cytoskeleton part 1 > Flashcards

Cytoskeleton part 1 Flashcards

1
Q

Function of cytoskeleton

A 
gives shapes
able to move or alter shape of cell
organisation of organelles
transport of organelles
cell division
chromosome organisation and movement
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2
Q

component - microfilaments

A

constant flux that lengthen and shorten, disassemble and assemble

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3
Q

component - intermediate filament

A

made of more stable fibrous protein subunit - slow to break down

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4
Q

component - microtubules - tubulin

A

lowest in abundance

also made up of subunits that can rapidly assemble and disassemble

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5
Q

actin subunit molecular weight

A

42000

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6
Q

tubulin subunit molecular weight

A

50000 for both alpha and beta tubulin

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7
Q

actin unpolymerized form

A

globular, monomer

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8
Q

tubulin unpolymerized form

A

globular, dimer

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9
Q

actin - bound nucleotide in unpolymerized state

A

ATP

1/monomer

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10
Q

tubulin - bound nucleotide in unpolymerized state

A

GTP

2/dimer

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11
Q

actin - factors required for polymerization

A

Ca+/Mg2+ in presence of NaCl

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12
Q

tubulin - factors required for polymerization

A

Mg2+ Chelator to remove Ca2+ NaCl

cause absence of calcium

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13
Q

actin - form of polymer

A

2 stranded helix - 2 strand wound round each other

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14
Q

tubulin - form of polymer

A

hollow tube composed of 13 protofilaments

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15
Q

actin - filament diameter

A

7nm

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16
Q

tubulin - filament diameter

A

25nm

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17
Q

what is microfilaments made up of

A

actin monomers - 43kDa in a linear assemlies

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18
Q

formation of microfilaments

A

4 domain and a central cleft - divalent cation and nucleotide binding site

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19
Q

divergence in actin

A

variation of actin increasing from amphibia to mammals

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20
Q

actin types - a(sk)

A

skeletal muscle

21
Q

a(c)

A

cardiac muscle

22
Q

a(sm)

A

smooth aorta muscles

23
Q

beta or Y

A

non-muscles tissue

24
Q

Y(sm)

A

smooth stomach muscle

25
Q

G-actin globular

A

form of actin

has 1 tightly bound Ca2+

26
Q

what G-actin contain

A

non-covalently bound ATP

27
Q

actin polymerization

A

G-actin polymerized to form filamentous F-actin

actin filaments have 2 F-actin twisted with 13.5 molecules per repeat - 36nm

28
Q

ATP during actin polymerization

A

hydrolysed but energy is not essential

29
Q

actin depolymerization

A

F-actin returns to G-actin form

30
Q

actin monomer shape

A

per shaped as it has polarity

31
Q

assembly of actins

A

has a barbed and pointed end

32
Q

barbed end

A

positive

easier for subunits to add to

33
Q

pointed end

A

negative

slower to add subunits

34
Q

cytoskeleton as dynamic structure

A

able to change quickly

35
Q

disassembly of cytoskeleton

A

rapid diffusion of subunits

36
Q

reassembly of cytoskeleton

A

filaments at new sites

37
Q

what microfilament synthesis is controlled by

A

2 proteins called ArP2 and ArP3

38
Q

ArP2 and ArP3 function

A

act as primer for actin polymerization

39
Q

How microfilament synthesis is initiated

A

ArP2 and ArP3 bond together - recruiting other protein forming nucleation site
attracting active monomer

40
Q

binding of ArP2 and ArP3

A

can cause branching of microfilament network

by binding to existing filaments

41
Q

profilin and thymosin

A

regulate rate of microfilament synthesis

controlled by availability of free actin monomers

42
Q

thymosin function

A

bind free actin and remove it from pool of actin

43
Q

profilin function

A

similar to thymosin

promotes addition of plus end causing rapid growth

44
Q

gelsolin

A

bind to pre-existing MF and cleave it off - free filament so new end for addition of free actin subunits

45
Q

gelsolin regulating MF length

A

released by PIP2 - free +ve ends for rapid MF elongation

46
Q

regulation of microfilament association

A

filamin homodimers crosslink microfilaments forming gel-like network

47
Q

function of filamin homodimers

A

form dimer bind to itself at one end and other end bind to MF

48
Q

villin

A

similar to gelsolin but not cleave MF

crosslinking therefore bundling

BIOL1025 - Fundamentals of cell biology and physiology (21 decks)

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