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CMB 1 > cytoskeleton > Flashcards

cytoskeleton Flashcards

(53 cards)

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1
Q

Which three polymers make up the cytoskeleton

A

microtubules, intermediate filaments, actin filaments

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2
Q

general functions of microtubules

A

organelle positioning,

intracellular transport

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3
Q

general functions of intermediate filaments

A

mechanical strength

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4
Q

general functions of actin filaments

A

cell shape
organelle shape
cell migration

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5
Q

What do accessory proteins regulate?

A
  1. size and rate of filament formation (nucleation)
  2. polymerization/depolymerization
  3. function
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6
Q

Describe the structure of microfilaments

A

helical polymers made of actin, flexible, organsied into 2D networks and 3D gels

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7
Q

describe the structure of IF’s

A

heterogeneous group of filamentous proteins, rope like structure

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8
Q

describe the structure of microtubules

A

hollow tubes made of tubulin

rigid, long, straight

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9
Q

what monomer makes up actin filaments

A

g actin

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10
Q

how does g actin polymerize

A

twisted chain - structural polarity

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11
Q

how thick are actin filaments

A

7nm

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12
Q

What proteins are actin filaments associated with

A

actin binding proteins

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13
Q

what are the three isoforms of g actin

A

alpha - muscle cells

beta and gamma - non muscle cells

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14
Q

how do actin filaments (f-actin) grow

A

addition of g actin at either end

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15
Q

what two factors determine the length of an actin filament

A

concentration of g actin, presence of actin binding proteins (ABPs)

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16
Q

Which 2 ABPs mainly control G actin levels

A

PROFILIN - facilitates polymerization

THYMOSIN B4 - prevents addition of G actin to F actin

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17
Q

What do actin bundling proteins do

A

keep f actin in parallel bundles eg microvilli in epithelial cells

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18
Q

what do cross linking proteins do

A

maintain f actin in a gel like mesh eg cell cortex beneath plasma membrane

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19
Q

what do f actin severing proteins do

A

break f actin into smaller filaments

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20
Q

what do motor proteins do (myosin)

A

transport of vesicles/organelles through actin filaments

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21
Q

function of actin filaments in skeletal muscle

A

arranged in para-crystalline array integrated with different ABPs.
interaction with myosin motors allow muscle contraction

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22
Q

function of actin filaments in non muscle cells

Study These Flashcards
A

cell cortex - forms thin sheath around plasma membrane

associated with myosin forms a purse string ring resulting in cleavage of mitotic cells

23
Q

how do actin filaments aid in cell migration

Study These Flashcards
A
  1. cell pushes out lamellipodia and filopodia at its front - actin polymerization
  2. protrusions adhere to surface - INTEGRINS link actin filaments to ECM surrounding cell
  3. cell contraction and retraction at rear - interaction between myosin and actin filaments
24
Q

what makes IFs tough

Study These Flashcards
A

resistant to detergents, high salt etc.

25
width of IFs
8-12nm
26
nuclear function of IFs
strengthen nuclear envelope
27
how do IFs form a network
join up to desmosomes throughout cytoplasm - withstands mechanical strength when stressed
28
what are the three parts of an IF unit
N terminal globular head C terminal globular tail central elongated rod like domain
29
what do to IF units form
a dimer
30
what do every 2 IF dimers form
tetramere
31
how do IF tetrameres form a filament
bind to each other and twist to constitute rope like filament
32
what types of IF are found in the cytoplasm
KERATIN - in epithelia VIMENTIN (related) - connective tissue, muscle cells, neuroglial cells NEUROFILAMENTS - in nerve cells
33
what are the nuclear IFs
nuclear lamins - in all nucleated cells
34
what do Intermediate Filament Binding Proteins do
linkers of IF structures/stabilize and reinforce IF into 3D networks
35
what is fillagrin
an IFBP than binds keratin filaments into bundles
36
what are synamin and plectin
IFBPs that bind desmin and vimentin, link IF to other cytoskeleton compounds eg actin/desmosomes
37
what are Plakins
IFBPs that keep contact between desmosomes of epithelial cells
38
functions of IFs in the cytoplasm
provide tensile strength | structural support - create deformable 3D network, reinforce cell shape and fix organelle localization
39
functions of IFs in nucleus
form mesh, line inner face of NE to strengthen and provide attachment sites for chromatin
40
role of IFs in cell division
dissemble and reform at each cell division as nuclear envelope disintegrates
41
structure of microtubules
hollow tubes made of tublin, relatively stiff 25nm, polarized
42
microtubules are dynamic - what does this mean
assesmble and disassemble in response to cell needs
43
how is tubulin distributed in the cell
roughly 50:50 free or in filament
44
how do microtubules polymerize
starts at Microtubule Organizing Centre (MTOC) - αandβ heterodimers - growth is polarized; faster at +ve end
45
where is the MTOC in most cells
centrosome - contains gamma tubulin ring that initiates microtubule growth
46
function of microtubules in intracellular transport
act like railway tracks for molecular motors - different motors for different cargoes - directionality is vital
47
function of microtubules in organelle positioning
organizes their position - providing polarisation of cells - directionality is vital
48
how do microtubules contribute to rhythmic beating of cilia and flagella
motile processes w/ highly organized microtubule core
49
what is an axoneme
core of cilia and flagella
50
what constitutes an axoneme
9 pairs of microtubules around 2 central axonemes
51
what is bending of cilia and flagella driven by q
motor protein dynein
52
whats the basal body
at base of tubule, controls axoneme assembly
53
big microtubule examples
cilia - resp tract - sweeps mucus and debris from lungs | flagella on spermatozoa

CMB 1 (3 decks)

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