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Cell and molecular biology > The Cyatoskeleton > Flashcards

The Cyatoskeleton Flashcards

1
Q

what is cytoskeleton and its function

A

it is proteins organised in fliament structures
function
- making cell shape
-providing mechanical strength
chromosome seperation
intracellular transport of organelles
cell movement

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2
Q

structure of cytoskeleton

A

actin filaments
intermediate filaments
microtubules

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3
Q

accessory proteins to cytoskeleton and why

A

cytoskelton binding, cytoskeleton associated and motor proteins
needed to maintain and regulate properties of each filament

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4
Q

dynamic cytoskeleton

A

made of polymers and can change quickly from polymer and moneymer
no covalent bonds
does not mean chaotic

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5
Q

Intermediate filaments (IF) structure

A

made of several proteins
order
alpha helical monomer
coiled coil dimer
staggered tetramer of two coiled dimer
two tetramers packed together
eight tetramers twisted into a ropelike filament
cross linked to actin and microtubules

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6
Q

intermediate differences from actin and microtubules

A

no defined polarity
no associated motor proteins
do not bind to nucleotides atp or gtp etc
very stable

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7
Q

why is IF useful for diagnostics

A

gene expression of IF is often unaffected
cancer cells lose shape of parent tissue
identification of IF proteins can pinpoint origin of tumors

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8
Q

4 types of IF proteins

A

Cytoplasmic
-Keratins - epthelia
neurofilaments - nerve cells
vimenting/vimentin-related - in connective tissue,muscle cell and neuroglial cell

Nuclear
nuclear lamins - in all animal cells

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9
Q

function of IF

A

Tensile strength; enable cells to withstand mechanical stress aka to stretch
structural support - deformable and reinforce

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10
Q

Keratins- info / location

A

make up hair nails skin etc
form strong network indirectly linked to neighour cells throught desmosome
hemidesmosomes connect epithelial cell to basal lamina
integrind bind to protein in plaques and to laminin in extracellular matrix

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11
Q

Vimenting info

A

required for trans-epithelial migration
endotehlial transmigation - ehite blood cells leave blood stream - process is impaired in vimentin mutant mice

desmin filaments maintain muscle structural integrity - filaments are tehered to z disk and develiop sarcomere - do not contract

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12
Q

Neurofilaments

A

have side arms
fill and pack cytoplasm of neurons
neurons in KO mice make axons with smaller diameter

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13
Q

IF in nucleus

A

meshlike rather than rope
cell shape, fix organelle localisation
present in all nucleated cells
line in inner face of nuclear envolope to strenthen and provide attachment site for chromatin
dissemble and reform at each cell division - different from stable cytoplasmic IF
process controlled by post translational modifications - aka phosphorylation/DEphophorylation

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14
Q

IF binding protein

A

Fillagrin - binds keratin into bundles
Synamin and plectin - bind desmin and vimentin link IF to other cytoskel as well as cell to desmosomes
Plakins - keep contact betwen desmosomes

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15
Q

Microtubules function

A

Establish polarity to movements and structures in interphase cell
participate in chromosome segregation during cell divison
estab;ish cell polarity during cellular movement
produce extracellular movement via cillia, flagella

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16
Q

microtubule structue

A

Made up of tubulin which has three formes alpha beta and gamma
alpha and beta form the tubule and gamma the core
tubulin subunit addition happens on plus end of microtubule with gtp+ tubulin

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17
Q

explain the “cap” of gtp on microtubules

A

growing microtubule
tublin with gtp binds to end addition faster than hydrolysis makes gtp cap

Shrinking
protofilament center peels away
gdp tublin is released to cytosol

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18
Q

explain the term dynamic instablity of microtubules

A

total mass of polymerized tubulin is constant but indicidual microtubules are dynamic
aka they can quickly dissasemble and change shape
goes from growth shrinkage catastrophe and rescue

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19
Q

Centrosome info ?

A

is the primary microtubule nucleation site aka from where micro tubules grow
contains ring of gamma tublin
often abnormal in cancer

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20
Q

cell polarity determined by ?

A

by muicrotubule-organising centers aka centrosome facing decided organisation of organelles and orientation of microtubules

21
Q

why are mictobubles dynamic

A

Microtubule dynamics allow cell to quickly reorganise when building spindle
dynamics allow tubules to prob cytoplasm for specific object and sites aka search and capture

22
Q

Search and capture

A

basically the tubules bound to the capping proteins remain where as the ones that dont are unstable

23
Q

Microtubule associated proteins MAPS

A
  • function as cross bridges connecting MTs
    can affect MT rigidity and assembly rate
23
Q

Microtubule associated proteins MTPS

A
  • function as cross bridges connecting MTs
    can affect MT rigidity and assembly rate
24
MAP functions
katanin - severs microtubules stathmin - binds subunits, prevents assembly
25
Motor proteins
enzymes that convert atp hydrolysis directly into movement along cytoskeletal filaments can move toward plus or minus end carry cargo and mediate MT sliding
26
how MT motor found
cytosol squeezed from axon atp added = movement
27
two fam of MT motor
Kinesins move cargo to plus end in mitosis pariticpate in spindle dynamics dimers of 2 heavy and light chains - microbutbule and atp site on hea, cargo site on tail and ligth chains Dyneins move to minus participate in spindle dynamics power beating of cillia and flagella large protein complex with many subunits
28
Kinesins and related proteins
look different but same motor domain
29
kinesin movement
they walk across MTS using clefts in tubules use atp
30
dynein structure and movement
made up of lots of proteins ankyrin,spectirn etc two classes cytoplasmic -carry in cytoplasm axonemal in cilla and flagella motors that power them
31
celia and flagella
specilaised MT structures cillia- line epithelial tissue in resp track to move matter out line oviduct o push egg non motile - detect signals flagella - allow sperm to swim - done by dynein disease - fertility , respiratory
32
motile axoneme
nine duplets one center and multiple proteins
33
Actin functions
allows cell to adopt different shapes e.g. villi, contractile bundles, sheetlike protusions and contractile ring
34
Actin structure
7nm in diameter less rigid than MTS plus end - fast grow minus - slow monomers polymerise into helical chain
35
Actin binding
using polymerisation actin atpase cleave atp to adp atp hydrolysis actds as a molecular clock older actin filaments with adp are unstable and dissasemble
36
Nucleation of actin
is the rate limiting step in the formation of a cytoskeletal polymer
37
what controls actin structure and function
actin binding proteins they bundle protein, act as motor protein, side binding protein, severing protene
38
explain structure of actin in microvili
plus end near top crosslink of villin and fimbrin and lateral sidearm
39
actin in cell cortex
mesh and used filamin dimer to link filaments
40
Actin polymerisation
can produce pushing force at front of cell can edge cell foward used in phagocytosis - formation of pseudopods intracellular movement and cell to cell spreading of pathogens also drives protusion of membrane
41
model for actin polymerization
Nucleation is catalyzed by proteins including actin related proteins (ARPS) differenses on sides and minus end prevents arps from forming filaments on their own ARP complex nucleates actin growth from minus end allowing elongation on plus end ARP complex can attach to side of another actin filament while remaing bount to minus end of nucleated one arp is more efficient when bond to previous actin filament
42
what do we need for no branching in actin
formins which are able to form straight unbranched filaments . they are dimeric and each subunit has a binding site for actin monomer
43
Diferent proteins useful for actin
Thymosin - actin monomers bound to this are locked and cannot associate to either end of actin filament Profilin- binds to opposit of atp binding cleft, binds to plus end and unable to bind to minus Tropomyosin - stabiliseis filament by binding to 7 adjacent actin subunits prevents other proteins binding to actin cofilin -destabilises actin filaments by twisting tightly and breaking it
44
examples of cross linking assemblies of actin
contractile bundle- stress fibre gel-like networjk - cell cortex tight parallel bundle - protusions of cell
45
contractile vs parallel bundle
contractile - loose packing allows myosin 2 to enter parallel - tight pack no myosin 2 entry
46
Listeria
colonises epithelial cells uses actin to shoot protusion into em uses actin based comet tail to move
47
Myosins
actin based motor proteins convert ATP hydrolisis into movement along filament some move cargo others slide actin actin and atp binding sites in n-terminal head domain walk along filaments

Cell and molecular biology (5 decks)

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