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Cell and molecular biology > The Cyatoskeleton > Flashcards

The Cyatoskeleton Flashcards

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AP® Biology flashcards Biology 101 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
Q

MAP functions

A

katanin - severs microtubules
stathmin - binds subunits, prevents assembly

25
Q

Motor proteins

A

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
Q

how MT motor found

A

cytosol squeezed from axon
atp added = movement

27
Q

two fam of MT motor

A

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
Q

Kinesins and related proteins

A

look different but same motor domain

29
Q

kinesin movement

A

they walk across MTS using clefts in tubules use atp

30
Q

dynein structure and movement

A

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
Q

celia and flagella

A

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
Q

motile axoneme

A

nine duplets one center and multiple proteins

33
Q

Actin functions

A

allows cell to adopt different shapes
e.g. villi, contractile bundles, sheetlike protusions and contractile ring

34
Q

Actin structure

A

7nm in diameter
less rigid than MTS
plus end - fast grow
minus - slow
monomers polymerise into helical chain

35
Q

Actin binding

A

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
Q

Nucleation of actin

A

is the rate limiting step in the formation of a cytoskeletal polymer

37
Q

what controls actin structure and function

A

actin binding proteins
they bundle protein, act as motor protein, side binding protein, severing protene

38
Q

explain structure of actin in microvili

A

plus end near top
crosslink of villin and fimbrin
and lateral sidearm

39
Q

actin in cell cortex

A

mesh and used filamin dimer to link filaments

40
Q

Actin polymerisation

A

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
Q

model for actin polymerization

A

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
Q

what do we need for no branching in actin

A

formins which are able to form straight unbranched filaments . they are dimeric and each subunit has a binding site for actin monomer

43
Q

Diferent proteins useful for actin

A

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
Q

examples of cross linking assemblies of actin

A

contractile bundle- stress fibre
gel-like networjk - cell cortex
tight parallel bundle - protusions of cell

45
Q

contractile vs parallel bundle

A

contractile - loose packing allows myosin 2 to enter

parallel - tight pack no myosin 2 entry

46
Q

Listeria

A

colonises epithelial cells
uses actin to shoot protusion into em
uses actin based comet tail to move

47
Q

Myosins

A

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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