Cytoskeleton Flashcards
prokaryotes cytoskleton
do not have cytoskleton, have structural proteins to allow them to maintain shapes
how can eukaryotic cell be sptially organsied by cytoskeleton proteins which are 2000x smaller
polymerization
each major types of cytoskeleton proteins are formed from identical subunits
what do cytoskeleton proteins form into
helical polymers
what do microtubules provide
rigid intracellular skeleton
tracks for motor proteins to move along
form from polymerisation of tubulin monomers
describe microtubules
polar
one end rapid growth
other loses subunits if not stablised
stabilised by embedding in centrosome
centrosome lies nect to nucleus in centre of cell
how are microtubules polar
tubulin polymerises, one end has alpha subunits exposed other beta subunits
elongation typically occurs at positive end
what are centrosomes
main microtubule organising centre in animal cells (MTOC)
mitosis
PCM = proteins responsible for microtubule nucleation and anchoring
what grows out of centrosome
hundreds of microtubules
highly dynamic (constantly growing and shrinking in size)
visible use for microtubules
fish scales change colour
celsl contain granules that atach to microtubules
aggregate centre of cell
movement of granuels controls colour
increase cAMP = dispersed melanosomes
decrease = aggregated
what are microtubules sensitive to
colchizine binds to single tubulin and prevents polymerisation
cannot bind to tubulin once it has polymerized into a microtbule
exposure of cell to colchizine prevents spindle formation and celll division
taxol does opposite
motor proteins use
microtubule scaffolds to position organelles
enery from repeated cycles of ATP hydrolysis allows motor proteins to move along microtubules
diff motor proteins move along diff filaments in diff directions
two types of motor proteins
kinesin FAMILY = move towards +
dyneins = move towards -
what organelles have which motor proteins
Endoplasmic reticulum = kinesins
golgi apparatus = dyneins
kinesin family
not a single protein
-Organelle movement
-Trnasport of RNAs and proteins
-Assembly of ciliar/ flagella
-Signalling pathways
-Mitotic spindle formaiton and chromosome movement
two types of dynein
cytoplsamic dynein = positioning of nucleus and organelles
ciliary dynein = cilia and flagella, cell locomotion (sperm movement)
describe microfilaments
actin
exist in filaments, bundles or networks
determine
help entire cell or parts of cell move
cytoplasmic streaming and formation of pseudopodia
wha does immunostaining in fish keratocytes show
intermediate filaments and microtubules present in edge of cells around nucleus
how does good poisoning affect actin
1) bacteria enters by phagocytosed
2) phagosome uses enzyme to break down membrane
3) nucleates actin filaments at one region on surface
4) Actin filaments grow and push bacterium in front of them
5) Form micro-spike in cell membrane with bacterium at tip
6) Engulfed by neighbouring cell, bacteria in new cell without exiting = exposed to immune system
what does myosin do
moves along actin filements
skeletal muscle
have simiar motor units but different adaptor domains which allow them to bind to cell components
polarisation in plasma membrane
1) plasma senses difference on one side
2) transmembrane signal generation
3) actin cortex reorganised beneath membrane
4) Centrosome moves to that part and repositions internal membrane
5) Cell with strong directional focus formed
how do Cytotoxic T cells work
1) recognise infected cells surface using TCR
2) sends signal to cortex of T cell
3) alters cytoskeleton
4) Proteins with actin filaments reoganise under zone of contact
5) Centrosome reorients, moved its microtubules to ZOC
6) microtubules position golgi under ZOC
7) focusses t cel to target cell
what are intermediate filement protein monomers
elongated fibrous molecules
non oplarised
what do vimentin related proteins form
polymers of single protein species
do kertain and vimentin co polymerise
no but found in same cell
what happens when kerain gene in basal layers of epidermis are disrupted
skin of sufferes susceptible to mechanical injury and blistering
