Cytoskeleton Flashcards
(26 cards)
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
polarity, what each end does, how is it stabilised
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:
-granules (in cells) attach to microtubules
-aggregate centre of cell
-granules move = controls colour
-increase cAMP = dispersed melanosomes
decrease = aggregated
what makes microtubules work incorrectly and correctly
-colchizine = no spindle formation and mitosis
colchizine + single tubulin -> prevents polymerisation
cannot bind to tubulin once it has polymerized into a microtbule
-taxol does opposite (work correctly)
How do motor proteins use microtubules to move organelles?
-Microtubules scaffold position organelles
-Motor proteins use ATP hydrolysis to move microtubules along
-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
what does the kinesin family do
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
what made of, how they exist, what they help, what they form and determi
actin
exist in filaments, bundles or networks
help entire cell or parts of cell move
determine cytoplasmic streaming
form pseudopodia
wha does immunostaining in fish keratocytes show
intermediate filaments and microtubules present in edge of cells around nucleus
how does food poisoning affect actin
in 5 steps how they get rid of bacteria from food poisoning
1) bacteria enters (phagocytosed)
2) phagosome breaks down membrane
3) nucleates actin filaments at one region of surface
4) Actin fil 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
simiar motor units but diff adaptor domains = can bind to cell component
how is the plasma membrane polarised (step by step)
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 cell using TCR
2) signal to cortex of T cell
3) alters cytoskeleton
4) Actin filament proteins reoganise
5) Centrosome reorients = moves 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
