lec 4-5 cytoskeleton Flashcards
how does cytoskeleton help cell structure
cell shape/polarity
cell motility/plasticity
segregation of chromosomes
how does cytoskeleton involved with cell transport
endocytosis
secretion
segregation of organelles
communication between organelles
cytoskeleton and disease
route of entry for bacterial and viral pathogens
pathogens can exploit cytoskeleton to cause damage within a cell
mtoc
microtubule organising centre
role of microtubules in interphase
make up flagella - cell motility
if cytoskeleton is abnormal then affect cell shape/structure
positioning and movement of organelles
role of microtubules in mitosis
attach to chromosomes and pull them apart
ensure daughter cells have same amount of chromosome
partition of organelles
regulate cytokinesis
structure of microtubules
made of alpha and beta tubulin monomers that form dimers
heterodimers
made of alpha and a beta monomer in a dimer
bind to others to form microtubules
very straight and stable
minus end microtubule
alpha tublin
plus end microtubule
beta tubulin
controls dynamic of microtubules
GTP cap
dynamic instability of microbtubules
constantly growing and shrinking
polymerising
catastrophe
transition between growth and shrinkage
transition between shrinkage and growth
rescue
rate of shrinkage
depolymerisation
GTP
Guanine TriPhosphate
hydrolysed microtubules
less straight and stable
depolymerise
formation of microtubules
nucleation
pericentriolar material
PCM makes up the centrosome
surrounds the two centrioles
contains proteins for microtubule nucleation
effect of temperature on microtubules
high temperature favours polymerisation/growth
colchicine drug
inhibits polymerisation of microtubules
used to treat gout
paclitaxel drug
favours GTP state of tubulin
used in chemotherapy to destabilise mitotic spindle
MAPs
microtubule associated proteins
stathmin
binds to free tubulin and prevents it binding to microtubules
motor protein
move along microtubule filaments using energy from hydrolysis of ATP
E.G. kinesin, dynein
kinesin
move towards plus end of microtubule filament
dynein
moves towards minus end of microtubule filament
functions of actin
cytokinesis - contractile ring cell adhesion cell migration transport of cargo between cells cell polarity
actin structure
G actin polymerises to form linear F actin
2 filaments form a thread
plus end actin
barbed
molecules added
minus end actin
pointed
molecules removed
treadmilling
molecules added to plus end of actin and removed from the other
filament moves in plus end direction
function of branch filament
push plasma membrane
nucleation of straight actin filaments
formins
nucleation of branched actin filametns
Arp 2/3 complex
nucleation by formins
2 domains - homodimer
2FH1 domain and 2FH2
binds to plus-end of existing filament
nucleation by Arp 2/3
Arp2/3 have similar structure to actin
serves as nucleation sites for new actin filaments
actin binds to complex
causes elongation
what causes branching in actin filaments
Arp2/3 complex nucleation
Arp 2/3 complex
7 protein subunits
found at minus end of actin
more F-actin..
..means more polymerisation induced
myosin
motor protein
head domain binds to actin energy used from hydrolysis of ATP moves by temporarily detaching from filament moves towards barbed plus end short distances only
plasma to synapse is long distance…
microtubule transport more effective
why do intermediate filament proteins lose their polarity
monomers interact in both parallel and anti-parallel manners to form dimers
why is no energy needed for formation of intermediate filaments
intra-binding
many N- and C- terminals, they bind to one another
causes them to be very strong
where are intermediate filaments foudn
tissues: connective epithelial muscual nervous
keratin monomers
bind to form intermediate filaments
found in epithelial tissue
hair/nails/cornea
