W9 Cytoskeleton and Motility Flashcards
what is the cytoskeleton
a network of interconnected filaments and tubules
what’s the function of the cytoskeleton
cell structure and mechanics
what are the 3 major structural elements
make up the cytoskeleton
microfilaments
intermediate filaments
microtubules
what are microfilaments made of
coiled-coil chain of actin monomers
how small are microfilaments
7nm
what are the main job function of microfilaments
muscle contraction
cell migration
what are the monomers of F-actin microfilaments
polymerized G-Actin
what are intermediate filaments made of
8 overlapping protofilaments
do microfilaments have polarity
yes
do intermediate filaments have polarity
no
what’s the role of intermediate filaments
structural support for animal cell shape
what are intermediate filaments the most at
the most stable
the most diverse
the most insoluble
how are intermediate filaments assembled
2 polypeptides intertwined into a coiled-coil
what are 2 examples of intermediate filaments
desmin
keratin
what are microtubules made of
hollow tube of 13 protofilaments
what is the main job of the microtubules
chromosome movement
what are the 2 microtubules
- cytoplasmic microtubules
- axonemal microtubules
what’s the functions of cytoplasmic microtubules
regulation of cell shape
vesicle transport
axon formation
mitotic spindle formation
what’s the function of axonemal microtubules
cell mobility
how are actin filaments regulated
binding proteins
what does profilin do
binds ATP actin and promotes polymerisation
what does thymosin do
binds ATP actin and blocks polymerisation
what does formins do
bind actin filaments and promote elongation
what does Arp2/3 do
promotes nucleation and branching
where do microtubules get fromed
centrosome
how are microtubules made
- tubulin dimers are formed into oligomers in the nucleation step
- during elongation phase more tubulins are added to ends of microtubules
- at the plateau stage tubulins will treadmill
what is critical concentration for microtubules
tubulin concentration needs to be above the critical concentration for microtubule growth
what is treadmilling of microtubules
adding subunits at plus end
removing subunits at minus end
what is microtubule dynamic instability
populations of MTs will undergo polymerization and depolymerization simultaneously
what is microtubule catastrophe
switch from growth to shrinkage
what is microtubule rescue
switch from shrinkage to growth
what’s the role of GTP in microtubules
provides energy for MT growth
what are MT stabilizing proteins called
tau proteins
what are MT destabilizing proteins called
stathmin
how is the cytoskeleton linked
integrin and cadherin
what do cadherin receptors do
bind onto adjacent cells
what do adherents junctions do
link to F-actin microfilaments
what do desmosomes do
link intermediate filaments
how do eukaryotes mobility systems work
interactions between motor proteins and microtubules
interactions between myosin proteins and mcirofilament
how does Microtubule-based movement work
kinesins or dynein move along microtubules
what are kinesins made of
- globular head that attaches to MT
- coiled helical region
- light chain region
how do kinesins move
using ATP the “foots” will move along the MT
how do dynein motor proteins work
heavy chain and dynactin complex bind and move along MT
how do cilia and flagella move
ATP hydrolysis of dynein proteins
what are myosins
tetramers which are ATP-dependant motors
how does myosin move
globular heads bind to actin and move towards plus end
what are myofibrils made of
sarcomeres
what are thick filaments
bundles of myosin
what are thin filaments
F-actin intertwined with tropomyosin and troponin
what causes muscle contraction
release of Ca2+ to bind myosin head to myosin binding site on actin
what are 2 examples of actin based motility
cytokinesis and endocytosis
how to cells crawl
extend protrusions
how do cells extend protrusions
actin polymerisation so acto-myosin contractility can happen
how do amoebas and white blood cells migrate
amoeboid movement
what is amoeboid movement
protrusions of pseudopodium
what is pseudopodia
depolymerized F-actin
which type of migration is faster amoeboid or extended protrusions
amoeboid movement
how can we prevent amoeboid migration for cancer cells
myosin inhibition
block metastasis
what’s the importance of fast amoeboid movement
immune responses
what does GTP cap do for cytoskeleton
allows tubulin to add to microtubules without falling off
