Cytoskeleton Flashcards
What is the purpose of the cytoskeleton
- cell movement
- cell shape
- delivery of cargo
- intracellular location of organelles
three types of cytoskeletal proteins
- intermediate filaments
- actin filaments
- microtubules
form a network throughout the cell, nuclear lamina, high tensile strength
intermediate filaments
intermediate filaments are assembled similarly to a
twisted rope
assembly of intermediate filaments
- alpha helical rod of monomer
- coil-coil dimer
- staggered tetramer of two coiled dimers
- two tetrameters packed together
- 8 tetrameres — filament
2 main classes of intermediate filaments
- cytoplasmic
- nuclear
3 types of cytoplasmic intermediate filaments
- keratin filaments
- vimentin
- neurofilaments
IF found in epithelial cells
keratin filaments
IF found in CT cells, muscle cells, and glial cells
vimentin
IF found in nerve cells
neurofilaments
class of intermediate filaments under nuclear intermediate filaments
nuclear lamina (in all animal cells)
What is the disease associated with keratin?
epidermolysis bullosa simplex
(do not form keratin filaments in the skin, skin has mechanical stress blisters)
mutation in keratin 5 and keratin 14
What disease is associated with the nuclear laminin?
progeria
- long hollow tubes
- can rapidly assemble and disassemble
- form basis of mitotic spindle, cilia, and flagella
microtubules
what are the organized centers that microtubules form
- centrosomes
- mitotic spindle poles
- basal body of cilia
form of a microtubule
alpha and beta tubules that make a protofilament, 13 protofilaments
+ part of tubulin
beta, away from body cell
- part of tubulin
alpha, towards cell body
when microtubules switch back and forth between polymerization and depolymerization
dynamic instability
a type of drug that can affect microtubules, will bind and stabilize microtubules (gain more tubular, more growth)
taxol
a type of drug that can affect microtubules, binds tubular dimers and prevents polymerizations (loose tubulin proteins)
colchicine, colcemid, vinblastine, cincristine
guide the transport of organelles, vesicles, and macromolecules
microtubules
motor proteins that move along cytoplasmic microtubules belong to two families:
- Kinesin
- Dyneins
generally move towards the plus end of microtubule (outward from the cell body)
kinesin
move toward the minus end (toward cell bod)
dyneins
use ATP to walk down microtubules
kinesins
longer, wave like motion
flagella
small hair like projections, whip like motion
ciliar\
essential for cell movement
actin
how are microtubules arrange in flagella and cilia
9+2
actin bound with ATP
polymerizes
actin bound with ADP
loose and depolymerizes
actin needs —- while microtubules need —
ATP, GTP
bind actin monomers to prevent them from being added to filaments
thymosin and profilin
promote filament formation, actin-related biding proteins
formins and ARP’s
cell crawling depends on
actin
3 steps of cell crawling:
- cell pushes out protrusion at the front (leading edge)
- the protrusions adhere to the surface
- the rest of the cell drags itself forward as a result of anchorage points
two filaments at the leading edge that allows movement
lamelipodium, filopodium
sheet like
lamelipodium
finger like projection
filopodium
actin arrangement is regulated by the
Rho family of GTPases
muscle contraction is dependent of the interaction of
myosin and actin
