cytoskeleton Flashcards
3 fibers that make up eukaryotic cytoskeleton
microfilaments
intermediate filaments
microtubules
microtubules structure
comprised of alpha and beta tubulin dimers
hollow tube shape
microtubules function
cell shape movements
movement of chromosomes during cell division
used by cell to move organelles, proteins, viruses
has specialized motor proteins
microtubules dynamic instability
constantly switching between growth and shortening at microtubules ends
treadmilling microtubules
there are areas that dimmers were more likely to fall off or more likely to join the microtubules at
dimers that fell off came back and joined the microtubule at the end where it was more likely to join back
what eukaryotic motility structures do the microtubules comprise
flagella
cilia
specialized motor proteins of microtubules
kinesin
dynein
kinesin
is the motor protein that moves towards the plus end
end of microtubule where polymerization occurs at a higher rate (more dimers being added than removed)
dynein
the motor protein that moves towards the minus end
minus end: end of microtubule where dimers fall off at a higher rate
what allows movement of motor proteins
what allows movement of motor proteins
ATP hydrolysis changes the shape of the proteins, allowing them to move along the microtubule
how do flagella and cilia differ
in terms of movement and length of the structures
flagella
rotational movement
cilia
whip like motion
MTOCs
microtubules are organized in cells by MTOCs
barrel shaped structures made of 9 sets of triplet microtubules
usually found very close to the nucleus
surrounded by an ill-defined pericentriolar matrix
microfilaments - composition
comprised out of actin monomers
f actin are actin that are bound to microfilaments
g actin are floating actin
actin bind only when carrying ATP
microfilaments function
cell shape
cell movement
plus and minus ends of micro filament depend on rate of addition and falling off of actin
polymerization –> gactin turn into factin
depolymerization –> factin –> gactin
treadmilling with microfilaments
governed by ATP hydrolysis
actin with bound ATP join the microfilament
actin with bound ADP fall off
motor protein
microfilaments
myosin
use ATP to move in both directions
different microfilaments and their role in cell shape
stress fibers: bundles of actin filaments that help maintain skin cell shape and keeps cells elongated
focal adhesions
places where stress fibers attach to the plasma membrane and anchor cells to the substrate or to adjacent cells
microvilli
protrusions filled with stable actin bundles projecting from the cell surface
intermediate filaments
many different intermediate filament proteins exist but they all build similar cable like filaments
very stable networks
provide structural support
lamins
not dynamic
outside of the plasma membrane
plant cells are encased in
cellulose which acts as a cell wall
primary cell wall and a secondary cell wall laid on when the cell stops expansion
two cell walls stuck together by middle lamella
plant cells linked to neighboring cells through
pores that link plasma membranes called plasmodesmata
animal cells dont have a cell wall
how does this change things for them
less rigid
anchor themselves to the ECM
matrix of glycoproteins and carb-containing cells
what three adhesion molecules do animal cells have
tight junction
sealant on ship
desmosome
less adhesion
gap junction
small protein pores that allow ions sugars and small molecules to pas between cells
