The Cytoskeleton Flashcards
The cytoskeleton is also called the
the skeleton of our cells
3 components of the cytoskeleton
intermediate filaments, microtubules, and actin filaments
what is the location of intermediate filaments
area where cells come in contact with one another
what do intermediate filaments help with?
anchoring the cells with cell junction
where do microtubules start and go out too?
start in the nucleus and go out to the cell membrane
where do actin filaments lie
beneath the plasma membrane and help with cell shape
what helps with providing strength to axons and gives meshwork inside the nucleus giving shape and structure
intermediate filaments
whats in the middle of microtubules and actin filaments
intermediate filaments
where are intermediate filaments more prominent
neurons
can motor proteins figure out direction with intermediate filaments
no they can not
in intermediate filaments, the alpha helix wraps around one another to form a
coil coil dimer
is there polarity in the structure of intermediate filaments
yes
when do you lose polarity in an intermediate filament
tetramer
how do motor proteins know where to go
they look for polarity
are intermediate filaments hard or easy to break down
they are very hard to break down
how many tetramers do you put together to form the intermediate filaments
8 tetramers
definition for a molecule cannot be broken by the energy of the environment
thermal stability
how must intermediate filaments be disassembled
with cellular machinery
neurofilaments are composed of
intermediate filaments
what are essential for growth and stability of neurons
neurofilaments
what intermediate filaments is abundant in hair and nails
keratin
a genetic skin disorder from mutations in keratin is called
epidermolysis bullosa simplex
what share structural similarities
microtubules and actin
are noncovalent bonds strong or weak
weak
microtubules are composed of
tubulin protein monomers
actin filaments are composed of
G-actin protein monomers
single protofilaments are
thermally unstable
where are multiple protofilaments assembled and disassembled usually
at the ends
microtubules originate from
MTOC
MTOCs are also called
centrosomes
microtubules are crucial for
cell division
what look like long straight cylinders / drinking straws
microtubules
the tubulin monomer protein is composed of an
alpha-beta heterodimer
how does a microtubule assemble
alpha beta alpha beta
what are the ends of the microtubules called
beta and alpha tubulin
the beta end of a microtubule can bind and hydrolyze
GTP
is beta tubulin a slow or fast hydrolyzer
slow
where is GTP stuck in the microtubule
alpha end
can GTP be hydrolyzed in the alpha end of a microtubule
no it is stuck
how many protofilaments does it take to form a hollow straw
13
alpha and beta contacts in what
heterodimer and filament
any changes that need to happen in a microtubule occur where
one end or the other
microtubule filaments are nucleated from the
centrosome
motor protein in the MTOC can sense alpha and beta which tell it if it is going
inside or outside
what is around the pair of centrioles
pericentriolar
what are microtubules growing from gamma tubulin ring complexes of the centrosome called
y-TuRC
what side are the MTOCs at
minus side
what side are the TuRC at
plus ends
in the MTOC do the negative or positive sides face out
the plus ends face out
is GTP- tubulin or GDP-tubulin more stable
GTP-tubulin
where is majority of microtubule growth
the plus end
the plus end of microtubules are fast which means
hydrolysis lags behind
most of the minus ends are held at the? which mean
MTOCS, no growth or loss
whenever we add tubulin to a microtubule its in its
GTP bound form
is t-tubulin being added to both sides of the microtubule
yes, but falls off the minus end as fast as it is added
why does the t-tubulin fall off the minus end so fast
is it hydrolyzed right away to d-tubulin
growth to shrinkage is called
castastrophe
shrinkage to growth is called
rescue
growing is when
addition of GTP tubulin outpaces hydrolysis
shrinkage is when
hydrolysis has outpaced addition
if the t-tublin addition to the plus end slows, then
GTP cap gets hydrolyzed
does shrinking and growing happen together or independently
independently
what bundles filaments into higher-order structures by stabilizing and cross-linking
MAPs
what protein binds to the microtubule to help prevent it from being broken down
tau
what are some linkage points between microtubules and cancer
cell division, microtubules is what pools apart the sister chromatids, and improper sister chromatid separation can lead to cancer
what is the smallest of the cytoskeleton elements
actin
actin forms a helical polymer how many nm in diameter
8 nm
what is a main component of actin
muscle contraction
actin is also called
microfilaments
what does actin bind too
ATP
what does tubulin bind to
GTP
actin can hydrolyze ATP to
ADP
is there a plus and minus end in actin
yes
is actin a slow or fast ATPase
slow
growth is mainly at what end of actin
the plus end
actin polymers filaments are nucleated by
ARP2/3 complex
where does ARP2/3 bind
the minus end
what does ARP2/3 do
binds to minus end and facilitates growth outward from the plus end
the ARP is usually at the
cell periphery
ARP2/3 arranges into what upon activation
scaffold
where is gamma turc usually
at the nucleus
does gamma turc or arp facilitate branching
arp
how many filaments can ARP2/3 complex bind to
2 at once
actin filament end can be
capped for stability
what is happening in listeriosis
an intracellular parasite hijacks ARP2/3 and uses actin like a rocket
what has loose packing which allows myosin II to enter the bundle
contractile bundle
what consists of a contractile bundle
actin filaments and alpha actinin
what bundle packs much tighter and prevents myosin II from binding
parallel bundle
what consists of a parallel bundle
actin filaments and fimbrin
what is fimbrin
smaller alpha actinin that results in tighter packing of actin
actin bundles give cells their
shape
what do intermediate filaments anchor the cells to
gut epithethial cells
what determines and maintains the polarity of a cell
cytoskeleton
what forms contractile rings and pinches two daughter cells in distinct units
actin
a mutation in smooth muscle cell actin correlates with higher instances of premature onset of
coronary artery disease and premature ischemic strokes
Fluid shear stress plays an essential role in
maintaining vascular homeostasis
laminar blood flow with higher FFS means
atheroprotective areas
turbulent blood flow with low FSS means
atheroprone areas
what do motor proteins look for on a cytoskeleton element
polarity
does actin respond to inflammatory stress
yes
microtubule motor proteins are
kinesin and dynein
actin motor proteins are
myosin
what side does kinsein walk towards
plus end
what side are motor domains on kinesin
n terminus
what side are cargo domains on kinesin
c terminus
what side of kinesin does cargo bind
c terminus
multiple rounds of ATP hydrolysis allow cyclical binding and release of the
kinesin heads
does kinesin walkins consume a lot of atp
yes
kinesin requires what pathway and what coat proteins
exocytic pathway and COPII coats
what do dyneins require
accessory proteins to binds to its cargo
what direction are dyneins going in
the minus side
what does dynactin use to bind to the vesicle
dynactin complex
what pathways would dynein use
endocytosis, clathrin and retrieval
what does nocodazole do
depolymerizes microtubules
where does myosin move towards
the minus end
does myosin walk
no it is more like a power stroke
what does myosin use to facilitate myosin heads binding to actin to push along the actin filament
ATP binding hydrolysis
skeletal muscles are bundles of
muscle fibers
how are muscle fibers formed
by fusion of many individual cells during development
what are thin filaments in myofibril structure
actin
what are thick filaments in myofibril structure
myosin
sarcomeres are
one z disc to another
what causes muscle contraction? when comes together or goes apart
comes together
what prevents myosin from binding
tropomyosin
what happens which exposes myosin binding
Ca
myosin permits
cell movement
cells are able to crawl along a substrate by using a
four-wheel drive type mechanism
what do we rely on when we want to push the plasma membrane forward
ARP2/3 because it provides branching
true or false: anything that happens in the cytoplasms is indirectly connected to the nucleus
true
what proteins do we use for indirect coupling
Kash and SUN
cells are indirectly couples across their
cell-cell junctions
what can we target in order to target cancer
microtubules
what is a very common chemotherapy medication which prevents microtubule disassembly, thereby killing rapidly dividng cells
taxol
what stabilizes MTS and prevents cell division
taxol
what sends a signal
action potential
what is the source of depolarization
the opening of ion channels
order of a nerve stimulus
closed, open, inactivated, closed
what happens during synapse for action potential
where we convert the electrical signal into a chemical signal and back to an electrical signal
what is rapidly removed from cleft after activation of post-synaptic cell
neurotransmitter
what causes muscle contraction
release of calcium
muscle contraction is active or passive
passive process
what has a low concentration of ca2+ when muscle is releaxed and a high concentration when contracted
sarcoplasm
ATP hydrolysis changed the conformation of the calcium pump, allowing it to move calcium ions from
sarcoplasm into sarcoplasmic reticulum
