2.2: Cytoskeletal Networks Flashcards
polarized cells can: (3)
- define inside vs outside
- have different functions at different cell regions
- transmit signals
what can polar microtubules do?
transport vesicle and proteins to different ends of the cell
what can polarized actin do
define cell shape and behaviour
intermediate filaments can also contribute to cell _________
polarity
the cytoskeleton undergoes __________ rearrangements
dynamic
describe how microtubules and actin contribute to interphase crawling/migrating cell, mitosis, cytokinesis
- interphase crawling/migrating cell: microtubules radiate from cell centre, actin enriched at cell cortex
- mitosis: microtubules form mitotic spindles, actin at cell cortex disassembles
- cytokinesis: microtubules keep cell components separate, actin forms the contractile
== main point is that you can rearrange the cytoskeleton
which monomeric proteins form tubulin dimers
alpha (-) and beta (+) tubulin
tubulins can bind and hydrolyze ____
gtp
tubulin heterodimers assemble head to tail to make what
polarized protofilaments
___ protofilaments associate to form a hollow ____________
13, microtubule
what conditions lead to faster depolymerization
100x faster at an exposed d form heterodimer
describe the growth of microtubules
- microtubules undergo dynamic instability.
- after they’ve been in the protofilament for awhile, b tubulin will cut the gtp to gdp (a tubulin always gtp)
- growing and shrinking only happens at the end - if you have gtp bound heterodimers at the end you’re more likely to have growth (gtp cap)
- if there is random loss of the gtp cap it’ll lead to rapid shrinkage
which form of tubulin helps to nucleates/stabilizes microtubules and which tubulin does it interact w
γ-tubulin, interact w a-tubulin at the minus end
what does γ-tubulin protect microtubules from at the - end
depolymerization
____-ends in microtubules grow away from the nucleation site
plus-ends (b)
in animal cells, where is γ-tubulin found nearby and state other features of this
γ-tubulin is found NEAR centrioles, there is a pair of them in the centrosome. γ-tubulin ring complexes (nucleating sites) are on the pericentriolar material (γ-tubulin attaches to accessory proteins in the γ-tubulin ring complex ie augmin) - this is what nucleates/stabilizes the - end.
γ-tubulin can only be found on other microtubules
γ-tubulin can be found on other microtubules leading to branches, what protein joins the γ-tubulin to the other microtubule
augmin
explain how vesicles and organelles can be transported along microtubules
- maps = microtubule associated proteins
- some kinesins can walk towards + end
- some dyneins can move towards the - end
- both motors can hold onto vesicles or organelles with their other domain
- both motors use atp hydrolysis for energy
contrast how fish eg tilapia can change color using microtubule motors
- dark fish: kinesins and dyneins compete for pigment-containing vesicles (melanosomes)
- light fish: kinesins are inhibited, vesicles are moved to minus ends near centrioles due to dyneins
Which of these statements about microtubules is true?
a) When a centrosome is present, each microtubule contains a variable number of protofilaments.
b) Long, growing microtubules will contain GTP and GDP.
c) A cell with many microtubules will not have any actin filaments.
d) ɣ-tubulin stabilizes microtubule minus ends by anchoring them onto a cylindrical centriole core
b.
a is wrong bc it doesn’t matter if centrosome is present. c is wrong bc it’s not mutually exclusive. d is wrong bc it’s not on the centrioles, its on γ-tubulin ring complexes.
actin monomers can bind and hydrolyze atp/gtp
atp
polar actin monomers assemble into polarized actin filaments, usually ___ strands twisted
2
for actin filaments, which conditions is depolymerization much faster
at an exposed d form monomer
soluble actin subunits are in t/d form, polymers are/are not a mix of t form and d form
soluble actin subunits are in t form, polymers are a mix of t form and d form
