microtubules 1 Flashcards
what does the cytoskeleton comprise of
-microfilaments
-microtubules
-intermediate filaments
who first observed microtubules?
keith porter
what are the 2 different tubulin genes?
alpha and beta tubulin
how many protofilaments is the hollow tube made of?
13
what are the 2 roles of microtubules?
-transport
-structure to cells
where do microtubules emerge from?
centrosome (near the nucleus)
true or false, microtubules are found in certain eukaryotes
false, all eukaryotes
where are 3 important things that microtubules are found in?
-mitosis (microtubules form the mitotic spindle)
-neural functions: microtubules are jam packed in neurons
-cilia: trachea/lungs lined with cilia and helps get rid of of waste
how are microtubules organized in animal cells?
-organized by the centrosome in radial array
-negative ends near centrosome
-positive ends in periphery
true or false, microtubules are static structures
true, they are continuously built, and broken down (shoot from centrosome, out to cell periphery)
true or false, microtubules are “roadways” for intracellular transpot
true
true or false, neurons are slightly packed with microtubules
false, they are densely packed
what is the difference between the organization of microtubules in the axons and in the dendrites?
-axons: all + ends of microtubules are pointing outwards
-dendrites: mixed polarity in dendrite (pointing in diff directions)
what determines the density of the packing of microtubules in neurons?
microtubule associated proteins
what type of structure are cilia?
specialized microtubule-based structures (contain microtubules)
true or false, cilia and flagella are completely different
false. flagella are also cilia
what are flagella? where can we find them?
tail used for swimming, type of cilia. sperm tail (allow them to swim), and chlamydomonas arms (also to swim)
what do we mean by the 9+2 symetry?
refers to the inside of the cilia. 9 microtubule doublets on outside and then central pair in the center
what is a microtubule doublet?
two microtubules stuck to each other. one is whole, and the other is cracked open and stuck to side of the other one
what are microtubules made of?
tubulin heterodimers
what is a tubulin heterodimer?
an alpha and a beta tubulin put together
true or false, you can find alpha and beta tubulin alone in the cytoplasm
false, alpha and beta tubulin are always together
what drives the polymerization of microtubules?
hydrolysis and exchange of GTP in and out of beta tubulin pocket drives polymerization process
true or false, alpha and beta tubulin come from same gene
false, different genes
why is tubulin a GTPase?
it uses GTP hydrolysis to drive its polymerization
how was tubuliin first identified?
first identified as the target of the drug colchicine
what does colchicine treat?
gout
where did colchicine first appear?
in the ebers papyrus which is the oldest medical document
what does colchicine do?
binds to microtubules
why are the rate constants for the polymerization of microtubules
cause there are 13 diff places where incoming tubulin could bind, and we dont know what it looks like when its growing
whats at the negative end of the microtubule?
alpha tubulin
whats at the positive end of the microtubule?
beta tubulin
which end of the microtubule has the highest critical concentration?
negative end
what does the loss of the GTP cap lead to?
rapid shrinkage
what does the GTP cap do?
keeps the microtubule stale
what state makes microtubule fall apart?
GDP state
when does a catastrophe happen?
if GTP cap is lost: GTP hydrolysis happens before addition of GTP-tubulin
when is tubulin curved?
when its falling apart
when is tubulin straight?
when its growing
what are the curved GTP complexes?
-Rb3
-darpin
-TOG1
what are the intermediate complexes?
GMPCPP
what are the straight complexes?
1JFF
what allows the cell to quickly restructure their microtubules?
dynamic instability
what does dynamic instability allow the cell to do? give a specific example
allows it to be able to easily control its cytoskeleton. for example, as the cell goes into mitosis, need radial array of microtubules, so it will break down old ones, and build completely new one
how did they discover dynamic instability?
-purifiy tubulin from brains in cuvette
-shoot ultraviolet light through cuvette
-by sticking needle into cuvette and rapidly pushing solution through narrow gauge needle, breaks microtubules in half, which leads to a decrease in polymer length
-since center is now unstable cause no more caps, whole thing falls apart
-they observed that after it breaks down, it would rebuild
what is the link between absorbance and polymerization of tubulin?
if polymers form, absorbance increases
which cytoskeleton component is the target of a broad class of chemotherapy drugs? give an example
microtubules
example: taxol
what does taxol do? what is the downside of it?
freezes microtubules, but it freezes ALL microtubules, so it ends up also freezing neurons since they contain lots of microtubules, which leads to neuropathic pain
what is an alternative to taxol, but not enough reasearch has been done about it (No funding)?
DZ-2384
apparently would not cause neuropathic pain
how do tubulin dimers associate?
head to tail (beta on top, alpha at the bottom)
