cytoskeleton I 2.3 Flashcards
what is the progression of the size of cytoskeletal components?
actin is smallest, then intermediate, the microtubules
what is the distribution of cytoskeletal elements in a cell?
you have actin making up the scafold of microvili. intermediate filaments interspersed off the desmosomes. and micotubules running up and down ready to move the cell
what bond holds cytoskeletal monomers together and why?
no n covalent bonding because you want it to be dynamic and be able to assemble and disassemble in a moments notice
what does it mean for intermediate filaments to be arranged in an antiparallel tetramer
it means it will have no polarity thus cannot be used as a motor protein
how does the growing chain of actin or mocrotubulesuse the energry from the ATP or GTP to grow
it doesnt. there is no energy of hydrolysis used. The ATP and or GTP to ADP/ GDP is really meant as a signal to grow or shrink for the polymer.
what is the rate limiting for the growing chain?
“nucleation” which essentially means the binding of the ATP or GTP
what is the order of events in the growing chain in relation to the adding the polymer vs. hydrolysis of ATP to ADP
the addition of the polymer to the growing chain happens first and then the NTP is hydrolysed to NDP after. theres a faily significant lag of a few polymers
explain dynamic instability and what role GTP plays in microtubule growth
dynamic instability is the phenomenon whereby when GTP is bound to the + end of the growing microtubule chain, it continues to grow but when the GTP cap is taken off, then the microtubule rapidly disasembles (catastrophe) until another GTP cap is put back on (rescue) and the chain grows again.
what role do actin binding proteins play in the stability
each actin filament can either stay as a filamentous polymer or assenmbled into different structures by the actin binding proteins
what is te difference between cilia/flagella and centriole in structure.
they are both made of tubulin but the cilia and flagella have a 9 doublets and a doublet in the middle but centriole has 9 triplets with nothing in the middle
Who is Tau and what is its function?
Tau is a microtubule associated protein. they bind to and stabilize or destabilize the plus and minus ends of the microtubule
what is the physiological consequence of consuming colchicine?
colchicine depolymerizes microtubules
what does Taxol do?
binds and stabilizes microtubules. this prevents cell division (centrioles cannot assemble and disassemble) they are used in cancer treatment
what is the process by which actin maximizes its force of movement?
by creating as many +/ growing ends as possible. It can
- nucleate more actin filaments (thus grows) (Arp2/3 complex in Rho dependent signalling
- cut one filament which creates two positive ends
- form branches from existing actin filaments
Arp dependent polymerization is involved in
nutriphil migration to infection site
invasion of cancer cells
bacterial infections
clatherrin dependent endocytosis
