Cytoskeleton Flashcards
Describe intermediate filaments
for strength; usually not dynamic; LACK structural polarity
describe microtubules
organize cytoplasmic organelles, move xs, are dynamic
describe microfilaments
actin, dynamic, important for cell shape determination
What complex allows for branching of actin for lamellipodia formation?
actin related complex
ARP
in which direction does Myosin-II head move?
toward + end of actin filament
how is muscle contraction mediated?
tropomyosin blocks myosin’s binding site for actin
Ca2+ binds troponin C
tropomyosin dissociates
myosin can bind actin
what happens to Ca2 in the SR upon muscle contraction?
SR Ca2+ channels open -> release Ca2+
what happens to Ca2 in the SR upon muscle release?
Ca-ATPase pumps Ca2+ back into SR
what are the four types of intermediate filaments and where are they found?
- keratin - epithelia
- vimentin - connective tissue, muscle cells, glial cells
- neurofilaments - nerve cells
- nuclear lamina - all animal cells w/ nuclei
what happens to unstable microtubules? how can they be rescued?
disassemble
GTP-tubulin add to end
what are MT nucleating centers?
centrosomes
pair of centrioles associate with nucleus –> gamma tubulin around them = nucleating sites for MT
what are the microtubule motors?
dynein and kinesin
what are microtubule motors powered by?
ATP hydrolysis - dynein and kinesin
in what direction do dynein and kinesin move?
dynein toward - end of MT
kinesin toward + end of MT
How do MT and their motors position ER and golgi?
Kinesin: stretches ER out from nucleus toward MT+ end
Dynein: keeps golgi near nucleus at MT- end
