They grow in mass and split like cells but are appropriated to daughter cells after cell division.
3 purposes of the cytoskeleton
Order organelle, support membrane, help fix cell environment (communication).
Types of cytoskeletal proteins and diameter
Actin, 7nm
Intermediate filaments, 10 nm
Tubulin, 25 nm
Where are intermediate filaments located and their role?
They surround the nucleus and extend out to peripheral organelle and membrane. The role is to resist stress (high conc. in cells w/ lots of mechanical stress).
Structure of intermediate filaments and organization
Heptad (repeat of specific 7 aa) with hydrophobic residue on position 1 and 4.
Exists as an dimer.
Dimers form tetramers that are antiparallel.
Tetramer pack together to make a rope/scaffold.
Microtubule production
Made from tubulin. a-tubulin and b-tubulin form a dimer and act as the building block for microtubules.
13 protofilaments come together to form microtubule (hollow tubule).
How do microtubules assemble and disassemble
It depends on the GTP bound to b-tubulin (bot have GTP though). In the GTP form, it can bind. In the GDP form (after hydrolysis), it disassembles.
Grow on the (+) end.
Microtubule-centrosome interaction
(-) bound to centrosome (nucleation center for microtubules) and grow away from it.
GTPyS
GTP analogue that binds tubulin but cannot be hydrolyzed so microtubules can't break down easily