8.2 Microtubules & MAPs Flashcards
Dynamic Instability
Cycle of assembly/disassembly occurs randomly in a population of microtubules. Some are growing, some are shrinking at the same time even tho as a whole they might have a constant amount of free polymer and dimer
Catastrophe
Accidental loss of the GTP cap on the + end of the growing microtubule. When this occurs, the microtubule will shrink rapidly and depolymerize completely unless it is rescued by some stabilizing factor
What structures are responsible for nucleating microtubules in cells?
The Y-tubulin ring complexes on the centrosome. The microtubule starts at the Y-tubulin and it’s + end points away from the centrosome complex. There are many Y-tubulin locations around the centrosome.
What is the smallest unit of a microtubule?
A tubulin dimer made up of an alpha and a beta monomer.
Protofilament
A series of tubulin heterodimers attached in a line. A microtubule is made up of 13 tubulin protofilaments arranged in a circle around a lumen center.
Microtubule assembly and disassembly occurs preferentially at the ____ end.
+ end
What proteins transport organelles, chromosomes and other cargo molecules along microtubules?
Dyneins and Kinesins
Which tubulin subunits hydrolyzes GTP?
Only the beta subunit hydrolyzes GTP. Although GTP binds to both alpha and beta subunits.
Loss of the GTP cap causes ______ .
Conformational change and microtubule disassembly.
Microtubules do not typically exhibit ______ .
Treadmilling. They can perform it tho.
Centrosomes contain 2 _________.
Centrioles.
Microtubule + ends associate with the __________ .
Cell periphery
Microtubule - ends associate with the __________ .
Centrosome
Plant and fungi centrosomes lack _________ .
Centrioles
MAPs
Microtubule associated proteins. Function = regulate stability, distribution and organization of microtubules.