Microtubules Flashcards
Polar microtubules
Microtubules that do not make contact w/ the kinetochore
Astral microtubules
Microtubules in a starburst around the centrosome
Kinetochore microtubules
Microtubules that make contact w/ the kinetochore of a pair of sister chromatids
Functions of MTs
- Guiding intracellular transport
- Segregating chromosomes during mitosis
- Propulsion or sweeping of fluids over membranes
Microtubules are rigid, hollow tubes made of __________.
Tubulin
Tubular is itself a dimer of ______________.
α-tubulin & β-tubulin
In cells, you almost always see polymerization/depolymerization at the ________ end, but it is possible at either end.
(+) plus end
Diameter of MT
25 nm
The __________ ends are anchored to something in ________.
(-) minus, vivo
____________ polymerize to form microtubules.
Tubulin dimers
Both α-tubulin and β-tubulin have ________ binding sites.
GTP
MTs are made in the __________.
Microtubular Organizing Center
In animal cells, the major MTOC is the ___________.
centrosome
Inner diameter of an MT
15 nm
The wall of the MT cylinder consists of ___________.
13 protofilaments
Protofilaments
The vertical sticks in MTs, consisting of αβαβαβαβαβαβ
MT length
From than some micrometers
As soon as α-tubulin and β-tubulin are synthesized, they bind together ___________ to produce a __________.
non covalently; heterodimer
The aggregation of tubulin dimers into clusters called ________.
oligomers
These oligomers serve as nuclei from which new MTs can grow and is called _________.
Nucleation
MT formation is initially……
Slow
Elongation, after nucleation, is …
Fast
Critical concentration
The tubulin heterodimer concentration at which MT assembly is exactly balanced with disassembly
The critical concentration is _______ for the plus end than for the minus end.
lower
