Microtubules

Question 1

Polar microtubules

Answer 1

Microtubules that do not make contact w/ the kinetochore

Question 2

Astral microtubules

Answer 2

Microtubules in a starburst around the centrosome

Question 3

Kinetochore microtubules

Answer 3

Microtubules that make contact w/ the kinetochore of a pair of sister chromatids

Question 4

Functions of MTs

Answer 4

1. Guiding intracellular transport
2. Segregating chromosomes during mitosis
3. Propulsion or sweeping of fluids over membranes

Question 5

Microtubules are rigid, hollow tubes made of __________.

Answer 5

Tubulin

Question 6

Tubular is itself a dimer of ______________.

Answer 6

α-tubulin & β-tubulin

Question 7

In cells, you almost always see polymerization/depolymerization at the ________ end, but it is possible at either end.

Answer 7

(+) plus end

Question 8

Diameter of MT

Answer 8

25 nm

Question 9

The __________ ends are anchored to something in ________.

Answer 9

(-) minus, vivo

Question 10

____________ polymerize to form microtubules.

Answer 10

Tubulin dimers

Question 11

Both α-tubulin and β-tubulin have ________ binding sites.

Answer 11

GTP

Question 12

MTs are made in the __________.

Answer 12

Microtubular Organizing Center

Question 13

In animal cells, the major MTOC is the ___________.

Answer 13

centrosome

Question 14

Inner diameter of an MT

Answer 14

15 nm

Question 15

The wall of the MT cylinder consists of ___________.

Answer 15

13 protofilaments

Question 16

Protofilaments

Answer 16

The vertical sticks in MTs, consisting of αβαβαβαβαβαβ

Question 17

MT length

Answer 17

From than some micrometers

Question 18

As soon as α-tubulin and β-tubulin are synthesized, they bind together ___________ to produce a __________.

Answer 18

non covalently; heterodimer

Question 19

The aggregation of tubulin dimers into clusters called ________.

Answer 19

oligomers

Question 20

These oligomers serve as nuclei from which new MTs can grow and is called _________.

Answer 20

Nucleation

Question 21

MT formation is initially……

Answer 21

Slow

Question 22

Elongation, after nucleation, is …

Answer 22

Fast

Question 23

Critical concentration

Answer 23

The tubulin heterodimer concentration at which MT assembly is exactly balanced with disassembly

Question 24

The critical concentration is _______ for the plus end than for the minus end.

Answer 24

lower