Microtubules (Lecture 20)

Question 1

______ are used for organization and long range transport of organelles.

Answer 1

Microtubules

Question 2

What is the major protein in microtubules?

Answer 2

Tubulin

Question 3

Where are microtubules found?

Answer 3

Found in mitotic spindle, axons, cilia, flagella

Question 4

True or False: Each ab-tubulin dimer binds one molecule of ATP.

Answer 4

False, one GTP molecule.

Question 5

______-tubulin exposed at + end and ______-tubulin exposed at negative end.

Answer 5

B, A

Question 6

______ is found in cytoplasm, ______is found in cilia and flagella and ______ is found in basal bodies and centrioles.

Answer 6

SInglet, doublet, Triplet

Question 7

Assembled from specific sites called ______ in the cell to generate many different configurations

Answer 7

MTOCs

Question 8

True or False: All microtubules are nucleated from MTOCs.

Answer 8

True

Question 9

_______ is the main MTOC of animal cells and ______ is the MTOC for cilia and flagella.

Answer 9

Centrosome, Basal body

Question 10

______ forms the template for the - end in the Y-tubulin ring complex.

Answer 10

Y-TuRC

Question 11

True or False: Centrosome MTOCs consist of two centrioles and the surrounding pericentriolar material

Answer 11

True

Question 12

True or False: Microtubules Disassemble when cells cooled to 4 °C and reform at 37 °C

Answer 12

True

Question 13

Do microtubules grow and shrink at the same time?

Answer 13

False, independently

Question 14

Growing microtubules can experience a ______ and start rapidly depolymerizing (shrinking)

Answer 14

Catastrophe

Question 15

Shrinking microtubules can experience a ______ and start rapidly polymerizing (growing)

Answer 15

Rescue

Question 16

GTP-β-tubulin ______ can persist along the length of an assembled microtubule.

Answer 16

islands

Question 17

True or False: When a disassembling microtubule encounters a GTP-β-tubulin island, disassembly pauses and rescue may be initiated

Answer 17

True

Question 18

______ favours assembly by adding more GTP tubulin where ______ cause protofilaments to curve and undergo rapid disassembly.

Answer 18

GTP-β-tubulin cap

GDP-β-tubulin cap

Question 19

The switch from assembly to dissassbly happens when GTP hydrolysis is ______ then GTP-tubulin addition

Answer 19

greater, vice versa

Question 20

True or False: Contact of microtubule to structure or organelle can stabilize the positive end and protect from catastrophe.

Answer 20

True

Question 21

True or False: MAP2 spacing is less than tau spacing.

Answer 21

False, MAP2 greater than tau

Question 22

(+) end tracking proteins called ______ associate only with (+) ends that are growing

Answer 22

+TIPs

Question 23

______ is an example of a +TIP and promotes growth at + end.

Answer 23

EB1

Question 24

What are the 4 main ways +TIPs interact with microtubules.

Answer 24

Enhance polymerization at (+) end

Reduce frequency of catastrophes

Link microtubule to other cell
structures

Link microtubule (+) ends to membranes

Question 25

What + end binding MAP enhance disassembly of microtubules?

Answer 25

Kinesin 13 family

bind and turn into GDP-B-tubulin