Final: Ch 18 Mictotubule Structure, Dynamics, Regulation Flashcards Preview

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Flashcards in Final: Ch 18 Mictotubule Structure, Dynamics, Regulation Deck (47):
1

microtubule

stiff tubes that can exist as a single structure, or as a bundled arrangement

generate pushing and pulling forces that allow single tubules to extend long distances, and bundles to slide past each other

tracks for kinesins and dyneins

2

intermediate filament

have great tensile strength and are like molecular ropes

do not have polarity, and are not used as tracks

3

microtubules are made of the major protein _____, and associated proteins called...

tubulin, microtubule-assembling proteins (MAPs)

13 longitudinal repeat units called protofilaments

4

microtubule walls are polarized structures built from....

alpha-beta tubulin dimers

5

the alpha and beta subunits of tubulin can each bind a molecule of ____

GTP

6

the GTP is the _____-tubulin subunit is never hydrolyzed, and is trapped inbetween the alpha and beta subunits

alpha

7

GTP bound by the ____ subunit can be hydrolyzed

beta

binding site is on the surface of the dimer

8

subunits in microtubules are preferentially added to which end

+ end

9

which end is which in microtubules

end with beta subunits is +

end with alpha subunits is -

there is polarity

10

what structures are doublets

cilia, flagella

has an A tubule of 13 protofilaments and a B tubule of 10

11

what structures are triplets

centrioles, basal bodies

has an A tubule of 13 protofilaments and a B and C tubule of 10

12

all microtubules are nucleated from structures known as...

microtubule organizing centers (MTOCs)

- end bound to MTOC while + end extends away

13

centrosome

the main MTOC in animal cells

14

non-mitotic cells are in what phase

interphase cells

centrosome is located near the nucleus and produces microtubules with + ends radiating toward the periphery

serve as tracks

15

during mitosis, cells reorganize their microtubules to form a ______ ______ assembled from 2 centromeres to segregate copies of the duplicated chromosomes

bipolar spindle

16

how are organelles transported along axons

by microtubules

17

in cilia and flagella, microtubues are assembled from an MTOC called a ____ _____

basal body

18

centriole

cylindrical structures related to basal bodies

make up centrosomes

surrounded by pericentriolar material

19

gamma-tubulin ring complex

located in pericentriolar material and is a template that alpha-beta tubulin binds to, to form a new microtubule

- end bound to gamma-tubulin, + end grows

20

individual microtubules exhibit ______ _______

dynamic instability

21

polymerization of dimeric alpha-beta tubulin into microtubules is greatly catalyzed by the presence of ____

MAPs

22

theres are 2 distinct populations of microtubules

those that grow in length

those that shorten rapidly

23

dynamic instability

the alternation between growing and shrinking states of microtubules

depends on the presence or absence of a GTP-beta-tubulin cap

24

end of a growing microtubule

has a blunter end and a GTP-beta-tubulin cap

25

end of a shrinking microtubule

curls like a ram's horns

has a GDP-beta tubulin cap

26

why don't GDP-beta tubulin capped protofilaments attached to an assembled microtubule peel away?

the protofilament-protofilament interactions in the GTP-beta-tubulin are strong enough

27

how can a disassembling microtubule be rescued to grow

islands of GTP-beta-tubulin on the length of the assembled microtubule

28

organelle or cell structure capture by the microtubule does what

stabilizes its + end and protects it from a catastrophe

29

drug colchicine

sequesters all free dimers, resulting in loss of microtubules

relieve joint point/gout (WBC can't migrate correctly so less inflammation)

30

functions of microtubule associated proteins (MAPs)

stabilize/destabilize microtubules

crosslink between microtubules (cilia/flagella)

motor proteins

31

microtubules are stabilized by _____-binding proteins

side

32

Tau proteins

tau (axons and dendrites), MAP2 (neuron dendrites), and MAP4 (other cell types)

stabilize microtubules and act as spacers

33

when stabilizing MAPs coat the outer wall of a microtubule, they can ____ the growth rate or suppress the ______ frequency

increase, catastrophe frequency

34

activity of MAPs is regulated by...

reversible phosphorylation of their projection domains

if phosphorylated, unable to bind microtubules

35

what kinase is a key modulator of tau proteins

microtubule-affinity-regulating kinase (MARK)

cyclin-depending kinase (CDK)

36

+TIPs (type of MAP) regulate the properties and functions of the microtubule __ end

+ end

EB1 binds more blunt growing end (+ end)

modifies properties like enhancing polymerization or reducing catastrophes

37

+TIPs can also link....

microtubule + ends to cell cortex, F-actin, and membranes

38

other end binding proteins can enhance the frequency of ________, helping to remove tubulin dimers

catastrophes

39

augmin complex

binds the side of a microtubule and attracts gamma-tubulin ring complex to assemble

40

what is microtubular protein

alpha-beta tubulin plus microtubule associated proteins

41

what is a catastrophe

when individual microtubules grow, and then suddenly shrink (rapid depolymerization)

42

what is a rescue

when a depolymerizing microtubule begins growing again

43

2 domains of tau proteins

positively charged area that binds negatively charged tubulin surface

2nd domain projects at a right angle from the microtubule

44

+TIP linkage to the ER transmembrane protein STIM does what

causes microtubule-dependent extension of the ER membrane

45

kinesin-13

bind tubulin and curve it like GDP-beta-tubulin to facilitate depolymerization

46

Op18/stathmin

increases rate of catastrophes

enhances hydrolysis of GTP to GDP

47

what regulates Op18/stathmin

phosphorylation by kinases