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Cellular and Molecular Biology > Final: Ch 18 Mictotubule Structure, Dynamics, Regulation > Flashcards

Final: Ch 18 Mictotubule Structure, Dynamics, Regulation Flashcards

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1
Q

microtubule

A

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

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2
Q

intermediate filament

A

have great tensile strength and are like molecular ropes

do not have polarity, and are not used as tracks

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3
Q

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

A

tubulin, microtubule-assembling proteins (MAPs)

13 longitudinal repeat units called protofilaments

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4
Q

microtubule walls are polarized structures built from….

A

alpha-beta tubulin dimers

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5
Q

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

A

GTP

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6
Q

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

A

alpha

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7
Q

GTP bound by the ____ subunit can be hydrolyzed

A

beta

binding site is on the surface of the dimer

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8
Q

subunits in microtubules are preferentially added to which end

A

+ end

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9
Q

which end is which in microtubules

A

end with beta subunits is +

end with alpha subunits is -

there is polarity

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10
Q

what structures are doublets

A

cilia, flagella

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

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11
Q

what structures are triplets

A

centrioles, basal bodies

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

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12
Q

all microtubules are nucleated from structures known as…

A

microtubule organizing centers (MTOCs)

  • end bound to MTOC while + end extends away
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13
Q

centrosome

A

the main MTOC in animal cells

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14
Q

non-mitotic cells are in what phase

A

interphase cells

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

serve as tracks

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15
Q

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

A

bipolar spindle

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16
Q

how are organelles transported along axons

A

by microtubules

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17
Q

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

A

basal body

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18
Q

centriole

A

cylindrical structures related to basal bodies

make up centrosomes

surrounded by pericentriolar material

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19
Q

gamma-tubulin ring complex

A

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
Q

individual microtubules exhibit ______ _______

A

dynamic instability

21
Q

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

A

MAPs

22
Q

theres are 2 distinct populations of microtubules

A

those that grow in length

those that shorten rapidly

23
Q

dynamic instability

A

the alternation between growing and shrinking states of microtubules

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

24
Q

end of a growing microtubule

A

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

25
Q

end of a shrinking microtubule

A

curls like a ram’s horns

has a GDP-beta tubulin cap

26
Q

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

A

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

27
Q

how can a disassembling microtubule be rescued to grow

A

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

28
Q

organelle or cell structure capture by the microtubule does what

A

stabilizes its + end and protects it from a catastrophe

29
Q

drug colchicine

A

sequesters all free dimers, resulting in loss of microtubules

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

30
Q

functions of microtubule associated proteins (MAPs)

A

stabilize/destabilize microtubules

crosslink between microtubules (cilia/flagella)

motor proteins

31
Q

microtubules are stabilized by _____-binding proteins

A

side

32
Q

Tau proteins

A

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

stabilize microtubules and act as spacers

33
Q

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

A

increase, catastrophe frequency

34
Q

activity of MAPs is regulated by…

A

reversible phosphorylation of their projection domains

if phosphorylated, unable to bind microtubules

35
Q

what kinase is a key modulator of tau proteins

A

microtubule-affinity-regulating kinase (MARK)

cyclin-depending kinase (CDK)

36
Q

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

A

+ end

EB1 binds more blunt growing end (+ end)

modifies properties like enhancing polymerization or reducing catastrophes

37
Q

+TIPs can also link….

A

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

38
Q

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

A

catastrophes

39
Q

augmin complex

A

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

40
Q

what is microtubular protein

A

alpha-beta tubulin plus microtubule associated proteins

41
Q

what is a catastrophe

A

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

42
Q

what is a rescue

A

when a depolymerizing microtubule begins growing again

43
Q

2 domains of tau proteins

A

positively charged area that binds negatively charged tubulin surface

2nd domain projects at a right angle from the microtubule

44
Q

+TIP linkage to the ER transmembrane protein STIM does what

A

causes microtubule-dependent extension of the ER membrane

45
Q

kinesin-13

A

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

46
Q

Op18/stathmin

A

increases rate of catastrophes

enhances hydrolysis of GTP to GDP

47
Q

what regulates Op18/stathmin

A

phosphorylation by kinases

Cellular and Molecular Biology (34 decks)

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