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Mbb231 > Cytoskeleton-MT > Flashcards

Cytoskeleton-MT Flashcards

1
Q

Cytoskeleton role

A

1- structural support
2- movement of material
3- force generation for movements
4- framework for organelles
5- cell division

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2
Q

Structurally moch of cell polarity is due to

A

Cytoskeleton

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3
Q

Cytoskeleton is —— structure
Capable of reorganizing quickly

A

Dynamic

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4
Q

MT are —— component of cytoskeletal cell

A

Largest

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5
Q

MT two types

A

1- cytoplasmic MT: pervade cytosol
— maintaining axons
—formation mitotic spindles
—movement vesicles
—maintain/alter cell shape
2- axonemal MT
— structures specialized for movement: cilia/flagella/basal bodies

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6
Q

MT protein buildings are

A

Tubulin heterodimers:
One alpha tubulin
One betta tubulin
Bind non covalently to form ab-heterodimer

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7
Q

Protofilaments

A

MT are straight, hollow cylinders
Having 13 longitudinal arrays of polymers (ab-heterodimer)

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8
Q

Alpha and betta subunits have —— structure but —— identity

A

Similar 3D structures
40% amino acid

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9
Q

Each subunit has

A

N-terminal GTP binding domain
Central domain
C-terminal domain interacting with MAP

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10
Q

All dimers in MT oriented in ——

A

Same way

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11
Q

Because of dimer orientation

A

Protofilaments have an inherent polarity
Two end differ chemically and structurally
+ end
- end

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12
Q

Cytoplasmic MT are —— tubes

A

Simple (single tubes)

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13
Q

Axonemal MT are ——

A

Doublet or triplet MTs
One 13-protofilament tubule (A)
Additional incomplete rings (B/C) of 10-11-Protofilaments

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14
Q

Doublet MT can be found in —

A

Cilia and flagella

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15
Q

Triplets can be found in

A

Basal bodies and centrioles

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16
Q

Reversible polymerization of tubulin dimer can only ocuur in presence of

A

GTP ang Mg

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17
Q

Nucleation

A

Dimers aggregate into oligomers which serve as nuclei
MT grow is slow

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18
Q

Elongation

A

Addition of more subunits at either end
Much faster phase

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19
Q

Plateau phase

A

When concentration of tubulin becomes limiting. Assembly is balanced by disassembly

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20
Q

MT assembly depends on

A

Concentration of tubulin dimers

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21
Q

Concentration that MT assembly is balanced by disassembly is

A

Critical concentration

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22
Q

Higher than C(c)

A

MT grow

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23
Q

Lower than C(c)

A

MT disassemble

24
Q

Addition of tubulin dimers happen

A

More quickly at plus end

25
Q

Treadmilling

A

Addition of subunits at plus end
Removal from the minus end

Higher tubulin conc. Than C(c) in plus end and lowe tubulin conc. than C(c) in minus end

26
Q

Treadmilling occurs if

A

Tubulin conc. Is higher than plus end C(c) but lower than minus end C(c)

27
Q

If tubulin conc. Is higher than both C(c)

A

MT will grow from both side

28
Q

If MT conc. Is less than both C(c)

A

MT will shrink from both side

29
Q

Both alpha and betta tubulin in tubulin heterodimer binds ——

A

GTP
(Doesn’t let them to shrink)

30
Q

Betta subunit will ——— after heterodimer is added to MT

A

Hydrolyzed GTP to GDP

31
Q

—— is needed to promote heterodimer

A

GTP

32
Q

—— is not required for MT assembly

A

Hydrolysis
(Happen after assembly)

33
Q

Dynamic instability model

A

Polymerization at the plus end and shrinking in minus end

34
Q

Growing MT have —— and shrinking MT have

A

GTP at plus end
GDP at minus end

35
Q

—— prevent subunit removal

A

GTP cap at plus end

36
Q

When tubukin conc. Is high

A

GTP-tubulin is added to MT faster than GTP can be hydrolyzed, GTP cap stabilize the MT tip and promote further growth

37
Q

Low tubulin conc.

A

Rate of growth decrease allowing GtP hydrolysis to catch up

38
Q

Hydrolysis of GTP will

A

Change the conformation of subunit
Force protofilament in curved shape that is less able to pack into MT wall

39
Q

Gtp-bound betta tubulin —— MT tip

A

Stabilize

40
Q

Gdp-bound betta tubulin —— mt tip

A

Destabilize

41
Q

MT originate from

A

MTOC ( micro tubule organizing center)

42
Q

Mtoc serve as

A

Site of MT assembly and anchor for minus end

43
Q

During interphase many cell have and MTOC called

A

Centrosome

44
Q

In animal cells, centrosome is associated with

A

Two centrioles

45
Q

Centriole structure

A

-Centriole wall: 9 sets of triplet MT
-Oriented at right angle
-Involved in basal body formation
-Cell without centrioles have poorly organized mitotic spindles

46
Q

How MTOC speed up the nucleation?

A

Centrosome have large ring shaped y-tubulin ring complexes (y-TuRC) which nucleate the assembly of MT away from centrosome

47
Q

By y-TuRC effect ——

A

Only plus end extends but C(c) is still important

48
Q

MT polarity in non-diving cell

A

MT orientation may vary with cell function

49
Q

MT polarity in dividing cell

A

High MT nucleating activity during prophase and metaphase (spindle forming)

50
Q

——— regulate the assembly and structure of MT

A

Microtubule-binding proteins

51
Q

MT-binding proteins:

A

1- some MT-binding proteins use ATP to drive vesicle or organelle transport
2- MT-stabilizing proteins
3- MT-Destabilizing proteins
4- Plus end tubulin interacting proteins (+-TIP)

52
Q

MT-stabilizing proteins

A

Microtubule associated proteins (MAP)
Bind at regular intervals along MT wall
Tau cause MT to form tight bundles to axon
MAP2 promote formation of looser bundles in dendrite

53
Q

MAP binding

A

One region bind MT wall and another part extend at right angle to MT to allow interaction with other proteins

54
Q

Length of extended arm will

A

Contols spacing of MT in bundle

55
Q

MT are unstable to-remain intact for long periods and will depolarize unless ——

A

They stabilized in some way
+-TIP can stabilize by capturing the plus end and protecting from catastrophic subunit loss

56
Q

+-TIP kind

A

EB1 association with GTP-tubulin stabilize MT

57
Q

MT-destabilizing Protein

A

Promote depolarization
Stathmin/Op18 bind to tubulin heterodimer and prevent polymerization
catastrophins(kinesins) act at end of MT, promoting peeling of subunits from emd
katasins severe MTs

Mbb231 (19 decks)

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