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Cell Biology > Microtubules > Flashcards

Microtubules Flashcards

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1
Q

isoforms of tubulin

A

α tubulin, ß tubulin, gamma tubulin

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2
Q

α tubulin

A

always bound to & never hydrolyzes GTP; GTP binding site is blocked by beta tubulin

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3
Q

ß tubulin

A

can hydrolyze GTP

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4
Q

gamma tubulin

A

part of nucleation

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5
Q

building block of microtubules

A

αß tubulin dimer

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6
Q

describe how a microtubule is formed

A

an individual protofilament (linear) is formed & laterally associates protofilaments to create cylindrical structure

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7
Q

How do the plus and minus ends of microtubules differ?

A

”+” end has significantly lower critical concentration than “-“ end (preferential building at “+” end)
creates “treadmilling” effect

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8
Q

describe “treadmilling” effect

A

preferential addition of tubulin at “+” end, & disassembly at “-“ end

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9
Q

singlet

A

made of 13 porotofilaments; found in the cell body

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10
Q

doublet

A

made of 23 protofilaments (13+10); found in cilia/flagella

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11
Q

triplet

A

made of 33 protofilaments (13+10+10); found in basal body/centriole

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12
Q

MTOC

A

microtubule organizing center

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13
Q

MTOC types

A

centrosome & basal body

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14
Q

centrosome

A

MTOC in center of every cell, attaches to - end of microtubule singlets and triplets

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15
Q

basal body

A

MTOC found just inside cell body in cells with cilia/flagella, attaches to - end of microtubule doublets

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16
Q

gamma-TURC complex

A

made of gamma tubulin & other proteins; functions as a nucleation site for microtubule formation

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17
Q

dynamic instability

A

microtubules undergo regular cycles of growth and shrinkage; microtubules experience a growth phase until a “catastrophe” initiates the disassembly phase - continues until “rescue”; necessary for mitosis

18
Q

What proteins contribute to dynamic instability?

A

kinesin-13, stathmin, katanin

19
Q

kinesin-13

A

binds to dimers at the + end (uses energy), curves end of tubulin protofilament, removes GDP bound dimers

20
Q

stathmin

A

binds 2 dimers of curved protofilament & removes them

21
Q

katanin

A

severs microtubules

22
Q

What are kinesins and dyneins?

A

motor proteins

23
Q

kinesin

A

”+” end directed motor protein, head region binds/hydrolyzes ATP & walks “hand-over-hand” along microtubule (similar to myosin structure)

24
Q

dynein

A

”-“ end directed motor protein, large complex that includes dyanctin (which interacts with the microtubule), light & heavy chains, etc.

25
Q

microtubule structures in flagella

A 
axomeme = central bundle
nexin = connects outer doublets
dynein = moves flagella by allowing central singlets to slide past one another, creating a whipping motion
26
Q

roles of microtubules in cell division or mitosis

A

capture, alignment, and movement of chromosomes

27
Q

kinetochore

A

structure where kinetochore microtubules attach to chromosome

28
Q

centromere

A

structure where sister chromatids attach to each other

29
Q

classes of microtubules in the mitotic spindle

A

kinetochore microtubule, polar microtubule, & astral microtubule

30
Q

microtubule containing structures

A

cell body - contains singlets
cilia/flagella - contain doublets for motion
basal body/centriole - contain triplets

31
Q

MAPs

A

microtubule associated protein - stabilize microtubules

32
Q

What are the roles of motor proteins, microtubules, and microfilaments in the movement of cell contents?

A

Organelles will have motor proteins (kinesin/dynein/myosin) on them based on where they want to move materials & what structure the material will move along (microtubules/microfilaments). They will likely have more than one type.

33
Q

phases of mitosis

A

interphase, prophase, prometaphase, metaphase, anaphase, & telophase/cytokinesis

34
Q

interphase

A

microtubules radiate away from MTOC (microtubule organizing center)

35
Q

prophase

A

centrism has replicated and moved

36
Q

prometaphase

A

microtubules capture chromosomes - motor proteins move chromatids to end of the microtubules until attached on both sides and stabilized by the tension (bioriented)

37
Q

metaphase

A

microtubules line up the chromosomes through a combination of treadmilling and motor proteins

38
Q

anaphase

A

microtubules pull chromosomes to opposite poles through microtubules shrinkage & sliding

39
Q

telophase/cytokinesis

A

each cell has 1 centrisome and 1 set of chromosomes

40
Q

kinesin 3

A

located at kinetochore; enhances microtubule disassembly during mitosis

Cell Biology (16 decks)

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