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ETC > Cytoskeleton > Flashcards

Cytoskeleton Flashcards

1
Q

Alpha actin make up what type of cells

A

muscle

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2
Q

Beta and gamma actin make up what type of cells

A

non-muscle cells

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3
Q

Actin monomer

A

globular actin (G-actin)

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4
Q

When two actin filaments twist together what do they make what

A

F-actin

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5
Q

How big is F- actin

A

6-7 nm

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6
Q

What is required for actin to assemble?

A

1) Need ATP
2) need some fragment of G-actin
3) actin binding proteins (regulatory proteins)

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7
Q

Polarity of actin

A

+ end favors assembly, ATP

  • end favors disassembly, ADP
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8
Q

When does assembly stop for actin?

A

if all ATP bound filaments are consumed

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9
Q

Why is polarity for actin filaments necessary?

A

for myosin movement to + end

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10
Q

What is the RLS for actin filament assembly?

A

nucleation of fragments

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11
Q

3 important functions of actin cytoskeleton

A

1) cell migration
2) cytokinesis: contracile ring before cell divides
3) brain development: synapses

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12
Q

Functional classes of actin binding proteins

A

capping, ARP, thymosin, gelsolin, profilin, cofilin, tropomyosin

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13
Q

capping actin binding protein

A

prevents assembly/ disassembly at the + end

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14
Q

ARP actin binding protein

A

nucleates assembly, creates web, associated with - end

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15
Q

Thymosin actin binding protein

A

prevents assembly of actin

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16
Q

Gelsolin actin binding protein

A

severs filaments, binds + end, prevents monomer exchange

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17
Q

profilin actin binding protein

A

speeds elongation

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18
Q

cofilin

A

increases disassembly by binding ADP-actin

WS, ASD

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19
Q

tropomyosin

A

stabilizes filament

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20
Q

What is the motor protein for actin?

A

myosin

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21
Q

How myosin moves along the actin filament

A

1) ATP binds myosin head, causing it to lift off of actin filament
2) Hydrolysis: head pivots and binds new actin subunit further up the + end
3) power stroke: Pi released, head pivoted and moves filament
4) ADP release and cycle repeats (attached without ATP)

22
Q

Diseases associated with regulation of actin cytoskeleton

A 
bacterial infection 
williams syndrome (WS) 
ASD
AD
Fragile X 
ALS 
dementia
23
Q

How does Lim Kinase affect cofilin?

A

it inhibits it (so since cofilin increases disassembly, that means there is LESS disassembly happening)

24
Q

How does WS affect Lim Kinase and thus cofilin?

A

WS decreases Lim Kinase, which means less inhibiting of cofilin and means cofilin is still accelerating disassembly (active), which means there is MORE disassembly

25
Q

How does ASD affect Lim Kinase and thus cofilin?

A

ASD increases Lim kinase, which means more inhibiting of cofilin which means cofilin is NOT accelerating disassembly (inactive), which means LESS disassembly

26
Q

What is the smallest out of the cytoskeleton classes?

A

microfilaments (actin)

27
Q

3 main features of microtubule structure

A

1) non random organization in cells
2) has centrosome that is the MTOC
3) polar

28
Q

Microtubule polarity

A

+ , assembly end, distal to centrosome and cell body except dendrites

  • is closest towards centrosome (MTOC)
29
Q

How microtubule assembles

A

alpha and beta dimers form protofilaments,

13 protofilaments make up microtubule with - and + end

ASSEMBLES AT THE + END

30
Q

alpha tubulin

A

NEGATIVE (-) end

GTP
NO hydrolysis

31
Q

beta tubulin

A

POSITIVE (+) end

GDP
exchangeable–> hydrolysis in assembly

32
Q

dynamic instability

A

when the GTP is bound to beta tubulin = assembly, when GTP hydrolyzes to GDP on beta tubulin, that means = disassembly

33
Q

Treadmilling

A

when tubulin dimers are added at the same rate as the hydrolysis of GTP (if its faster then that it is when polymerization occurs)

actin being assembled and disassembled at same rate

34
Q

Taxol (anti tumor drug)

A

prevents disassembly of microtubules, arrests cell cycle

35
Q

Vinca alkaloids (colchicine)

A

prevents tubulin dimers from polymerizing

36
Q

What are the motor proteins associated with microtubules?

A

dyneins and kinesins

37
Q

Dynein

A

moves toward - end
retrograde
use ATP

38
Q

Kinesins

A

moves toward + end
anterograde
use ATP

have a tail and cargo binding domains –> diff kinesins have diff cargo

39
Q

cilia (definition, structure, 2 types)

A

Cilia are hairlike structures about 0.25 mm in diameter, covered by plasma membrane, that extend from the surface of many kinds of eucaryotic cells

motile(9+2, dynein) vs. primary (9+0, NO dynein))

40
Q

Flagella

A

motile cilia
like sperm
move entire cell

41
Q

How cilia is assembled (including IFT)

A

build on basal body (MTOC)
then add subunits on top

intraflagellar transport (IFT): assembly machinary required of all cilia

42
Q

IFT (intraflagellar transport)

A

start at basal body (-), anterograde transport with kinesin, unload at the tip (+) switch IFT complex, retrograde transprt with dynein back towards basal body

43
Q

What makes up a centrosome?

A 
2 centrioles 
pericentriolar material (PCM)

centrosome is located near nucleus in interphase

44
Q

what does the pericentriolar mateiral (PCM) do?

A

recruits gamma ring complex

45
Q

What does the gamma tubulin ring complex do?

A

helps nucleate microtubule

46
Q

How many times do centrosomes duplicate per cell cycle? and what does it create?

A

ONCE , chromosomes separate and then it creates bipolar mitotic spindle (TWO POLES)

47
Q

What mechanism is duplication of centrioles?

A

semi-conservative replication

48
Q

3 types of microtubules

A

astral microtubules: look like star out of centrosome

kinetochore microtubules: connect to kinetochore at the centromere on the chromosome

interpolar (overlap) microtubules: span overmiddle of chromosomes but don’t connect to kinetochores

ALL spindles must be attached for anaphase to occur

49
Q

Anaphase A

A

poles DO NOT move

chromosomes pulled poleward, kinetochore microtubules shorten by kinesin on + end toward centrosome

50
Q

Anaphase B

A

POLES move
chromosomes pulled to opposite poles as microtubules push and pull poles apart

1) pushing–> kinesin
2) pulling–> dynein

51
Q

if there are errors in chromosomal segregation it could result in what condition

A

aneuploidy (gain or loss of chromosome)

ie. down syndrome (trisomy 21)

ETC (11 decks)

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