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bio 340 > Cytoskeleton > Flashcards

Cytoskeleton Flashcards

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Biology 101 flashcards
1
Q

what are the 3 types of cytoskeleton fibers?

A

actin filaments, intermediate filaments, microtubules

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2
Q

actin filaments and microtubules are composed of?

A

globular subunits

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3
Q

intermediate filaments are composed of?

A

elongated and fibrous subunits, rod like

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4
Q

what are the interactions among all of the subunits?

A

not covalent. assemble and dissemble quickly

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5
Q

what are protofilaments?

A

thin filaments that link together to make big ones

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6
Q

what are the globular subunits called in actin filament?

A

actin

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7
Q

what are the globular subunits called in microtubules?

A

alpha-beta tubulin dimer

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8
Q

what is actin?

A

composed of actins, has binding site for ATP, are polarized plud end has the ATP binding cleft covered while the minus end the cleft is exposed. 2 protofilaments twisting around each other

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9
Q

how do you assembly actin?

A
  1. nucleation phase- actins comes together to form oligomers (rate limiting step)
  2. elongation phase
  3. steady-state- reach equilibrium and won’t get any longer.
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10
Q

actin grows longer on the ____ end but can grow on ____ ends

A

plus , both

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11
Q

what is critical concentraion (Cc)?

A

concentration of free actin when actin filament has reached a steady state.

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12
Q

what happens when you go above the critical concentration?

A

free actin polymerize and get into the filament to reduce the free actin

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13
Q

what happens when you go below critical concentration?

A

filament shortens to let free actin leave

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14
Q

describe the protofilament for miccrotubles

A

alpha and beta tubulin line up (non covalent interaction)

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15
Q

what is gamma-tublin

A

not part of heterodimer, used for nucleation

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16
Q

how are microtubules assembled?

A
  1. protofilament assemly from alpha+beta subunits
  2. protofilament associate to form a tube (13 in a ring)
  3. add more subunits to each end to elongation
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17
Q

what are doublets in microtubules?

A

in cilia and flagella, 2 mashed together

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18
Q

what are triplets in microtubules?

A

in basal bodies and centrioles, 3 mashed together

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19
Q

describe the polarity of microtubules

A

they have plus and minus ends
growth at plus end is faster.
minus end is associated with microtubule organizing center

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20
Q

stable, long-lived microtubules can be found in

A

in non-replicating cells like cilia flagella neurons

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21
Q

unstable and short-lived microtubules can be found in

A

cells that need assembly/disassembly in mitosis

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22
Q

what is the primary function of intermediate filaments?

A

for mechanical strength, prominent in cells that undergo stress regularly

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23
Q

what is the nuclear lamina?

A

inner lining of nuclear envelope

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24
Q

what is the structure of intermediate filaments?

A

no plus/minus ends, alpha-helical rods, coiled-coiled dimers (two rods twisted), then staggered tetramers (2 coiled-coiled dimers twisted)
no nucleotide binding

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25
Q

some toxins produced by organisms interfere with

A

actin/microtubule function, stabilizes them

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26
Q

actin filament formation is at or near

A

plasma membrane, in cell cortex

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27
Q

what is cell cortex?

A

layer just beneath plasma membrane

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28
Q

actin filament in cell cortex determines

A

cell shape and movement of cell surface

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29
Q

how does actin respond to a nutrient source?

A

filaments dissemble and they reassemble towards the source

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30
Q

what is ARP?

A

nucleation point where actins bind to on minus end

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31
Q

what is formin?

A

a ring like structure, another nucleation point

32
Q

how does formin work?

A

one side lifts up to let actin in then the other side lifts up to form actin filaments

33
Q

what is formin whisker?

A

long projection of formin bound to profilin. profilin grabs onto actin to pull it in

34
Q

what is thymosin?

A

prevents assembly. binds to free actin and takes it away

35
Q

what is profilin?

A

accelerates assembly

36
Q

what is cofilin?

A

accelerates disassembly at lagging end so leading edge can keep growing

37
Q

what is tight parallel bundle?

A

actin facing the same direction

38
Q

what is contractile bundle?

A

actin going in different directions

39
Q

what are gel-like network?

A

actin crossing over each other, spongy

40
Q

what is the lamellipodia?

A

leading edge of cell

41
Q

what are 3 bundle-forming proteins?

A

fimbrin, alpha-actinin, villin

42
Q

what is fimbrin?

A

tight bundles (can’t bind to myosin, not contractile)

43
Q

what is alpha-actinin?

A

contractile fiber bundles

44
Q

what is villin?

A

tight packed bundles in microvilli (along with fimbrin)

45
Q

what is the gamma-tubulin ring complex?

A

where the minus end of microtubule.

46
Q

what is the centrosome?

A

microtubule organization cell. where all of the minus ends of microtubules are bound. only one during interphase. knows where the center of the cell is

47
Q

centrosomes contains a pair of

A

centrioles

48
Q

what is kinesin-13?

A

binds to plus end of microtubules to unravel it

49
Q

what is xamp215?

A

stabilizes plus end, growth rate enhanced

50
Q

what is katanin?

A

severs microtubules (during mitosis/meiosis)

51
Q

what is MAPs (microtubule-associated proteins) ?

A

length determines how closely microtubules are packed (MAP2 longer than tau)

52
Q

how do cells move?

A

actin cytoskeleton polymerization in cortex. actin protrusion in actin while contraction in the back.

53
Q

what are the molecular motor proteins?

A

myosin (actin)
kinesin (microtubules)
dyenin (microtubules)

54
Q

how are molecular motor proteins differentiated?

A

what filament they bind to
which direction they move
what cargo they carry

55
Q

the head on the molecular motor protein

A

determines which filament and the direction of movement

56
Q

the tail on the molecular motor protein

A

carries the cargo

57
Q

describe the molecular motor protein cycle

A

filament binding, conformational change, filament release, conformational relaxation

58
Q

what is myosin?

A

have a head and tail, all but one move towards the plus end of actin filaments. motor domain in head

59
Q

what is the function of myosin V?

A

organelle transport. tail domain binds to organelle

60
Q

what is the function of myosin II?

A

muscle contraction, cytokinesis, cell migration

61
Q

what is the function of myosin I?

A

membrane movement like endocytosis

62
Q

what is kinesin?

A

most walk toward plus end

plays a role during mitosis meiosis

63
Q

organelles can move on

A

actin or microtubules

64
Q

what are some common kinesins and function?

A

organelle transport, microtubule sliding, catastrophe factor

65
Q

what are dyenins?

A

minus end directed microtubule motor proteins

largest and fastest of known molecular motors. turn donut heads to do movement

66
Q

why do z discs become closer to each other during muscle contraction?

A

myosin heads pulls actin closer together

67
Q

describe how myosin walks on actin

A
  1. myosin head binds to ATP and releases on actin
  2. ATP hydrolyzed to ADP+P ->conformational change into cocked state
  3. myosin binds to actin filament
  4. phosphate is released and elastic energy straightens myosin, moves actin
  5. ADP released and ATP binds again
68
Q

how does kinesin move?

A

rear head is bound tightly to microtubules and ATP. leading head is loosely bound to ADP. lagging head hydrolyzes to ADP. new ATP binds to leading head then lagging head swings to front.

69
Q

how does dyenin move?

A

the donut rotates and moves the microtubule

70
Q

what is the function of molecular motor proteins?

A

muscle contraction, organelle and vesicle movement, flagella and cilia, cell division

71
Q

what causes bending in flagella?

A

dyenin links the microtubules so they dont slide but bend (?????)

72
Q

cells undergoing mitosis/meiosis have __ centrosomes

A

2, become spindle poles

73
Q

what are astral microtubules?

A

plus ends interact with cell membrane

74
Q

what are kinetochore microtubules?

A

interact with chromosome at kinetochorse

75
Q

what are interpolar microtubules?

A

one centrosome sends out a microtubule and the other will send one out and they overlap with motor proteins in between.

bio 340 (13 decks)

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