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cell bio part 2 > The cytoskeleton > Flashcards

The cytoskeleton Flashcards

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Biology 101 flashcards
1
Q

What are the 5 functions that the cytoskeleton performs

A

Organization of the cytoplasm
Structural support
Transport
Movement
Cellular divisiond

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2
Q

Different types of proteins are involved in the different what of the cytoskeleton

A

Functions

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3
Q

There are three main types of cytoskeletal filaments, what are they?

A

Intermediate filaments
Microtubule filaments
Actin filaments

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4
Q

Each type of filament is a polymer of what

A

protein subunits

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5
Q

Mutations in filaments result in what

A

prominent disorders

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6
Q

The filaments polymerize and depolymerize as needed to perform their functions and these are processes targeted by what

A

specific chemotherapeutics

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7
Q

7nm

A

(actin)

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8
Q

25nm

A

(tubulin)

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9
Q

10nm

A

(varies)

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10
Q

Actin filaments (f-actin) are polymers of what

A

globular actin (g-actin)

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11
Q

Actin polymerization requires

A

ATP

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12
Q

G-actin is polar like tubulin monomers, meaning that f-actin has

A

plus and minus ends

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13
Q

F-actin primarily grows at what end

A

Plus ends

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14
Q

F-actin interacts with other proteins that modify the actin structure, allowing actin to do what

A

Perform various functions

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15
Q

Actin filaments associate with the cell cortex and mediate actions related to what

A

The cell membrane

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16
Q

What are the actions that actin filaments mediate

A

Membrane fusion (microvilli absorption, “hair” cell formation for hearing / balance)
Budding or Cytokinesis
Crawling of the cell
Muscle contractions

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17
Q

A signal like PDGF triggers a cell to do what

A

crawl directionally

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18
Q

Rac/Rap G-proteins are activated near this edge and create what

A

Create focal contacts, a loose type of cell footing

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19
Q

Rho/ROCK subfamily G-proteins trigger actin polymerization and creates and triggers what

A

Creates more firm, focal adhesions
Triggers crawling of the cell along substrate or other cells

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20
Q

Decreasing PDGF gradient away from the leading edge has multiple effects what are they

A

PDGF bound to the receptor is internalized behind the leading edge
GAPs become activated, shutting off actin polymerization back where the cell needs to lift up and off its prior contacts

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21
Q

The head domain of myosin-I interacts with

A

f-actin

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22
Q

The tail of myosin-I interacts with some other structures what are they

A

(a vesicle, a membrane, etc.)

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23
Q

Myosin “walks” towards what end

A

The plus end

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24
Q

If the myosin tail is attached to cargo, the cargo where

A

Along the actin

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25
Q

If the myosin tail is attached to the plasma membrane, the membrane moves

A

along the actin to affect cell shape

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26
Q

Myosin-II is a dimer that forms what

A

myosin-II filaments

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27
Q

Myosin filaments are made of multiple

A

dimers

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28
Q

The myosin heads extend from the edges of the

A

Filaments

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29
Q

The middle of a myosin filament has how many heads

A

No heads (bare)

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30
Q

Sliding of f-actin across myosin-II is a

A

muscle contraction

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31
Q

Muscle cells contain bundles of actin and myosin filaments called

A

Sarcomeres

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32
Q

Plus ends of f-actin in adjacent sarcomeres are connected by

A

by Z discs / lines

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33
Q

What do T-tubules do

A

carry the action potential along skeletal muscle cells (after acetylcholine bound to ion-channel coupled receptor)
Brings voltage change close enough to internal sarcoplasmic reticulum (SR) membrane (a specialized type of ER providing ions towards sarcomeres))
Triggers opening of Voltage-Gated Ca2+ channels
Ca2+ is released from the sarcoplasmic reticulum

34
Q

What does Tropomyosin do

A

binds actin (and troponin) and prevents myosin binding WHEN NOT in the presence of calcium

Upon activation, the released Ca2+ binds troponin, which moves Tropomysin slightly along the actin filaments
This shift allows myosin to bind its sites on actin

35
Q

With calcium BUT in the absence of ATP, myosin is able to be bound to actin in what conformations

A

in the “rigor” or “post-power stroke” conformation

36
Q

ATP binds myosin, causing a

A

conformation change in myosin

37
Q

Myosin releases

A

F-actin

38
Q

The ATP hydrolyzes to

A

ADP (very quickly)

39
Q

ATP hydrolysis causes another conformational change to myosin, causing what conformation

A

“cocked” conformation

40
Q

Once in the “cocked” conformation, the myosin head is positioned slightly shifted from its previous spot along actin (the next subunit) and what is released

A

Pi is released and myosin again binds f-actin tightly at this next actin subunit then
ADP is released, and the myosin head returns to the original conformation, generating a power stroke (the “pull”)

41
Q

Skeletal muscle contraction occurs multiple times and rapidly to

A

the actin along the myosin

42
Q

Not all heads are in sync so that subsets of heads bind actin while others are in the process of what

A

Release

43
Q

others are in the process of release
Muscles can only pull but can do what

A

you can still resist the force of a load while slowly lengthening a muscle

44
Q

Separate Ca2+ channels in the SR are continually pumping Ca2+ back into the SR, but will not be able to outcompete what

A

VG-Ca2+ channels while a contraction signal is sustained

45
Q

Once the action potential stops, the VG-Ca2+ channels closed and the Ca2+ can now be

A

be fully pumped back into the SR

46
Q

Loss of Ca2+ from troponin then causes tropomyosin to roll back over myosin binding sites and prevent

A

new myosin/actin interactions without a new signal

47
Q

The lack of interaction between myosin and f-actin causes

A

f-actin to slide back to the original position

48
Q

While mid-size in diameter, they are the STRONGEST cytoskeleton filaments

A

Intermediate filaments

49
Q

Diseases associated with mutations in different subsets of intermediate filaments include

A

ALS (Lou Gerhig’s disease)
Progeria (very early advanced aging)

50
Q

Intermiediate filaments

A

Extend throughout the cell, but anchor in the plasma membrane where the cell connects to other cells

51
Q

What do Desmosomes do

A

Desmosomes connect adjacent cells together to provide strength to epithelium

52
Q

Types of intermediate filaments

A

Keratin filaments
Vimentin filaments
Neurofilaments
Nuclear lamins

53
Q

What is keratin

A

Found in all epithelial cells
Distribute stress when skin (or other epithelial layers) are stretched

54
Q

what is vimentin

A

Provides support in connective tissues (ligaments and muscles)

55
Q

what is neurofilaments

A

Provide strength to neurons, particularly in the axon

56
Q

What are nuclear lamins

A

Nuclear filaments (lamins) provide structure to nuclei; degrade and reform during cell division

57
Q

What are microtubules involved in

A

Transport within the cell
Cell division (Form the mitotic spindle used to separate chromatids)
Locomotion (structural component of cilia and flagella)

58
Q

Microtubules are a polymer of

A

tubulin proteins

59
Q

α end referred to as

A

“minus end”

60
Q

β referred to as

A

“plus end”

61
Q

The ends of a microtubule are called polar because they

A

are different

62
Q

Microtubules grow quickly through addition of subunits at what end

A

the plus end

63
Q

Protofilaments have what type of structure

A

(hollow) structure

64
Q

Microtubules are produced by

A

microtubule organizing centers (MTOC)

65
Q

What is a MTOC called in an animal

A

Called a “centrosome” in animals

66
Q

What else to MTOC contain

A

Contain γ-tubulin – where tubule polymerization nucleates (hard to start polymerizing on their own)

67
Q

Centrosomes contain two

A

Centrioles

68
Q

Centriole function in centrosomes during interphase remains unclear, but they are involved in the structure of what

A

cilia and flagella structure

69
Q

Centrosomes are not present in

A

MOST Conifers, Flowering Plants, or Fungi

70
Q

Microtubules have

A

dynamic instability which means what they grow and fall apart quickly

71
Q

Tubules are constantly produced, but if they do not attach to something, what happens

A

they fall apart

72
Q

Stabilizing microtubules require what

A

Requires GTP, which produces a cap at the plus end

73
Q

If GTP is hydrolyzed before new subunits are added, the cap is lost and what happens to the tubule

A

It depolymerizes

74
Q

Motor proteins “walk” along microtubules, requiring what

A

ATP hydrolysis to propel “heads”

75
Q

What does Kinesin do

A

Moves towards the plus end of a microtubule
Carriers ER towards the plasma membrane like a net; In neurons moves towards axon terminals

76
Q

What does Dynein do

A

Moves towards the minus end of a microtubule
Carries Golgi towards nucleus; In neurons moves away from axon terminals

77
Q

Centrioles associate with cell membranes and form a

A

Basal body

78
Q

structure of a basal body

A

9 triplet array
The basal body produces microtubules inside cilia and flagella

79
Q

Microtubules provide support to cilia and flagella in what type of cells

A

Eukaryotic

80
Q

what is the array of microtubules in eukaryotic cells

A

9 + 2 doublet array

81
Q

Prokaryotic cells do not have

A

Cilia

82
Q

Prokaryotic flagella are the same or different than Eukaryotes

A

Different

cell bio part 2 (9 decks)

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