Cytoskeleton Flashcards

1
Q

main function of the cytoskeleton

A

cell shape, cell wall formation, intracellular movement, cell metabolism

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2
Q

cytoskeleton is composes of what 2 parts mainly

A

microtubules and actin filaments

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3
Q

Microtubules

structure of MTs (3 main pieces)

A

tubulin dimers, 13 protofilaments, polarity

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4
Q

MTs are composed of 2 types tubulin dimers:

A

alpha-tubulin and beta-tubulin

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5
Q

Microtubules are formed by 13 protofilaments that form [blank]

A

a hollow tube

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6
Q

MTs exhibit polarity, at what end does growth occur

A

growth at the (+) end, it also has a (-) end

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7
Q

Are MTs dynamic?

A

Yes, constantly growing and shrinking, which makes them a bit unstable

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8
Q

How is the instability of MTs regulated

A

regulated by the GTP/GDP state of the tubulin dimers

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9
Q

MTs are approx how long

A

25nm tubes

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10
Q

actin filaments are approx how long

A

7nm, aka microfilaments

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11
Q

GTP bound beta tubulin’s form? straight or bent? assembly or dissasembly?

A

GTP bound beta tubulin is straight, assembly

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12
Q

GDP bound beta tubulin is straight or bent? assembly or dissasembly?

A

GDP beta tubulin is bent, dissasembly

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13
Q

MT Polymerization and Catastrophe

how does a MT grow

A

add GTP dimers at the (+) end

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14
Q

how does MT catastrohpe happen

A

loss of GTP cap due to hydrolysis leads to rapid breakdown

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15
Q

how does EBI (End Binding Protein) influence MT dynamics

A
  • binds to (+) end to GTP cap
  • stablize elongation, prevent catastrophe
  • guides growth and speed
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16
Q

where does MT nucleation happen

A

nuclear envelope and pre-existing MTs

17
Q

what does γ-Tubulin Ring Complex (γ-TuRC) do

A

acts as a template for forming new MTs, providin starting point and polarity for GTP cap to attach and begin elongation and polymerization

18
Q

cell wall structure and formation

[blank] MTs guide the movement of [blank], which lays cellulose fibers in the cell wall.

A

cortical, cellulose synthase

19
Q

MTs are crucial for organizing cellulose production, impacting cell wall [blank]

A

rigidity

20
Q

Actin filaments are composed of [blank] monomers, which polymerize into [blank]

A

G-actin (globular), F-actin (filamentous)

21
Q

Actin filaments are flexible and they can be strenghtened by [blank]. They do not form [blank] bonds

A

bundling, covalent

22
Q

how does actin filament polymerization happen

A

ATP binds to G actin monomers, profilin plays a key role

23
Q

how does profilin regulate polymerization in actin filaments

A

makes sure atp binds to g-actin at (+ end)

24
Q

apart from prolifin, what else regulates polymerization

A

actin binding proteins regulate by promoting or repressing polymerization

25
Q

two types of nucleation (formation) for actin filaments

A

formin-mediated, ARP 2-3 complex- mediated

26
Q

formin mediated nucleation involves

A

unbranched, linear actin filaments, which recruits G-actin at the (+) end.

27
Q

ARP 2-3 complex mediated nucleation involves

A

nucleation of branched AFs by growing (nucleating) off existing filaments, aiding in cell shape and motility.

28
Q

function of AFs in plant cells

A

-vesicle delivery
-growth in pollen tubes
-found in cortical and transvacuolar strands of cytoplasm

29
Q

what is treadmilling

A

MTs glide through the addition and loss of dimers at opposite ends, maintaining their structure while changing

30
Q

Real-time observations reveal that MTs add or lose up to 20 dimers per second at the (+) end. What does this tell us?

A

allows for flexibility in cell structure

31
Q

Actin filaments can form branches via the ARP 2/3 complex. Why is this important?

A

helps cells adapt shape to environment, especially in epidermal cells

32
Q

Phalloidin, a toxin that binds to [blank]? What does it do?

A

F-actin, used to stain and visualize actin filaments

33
Q

α-tubulin always binds [blank], while β-tubulin cycles between [blank]

A

GTP, GTP and GDP states

34
Q
A