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BIO1090 Final Exam Review > Lecture 22 > Flashcards

Lecture 22 Flashcards

1
Q

Actin associated motor protein

A
  • like microtubules F-actin microfilaments are associated with motor proteins
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2
Q

Monomeric G-Actin Structure

A
  • 4 subdomains

- divided by central cleft creating 2 kinda equal-sized lobes

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3
Q

Microtubule Organizing Center types

A
  1. basal bodies: associated w/ cilia and flagella

2. centrosome: associated w/ spindle formation

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4
Q

Microtubule Organizing Center

A

MOTC: central site of MT assembly
- only in eukaryotic cells
- Motor MAPs generate sliding force between MTs
Important during mitosis and chromosome segregation

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5
Q

Microfilaments (MF)

A
  • thinnest cytoskeletal element- 8 nm

- polymer of actin protein

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6
Q

What is nucleation and polymerization?

A
  • early nucleation steps of G-actin polymerization are slow
  • ATP binding favors nucleation and stability of filaments
  • monomers can be added at + and - end
  • organization of these is regulated by actin-binding proteins
    G-action → dimers → trimers → short filaments
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7
Q

Are F-Actin filaments polar or non-polar?

A

-polar: + and - ends

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8
Q

Microfilaments (MF) Functions

A
  • maintenance of cell shape
  • cell movement
  • vesicle transport (plants)
  • muscle contraction
  • cytokinesis
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9
Q

F-Actin Filaments Structures

A
  • 2 strands of subunits: 1 units= 28 g-actin subunits (14 each)
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10
Q

What is a lamellipodium?

A

actin projection on leading cell edge

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11
Q

What is a profilin?

A

actin-binding protein, enhances filaments growth

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12
Q

Vesicle transport by microfilament- based motors

A
  • movement of pigment granules via cytoskeleton

- kinesin transfers vesicles to myosin motor protein

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13
Q

Actin nucleation by Arp2/3 complex

A
  • helps in the creation of branch points for polymerization of new actin fibers
  • F-actin networks highly branched (starts polymerization at branch points)
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14
Q

What are MF and Actin molecules?

A

Actin: central components of MFs

  • in cells as monomer (g-actin, globular) or as polymer (f-actin, fibrous)
  • enzyme binds and slowly hydrolyzes ATP
  • double helix of actin monomers
  • mass of globular actin molecule= 42 kDA
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15
Q

Motor proteins and their movement

A
  1. ATP binding to leading head induces a conformational change that swings trailing by 180 towards + microtubule end: force-generating step
  2. New leading head quickly binds to tubulin subunit and releases ADP (involves kinesin’s cargo forward)
  3. trailing head, ATP is hydrolyzed to ADP leading detachment form microtubule
  4. ATP binds to leading head to repeat reaction cycle
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16
Q

Directed cell mobility

A
  • the coordinated activity of actin-binding proteins

- control microfilaments formation in a lamellipodium to allow directed cell movement

17
Q

Intermediate Filament Strucutre

A
  • 10-12 nm diameter
  • exclusive to multicellular animal cells
  • provide structural support and mechanical strength
  • stable in comparison to MTs/microfilaments
  • arrangement of fibrous a-helical proteins
  • NOT polar (no + or - end)
  • not used for transport
  • composed of keratins in the cytoplasm
  • composed of lamins in the nucleus
  • abundant in axons of neurons
18
Q

What are the 2 groups of Actin associated motor proteins

A

1) conventional myosins
- type 2
- primary motors for muscle contraction
2) unconventional myosins
- type 1 and III-XVIII
- generate force and contribute to motility in non-muscle cells

19
Q

What is a phalloidin?

A 
belongs to toxin class found in death cap mushroom
- lethal after some days when injected into bloodstream
20
Q

Is nucleation and polymerization reversible?

A

yes, ATP hydrolysis stimulated destabilization of polymer

- arranged in loose array network/tight bundles/cables/fibers

21
Q

What is a capping protein?

A

blocks exchange of subunit at + end

22
Q

What is myosins?

A

motor protein superfamily associated with microfilaments

  • most myosin molecules move towards + end of microfilaments
  • based contraction pulls trailing edge forward
23
Q

What is colifin?

A

actin-binding protein, disassembles actin filaments

BIO1090 Final Exam Review (11 decks)

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