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BIOL 1090 > B: Motors, Actin, Cell Mobility (22) > Flashcards

B: Motors, Actin, Cell Mobility (22) Flashcards

1
Q

Define: exocytosis

A

Exocytosis: secretory vesicles deliver contents outside the cell

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2
Q

Define: endocytosis

A

Endocytosis: vesicles bring contents into cell

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3
Q

Define: autophagy

A

Autophagy: lysosomes recycle “used” organelles

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4
Q

Define phagocytosis

A

Phagocytosis: capture and destruction of pathogens like bacteria

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5
Q

What are the roles of Microtubule - associated Non Motor Proteins

A

Control MT organization in cytosol (ex. Tau protein)

Stabilize MTs or stimulate assembly

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6
Q

How are the +/- end different on MTs

A

+ end is dynamic

  • end is stable
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7
Q

Which was does kinesin and dynein move in MTs

A

Kinesin is + end directed

Dynein is - end directed

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8
Q

How do MT associated motor proteins move?

A

Use ATP to generate force

Can move material along MT tracks

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9
Q

What are the 4 steps of movement of MT associated motor proteins

A
  1. AMP binding to the leading head induces a conformational change that swings the trailing head 108 degrees toward the (+) end of the microtubule
  2. The new leading head quickly binds to a tubulin subunit and releases its ADP, moving the kinesin’s cargo forward
  3. In the trailing head, ATP is hydrolyzed to ADP
  4. ATP binds to the leading head to repeat the reaction cycle
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10
Q

What does the moments of MT associated motor proteins generate in MTs

A

Motar MAPs generate sliding force between MTs

Important during mitosis and chromosome segregation

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11
Q

How does Kinesin and Dynein help the survival of Zebrafish

A

Allows a survival mechanism that redistributes melanin-granules for camouflage

– In the dark, melanin granules are dispersed outward by kinesin, causing the embryo to be darkly coloured
– In the light, melanin granules are aggregated toward the center by dynein, causing the embryo to be lightly coloured

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12
Q

What is the MTOC

A

Microtubule-Organizing Center (MTOC)

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13
Q

What does the MTOC do

A

Central site of MT assembly

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14
Q

Where is the MTOC found

A

Only in eukaryotes

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15
Q

What are the 2 main types of MTOC

A

Basal bodies associated with cilia and flagella

The centrosome associated with spindle formation

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16
Q

What are MTs formed from

A

Hollow tube formed from tubulin dimers

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17
Q

What are MFs formed from

A

Double helix of actin monomers

18
Q

What are IFs formed from

A

Strong fiber composed of intermediate filament protein subunit

19
Q

Are IFs found in all cells?

A

Exclusive to multicellular animal cells

20
Q

What is the role of IFs

A

Provide structural support and mechanical strength

21
Q

Are IFs stable?

A

Stable in comparison to MTs and microtubules

Non polar

22
Q

What are IFs formed from

A

Arrangement of fibrous a-helical proteins

23
Q

Are IFs used for transport

A

No bc non polar

24
Q

What are examples of IFs

A

karatins : epithelial cells
Neurofilaments: neuron-specific
Lamins: nucleus of cells

25
Q

What are MFs made from

A

Polymer of actin protein

26
Q

What are the functions of MFs

A

Maintenance of cell shape
Cell movement
Vesicle transport (specifically in plants)
Muscle contraction
Cytokinesis (contractile ring)

27
Q

What are the types of MF

A

Exists as monomer (G-actin) or polymer (F-actin)

28
Q

Whats the role of Actin in MFs

A

Actin is the central component of MFs
Actin is an enzyme that binds and slowly hydrolyzes ATP
A MF is a double helix of actin molecule

29
Q

What is the structure of G-actin MFs

A

4 subdivisions
Divided by central cleft
2 approx equal lobes

30
Q

What is the structure of F-actin MFs

A

2 strands of subunit
One unit has 28 subunits of G-actin
——– 14 in each strand
Exactly 72nm

31
Q

Are MFs simular to MTs?

A

MFs are dynamic like MTs
– MF have similar properties to MTs

Like MTs, the + end quickly assementles/disassembles
– The - end assembles/disassembles slowly

32
Q

What are the 2 main steps of F-actin MF assembly:

A
  1. Nucleation
  2. Polymerization
33
Q

Explain
the Nucleation in MF assembly

A

Early nucleation steps of G-actin polymerization are slow

G-actin - dimers - trimers - short filaments

Monomers can be added at both ends (but always faster at + end)

Process always reversible - ATP hydrolysis stimulates the destabilization of the polymer

34
Q

Explain F-actin assembly

A

F-actin microfilaments can be arranged in loose array network (meshwork) or tight bundles/cables/fibers

Organization of these structures regulated by actin-binding proteins

35
Q

How does the ARP2/3 complex help actin nucleation

A

Complex helps in the creation of branch points for the polymerization of new actin fibers

Arp2/3 complex starts polymerization at branch points

36
Q

How does directed cell mobility work in MFs

A

Coordinated activity of actin-binding proteins controls microfilament formation in a lamellipodium to allow directed cell movement

37
Q

What are myosins

A

Myosins: a superfamily of motor proteins associated with microfilaments

– Most myosin molecules move toward the + end of microfilaments

38
Q

What are the 2 main types of myosins

A
  1. Conventional myosins
  2. Unconventional myosins
39
Q

Explain conventional myosins

A

Type II
Primary motors for muscle contraction

40
Q

Explain unconventional myosins

A

Types I and III - XVIII
Generate force and contribute to motility in non-muscle cells

41
Q

What are the Roles of Actin-Associated Motor Proteins

A

Actin-based protrusion of leading edge (lamellipodium) powered by actin growth

Myosin -based contraction pulls trailing edge forward

42
Q

Explain Vesicle Transport by MF-based motors

A

Microtubule-based and microfilament-based motors can cooperate in intracellular transport

Kinesin transfer vesicle to myosin motor protien

BIOL 1090 (19 decks)

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