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C Bio > Cytoskeleton - Part II Motor PROs (25) > Flashcards

Cytoskeleton - Part II Motor PROs (25) Flashcards

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Biology 101 flashcards
1
Q

how is the movement of vesicles & molecules in the cell controlled?

A

where MTs are placed - growth & direction is directed by the cell

Regulation of the motors:
Activation
Placement on their paths
Movement along path

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2
Q

MT motor PROs?

A

kinesin & dynein

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3
Q

microfilament motor PROs?

A

myosin

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4
Q

kinesin

A

MT motor PRO, move towards + end of MT

Smallest of motor PROs

Pair of globular ends – generate force (walk)

Stalk & fan shaped tail binds cargo

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5
Q

dynein

A

MT motor PRO, move towards – end of MT

Ubiquitous eukaryotic motor PRO

2 identical heavy chains which generate force

Variety of intermediate & light chains with diff cargo recognition domains

Cargo is attached by dynactin

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6
Q

myosin

A

microfilament motor PRO, moves along the actin network

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7
Q

how is movement of kinesin & dynein facilitated?

A

Kinesin & dynein attach to diff adapter PROs which then attach to diff PROs in membranes (vesicles, PM etc.) to generate movement, capture cargo before movement

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8
Q

what 2 motor PROs are involved in ATP dependent movement?

A

kinesin & dynein

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9
Q

how is ATP movement done?

A

ATP binding
ATP hydrolyzing
ADP release

causes a conformational change in the motor domain & alters the orientation of the neck linker

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10
Q

what are the heads in motor PROs responsible for?

A

attachment & movement

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11
Q

dendrites

A

neuron receives signal

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12
Q

axons

A

neuron sends signals

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13
Q

Axon MT orientation

A

minus end points towards cell body & plus end outwards

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14
Q

what is the movement of motor PROs in neurons?

A

kinesin moves towards the synapse

dynein moves away from the periphery

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15
Q

Kinesin uses ___ ATP/step

A

1

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16
Q

Kinesin moves along:

A

a single protofilament

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17
Q

kinesin move only on ____ & ____ are left in b/w steps

A

betas

alphas

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18
Q

where does kinesin attach to the vesicle?

A

integral PRO

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19
Q

how many kinesins are found in human cells

A

40

20
Q

how do kinesins bind to larger cargo?

A

aid of cargo or scaffolding PROs (Rab PROs)

21
Q

how do kinesin exist in the absence of cargo?

A

fold over & don’t bind MTs

22
Q

motor PRO ATP dependent movement (Kinesin & dynein)

A

Once cargo is bound, only one head with bound ADP binds to the MT

ADP is replaced with ATP on the bound head, causing the neck to pivot

Second head binds

Second head has ADP replaced with ATP & the neck bends

ATP is hydrolyzed to allow the trailing head to release from the MT

23
Q

what is the effect of ATP hydrolysis in motor PROs?

A

enables the trailing head to release from the MT

24
Q

what is the effect of swapping ADP with ATP in motor PROs?

A

neck will bend enabling the head to move

25
Q

where was kinesin first isolated?

A

brain tissue

26
Q

axonal flow

A

vesicles are carried along MTs from the centrosome in the cell body to axon endings

27
Q

what motor PRO is involved in carrying vesicles in axonal flow?

A

kinesin

28
Q

Myosin V

A

takes over transport from vesicles, moves along actin filaments to the PM at the synapse

29
Q

describe the axon endings

A

extensive actin cytoskeleton

30
Q

which MT motor PRO is the biggest?

A

dynein

31
Q

what are the 2 ways dynactin is involved with dynein?

A

dynein looks for dynactin

dynactin can be directly found in the membrane

other times dynactin is the intermediate area where it’s attached to Rab PRO

32
Q

what are the functions of dynein?

A

C’some movement in mitosis

Positioning of the Golgi, reassembles Golgi post mitosis

Movement of vesicles & organelles

Axonal retrograde organelle movement

Fibroblasts & endothelial cells move endosomes, lysosomes & Golgi derived vesicles toward the cell center

33
Q

how are motor PROs involved in changing the colour of skin in certain species?

A

movement of melanosomes

when kinesins are activated (by having more ATP) - they drag melanosomes outwards & darken the cell

when kinesins are inactivated (by having less ATP) - dynein drag melanosomes inwards lightening the cell & creating a dot

34
Q

chromatophores

A

pigment-containing cells

35
Q

melanosomes

A

organelles with chromatophores containing dark pigment

36
Q

cilia vs.flagella

A

CILIA
Shorter
More numerous
Cell movement is perpendicular to the direction of cilia

FLAGELLA
Longer
Rarely more than 2
Flagella are parallel in the direction of movement

37
Q

functions of cilia

A

in multicell organisms, move fluids

cilia clear particulates in lungs

cilia of the oviducts move the egg cell

38
Q

composition of cilia & flagella

A

MTs surrounded by a PM

all MTs have + ends at the tips & - ends at the base

39
Q

axoneme

A

9+2 array of MTs

9 pairs arranged in the circle & 1 pair in the center

Each doublet or pair has 1 complete MT (A-13 protofilaments) & 1 incomplete MT (B- 10-11 protofilaments) 

B is fused to A 

Middle pair aren’t fused, held together by bridges & necks
40
Q

basal body

A

the MTOC at the base of the flagellum (looks exactly like a centriole)

41
Q

how does cilia movement occur?

A

Dynein arms are anchored to A MT, they attach to B MT neighbour

Dynein molecules undergo a conformational change causing A MT to move slightly towards the base of the B MT. Facilitated by ATP hydrolysis

Dynein releases B MT

Nexin holds MT until dynein reattaches to the base of the B MT

Nexin breaks & cycle repeats or, nexin is stretched & the cilia can bend back

42
Q

in what motion do cilia move?

A

Sliding of one axoneme alternates with the sliding of the other
Cilia will bend one way & then the other
Cilia bend & move in a circle, do a full rotation

43
Q

what hypothesis is currently used to describe how cilia move? & what evidence is there?

A

dynein arm activity is regulated by the central MT pair & radial spokes

cilia that lack an inner core lacks motion

44
Q

primary cilium

A

lack the central pair of MT

1/cell

No locomotor function, act as an antenna

Covered with receptors p/u chemical signals & carry them up & down MTs throughout the cell

Mechanoreceptors: bending of the cilium causes triggers the signal to send

45
Q

ex of the primary cilium sending signals

A

Kidney epithelium –> fluid flow causes cilia to bend & opens calcium channels which send signals to the rest of the kidney ducts to regulate the flow

Mechanically gated

Ca2+ induced Ca2+ release

Defects in primary cilium lead to kidney disease

46
Q

how are motor PROs being used in nanotechnology?

A

Motor PROs can be fixed to microchips

Will shuttle MTs across the cell’s surface, leads to enhanced detection

MTs can be fused with an antibody which will direct the motion of kinesin, can sort through & concentrate components accurately
Sort through blood samples

C Bio (30 decks)

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