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BS202 > 14.4 Microtubule Motors and Movement > Flashcards

14.4 Microtubule Motors and Movement Flashcards

1
Q

what are the 2 protein motors involved in powering microtubule movement?

A
  1. kinesins - move towards plus ends of microtubules
  2. dyneins - move towards minus ends of microtubules
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2
Q

compare and contrast the general structure of kinesins and dyneins

A
  • both kinesins and dyneins have heavy and light chains
  • only dyneins have intermediate chains
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3
Q

motor movement of kinesins and dyneins is powered by ()

A

ATP

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4
Q

how does ATP allow for kinesin/dynein movement along microtubules

A

interaction of motor protein globular head domains (motor domains) with ATP causes a conformation change in the head domains, thus allowing them to move along microtubules

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5
Q

experiments (isolation of kinesin) found that in the presence of ATP, motor proteins (i.e. kinesins) ()

A

interact and release from microtubules

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6
Q

how are kinesins and dyneins involved in cargo transport

A
  • microtubules are usually oriented with their minus ends anchored at the centrosome and their plus ends extending toward the cell periphery
  • kinesins usually bring cargo (usually vesicles/organelles) towards cell periphery, where as dyneins usually bring cargo towards the center of the cell
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7
Q

cargo selection can be very specific → dyneins and kinesins recognize different microtubules by the ()

A

posttranslational modifications of tubulin

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8
Q

which motor proteins are involved in position which membrane-bound organelles in the cell?

A
  • kinesins play a role in positioning and pulling the ER towards cell periphery
  • dyneins play a role in positioning the Golgi at the center of the cell
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9
Q

the ER extends to the periphery of the cell through ()

A

association with microtubules

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10
Q

() are microtubule-based projections of the plasma membrane that are found on almost all types of animal cells

A

cilia and flagella

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11
Q

() act as antennae that sense a variety of extracellular signals as well as being responsible for movement

A

cilia

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12
Q

some bacteria have (), but these are protein filaments projecting from the cell surface rather than microtubule-based projections

A

flagella

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13
Q

() are found on most animal cells and are involved in sensing extracellular signals; they play an important role during development but have no motor function in adults

A

primary cilia

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14
Q

() are responsible for movement (same with flagella) either across a surface or movement of fluid/mucus across cell surface (e.g. in epithelial cells)

A

motor cilia

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15
Q

structures of cilia and flagella are similar; both have:

A
  1. basal body - where the protrusion (i.e. cilia or flagella) extends from cell body
  2. axoneme - actual protrusion of cell
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16
Q

describe the structure of the basal body

A
  • centriole containing 9 triplets of microtubules (triplet microtubules)
  • derived from centrioles that have been transported to the plasma membrane
  • serve to initiate the growth of axonemal microtubules as well as anchor cilia to the surface of the cell
17
Q

describe the general structure of an axoneme

A

contains 9 doublet microtubules (two from each of the triplets in the basal body extend into axoneme); contains a complete A tubule (13 protofilaments) and an incomplete B tubule (10-11 protofilaments)

18
Q

axonemes of motile cilia and flagella contain an additional () and () that are responsible for motility

A
  1. central pair of microtubules
  2. associated proteins
19
Q

in motor cilia and flagella, doublet microtubules are arranged in a ()

A

”9+2 pattern” → central pair is surrounded by 9 doublets

20
Q

in motor cilia and flagella, outer doublets are connected to the central pair by ()

A

radial spokes

21
Q

in motor cilia and flagella, outer doublets are connected to each other by links of a protein called ()

A

nexin

22
Q

what proteins/structures are present in motor cilia/flagella but not in primary cilia?

A
  1. central pair of microtubules
  2. radial spokes
  3. nexin
  4. dyneins
23
Q

in motor cilia and flagella, () → motor activity drives movement of cilia/flagella

A

dynein bases are attached at each A tubule; head groups attach to the B tubule of the adjacent microtubule doublet

24
Q

how do motor cilia/flagella bend?

A
  • dynein motor heads move along B tubules (towards minus ends) → A tubule of one doublet slides towards the base of the adjacent B tubule
  • because the doublets are linked and held in place by nexin, the doublets bend
25
Q

during mitosis, dynamic instability accelerates as a result of ()

A

increased microtubule growth and catastrophe rates

26
Q

microtubule array in interphase cells disassembles to form the () (responsible for separation of daughter chromosomes)

A

mitotic spindle

27
Q

restructuring of microtubule cytoskeleton is directed by duplication of (1) → forms 2 separate (2)

A
  1. centrosome
  2. microtubule organizing centers at opposite poles
28
Q

what are the 3 kinds of microtubules involved in the formation of the mitotic spindle

A
  1. kinetochore microtubules
  2. interpolar microtubules
  3. astral microtubules
29
Q

microtubules that attach to the condensed chromosomes of mitotic cells at their centromeres

A

kinetochore microtubules

30
Q

microtubules that aren’t associated with chromosomes but are stabilized by overlapping with each other in the center of the cell

A

interpolar microtubules

31
Q

microtubules that extend outward from the centrosomes to the cell periphery; plus ends are anchored in cell cortex

A

astral microtubules

32
Q

how are duplicated chromosomes aligned at the metaphase plate

A

alignment of chromosomes is mediated by rapid growth of kinetochore microtubules and capture of their plus ends by kinetochores

33
Q

what happens during Anaphase A

A
  1. chromosomes move towards the spindle poles along the kinetochore microtubules
  2. kinetochore microtubules shorten as they are disassembled by kinesins (act as microtubule-depolymerizing enzymes)
34
Q

what happens in Anaphase B

A
  1. both interpolar and astral microtubules contribute to chromosome movement by pushing the spindle poles apart
  2. kinesins cross-linking interpolar microtubules move towards plus ends → causes overlap between interpolar microtubules to decrease and spindle pole to be pushed apart
  3. dyneins anchored on the cell cortex pull the spindle poles apart by pulling them closer to the cell cortex; this is aided by the depolymerization of astral microtubules as the dyneins move towards their minus end

BS202 (36 decks)

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