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Cells: Form and Function > 20-21 > Flashcards

20-21 Flashcards

1
Q

what are protofilaments?

A

13 longitudinal repeating units in microtubules

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2
Q

what is the major protein in microtubules?

A

tubulin

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3
Q

what are heterodimers?

A

staggered forming tilted rows in the microtubule wall

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4
Q

each subunut of alpha beta tublin dimers bind one molecule of _____

A

GTP

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5
Q

GTP in alpha tubulin is _______ and never hydrolyzed or released

A

trapped

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6
Q

GTP in beta tubulin can be ___________ to GDP and exchanged for free GTP

A

hydrolyzed

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7
Q

how many ends of beta tubulin are there?

A

two one at + end and one at - end

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8
Q

where are microtubules assembled from?

A

MTOCs

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9
Q

are all microtubules nucleated from MTOCs?

A

yes

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10
Q

what is the orientation of the + and - end in the MTOC?

A
  • end stays anchored in the MTOC while the + end extends away from it
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11
Q

what is the MTOC for cillia and flagella?

A

basal body

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12
Q

what is the MTOC for animal cells?

A

centrosome

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13
Q

when do microtubules assemble and disassemble?

A

when cells are cooled to 4 degrees celsius they disassemble and reform at 37 degrees celsius

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14
Q

individual microtubules grow and shrink independently (t or f)

A

true

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15
Q

what is a catasptrophe?

A

growing microtubules rapidly depolymerizing

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16
Q

what is a rescue?

A

when microtubules start rapidly polymerizing/growing

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17
Q

GTP beta tubulin cap is located where?

A

microtubule with gtp b tubulin is located on the end of each protofilament

18
Q

do microtubules favour assembly or dissasembly?

A

assembly by adding more GTP tubulin

19
Q

what is the GDP tubulin cap?

A

protofilaments curve and undergoe diasassembly

20
Q

when do microtubules switch from assembly to dissasembly?

A

when the rate of GTP hydrolysis is greater than the rate of GTP tubulin addition

  • switch from dissasemb,y to assembly when rate of GTP tubulin addition is greater than the rate of GTP hydrolysis
21
Q

how do microtubules come in contact with a cell structure?

A

via the + end of the microtubule

22
Q

what are TIPs?

A

+ end trafficking protiens that associate only with + ends that are growing

23
Q

_____ binds EB1

A

TIPs

24
Q

what are the main ways in which TIP interacts with microtubules?

A
  1. enhance polymerization at the + ends
  2. reduce frequency of catastrophies
  3. link microtubule + end to membranes
25
Q

what is kinesin 13?

A

bind and curve at the + end of tubulinprotofilaments into the GDP beta tubulin conformation, faciliates the movement of terminal tubulin dimers, require ATP for hydrolysis

26
Q

what are the two microtubule based motor proteins?

A

kinesins and dyneins

27
Q

antergrade is ______ from the cell while retrograde is ______ to the cell

A

away, back

28
Q

most kinesins power transport toward the ___ end of microtubules?

A

+

29
Q

kinesin 14 moves toward the ___ end

A

-

30
Q

what does the tail and head domain of kinesin bind?

A

tail binds to receptors on cargo, head binds microtubules and ATP

31
Q

how does kinesin 1 move?

A

takes 16nm steps from - end of tubulin dimer to next unbound tubulin dimer at the + end

32
Q

what are the two steps in kinesin 1 regulation?

A
  1. motor bidning to vesicle receptor unfolds kinesin, activating ATPase activity
  2. transport cargo toward the + end of a microtubule
33
Q

what is the function of cytoplasmic dynein?

A

transports organelles retrograde toward - end of microtubules

34
Q

what is the force generation mechanism?

A

atp dependent change in the position of the linker causes movement of the microtubule binding stalk

35
Q

cytoplasmic dynein need _______ ______to link dynein to cargo

A

dynactin complex

36
Q

what does the dynactin complex consist of ?

A

one actin subunit and cap Z at the + end

37
Q

retrograde transport occurs of late endosome by cytoplasmic _______

A

dynein

38
Q

anterograde transport of seceratory vesicle occurs by ________

A

kinesin

39
Q

kinesin prefers ____ and ________ microtubules?

A

destrosylated and acetylated

40
Q

what is the major motor protein of cillia and flagella?

A

axanomel dynein

Cells: Form and Function (6 decks)

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