20-21

Question 1

what are protofilaments?

Answer 1

13 longitudinal repeating units in microtubules

Question 2

what is the major protein in microtubules?

Answer 2

tubulin

Question 3

what are heterodimers?

Answer 3

staggered forming tilted rows in the microtubule wall

Question 4

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

Answer 4

GTP

Question 5

GTP in alpha tubulin is _______ and never hydrolyzed or released

Answer 5

trapped

Question 6

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

Answer 6

hydrolyzed

Question 7

how many ends of beta tubulin are there?

Answer 7

two one at + end and one at - end

Question 8

where are microtubules assembled from?

Answer 8

MTOCs

Question 9

are all microtubules nucleated from MTOCs?

Answer 9

yes

Question 10

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

Answer 10

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

Question 11

what is the MTOC for cillia and flagella?

Answer 11

basal body

Question 12

what is the MTOC for animal cells?

Answer 12

centrosome

Question 13

when do microtubules assemble and disassemble?

Answer 13

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

Question 14

individual microtubules grow and shrink independently (t or f)

Answer 14

true

Question 15

what is a catasptrophe?

Answer 15

growing microtubules rapidly depolymerizing

Question 16

what is a rescue?

Answer 16

when microtubules start rapidly polymerizing/growing

Question 17

GTP beta tubulin cap is located where?

Answer 17

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

Question 18

do microtubules favour assembly or dissasembly?

Answer 18

assembly by adding more GTP tubulin

Question 19

what is the GDP tubulin cap?

Answer 19

protofilaments curve and undergoe diasassembly

Question 20

when do microtubules switch from assembly to dissasembly?

Answer 20

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

Question 21

how do microtubules come in contact with a cell structure?

Answer 21

via the + end of the microtubule

Question 22

what are TIPs?

Answer 22

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

Question 23

_____ binds EB1

Answer 23

TIPs

Question 24

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

Answer 24

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

Question 25

what is kinesin 13?

Answer 25

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

Question 26

what are the two microtubule based motor proteins?

Answer 26

kinesins and dyneins

Question 27

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

Answer 27

away, back

Question 28

most kinesins power transport toward the ___ end of microtubules?

Answer 28

+

Question 29

kinesin 14 moves toward the ___ end

Answer 29

-

Question 30

what does the tail and head domain of kinesin bind?

Answer 30

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

Question 31

how does kinesin 1 move?

Answer 31

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

Question 32

what are the two steps in kinesin 1 regulation?

Answer 32

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

Question 33

what is the function of cytoplasmic dynein?

Answer 33

transports organelles retrograde toward - end of microtubules

Question 34

what is the force generation mechanism?

Answer 34

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

Question 35

cytoplasmic dynein need _______ ______to link dynein to cargo

Answer 35

dynactin complex

Question 36

what does the dynactin complex consist of ?

Answer 36

one actin subunit and cap Z at the + end

Question 37

retrograde transport occurs of late endosome by cytoplasmic _______

Answer 37

dynein

Question 38

anterograde transport of seceratory vesicle occurs by ________

Answer 38

kinesin

Question 39

kinesin prefers ____ and ________ microtubules?

Answer 39

destrosylated and acetylated

Question 40

what is the major motor protein of cillia and flagella?

Answer 40

axanomel dynein