microtubules 1

Question 1

what does the cytoskeleton comprise of

Answer 1

-microfilaments
-microtubules
-intermediate filaments

Question 2

who first observed microtubules?

Answer 2

keith porter

Question 3

what are the 2 different tubulin genes?

Answer 3

alpha and beta tubulin

Question 4

how many protofilaments is the hollow tube made of?

Answer 4

13

Question 5

what are the 2 roles of microtubules?

Answer 5

-transport
-structure to cells

Question 6

where do microtubules emerge from?

Answer 6

centrosome (near the nucleus)

Question 7

true or false, microtubules are found in certain eukaryotes

Answer 7

false, all eukaryotes

Question 8

where are 3 important things that microtubules are found in?

Answer 8

-mitosis (microtubules form the mitotic spindle)
-neural functions: microtubules are jam packed in neurons
-cilia: trachea/lungs lined with cilia and helps get rid of of waste

Question 9

how are microtubules organized in animal cells?

Answer 9

-organized by the centrosome in radial array
-negative ends near centrosome
-positive ends in periphery

Question 10

true or false, microtubules are static structures

Answer 10

true, they are continuously built, and broken down (shoot from centrosome, out to cell periphery)

Question 11

true or false, microtubules are “roadways” for intracellular transpot

Answer 11

true

Question 12

true or false, neurons are slightly packed with microtubules

Answer 12

false, they are densely packed

Question 13

what is the difference between the organization of microtubules in the axons and in the dendrites?

Answer 13

-axons: all + ends of microtubules are pointing outwards
-dendrites: mixed polarity in dendrite (pointing in diff directions)

Question 14

what determines the density of the packing of microtubules in neurons?

Answer 14

microtubule associated proteins

Question 15

what type of structure are cilia?

Answer 15

specialized microtubule-based structures (contain microtubules)

Question 16

true or false, cilia and flagella are completely different

Answer 16

false. flagella are also cilia

Question 17

what are flagella? where can we find them?

Answer 17

tail used for swimming, type of cilia. sperm tail (allow them to swim), and chlamydomonas arms (also to swim)

Question 18

what do we mean by the 9+2 symetry?

Answer 18

refers to the inside of the cilia. 9 microtubule doublets on outside and then central pair in the center

Question 19

what is a microtubule doublet?

Answer 19

two microtubules stuck to each other. one is whole, and the other is cracked open and stuck to side of the other one

Question 20

what are microtubules made of?

Answer 20

tubulin heterodimers

Question 21

what is a tubulin heterodimer?

Answer 21

an alpha and a beta tubulin put together

Question 22

true or false, you can find alpha and beta tubulin alone in the cytoplasm

Answer 22

false, alpha and beta tubulin are always together

Question 23

what drives the polymerization of microtubules?

Answer 23

hydrolysis and exchange of GTP in and out of beta tubulin pocket drives polymerization process

Question 24

true or false, alpha and beta tubulin come from same gene

Answer 24

false, different genes

Question 25

why is tubulin a GTPase?

Answer 25

it uses GTP hydrolysis to drive its polymerization

Question 26

how was tubuliin first identified?

Answer 26

first identified as the target of the drug colchicine

Question 27

what does colchicine treat?

Answer 27

gout

Question 28

where did colchicine first appear?

Answer 28

in the ebers papyrus which is the oldest medical document

Question 29

what does colchicine do?

Answer 29

binds to microtubules

Question 30

why are the rate constants for the polymerization of microtubules

Answer 30

cause there are 13 diff places where incoming tubulin could bind, and we dont know what it looks like when its growing

Question 31

whats at the negative end of the microtubule?

Answer 31

alpha tubulin

Question 32

whats at the positive end of the microtubule?

Answer 32

beta tubulin

Question 33

which end of the microtubule has the highest critical concentration?

Answer 33

negative end

Question 34

what does the loss of the GTP cap lead to?

Answer 34

rapid shrinkage

Question 35

what does the GTP cap do?

Answer 35

keeps the microtubule stale

Question 36

what state makes microtubule fall apart?

Answer 36

GDP state

Question 37

when does a catastrophe happen?

Answer 37

if GTP cap is lost: GTP hydrolysis happens before addition of GTP-tubulin

Question 38

when is tubulin curved?

Answer 38

when its falling apart

Question 39

when is tubulin straight?

Answer 39

when its growing

Question 40

what are the curved GTP complexes?

Answer 40

-Rb3 -darpin -TOG1

Question 41

what are the intermediate complexes?

Answer 41

GMPCPP

Question 42

what are the straight complexes?

Answer 42

1JFF

Question 43

what allows the cell to quickly restructure their microtubules?

Answer 43

dynamic instability

Question 44

what does dynamic instability allow the cell to do? give a specific example

Answer 44

allows it to be able to easily control its cytoskeleton. for example, as the cell goes into mitosis, need radial array of microtubules, so it will break down old ones, and build completely new one

Question 45

how did they discover dynamic instability?

Answer 45

-purifiy tubulin from brains in cuvette -shoot ultraviolet light through cuvette -by sticking needle into cuvette and rapidly pushing solution through narrow gauge needle, breaks microtubules in half, which leads to a decrease in polymer length -since center is now unstable cause no more caps, whole thing falls apart -they observed that after it breaks down, it would rebuild

Question 46

what is the link between absorbance and polymerization of tubulin?

Answer 46

if polymers form, absorbance increases

Question 47

which cytoskeleton component is the target of a broad class of chemotherapy drugs? give an example

Answer 47

microtubules example: taxol

Question 48

what does taxol do? what is the downside of it?

Answer 48

freezes microtubules, but it freezes ALL microtubules, so it ends up also freezing neurons since they contain lots of microtubules, which leads to neuropathic pain

Question 49

what is an alternative to taxol, but not enough reasearch has been done about it (No funding)?

Answer 49

DZ-2384 apparently would not cause neuropathic pain

Question 50

how do tubulin dimers associate?

Answer 50

head to tail (beta on top, alpha at the bottom)