cytoskeleton, motility

Question 1

why helical, wrapped structure of filaments?

Answer 1

• strength (break longitudinal AND lateral bonds w/ subunit loss)
• resist thermal breakage (not covalently bound, so susceptible to high temps as single protofilaments)
• can still grow/shrink on ends

Question 2

microtubule function

Answer 2

resist compression and bending.
“cellular highway” - for cellular transport,
determine cell polarity (+ end to periphery)

Question 3

microtubule organization

Answer 3

alternating alpha and beta tubulin,
- end = at centrosome (MTOC), + end (with beta) grows faster
GTP cap w/ growth, prevents shrinking.
*plant toxins disrupt dynamic change

Question 4

centrioles

Answer 4

microtubule triplet structures in centrosome of microtubules,
*at 90 angle
ensure duplication of centrosome in cell division

Question 5

rate limiting step of microtubule assembly

Answer 5

nucleation!
need to form stable aggregate w/ many bonsd btwn subunits.
once form, growth = fast

Question 6

accessory proteins

Answer 6

regulate length, stability and spacing of microtubules.

• stathmin
• katanin
• MAPs
• Capping proteins

Question 7

stathmin

Answer 7

limits subunit availability

- promote shrinking

Question 8

katanin

Answer 8

severs micotubules

–> RAPID shrinkage

Question 9

microtubule associated protein (MAP)

Answer 9

adjust spacing/organization of microtubules.

ie: tau

Question 10

molecular motors

Answer 10

w/ heavy and light chains, + head and tail domains.
bind to polarized filaments (actin or microtubules)
& move cargo along filament
- kinesin (to + end/periphery)
- dynein (to - end/center)

Question 11

2 types of dynein

Answer 11

1. cytoplasmic - cargo = vesicles, localize golgi near cell center
2. axonemal - in cilia and flagella, slide microtubules past each other

Question 12

anterograde

Answer 12

movement in direction from cell body (center) to axon