Exam 3

Question 1

Functions of the cytoskeleton

Answer 1

• cell shape
• support
• movement
• organization
• signaling

Question 2

Intermediate filaments

Answer 2

Nuclear structure
Cell reinforcement
- neurons
- epithelial cells

Question 3

Microtubules

Answer 3

• Cell organization
• Cillia and flagella
• Environmental sensing

Question 4

Actin filaments

Answer 4

• cell shape and reinforcement
• Cell migration via ‘crawling’
• Cell organization

Question 5

Characteristics of cytoskeletal filaments

Answer 5

Many weak noncovalent interactions

Question 6

Microtubules
GTP on on β-tubulin is ____

Answer 6

hydrolyzable and exchangeable

Question 7

microtubules
Nucleation

Answer 7

Alpha and beta dimers bind together to form a ring with all the β-tubulin head at the plus end

Question 8

Microtubules lengthen from the ___

Answer 8

Plus end

Question 9

Catastrophe

Answer 9

When the rate of addition is slower than the rate of hydrolysis

Question 10

MAPS

Answer 10

Stabilizes plus end, increased rate of addition

Question 11

Kinesin-13

Answer 11

Destabilizes plus end, increases rate of catastrophe

Question 12

Microtubules have dynamic instability

Answer 12

Catastrophe and rescue
- microtubules spontaneously grow and shrink

Question 13

Microtubules
Critical concentration

Answer 13

Concentration of tubulin dimers required to initiate assembly of microtubules
- koff/kon

Question 14

Colchicine

Answer 14

Binds to tubulin dimers, causes disassembly of microtubules

Question 15

Taxol

Answer 15

Binds to microtubules, stabalizes microtubules

Question 16

Microtubules organizing centers (MTOCs)

Answer 16

Nucleate assembly and anchor the minus ends

Question 17

How do microtubules work as ‘tracks’

Answer 17

Motor proteins couple ATP hydrolysis to a change in protein conformation, allowing the protein to ‘walk’ along a microtubule track

Question 18

Kinesins

Answer 18

Plus end directed motors

Question 19

Dyneins

Answer 19

Minus end directed motors

Question 20

Actin cytoskeleton forms

Answer 20

G (globular) - monomer
F (filamentous)

Question 21

Actin filaments are (polar/nonpolar)

Answer 21

polar

Question 22

G actin binds__

Answer 22

ATP

Question 23

Cytochalasin D

Answer 23

Binds F-actin plus end to prevent assembly, leads to filament disassembly

Question 24

Latrunculin

Answer 24

binds G-actin, prevents assembly

Question 25

Phalloidin

Answer 25

Stabilizes actin filaments, fluorescent phalloidin can be used to localize actin filaments

Question 26

Arp2 / Arp3

Answer 26

Actin related proteins, nucleates filament assembly and facilitates filament branching

Question 27

Sequestering proteins

Answer 27

Inhibit assembly by binding G-actin ATP (thymosin) Promote filament assembly at the pls end (profilin)

Question 28

Axoneme

Answer 28

Cilium or flagellum without the PM Grows out of the basal body (centriole)