Cytoskeleton I/II

Question 1

What is the cytoskeleton?

Answer 1

Scaffolding and structural framework. Also responsible for cell movements.

Question 2

Three predominant proteins in cytoskeleton

Answer 2

Actin, intermediate filaments, microtubules

Question 3

Steps of Actin Assembly

Answer 3

G Actin -> Dimer -> Trimer -> F Actin (filament)

Question 4

The pointed end is also called…

Answer 4

(-) end

Question 5

The barbed end is also called…

Answer 5

(+) end

Question 6

Which protein facilitates the nucleation of actin?

Answer 6

Formin

Question 7

Which protein “recharges” G-Actin with ATP?

Answer 7

Profilin

Question 8

What does Arp2/3 do?

Answer 8

Binds to actin filament near barbed (+) end; initiates formation of branch. Don’t forget that it stays on.

Question 9

ADF/cofilin

Answer 9

Binds to ADP-actin at negative end. Enhances the rate of dissociation, remaining bound to the monomers to prevent re-polymerization.

Question 10

Actin capping proteins and which side they cap (2)

Answer 10

CapZ - (+)

Tropomodulin - (-)

Question 11

Which protein links parallel actin filaments?

Answer 11

Fimbrin

Question 12

α-actinin

Answer 12

Holds two active filaments together to form an actin bundle

Question 13

Filamin

Answer 13

“Fill ‘em in!”

cross-links actin filaments in an actin network. Important for supporting the cell surface.

Question 14

What is filopodia?

Answer 14

Protruding actin filaments at the leading edge for cell movement

Question 15

What is lamellopodia?

Answer 15

Actin bundles which fill in the cytoskeleton at the leading edge.

Question 16

What is the progression of cell leading edge extension?

Answer 16

The WASP/Scar complex activates Arp2/3 to form a branch. Barbed-end tracking proteins then connect the growing actin filament to the plasma membrane.

Question 17

Wiskott-Aldrich Syndrome

Answer 17

Defect in the WASP protein. It’s X-linked, therefore usually in males. Function of white blood cells disrupted because actin cytoskeleton messed up.

Question 18

What are microvilli anchored to at their base?

Answer 18

Terminal web. Actin filament-rich part of the cell cytoskeleton.

Question 19

Purpose of microvilli?

Answer 19

Increase surface area.

Question 20

Proteins linking actin filament bundles in microvilli?

Answer 20

Fimbrin and villin

Question 21

Which is the strongest, most stable of the three cytoskeleton proteins?

Answer 21

Intermediate filaments

Question 22

Three domains of intermediate filaments

Answer 22

N-terminus, central rod, and C-terminus domains

Question 23

Formation of intermediate filaments

Answer 23

dimerize, dimers form an anti-parallel tetramer. tetramers form protofilaments. eight protofilaments form a filament

Question 24

Intermediate filaments anchor… what? (2)

Answer 24

cell-to-cell and cell-to-ECM

Question 25

Epidermolysis Bullosa Simplex

Answer 25

Intermediate filament / keratin defect. Mildest form of epidermolysis bullosa. Skin splits and blisters.

Question 26

Function of WASP?

Answer 26

Activate Arp2/3

Question 27

Functions of microtubules? (5)

Answer 27

1. Determining cell shape 2. cell locomotion 3. intracellular transport 4. organelle positioning 5. separation of chromosomes during mitosis

Question 28

Components of tubulin

Answer 28

alpha/beta tubulin dimer

Question 29

Dimerization of tubulin

Answer 29

Alpha/beta tubulin must be bound to GTP. GTP hydrolyzes off the beta tubulin soon after binding but stays attached to the alpha subunit.

Question 30

Microtubule consists of...

Answer 30

13 protofilaments arranged around a hollow core

Question 31

Catastrophe

Answer 31

Rapid collapse of the microtubule

Question 32

Which drugs inhibit microtubule polymerization by binding to tubulin?

Answer 32

Vincristine and Vinblastine

Question 33

What does taxol do?

Answer 33

stabilizes microtubules and prevents disassembly. cancer drug

Question 34

What is the microtubule organizing center?

Answer 34

the centrosome

Question 35

function of gamma tubulin?

Answer 35

Anchoring the minus end for the beginning of a microtubule in the centrosome

Question 36

The name of the region rich in tubulin responsible for formation

Answer 36

Pericentriolar material

Question 37

Centrioles are necessary for the formation of?

Answer 37

Cilia and flagella

Question 38

How are microtubules stabilized? (2)

Answer 38

Post-translational modifications and binding of microtubule-associated proteins (MAPs)

Question 39

Types of MAPs?

Answer 39

Microtubule-associated proteins. 1. polymerase 2. depolymerase 3. CLASP

Question 40

Function of polymerase in microtubule assembly

Answer 40

Brings in GTP-bound tubulin to the (+) end

Question 41

Function of depolymerase in microtubules

Answer 41

Speeds up microtubule disassembly by dissociating GTP-tubulin from (+) end

Question 42

CLASP

Answer 42

Rescues microtubules from catastrophe by stopping disassembly and restarting growth at (+) end. Moves along the (+) end.

Question 43

Organization of microtubules in axons

Answer 43

(+) end pointed away from cell body

Question 44

Protein found in axonal microtubules

Answer 44

Tau

Question 45

Organization of microtubules in dendrites

Answer 45

Pointed either way

Question 46

Protein found in dendritic microtubules

Answer 46

MAP2

Question 47

Dynein

Answer 47

Moves along microtubule to (-) or cell body end

Question 48

Kinesin

Answer 48

Moves along microtubule to (+) or peripheral end

Question 49

Which cytoskeletal protein makes up the basis for cilia and flagella projections from the cell?

Answer 49

microtubules

Question 50

What is the name for the 9+2 pattern in cilia/flagella?

Answer 50

Axoneme

Question 51

Describe the important parts of an axoneme

Answer 51

* 9 outer pairs of microtubules, 2 inner microtubules. * Doublets are A/B tubules. A is complete, B incomplete. * doublets connected to each other by nexin; to central pair by radial spokes

Question 52

Basal body of flagella/cilia

Answer 52

* no inner pair | * 9 triplets on the edges (become a pair in the axoneme)

Question 53

Which tubule (A or B) are the motor head groups of dynein bound to in cilia/flagella?

Answer 53

B

Question 54

Which tubule (A or B) is the dynein light chain bound to in cilia/flagella?

Answer 54

A

Question 55

What are the main differences between regular cilia and primary cilium?

Answer 55

Non-motile and no central pair/dynein arms.

Question 56

What do primary cilium do?

Answer 56

Act as sensory organelles to detect extracellular signals

Question 57

Alzheimer's and microtubules

Answer 57

Tau aggregates

Question 58

What genetic disorder causes upper and lower respiratory tract distress due to dysfunctional cilia?

Answer 58

Primary Ciliary Dyskinesia