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Elements of Medicine > Cytoskeleton I/II > Flashcards

Cytoskeleton I/II Flashcards

1
Q

What is the cytoskeleton?

A

Scaffolding and structural framework. Also responsible for cell movements.

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2
Q

Three predominant proteins in cytoskeleton

A

Actin, intermediate filaments, microtubules

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3
Q

Steps of Actin Assembly

A

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

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4
Q

The pointed end is also called…

A

(-) end

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5
Q

The barbed end is also called…

A

(+) end

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6
Q

Which protein facilitates the nucleation of actin?

A

Formin

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7
Q

Which protein “recharges” G-Actin with ATP?

A

Profilin

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8
Q

What does Arp2/3 do?

A

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

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9
Q

ADF/cofilin

A

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

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10
Q

Actin capping proteins and which side they cap (2)

A

CapZ - (+)

Tropomodulin - (-)

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11
Q

Which protein links parallel actin filaments?

A

Fimbrin

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12
Q

α-actinin

A

Holds two active filaments together to form an actin bundle

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13
Q

Filamin

A

“Fill ‘em in!”

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

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14
Q

What is filopodia?

A

Protruding actin filaments at the leading edge for cell movement

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15
Q

What is lamellopodia?

A

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

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16
Q

What is the progression of cell leading edge extension?

A

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.

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17
Q

Wiskott-Aldrich Syndrome

A

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

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18
Q

What are microvilli anchored to at their base?

A

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

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19
Q

Purpose of microvilli?

A

Increase surface area.

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20
Q

Proteins linking actin filament bundles in microvilli?

A

Fimbrin and villin

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21
Q

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

A

Intermediate filaments

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22
Q

Three domains of intermediate filaments

A

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

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23
Q

Formation of intermediate filaments

A

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

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24
Q

Intermediate filaments anchor… what? (2)

A

cell-to-cell and cell-to-ECM

25
Q

Epidermolysis Bullosa Simplex

A

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

26
Q

Function of WASP?

A

Activate Arp2/3

27
Q

Functions of microtubules? (5)

A
  1. Determining cell shape
  2. cell locomotion
  3. intracellular transport
  4. organelle positioning
  5. separation of chromosomes during mitosis
28
Q

Components of tubulin

A

alpha/beta tubulin dimer

29
Q

Dimerization of tubulin

A

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

30
Q

Microtubule consists of…

A

13 protofilaments arranged around a hollow core

31
Q

Catastrophe

A

Rapid collapse of the microtubule

32
Q

Which drugs inhibit microtubule polymerization by binding to tubulin?

A

Vincristine and Vinblastine

33
Q

What does taxol do?

A

stabilizes microtubules and prevents disassembly. cancer drug

34
Q

What is the microtubule organizing center?

A

the centrosome

35
Q

function of gamma tubulin?

A

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

36
Q

The name of the region rich in tubulin responsible for formation

A

Pericentriolar material

37
Q

Centrioles are necessary for the formation of?

A

Cilia and flagella

38
Q

How are microtubules stabilized? (2)

A

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

39
Q

Types of MAPs?

A

Microtubule-associated proteins.

  1. polymerase
  2. depolymerase
  3. CLASP
40
Q

Function of polymerase in microtubule assembly

A

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

41
Q

Function of depolymerase in microtubules

A

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

42
Q

CLASP

A

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

43
Q

Organization of microtubules in axons

A

(+) end pointed away from cell body

44
Q

Protein found in axonal microtubules

A

Tau

45
Q

Organization of microtubules in dendrites

A

Pointed either way

46
Q

Protein found in dendritic microtubules

A

MAP2

47
Q

Dynein

A

Moves along microtubule to (-) or cell body end

48
Q

Kinesin

A

Moves along microtubule to (+) or peripheral end

49
Q

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

A

microtubules

50
Q

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

A

Axoneme

51
Q

Describe the important parts of an axoneme

A
  • 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
52
Q

Basal body of flagella/cilia

A
  • no inner pair

* 9 triplets on the edges (become a pair in the axoneme)

53
Q

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

A

B

54
Q

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

A

A

55
Q

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

A

Non-motile and no central pair/dynein arms.

56
Q

What do primary cilium do?

A

Act as sensory organelles to detect extracellular signals

57
Q

Alzheimer’s and microtubules

A

Tau aggregates

58
Q

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

A

Primary Ciliary Dyskinesia

Elements of Medicine (8 decks)

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