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CTO Quiz 1 > Cytoskeleton > Flashcards

Flashcards in Cytoskeleton Deck (23):
1

Width of actin filament

7 nM

2

Polarization of actin

Grow fastest at + end, depolymerize at - end

3

Polymerization of actin

G actin binds to ATP
Polymerizes into F-actin (mostly at + end)
ATP later hydrolyzes to ADP
Polymerization also requires K+ and Mg+

4

Structure of actin

G = granular, polymerizes into F (fibrillar) in presence of ATP

5

Functions of actin

Anchor membranes, structure (terminal web)
Contractile (shape, movement, cell separation)
Transport around cell (actin binding proteins)
Form microvilli, lamellae, filopodia

6

Actin and ATP cycling

Requires ATP presence to polymerize (reflects concentrations of ATP in cell)
Hydrolysis while polymerized
ADP tends to depolymerize

7

Actin binding proteins (6)

Myosin - motor
Tropomyosin - stabilizes
Gelsolin - breaks filaments in middle
Actin bundling proteins - fimbrin, villin, alpha actinin
Branching proteins - formin
Integrin - intermembrane, anchors to ECM

8

Actin and cell movement

Polymerization can move cell membrane
Myosin can be bound to organelle, vesicle or to membrane

9

Actin disrupters

Cytochalasins B+D - prevent polymerization (chemo)
Phalloidin - prevents depolymerization (mushroom toxin)

10

Microtubule size

25 nM (biggest cytoskeleton element)

11

Microtubule structure

Tubulin dimers (alpha and beta) in
13 chains around
hollow core
Originate from MTOC

12

Microtubule polarization

- end at MTOC
+ end at periphery - growth and depolymerization at + end (MTOC caps - end)

13

Microtubules and GTP cycling

GTP binding promotes assembly
Depolymerizes closer to bottom

14

MTOC

AKA centrosome
Nine sets of triplets of MTs
Rings of gamma tubulin and capping proteins that stabilize - end of all microtubules

15

Functions of microtubules

Organize and transport organelles (vesicles, Golgi, ER)
Mitosis (create spindle)
Can contribute to cell movement and shape
Cilia

16

Microtubule movement

Kinesins to + end
Dynein to - end
Both are ATPases (bind for conformational change, hydrolisis for release and resetting)
Responsible for relative movement (ie cilia)

17

Cilia structure

9 doublets + 2 central MTs
Dynein attach to next doublet, bend and release for movement
Basal body is 9 triplets (like MTOC)

18

Microtubule disruptors

Vinblastine - chemo, prevents polymerization
Taxol - chemo, stabilizes (prevents mitosis)
Colchicine - gout, prevents polymerization (decreases inflammatory cell movement)

19

Size of intermediate filaments

8-10 nm

20

Intermediate filament structure

2 coiled dimers form tetramer
8 staggered tetramers form filament

21

Characteristics of intermediate filaments

Non-polar (each tetramer is symmetrical)
Don't regularly (de)polymerize
Very stable and strong

22

Types of intermediate filaments (6)

Keratin - epithelia
Vimentin - connective tissue, mesenchyme
Desmin - skeletal muscle
Glial fibrillary acidic protein - glial cells
Neurofilaments
Lamins - all nuclei

*Type of intermediate filament can identify cancer cell origins
*Helical/rod domain is conserved, ends have identifiable differences

23

Functions of intermediate filaments

Key for structure, mechanical stress (ie desmosomes)
Support other cytoskeleton elements
Lamin supports nuclear envelope