W9 Cytoskeleton and Motility

Question 1

what is the cytoskeleton

Answer 1

a network of interconnected filaments and tubules

Question 2

what’s the function of the cytoskeleton

Answer 2

cell structure and mechanics

Question 3

what are the 3 major structural elements
make up the cytoskeleton

Answer 3

microfilaments
intermediate filaments
microtubules

Question 4

what are microfilaments made of

Answer 4

coiled-coil chain of actin monomers

Question 5

how small are microfilaments

Answer 5

7nm

Question 6

what are the main job function of microfilaments

Answer 6

muscle contraction
cell migration

Question 7

what are the monomers of F-actin microfilaments

Answer 7

polymerized G-Actin

Question 8

what are intermediate filaments made of

Answer 8

8 overlapping protofilaments

Question 9

do microfilaments have polarity

Answer 9

yes

Question 10

do intermediate filaments have polarity

Answer 10

no

Question 11

what’s the role of intermediate filaments

Answer 11

structural support for animal cell shape

Question 12

what are intermediate filaments the most at

Answer 12

the most stable
the most diverse
the most insoluble

Question 13

how are intermediate filaments assembled

Answer 13

2 polypeptides intertwined into a coiled-coil

Question 14

what are 2 examples of intermediate filaments

Answer 14

desmin
keratin

Question 15

what are microtubules made of

Answer 15

hollow tube of 13 protofilaments

Question 16

what is the main job of the microtubules

Answer 16

chromosome movement

Question 17

what are the 2 microtubules

Answer 17

• cytoplasmic microtubules
• axonemal microtubules

Question 18

what’s the functions of cytoplasmic microtubules

Answer 18

regulation of cell shape
vesicle transport
axon formation
mitotic spindle formation

Question 19

what’s the function of axonemal microtubules

Answer 19

cell mobility

Question 20

how are actin filaments regulated

Answer 20

binding proteins

Question 21

what does profilin do

Answer 21

binds ATP actin and promotes polymerisation

Question 22

what does thymosin do

Answer 22

binds ATP actin and blocks polymerisation

Question 23

what does formins do

Answer 23

bind actin filaments and promote elongation

Question 24

what does Arp2/3 do

Answer 24

promotes nucleation and branching

Question 25

where do microtubules get fromed

Answer 25

centrosome

Question 26

how are microtubules made

Answer 26

- tubulin dimers are formed into oligomers in the nucleation step - during elongation phase more tubulins are added to ends of microtubules - at the plateau stage tubulins will treadmill

Question 27

what is critical concentration for microtubules

Answer 27

tubulin concentration needs to be above the critical concentration for microtubule growth

Question 28

what is treadmilling of microtubules

Answer 28

adding subunits at plus end removing subunits at minus end

Question 29

what is microtubule dynamic instability

Answer 29

populations of MTs will undergo polymerization and depolymerization simultaneously

Question 30

what is microtubule catastrophe

Answer 30

switch from growth to shrinkage

Question 31

what is microtubule rescue

Answer 31

switch from shrinkage to growth

Question 32

what's the role of GTP in microtubules

Answer 32

provides energy for MT growth

Question 33

what are MT stabilizing proteins called

Answer 33

tau proteins

Question 34

what are MT destabilizing proteins called

Answer 34

stathmin

Question 35

how is the cytoskeleton linked

Answer 35

integrin and cadherin

Question 36

what do cadherin receptors do

Answer 36

bind onto adjacent cells

Question 37

what do adherents junctions do

Answer 37

link to F-actin microfilaments

Question 38

what do desmosomes do

Answer 38

link intermediate filaments

Question 39

how do eukaryotes mobility systems work

Answer 39

interactions between motor proteins and microtubules interactions between myosin proteins and mcirofilament

Question 40

how does Microtubule-based movement work

Answer 40

kinesins or dynein move along microtubules

Question 41

what are kinesins made of

Answer 41

- globular head that attaches to MT - coiled helical region - light chain region

Question 42

how do kinesins move

Answer 42

using ATP the "foots" will move along the MT

Question 43

how do dynein motor proteins work

Answer 43

heavy chain and dynactin complex bind and move along MT

Question 44

how do cilia and flagella move

Answer 44

ATP hydrolysis of dynein proteins

Question 45

what are myosins

Answer 45

tetramers which are ATP-dependant motors

Question 46

how does myosin move

Answer 46

globular heads bind to actin and move towards plus end

Question 47

what are myofibrils made of

Answer 47

sarcomeres

Question 48

what are thick filaments

Answer 48

bundles of myosin

Question 49

what are thin filaments

Answer 49

F-actin intertwined with tropomyosin and troponin

Question 50

what causes muscle contraction

Answer 50

release of Ca2+ to bind myosin head to myosin binding site on actin

Question 51

what are 2 examples of actin based motility

Answer 51

cytokinesis and endocytosis

Question 52

how to cells crawl

Answer 52

extend protrusions

Question 53

how do cells extend protrusions

Answer 53

actin polymerisation so acto-myosin contractility can happen

Question 54

how do amoebas and white blood cells migrate

Answer 54

amoeboid movement

Question 55

what is amoeboid movement

Answer 55

protrusions of pseudopodium

Question 56

what is pseudopodia

Answer 56

depolymerized F-actin

Question 57

which type of migration is faster amoeboid or extended protrusions

Answer 57

amoeboid movement

Question 58

how can we prevent amoeboid migration for cancer cells

Answer 58

myosin inhibition block metastasis

Question 59

what's the importance of fast amoeboid movement

Answer 59

immune responses

Question 60

what does GTP cap do for cytoskeleton

Answer 60

allows tubulin to add to microtubules without falling off