2-cell anatomy: cytoskeleton

Question 1

the cytoskeleton can form ________ and can be ____ and _____

Answer 1

stable structures
dynamic
adaptable

Question 2

the cytoskeleton is involved in numerous processes related to ______, ______, and ______

Answer 2

shape
support
locomotion

Question 3

3 main types of protein filaments

Answer 3

1. microtubules
2. actin filaments
3. intermediate filaments

Question 4

_______ regulate filament assembly and dynamics

Answer 4

cytoskeletal associated proteins (accessory factors)

Question 5

cytoskeleton general properties:

Answer 5

1. filaments self assemble from small subunits
2. subunits associations with a filament are weak and noncovalent
3. filaments consist of multiple protofilaments that associate laterally with each other which allows for overall thermal stability for filaments
4. accessory proteins regulate assembly of new filaments

Question 6

breaking a filament in the middle requires breaking sets of _____ in several protofilaments. This results in overall _________ for the filaments

Answer 6

longitudinal bonds
thermal stability

Question 7

removing a subunit from the ends requires less energy, leaving the filament ends as _________

Answer 7

dynamic structures

Question 8

what are microfilaments composed of

Answer 8

globular actin monomer

Question 9

MF: actin monomers bind

Answer 9

ATP

Question 10

MF: actin monomers assemble to form

Answer 10

a filament

Question 11

MF: 2 parallel _____ twist around each other to form a ___________

Answer 11

protofilaments
right handed helix

Question 12

MF: actin subunits assemble _____ to ____ and generate filaments with a distinct ______

Answer 12

head to tail
polarity

Question 13

MF: filaments “grow” from the _____ end

Answer 13

plus

Question 14

MF: actin filaments are ________ and ______

Answer 14

relatively flexible and easily bent

Question 15

MF: in living cells, accessory proteins crosslink and bundle MFs together to create __________ actin structures much _____ than individual MFs

Answer 15

large-scale
stronger

Question 16

localization of MFs

Answer 16

-MFs are often concentrated near the cell periphery
-Actin filaments are also observed running the length of cells

Question 17

main roles of MFs determine the ___________ and to facilitate__________

Answer 17

shape of the cell’s surface
whole cell locomotion

Question 18

Microtubules (MT) made up of:

Answer 18

-globular tubulin subunits
-tubulin monomers bind GTP
-alpha nad beta tubulin monomers form tubulin heterodimers
-protofilament is composed of alternating alpha and beta tubulin

Question 19

MTs: cylinder structure

Answer 19

13 protofilaments build the MT cylinder
Cylinder is long and hollow

Question 20

MT has an associated _______ .

Answer 20

polarity
- subunits point in one direction
-protofilaments are parallel
-growing end =plus end

Question 21

the multiple contacts in the MT lattice make MT __________

Answer 21

stiff and difficult to bend

Question 22

MT localization:

Answer 22

-nucleation occurs at the MTOC
-MTOC anchors and protects minus end of growing filament
-in animal cells, centrosome is near the nucleus
-from the MTOC, the MTs emanate in a star like conformation often out to the cell periphery

Question 23

the main role of MTs:

Answer 23

determine the positions of membrane enclosed organelles and to direct intracellular transport

Question 24

IFs structure:

Answer 24

-heterogenous family of rope-like filaments
-assembled from distinct subunits (inc. keratins, neurofilaments, vimentin-like proteins, lamins)
-does not contain an associated nucleotide (NTP)

Question 25

IFs: are made by:

Answer 25

-elongated alpha helical monomeric subunits dimerize and then associate to form staggered tetrameric subunits -tetramers pack together to form protofilament -filament formed from 8 parallel protofilaments -non-polar -easily bent but hard to break

Question 26

IFs localization:

Answer 26

-IFs provide strength to cells and tissues -in general, IFs are prominent in cells that are subject to mechanical stress

Question 27

main role of IFs

Answer 27

provide mechanical strength and provide shape to cells and help resist pulling forces

Question 28

_______ are a diverse population of proteins that bind to filaments or subunits to control filament behavior and organization

Answer 28

accessory proteins

Question 29

accessory proteins can:

Answer 29

1 . crosslink or bundle filaments 2. nucleate filament polymerization 3. cap and block polymerization 4. sever filaments

Question 30

motor proteins overview:

Answer 30

-unique cytoskeleton binding protein -function to move molecules and membrane enclosed organelles throughout cell -can be used to generate force required to move filaments

Question 31

molecular motors convert energy from _____ into _______ to _______

Answer 31

ATP hydrolysis mechanical force 'walk' along MF and MT filaments

Question 32

what are the 3 major families of motor proteins:

Answer 32

1. myosin 2. kinesin 3. dynein

Question 33

what is the associated filament for myosin

Answer 33

microfilaments (actin)

Question 34

what is the associated filament for kinesin ?

Answer 34

microtubules

Question 35

what is the associated filament for dynein

Answer 35

microtubules

Question 36

what direction does myosin go

Answer 36

POS

Question 37

what direction does kinesin go

Answer 37

POS

Question 38

what direction does dynein go

Answer 38

NEG

Question 39

motor proteins associate with filament tracks via what?

Answer 39

a "head" region, or motor domain

Question 40

what does the head region of motor proteins do?

Answer 40

binds and hydrolyzes ATP

Question 41

what does the tail region do of motor proteins

Answer 41

contains the binding site for cargo

Question 42

which molecular motor is the largest and fastest

Answer 42

dynein

Question 43

in kinesin, the binding/hydrolysis of ATP by the head/motor domains _________

Answer 43

changes the conformation of the protein which allows kinesin to "walk" or "step" down the MT towards the plus end

Question 44

for dynein, nucleotide hydrolysis is coupled to _____

Answer 44

MT bindning and unbinding as well to a force-generating conformational change

Question 45

dynein's power stroke is driven by the _______

Answer 45

binding and hydrolysis of ATP which causes the motor head to rotate relative to the tail

Question 46

what is the function of kinesins

Answer 46

-bring cargo to the periphery of the cell -organelle positioning -axonal transport -mitosis

Question 47

what is the function of dyneins?

Answer 47

-bring cargo to the periphery of the cell -cilia/flagella beating -vesicle transport -mitosis

Question 48

clinical relevance of cytoskeleton

Answer 48

disruption of filament structure and dynamics is associated with many disease pathologies

Question 49

example of mutation in actin binding protein, dystophin

Answer 49

canine x lined muscular dystrophy

Question 50

mutations in a range of actin/actin associated proteins are observed in patients with

Answer 50

cardiomyopathy

Question 51

_____ binds and stabilizes microtubules

Answer 51

taxol

Question 52

cilia structure

Answer 52

9 sets of MT doublets and center pair of MTs (9+2) dynein motors

Question 53

microfilaments are made of what subunits

Answer 53

actin

Question 54

microtubules are made of what subunit

Answer 54

tubulin

Question 55

intermediate filaments are made of what

Answer 55

keratin, neurofilaments, vimentin, lamin