lecture 11

Question 1

what are the three filamentous structures in the cytoskeleton

Answer 1

intermediate filaments
actin filaments
microtubules

Question 2

what filaments determine apical membrane

Answer 2

actin

Question 3

whats the structure of intermediate filaments

Answer 3

strong
unbranched
ropelike

Question 4

what strengthens cells against mechanical stress

Answer 4

intermediate filaments

Question 5

what connects epethelial cells to the extracellular matrix via desmosomes or hemidesmosomes

Answer 5

intermediate filaments

Question 6

is an intermediate filament minor polar or nonpolar

Answer 6

polar

Question 7

is an intermediate filament dimer polar or non polar

Answer 7

polar

Question 8

is the staggered antiparallel tetramer of two coiled coil dimers of intermediate filaments polar or non polar

Answer 8

non polar

Question 9

what 4 classes are intermediate filaments divided into? which parts are in the cytoplasm?

Answer 9

keratin filaments
vimentin filaments (connective tissue)
neurofilaments
nuclear lamins

first 3 in cytoplasm

Question 10

whats the structural protein of epithelial cells

Answer 10

keratin containing intermediate filaments

Question 11

what are intermediate filaments anchored to the outer edge of the cell by

Answer 11

desmosomes and hemidesmosomes

Question 12

how are intermediate filaments connected to mictrotubes and F-actin

Answer 12

plectins

Question 13

what filament absorbs mechanical stress

Answer 13

intermediate filaments

Question 14

what does a mutant form of keratin do to skin

Answer 14

blisters

Question 15

what are nerurofilaments

Answer 15

bundles of intermediate filaments in the cytoplasm of mature neurons

Question 16

does intermediate filaments formation require energy

Answer 16

no there is no need of direct ATP or GTP

Question 17

what are assembly of intermediate filaments controlled by

Answer 17

subunit phosphorylation and dephosphorylation

Question 18

what are the binding sites on plectin

Answer 18

each plectin dimer has a binding site for an intermediate filament and another bind site for another intermediate filament, microtubule, or F actin

Question 19

what are cytoskeleton elements connected by

Answer 19

plectin

Question 20

whats the most abundant protein within cells

Answer 20

antin filament structure

Question 21

what is an antin filament composed of

Answer 21

actin monomers `

Question 22

what is the structure of F actin

Answer 22

a two stranded helix with a + and - end (polar)

Question 23

how do antin filament grow

Answer 23

by the addition of monomers at either end

Question 24

what end of antin filaments have faster growth

Answer 24

plus end

Question 25

what can an actin monomer bind? what does that make it

Answer 25

binds an ATP molecule it is an ATPase

Question 26

once ATP is incorporated with an actin filament into the growing filament what happens

Answer 26

it gets hydrolyzed into ADP

Question 27

what is tread milling referred to with actin filaments

Answer 27

1 comes on to grow, one leaves is achieved then equal concentration of reaction is reached on both sides F actin moves in direction of assembly

Question 28

what leads to cell mobility

Answer 28

tread milling

Question 29

whats the pattern of F actin in living cells

Answer 29

various bundles and cross linked branches

Question 30

what is the organization and behaviour of actin filaments determined by

Answer 30

interaction of actin with a variety of actin-binding proteins

Question 31

do intermediate filaments have actin binding proteins

Answer 31

no

Question 32

what actin binding proteins stop assembly

Answer 32

monomer sequestering capping severing

Question 33

what is essential for cell locomotion

Answer 33

actin cortex - the actin filaments under the plasma membrane

Question 34

what are focal contacts ? what do they contain

Answer 34

they support the protrusion to give support and anchorage contains integrins

Question 35

what protrudes polymerization

Answer 35

actin polymerization at the plus end

Question 36

what is a lamellipodium

Answer 36

strong actin filament involved in the projection of the cell

Question 37

what are the molecular motors of F actin

Answer 37

myosins

Question 38

what are myosin II

Answer 38

muscle cells (muscle contraction) conventional

Question 39

what is myosin I

Answer 39

other cells unconventional (present in almost all cells)

Question 40

what end of actin does a myosin move towards

Answer 40

plus end

Question 41

whats the structure of both myosin

Answer 41

they have the same head because they both interact with actin, but they have different tails to transport different cargo

Question 42

what does the head domain of myosin look like

Answer 42

2 sites 1 binds an actin filament 1 binds and hydrolyzes ATP to drive the myosin motor

Question 43

what does myosin I tail interact with

Answer 43

interacts with the plasma membrane to pull it as its bound to growing actin

Question 44

what do type II myosin form (structurally)

Answer 44

dimers with two heads at one end and a single coiled tail

Question 45

what kind the fibrous tail of myosin II do

Answer 45

form a myosin II filament

Question 46

what does a myofibril contain

Answer 46

a chain of contractile units called sarcomeres

Question 47

where are myosin II filaments positioned in sarcomere

Answer 47

centrally

Question 48

what zones of a sarcomere contract

Answer 48

H and I

Question 49

what causes a myosin to "cock" its head

Answer 49

ATP hydrolysis

Question 50

what causes the power stroke

Answer 50

dissociation of the phosphate from the head