11.12-11.16

Question 1

what must all motor proteins be able to do?

Answer 1

• bind ATP, hydrolyze it, and undergo a very large conformational change
• bind and let go of surface

Question 2

2 possible mechanisms of bidirectional movement

Answer 2

1. inchworm
2. head-over-head

Question 3

which bidirectional movement mechanism is more likely?

Answer 3

head-over-head

Question 4

should one head always be attached to microtubule?

Answer 4

• for kinesin yes
• for motors in cilia and flagella: not always

Question 5

length of steps taken by kinesin and dynein

Answer 5

8 nm

Question 6

length of single tubulin heterodimer

Answer 6

8 nm

Question 7

why do motors in cilia and flagella not always need one head bound to micro tubule

Answer 7

so other motors can generate force on same microtubule

Question 8

for organelles that move bidirectionally, how many dif motors are they bound to?

Answer 8

2
- one set of motors turned off while other is active

Question 9

2 mechanisms of generating bidirectional movement

Answer 9

1. tug of water between motors
2. coordination of motor activity

Question 10

binding cargo to the correct motor is mediated by what?

Answer 10

motor’s tail domain

Question 11

for kinesin, are the motor or tail domains more similar

Answer 11

motor - tail different to allow binding to proper cargo

Question 12

does the tail domain bind directly or indirectly to cargo

Answer 12

indirectly - needs adaptor proteins

Question 13

adaptor AP-1

Answer 13

• links cytoplasmic domain of M6P receptor to tail of kinesin
• links clathrin to regions of TGN where vesicles bud

Question 14

adaptor AP-1 links the cytoplasmic domain of the M6P receptor to what?

Answer 14

tail of kinesin

Question 15

what does the dynactin complex link

Answer 15

cytoplasmic dynein to membranes

Question 16

dyanctin complex composition

Answer 16

7 polypeptides and a short filament composed of Arp1 (similar to actin)

Question 17

what does Arp1 link

Answer 17

dynein to spectrin

Question 18

how is spectrin attached to cytoplasmic face of vesicle

Answer 18

ankyrin

Question 19

are spectrin and ankyrin IMPs or PMPs

Answer 19

PMPs

Question 20

what is an important property of highly shaped and specialized cell types?

Answer 20

asymmetry

Question 21

what is movement, dynamic instability, and asymmetry often in conjunction with

Answer 21

actin and intermediate filaments

Question 22

what happens when growth cones of two cells encounter each other

Answer 22

react to contact signal by extending microtubules to point of contact

Question 23

why must orientation of spindle during cell division be carefully chosen/

Answer 23

so daughter cells have required orientation - maintain plane of tissue layer

Question 24

what helps move spindle to correct orientation during epithelial cell division?

Answer 24

dynein

Question 25

what helps move spindle to correct orientation during yeast budding?

Answer 25

dynein

Question 26

microtubules also function as what?

Answer 26

cytoskeletal directors - where actin should assemble and contract

Question 27

microtubules and actin seem to interact through what?

Answer 27

linkers like MAPs and motor proteins

Question 28

MAP2c

Answer 28

binds to both microtubules and actin in neurons to form and send out long projections

Question 29

what can linking microtubules to actin filaments also accomplish?

Answer 29

guiding growing microtubules to specific sites in cell

Question 30

true or false: actin filaments and microtubules must always be physically connected to work together

Answer 30

false - can really signals via signaling pathways, and respond to events from outside or inside the cell

Question 31

what does signaling between microtubules and actin filaments often involve

Answer 31

G proteins

Question 32

Rac1

Answer 32

G protein involved with microtubules and actin filaments

Question 33

steps of Rac1

Answer 33

- microtubule grows/polymerizes - Rac 1 activated - stimulates acting filament growth and lamellipodia formation - reduces effect of Oncoprotein 18 (destabilizer)

Question 34

composition of cilia and flagella

Answer 34

long bundle of microtubules surrounded by extension of plasma membrane

Question 35

cilia and flagella of unicellular eukaryotes or sperm

Answer 35

movement

Question 36

types of unicellular eukaryotes with flagella

Answer 36

- Trypanosoma - Euglena - Balantidium

Question 37

cilia covering apical domains of some epithelial cells

Answer 37

- clearing mucus and debris from respiratory tract - transporting eggs from ovary to uterus - circulating cerebrospinal fluid

Question 38

difference between cilia and flagella

Answer 38

cilia shorter and more numerous

Question 39

how does each cilia/flagella generate force

Answer 39

- power stroke: bending near base - recovery stroke: propagates bend from base to tip

Question 40

true or false: flagella continue to beat if removed from cell, even if plasma membrane is removed

Answer 40

true - just need ATP

Question 41

core of cilia/flagella

Answer 41

axoneme

Question 42

how many dif polypeptides in axoneme

Answer 42

at least 250

Question 43

arrangement of microtubules in motile cilia/flagella

Answer 43

9 + 2

Question 44

are the plus ends at the tips or base of cilia/flagella

Answer 44

- plus ends at tips - minus ends at base

Question 45

nexin

Answer 45

protein responsible for connecting adjacent doublet microtubules around circumference of axoneme

Question 46

radial spokes and spokeheads

Answer 46

connect doublet microtubules to central pair of microtubules

Question 47

some of radial spokes and spoke heads are what?

Answer 47

kinases and phosphates that are used in signal network

Question 48

axonemal dyneins connect what?

Answer 48

adjacent doublet microtubules to generate force within axoneme

Question 49

number of dif polypeptides of radial spokes and spokeheads

Answer 49

about 17

Question 50

activity of axonemal dyneins during beating motion

Answer 50

dynein active only with small region - activated sequentially

Question 51

what regulates the axonemal dyneins

Answer 51

central pair microtubules and radial spokes

Question 52

when central pair microtubules rotate rapidly, what happens?

Answer 52

transmit signals to radial spokes and regulate dynein activity through kinases and phosphatases

Question 53

true or false: a flagellum isn't function during regeneration

Answer 53

false

Question 54

how are axonemal components transported to the tip or base during flagellar reassembly

Answer 54

intraflagellar transport

Question 55

what is intraflagellar transport to the tip powered by

Answer 55

kinesin

Question 56

what is intraflagellar transport to the cell body powered by

Answer 56

cytoplasmic dynein (and C-terminal motor domain kinesin?)

Question 57

where are nonmotile/primary cilia found

Answer 57

on nearly all vertebrate cells

Question 58

how many primary cilia do cells typically have

Answer 58

one

Question 59

axoneme structure of nonmotile cilia

Answer 59

9+0 - lacks central pair of microtubules

Question 60

ex. of specialized domain on primary cilium

Answer 60

rod and cone cells

Question 61

what is the tip of the cilium expanded into for rod and cone cells

Answer 61

outer segment

Question 62

what does outer segment contain

Answer 62

stacks of membrane disks filled with rhodopsin (photoreceptor protein)

Question 63

what does IFT-type transport do in rod and cone cells

Answer 63

moves membrane vesicles containing rhodopsin from cell body to outer segment