Cytoskeleton

Question 1

what are the 3 types of cytoskeleton fibers?

Answer 1

actin filaments, intermediate filaments, microtubules

Question 2

actin filaments and microtubules are composed of?

Answer 2

globular subunits

Question 3

intermediate filaments are composed of?

Answer 3

elongated and fibrous subunits, rod like

Question 4

what are the interactions among all of the subunits?

Answer 4

not covalent. assemble and dissemble quickly

Question 5

what are protofilaments?

Answer 5

thin filaments that link together to make big ones

Question 6

what are the globular subunits called in actin filament?

Answer 6

actin

Question 7

what are the globular subunits called in microtubules?

Answer 7

alpha-beta tubulin dimer

Question 8

what is actin?

Answer 8

composed of actins, has binding site for ATP, are polarized plud end has the ATP binding cleft covered while the minus end the cleft is exposed. 2 protofilaments twisting around each other

Question 9

how do you assembly actin?

Answer 9

1. nucleation phase- actins comes together to form oligomers (rate limiting step)
2. elongation phase
3. steady-state- reach equilibrium and won’t get any longer.

Question 10

actin grows longer on the ____ end but can grow on ____ ends

Answer 10

plus , both

Question 11

what is critical concentraion (Cc)?

Answer 11

concentration of free actin when actin filament has reached a steady state.

Question 12

what happens when you go above the critical concentration?

Answer 12

free actin polymerize and get into the filament to reduce the free actin

Question 13

what happens when you go below critical concentration?

Answer 13

filament shortens to let free actin leave

Question 14

describe the protofilament for miccrotubles

Answer 14

alpha and beta tubulin line up (non covalent interaction)

Question 15

what is gamma-tublin

Answer 15

not part of heterodimer, used for nucleation

Question 16

how are microtubules assembled?

Answer 16

1. protofilament assemly from alpha+beta subunits
2. protofilament associate to form a tube (13 in a ring)
3. add more subunits to each end to elongation

Question 17

what are doublets in microtubules?

Answer 17

in cilia and flagella, 2 mashed together

Question 18

what are triplets in microtubules?

Answer 18

in basal bodies and centrioles, 3 mashed together

Question 19

describe the polarity of microtubules

Answer 19

they have plus and minus ends
growth at plus end is faster.
minus end is associated with microtubule organizing center

Question 20

stable, long-lived microtubules can be found in

Answer 20

in non-replicating cells like cilia flagella neurons

Question 21

unstable and short-lived microtubules can be found in

Answer 21

cells that need assembly/disassembly in mitosis

Question 22

what is the primary function of intermediate filaments?

Answer 22

for mechanical strength, prominent in cells that undergo stress regularly

Question 23

what is the nuclear lamina?

Answer 23

inner lining of nuclear envelope

Question 24

what is the structure of intermediate filaments?

Answer 24

no plus/minus ends, alpha-helical rods, coiled-coiled dimers (two rods twisted), then staggered tetramers (2 coiled-coiled dimers twisted)
no nucleotide binding

Question 25

some toxins produced by organisms interfere with

Answer 25

actin/microtubule function, stabilizes them

Question 26

actin filament formation is at or near

Answer 26

plasma membrane, in cell cortex

Question 27

what is cell cortex?

Answer 27

layer just beneath plasma membrane

Question 28

actin filament in cell cortex determines

Answer 28

cell shape and movement of cell surface

Question 29

how does actin respond to a nutrient source?

Answer 29

filaments dissemble and they reassemble towards the source

Question 30

what is ARP?

Answer 30

nucleation point where actins bind to on minus end

Question 31

what is formin?

Answer 31

a ring like structure, another nucleation point

Question 32

how does formin work?

Answer 32

one side lifts up to let actin in then the other side lifts up to form actin filaments

Question 33

what is formin whisker?

Answer 33

long projection of formin bound to profilin. profilin grabs onto actin to pull it in

Question 34

what is thymosin?

Answer 34

prevents assembly. binds to free actin and takes it away

Question 35

what is profilin?

Answer 35

accelerates assembly

Question 36

what is cofilin?

Answer 36

accelerates disassembly at lagging end so leading edge can keep growing

Question 37

what is tight parallel bundle?

Answer 37

actin facing the same direction

Question 38

what is contractile bundle?

Answer 38

actin going in different directions

Question 39

what are gel-like network?

Answer 39

actin crossing over each other, spongy

Question 40

what is the lamellipodia?

Answer 40

leading edge of cell

Question 41

what are 3 bundle-forming proteins?

Answer 41

fimbrin, alpha-actinin, villin

Question 42

what is fimbrin?

Answer 42

tight bundles (can't bind to myosin, not contractile)

Question 43

what is alpha-actinin?

Answer 43

contractile fiber bundles

Question 44

what is villin?

Answer 44

tight packed bundles in microvilli (along with fimbrin)

Question 45

what is the gamma-tubulin ring complex?

Answer 45

where the minus end of microtubule.

Question 46

what is the centrosome?

Answer 46

microtubule organization cell. where all of the minus ends of microtubules are bound. only one during interphase. knows where the center of the cell is

Question 47

centrosomes contains a pair of

Answer 47

centrioles

Question 48

what is kinesin-13?

Answer 48

binds to plus end of microtubules to unravel it

Question 49

what is xamp215?

Answer 49

stabilizes plus end, growth rate enhanced

Question 50

what is katanin?

Answer 50

severs microtubules (during mitosis/meiosis)

Question 51

what is MAPs (microtubule-associated proteins) ?

Answer 51

length determines how closely microtubules are packed (MAP2 longer than tau)

Question 52

how do cells move?

Answer 52

actin cytoskeleton polymerization in cortex. actin protrusion in actin while contraction in the back.

Question 53

what are the molecular motor proteins?

Answer 53

myosin (actin) kinesin (microtubules) dyenin (microtubules)

Question 54

how are molecular motor proteins differentiated?

Answer 54

what filament they bind to which direction they move what cargo they carry

Question 55

the head on the molecular motor protein

Answer 55

determines which filament and the direction of movement

Question 56

the tail on the molecular motor protein

Answer 56

carries the cargo

Question 57

describe the molecular motor protein cycle

Answer 57

filament binding, conformational change, filament release, conformational relaxation

Question 58

what is myosin?

Answer 58

have a head and tail, all but one move towards the plus end of actin filaments. motor domain in head

Question 59

what is the function of myosin V?

Answer 59

organelle transport. tail domain binds to organelle

Question 60

what is the function of myosin II?

Answer 60

muscle contraction, cytokinesis, cell migration

Question 61

what is the function of myosin I?

Answer 61

membrane movement like endocytosis

Question 62

what is kinesin?

Answer 62

most walk toward plus end | plays a role during mitosis meiosis

Question 63

organelles can move on

Answer 63

actin or microtubules

Question 64

what are some common kinesins and function?

Answer 64

organelle transport, microtubule sliding, catastrophe factor

Question 65

what are dyenins?

Answer 65

minus end directed microtubule motor proteins | largest and fastest of known molecular motors. turn donut heads to do movement

Question 66

why do z discs become closer to each other during muscle contraction?

Answer 66

myosin heads pulls actin closer together

Question 67

describe how myosin walks on actin

Answer 67

1. myosin head binds to ATP and releases on actin 2. ATP hydrolyzed to ADP+P ->conformational change into cocked state 3. myosin binds to actin filament 4. phosphate is released and elastic energy straightens myosin, moves actin 5. ADP released and ATP binds again

Question 68

how does kinesin move?

Answer 68

rear head is bound tightly to microtubules and ATP. leading head is loosely bound to ADP. lagging head hydrolyzes to ADP. new ATP binds to leading head then lagging head swings to front.

Question 69

how does dyenin move?

Answer 69

the donut rotates and moves the microtubule

Question 70

what is the function of molecular motor proteins?

Answer 70

muscle contraction, organelle and vesicle movement, flagella and cilia, cell division

Question 71

what causes bending in flagella?

Answer 71

dyenin links the microtubules so they dont slide but bend (?????)

Question 72

cells undergoing mitosis/meiosis have __ centrosomes

Answer 72

2, become spindle poles

Question 73

what are astral microtubules?

Answer 73

plus ends interact with cell membrane

Question 74

what are kinetochore microtubules?

Answer 74

interact with chromosome at kinetochorse

Question 75

what are interpolar microtubules?

Answer 75

one centrosome sends out a microtubule and the other will send one out and they overlap with motor proteins in between.