Cytoskeleton

Question 1

Alpha actin make up what type of cells

Answer 1

muscle

Question 2

Beta and gamma actin make up what type of cells

Answer 2

non-muscle cells

Question 3

Actin monomer

Answer 3

globular actin (G-actin)

Question 4

When two actin filaments twist together what do they make what

Answer 4

F-actin

Question 5

How big is F- actin

Answer 5

6-7 nm

Question 6

What is required for actin to assemble?

Answer 6

1) Need ATP
2) need some fragment of G-actin
3) actin binding proteins (regulatory proteins)

Question 7

Polarity of actin

Answer 7

+ end favors assembly, ATP

• end favors disassembly, ADP

Question 8

When does assembly stop for actin?

Answer 8

if all ATP bound filaments are consumed

Question 9

Why is polarity for actin filaments necessary?

Answer 9

for myosin movement to + end

Question 10

What is the RLS for actin filament assembly?

Answer 10

nucleation of fragments

Question 11

3 important functions of actin cytoskeleton

Answer 11

1) cell migration
2) cytokinesis: contracile ring before cell divides
3) brain development: synapses

Question 12

Functional classes of actin binding proteins

Answer 12

capping, ARP, thymosin, gelsolin, profilin, cofilin, tropomyosin

Question 13

capping actin binding protein

Answer 13

prevents assembly/ disassembly at the + end

Question 14

ARP actin binding protein

Answer 14

nucleates assembly, creates web, associated with - end

Question 15

Thymosin actin binding protein

Answer 15

prevents assembly of actin

Question 16

Gelsolin actin binding protein

Answer 16

severs filaments, binds + end, prevents monomer exchange

Question 17

profilin actin binding protein

Answer 17

speeds elongation

Question 18

cofilin

Answer 18

increases disassembly by binding ADP-actin

WS, ASD

Question 19

tropomyosin

Answer 19

stabilizes filament

Question 20

What is the motor protein for actin?

Answer 20

myosin

Question 21

How myosin moves along the actin filament

Answer 21

1) ATP binds myosin head, causing it to lift off of actin filament
2) Hydrolysis: head pivots and binds new actin subunit further up the + end
3) power stroke: Pi released, head pivoted and moves filament
4) ADP release and cycle repeats (attached without ATP)

Question 22

Diseases associated with regulation of actin cytoskeleton

Answer 22

bacterial infection 
williams syndrome (WS) 
ASD
AD
Fragile X 
ALS 
dementia

Question 23

How does Lim Kinase affect cofilin?

Answer 23

it inhibits it (so since cofilin increases disassembly, that means there is LESS disassembly happening)

Question 24

How does WS affect Lim Kinase and thus cofilin?

Answer 24

WS decreases Lim Kinase, which means less inhibiting of cofilin and means cofilin is still accelerating disassembly (active), which means there is MORE disassembly

Question 25

How does ASD affect Lim Kinase and thus cofilin?

Answer 25

ASD increases Lim kinase, which means more inhibiting of cofilin which means cofilin is NOT accelerating disassembly (inactive), which means LESS disassembly

Question 26

What is the smallest out of the cytoskeleton classes?

Answer 26

microfilaments (actin)

Question 27

3 main features of microtubule structure

Answer 27

1) non random organization in cells 2) has centrosome that is the MTOC 3) polar

Question 28

Microtubule polarity

Answer 28

+ , assembly end, distal to centrosome and cell body except dendrites - is closest towards centrosome (MTOC)

Question 29

How microtubule assembles

Answer 29

alpha and beta dimers form protofilaments, 13 protofilaments make up microtubule with - and + end ASSEMBLES AT THE + END

Question 30

alpha tubulin

Answer 30

NEGATIVE (-) end GTP NO hydrolysis

Question 31

beta tubulin

Answer 31

POSITIVE (+) end GDP exchangeable--> hydrolysis in assembly

Question 32

dynamic instability

Answer 32

when the GTP is bound to beta tubulin = assembly, when GTP hydrolyzes to GDP on beta tubulin, that means = disassembly

Question 33

Treadmilling

Answer 33

when tubulin dimers are added at the same rate as the hydrolysis of GTP (if its faster then that it is when polymerization occurs) actin being assembled and disassembled at same rate

Question 34

Taxol (anti tumor drug)

Answer 34

prevents disassembly of microtubules, arrests cell cycle

Question 35

Vinca alkaloids (colchicine)

Answer 35

prevents tubulin dimers from polymerizing

Question 36

What are the motor proteins associated with microtubules?

Answer 36

dyneins and kinesins

Question 37

Dynein

Answer 37

moves toward - end retrograde use ATP

Question 38

Kinesins

Answer 38

moves toward + end anterograde use ATP have a tail and cargo binding domains --> diff kinesins have diff cargo

Question 39

cilia (definition, structure, 2 types)

Answer 39

Cilia are hairlike structures about 0.25 mm in diameter, covered by plasma membrane, that extend from the surface of many kinds of eucaryotic cells motile(9+2, dynein) vs. primary (9+0, NO dynein))

Question 40

Flagella

Answer 40

motile cilia like sperm move entire cell

Question 41

How cilia is assembled (including IFT)

Answer 41

build on basal body (MTOC) then add subunits on top intraflagellar transport (IFT): assembly machinary required of all cilia

Question 42

IFT (intraflagellar transport)

Answer 42

start at basal body (-), anterograde transport with kinesin, unload at the tip (+) switch IFT complex, retrograde transprt with dynein back towards basal body

Question 43

What makes up a centrosome?

Answer 43

``` 2 centrioles pericentriolar material (PCM) ``` centrosome is located near nucleus in interphase

Question 44

what does the pericentriolar mateiral (PCM) do?

Answer 44

recruits gamma ring complex

Question 45

What does the gamma tubulin ring complex do?

Answer 45

helps nucleate microtubule

Question 46

How many times do centrosomes duplicate per cell cycle? and what does it create?

Answer 46

ONCE , chromosomes separate and then it creates bipolar mitotic spindle (TWO POLES)

Question 47

What mechanism is duplication of centrioles?

Answer 47

semi-conservative replication

Question 48

3 types of microtubules

Answer 48

astral microtubules: look like star out of centrosome kinetochore microtubules: connect to kinetochore at the centromere on the chromosome interpolar (overlap) microtubules: span overmiddle of chromosomes but don't connect to kinetochores ALL spindles must be attached for anaphase to occur

Question 49

Anaphase A

Answer 49

poles DO NOT move | chromosomes pulled poleward, kinetochore microtubules shorten by kinesin on + end toward centrosome

Question 50

Anaphase B

Answer 50

POLES move chromosomes pulled to opposite poles as microtubules push and pull poles apart 1) pushing--> kinesin 2) pulling--> dynein

Question 51

if there are errors in chromosomal segregation it could result in what condition

Answer 51

aneuploidy (gain or loss of chromosome) ie. down syndrome (trisomy 21)