Test 3: Cytoskeleton

Question 1

Cytoskeletons allow cells to…

Answer 1

organize itself and interact with environment mechanically

Question 2

3 classes of cytoskeletons are… they…

Answer 2

1. intermediate filmanets -> mechanical strength and cell integrity against sheer stress
2. microtubules -> positions cell components & transports, basis of cilia and flagella
3. actin filaments -> cell shape and motility

Question 3

Actin filmanets have formation between subunits that is…

Answer 3

weak; noncovalent

Question 4

Intermediate Filament: Provides mechanical strength by…

Answer 4

1. forming network thru cell

2. anchors at PM/ECM

Question 5

Intermediate Filament: 4 major classes. where are they?

Answer 5

1. keratin -> epithelia
2. vimentin -> connective, muscle, glial
3. neurofilemin -> nerve
4. nuclear lamin -> nucleus

Question 6

Intermediate Filament: are stabilized by x, which…

Answer 6

accessory proteins; connect intermediate filmanet to other cytoskeleton such as actin filmanet or microtubules

Question 7

Intermediate Filament: arrange in 2 shapes, they are

Answer 7

cross link and bundle

Question 8

Tubulin and Actin: Both have polarity. + end for (fast/slow) growing called (NTP/NDP), and - end for (fast/slow) growing called (NTP/NDP)

Answer 8

+: fast; NTP

-: slow, NDP

Question 9

Tubulin and Actin: Tubulin’s Nucleotide is x; Actin’s nucleotide is y.

Answer 9

Tubulin: G
Actin: A

Question 10

Dynamic Instability is

Answer 10

rapid change in growth and disassembly due to difference between NTP and NDP bound form; ratio of NDP and NTP determinesgrowth or disassembly

Question 11

Polymerization Time Corse is sigmoidal graph. 3 phases are…

Answer 11

1. Nucleation (log phase)
2. elongation (growth phase)
3. steady state (equilibrium)

Question 12

Microtubule: Unlike actin monomers, tubulin has…

Answer 12

dimers (α or β)

Question 13

Microtubule: Order from smallest to largest from dimers to microtubule; rigid/flexible?

Answer 13

dimers (α or β) –> protofilmanet (13) –> microtubule; rigid

Question 14

Actin: Order from smallest to largest from monomer to flmaent; rigid/flexible?

Answer 14

monomer -> 7 protofilament -> filament; flexible

Question 15

Growth: 1. Nucleation: for both actin and microtubule, based on…

Answer 15

2 subunits binding and remaining bound (stable enough for 3rd to bind)

Question 16

Growth: 1. Nucleation: Microtubule: nucleated by… from…

Answer 16

nucleated by γ-tubulin, from Microtubule Organizing Center (MTOC; centrosome in animal, spindle pole body in microorganism); MTOC only source of microtubulins

Question 17

Growth: 1. Nucleation: Actin: nucleated by…

Answer 17

nucleated by preexisting actin filament via protein Arp 2/3 complex, which binds to preexisting actin filament to nucleate it at 70’

Question 18

Growth: 2. Elongation: Also called

Answer 18

Dynamic Instability

Question 19

Growth: 2. Elongation: for both actin and microtubule, growth is due to presence of…

Answer 19

NTP-bound form, which stabilizes the filments

Question 20

Growth: 2. Elongation: for both actin and microtubule, NTP is constantly hyrdrolyzed into NDP. Hence, + rate means

Answer 20

shrinking

Question 21

Growth: 2. Steady State: for both actin and microtubule,

Answer 21

when growth = shrink

Question 22

Actin Filament cross-links in 2 different shapes with 2 different…

Answer 22

rigidity

Question 23

T/F Severing of filmanet change cell shape and rigidity

Answer 23

T

Question 24

Motor Proteins: binds to … and uses …

Answer 24

bind to filaments and move along them using ATP hydrolysis

Question 25

Motor Proteins: Microtubule Motors: Purpose?

Answer 25

Carry membrane bound organelle and moving chromosomes

Question 26

Motor Proteins: Microtubule Motors: 2 classes are…

Answer 26

1. kinesins: + end directed

2. dyneins: - end directed

Question 27

Motor Proteins: Actin Motors: Purpose?

Answer 27

carry vesicles, drives cytokinesis, motility, muscle function