Unit 8: The Cytoskeleton

Question 1

What is the cytoskeleton made up of?

Answer 1

microtubules, actin, and intermediate filaments

Question 2

Why are filaments not linear?

Answer 2

To be more resistant to breakage

Question 3

What is the advantage of dynamicity?

Answer 3

Provides ability to rapidly reorganize networks

Question 4

What is the advantage of static structures?

Answer 4

Provides structural support

Question 5

How do actin and microtubules help in transporting cellular cargoes.

Answer 5

provide “rail system”

Question 6

What is the primary role of intermediate filaments

Answer 6

To provide mechanical support and help cells withstand mechanical stress

Question 7

What motor protein walks toward the minus ends of microtubules

Answer 7

Dynein

Question 8

What motor protein walks toward the plus ends of microtubules

Answer 8

Kinesin

Question 9

What two proteins make up microtubules

Answer 9

Tubulin and GTP

Question 10

What is the function of GTP within a microtubules?

Answer 10

GTP cap forms the growing end of microtubules and when hydrolyzed to GDP, forms the shrinking (depolymerizing end)

Question 11

When do microtubules form the mitotic spindle?

Answer 11

During mitosis in metaphase

Question 12

What is the purpose of the centrosome?

Answer 12

Nucelates, anchors, and organizes microtubules.

Question 13

How do microtubules work in cilia and flagella

Answer 13

drive bending and therefore movement within them

Question 14

What cellular structures are composed of microtubules

Answer 14

cilia and flagella

Question 15

What tubulin is added to the plus end of microtubules?

Answer 15

GTP-bound tubulin

Question 16

What does a GTP cap do and where is it found?

Answer 16

Stabilizes microtubule from depolymerizing
Can be bound by end binding proteins

Question 17

What occurs when all tubulin in microtubule is GDP-bound

Answer 17

Catastrophe occurs and depolymerazion happens

Question 18

Whats a benefit of depolymerizing microtubule?

Answer 18

Move chromosomes during anaphase, move mitotic spindle

Question 19

What allows microtubules to nucleate more efficiently?

Answer 19

Gamma Tubulin ring complex is a template from which microtubules can grow

Question 20

What do end binding (EB) proteins do?

Answer 20

binds to caps on the plus end of microtubules

Question 21

What is the purpose of spastin and katanin?

Answer 21

sever/cut microtubules

Question 22

What is G-actin?

Answer 22

The momomeric form of actin

Question 23

What is F-actin?

Answer 23

Polymerized G-actin; forms long helical structures

Question 24

What is treadmilling?

Answer 24

The steady state of actin where:
the plus end gains actin
the minus end loses actin

Question 25

Where is treadmilling most notable?

Answer 25

at the leading edge of a crawling cell

Question 26

What subunits are added to the plus end of actin when treadmilling?

Answer 26

ATP-actin

Question 27

How does actin fall off the minus ends when treadmilling?

Answer 27

The once ATP bound actin is hydrolyzed to ADP bound actin which falls off when exposed to the minus end

Question 28

What protein(s) causes actin to branch?

Answer 28

Arp2/Arp3 complex proteins

Question 29

Where are branched actin found?

Answer 29

At the leading edge of a cell which is important for cell migration

Question 30

How does Cofilin interact with actin?

Answer 30

Twists and Depolymerizes actin

Question 31

What actin motor walks along F-actin?

Answer 31

Myosin

Question 32

What are thick filaments in muscle contraction?

Answer 32

Myosin motors

Question 33

What are the thin filaments in muscle contraction

Answer 33

actin filaments

Question 34

Which filament has the most tensile strength?

Answer 34

intermediate filaments

Question 35

Which filament is easily deformed and ruptured?

Answer 35

Microtubules

Question 36

Which filament is not very flexible and ruptures easily

Answer 36

Actin

Question 37

How do intermediate filaments strengthen a group of cells?

Answer 37

connect to desmosomes which link neighboring cells

Question 38

Why are Intermediate filaments non-polar

Answer 38

They have two coiled coils bound that make symmetric tetramer

Question 39

Which filament is rope-like?

Answer 39

Intermediate filaments

Question 40

What are nuclear lamins?

Answer 40

subtype of intermediate filaments in the nucleus

Question 41

How do Lamins protect the nucleus

Answer 41

Protect the nucleus from external forces with a mesh like network under nuclear envelope

Question 42

What happens when there is a mutation to a lamin

Answer 42

Muscle degeneration diseases

Question 43

What type of filament is keratin?

Answer 43

Intermediate filament

Question 44

What happens if there is a mutation of the keratin?

Answer 44

skin cells have looser connections

Question 45

What are neurofilaments?

Answer 45

intermediate filaments that provide strength and stability to long neuronal processes

Question 46

What is desmin?

Answer 46

an I.F that supports muscle cells by distributing mechanical force generated by actin and myosin.

Question 47

How are intermediate filaments different in size to the other two cytoskeleton components?

Answer 47

I.F's are thicker than actin but smaller than microtubules

Question 48

What are some cargoes dynein transports?

Answer 48

RNA's, proteins, vesicles, and the nucleus

Question 49

How do dynein move along microtubules?

Answer 49

With a power stroke, due to ATP binding and hydrolysis

Question 50

What does dynein being a "non-processive" motor mean?

Answer 50

It does not go long distances along microtubules

Question 51

What makes dynein more processive?

Answer 51

Dynein Activator which arranges them into a configuration that is optimal for motility

Question 52

How do adaptors affect dynein?

Answer 52

Allow dynactin to bind and also links dynein specific cargoes; make sure they bind to the appropriate cargoes