Chapter 17

Question 1

What is the purpose of the “dynamic scaffold” of the cytoskeleton

Answer 1

provides structual support and cell shape

Question 2

What is the purpose of the “network of tracks” in the cytoskeleton

Answer 2

microtubules and microfilaments act as an intracellular pathway, where cells move from one place to another

Question 3

What is the “Force Generating Apparatus” and what is its role in the cytoskeleton

Answer 3

it is the molecular machinery that moves cells from one place to another along the network of tracks

Question 4

What are the 3 types of Protein Filaments

Answer 4

1. Intermediate Filaments
2. Microtubules
3. Actin Filaments / microfilaments

Question 5

Which of the 3 protein filaments is the most stable?

Answer 5

Intermediate Filaments

Question 6

What is a Desmosome?

Answer 6

mechanical links that connect the intermediate filaments of adjacent cells

Question 7

What purpose do Desmosomes serve

Answer 7

provides mechanical strength in tissue

Question 8

what is the Epidermolysis Bullosa Simplex

Answer 8

a rare genetic mutation causing the skin to be vulnerable to mechanical injury

Question 9

a rare genetic mutation causing the skin to be vulnerable to mechanical injury

Answer 9

1.Cytoplasmic IF
2. Nuclear IF

Question 10

What are the 3 types of Cytoplasmic Intermediate Filaments?

Answer 10

1. Keratins
2. Vimentin
3. Neurofilaments

Question 11

Each of the intermediate filaments have a region called what?

Answer 11

a-helix region

Question 12

What feature causes a functional differentiation between intermediate filaments?

Answer 12

The globular head (NH2)
and tail region (COOH)
of the intermediate filament that each vary in size

Question 13

what is a Lamin?

Answer 13

a structure that lies below the nuclear membrane, and is part of the cytoskeleton - it provides structural support

Question 14

The meshwork of intermediate filaments provide support for what?

Answer 14

the nuclear envelope

Question 15

Which of the 3 kinds of Cytoskeletal Protein Filaments is the thickest

Answer 15

Microtubule

Question 16

What are the functions of the Microtubules?

Answer 16

1.guides organelles and chromosome movement
2. guides overall cell motility
3. is a delivery route in polar cells, acting as the “tracks”

Question 17

Miccrotubules transports cargo along what?

Answer 17

along the nerve axon

Question 18

What organizes the cells interior?

Answer 18

Microtubules

Question 19

True of False: all microtubule “tracks” are oriented in slightly diffferent directions

Answer 19

False: they are all oriented in the same direction

Question 20

If microtubules are the “track”, what would act as the “mechanical engine”

Answer 20

Motor Proteins

Question 21

How long does it take for deliveries from the spine to the shoulder?

Answer 21

~2 Days

Question 22

Define Tubulin

Answer 22

tubulin are dimers of alpha and beta tubulin subunits

Question 23

Define Protofilament

Answer 23

Protofilaments are what Tubulin Dimers assemle into

Question 24

What is the role of the centrosome?

Answer 24

Acts as the microtubule organizing centre

Question 25

Each centrosome contains a y-tubulin. What role does this y-tubulin play?

Answer 25

y-Tubulin acts as the nucleation site for polar microtubule growth

Question 26

What is defined as "dynamic intability"?

Answer 26

periods of growth and shrinkage, at the microtubule positive end.

Question 27

Dynamic Instability is caused by what?

Answer 27

The hydrolysis of GTP by tubulin

Question 28

Which end of the microtubules is more dynamic?

Answer 28

The plus end

Question 29

Polymerization of the plus end causes what?

Answer 29

growth of the plus end

Question 30

Shrinkage is a result of what reaction

Answer 30

depolymerization

Question 31

How does the plus end grow/what is added to it

Answer 31

The addition of GTP-Tubulin molecules to the plus end of a microtubule (when it is polymerized), provides energy; causing it to grow

Question 32

Explain GTP-Hydrolysis

Answer 32

after being incorporated into the microtubule, GTP-Tubulin is hydrolyzed and is converted into GDP

Question 33

What happens following the hydrolyis of GTP into GDP

Answer 33

Tubulin binds to GDP and is prone to depolymerization this resuts in likely shrinkage

Question 34

Shrinkage only occurs if..

Answer 34

if GTP-hydrolysis rate exceeds GTP-tubulin addition rate this results in the forming of GDP-Tubulin cap

Question 35

What effect does the GDP-Tubulin cap have on the microtubule?

Answer 35

It causes destabilization and leads to rapid shrinkage ("catastrophe")

Question 36

What is a protofilament?

Answer 36

alpha and beta dimers, stacked to form a linear chain (these make up the walls of the microtubule)

Question 37

What makes up the microtubule structure

Answer 37

13 protofilament chains, associated to form a cylindrical shape

Question 38

True or False: GDP-bound dimers pack better than GTP-bound dimers

Answer 38

False: GTP-Bound dimers pack better

Question 39

True or False :Microtubules in mature neurons have been capped and thus are stable

Answer 39

True

Question 40

Microtubule composition

Answer 40

a helical array of heterodimers of a- and b-tubulin