Chapter 9: The cytoskeleton and cell motility

Question 1

3 elements of the cytoskeleton:

Answer 1

• microtubules
• microfilaments
• intermediate filaments

Question 2

Roles of the cytoskeleton

Answer 2

• structural support/maintaining cell shape
• internal framework organizing organelles within the cell
• directs cellular locomotion and movement of materials within the cell

Question 3

T/F: Microtubules are highly branched

Answer 3

FALSE. Microtubules are long, hollow, UNBRANCHED tubes

Question 4

microtubues are composed of subunits of the protein ____

Answer 4

tubulin

Question 5

Microfilaments are ccomposed of the protein ____

Answer 5

actin

Question 6

a MICROTUBULE is a set of GLOBULAR proteins arranged in longitudinal rows called _________

Answer 6

PROTOFILAMENTS

Question 7

How many protofilaments does a microtubule contain?

Answer 7

13

Question 8

each PROTOFILAMENT is assembled from dimers of ___ and ____ subunits assembled into tubules with plus and minus ends.

Answer 8

dimers of ALPHA and BETA tubulin subunits

Question 9

is the core of cilia and flagella is composed of microtubules or microfilaments?

Answer 9

MICROTUBULES

…ya ninny

Question 10

what does MAPs stand for?

Answer 10

Microtubule-associated proteins

Question 11

How is the microtubule-binding activity of MAPs controlled?

Answer 11

primarily by the addition and removal of PHOSPHATE GROUPS from particular AMINO ACIDS

Question 12

T/F: MAPs attach to the surface of microtubules to increase their STABILITY and promote their ASSEMBLY

Answer 12

True.

Question 13

What is one cause of Alzheimer’s disease related to MAPs?

Answer 13

an abnormally high level of phosphorylation of a certain MAP called “tau.”
The brain cells of people with this disease contain tangled filaments called NEUROFIBRILLARY TANGLES containing excessively phosphorylated tau molecules that are UNABLE TO BIND to MICROTUBULES, contributing to death of nerve cells.

Question 14

the movement of vesicles and material in the axon is mediated by _________

Answer 14

microtubules

Question 15

What generate the forces required to move objects within a cell?

Answer 15

motor proteins

Question 16

T/F: Microtubules have no role in embryogenesis.

Answer 16

False. Microtubules play a role in AXONAL GROWTH during embryogenesis

Question 17

1. movement of material AWAY from the cell body

2. movement of material TOWARDS the cell body

Answer 17

1. anterograde

2. retrograde

Question 18

T/F: molecular motors can move in any direction.

Answer 18

False. Molecular motors move UNIDIRECTIONALLY along the cytoskeletal track in a stepwise manner.

Question 19

3 classes of molecular motors:

Answer 19

1. kinesin
2. dynein
3. myosin

Question 20

Along what tracks do kinesin, dynein, and myosin move?

Answer 20

Kinesin and dynein move along MICROTUBULE TRACKS.

Myosin moves along MICROFILAMENT TRACKS.

Question 21

Motor proteins convert ____ energy into ____energy.

Answer 21

chemical energy (ATP) into mechanical energy.

Question 22

Which motor protein family moves in an anterograde manner along the microtubule track and which moves in a retrograde manner?

Answer 22

kinesin = anterograde
dynein = retrograde

Question 23

What drives the stepwise movement of motor proteins?

Answer 23

binding and hydrolysis of ATP

Question 24

What does “KLPs” stand for?

Answer 24

kinesin-like proteins

Question 25

composition of kinesins

Answer 25

- 2 identical heavy chains - 2 identical light chains - each kinesin includes a PAIR OF GLOBULAR HEADS connected to a ROD-LIKE STALK.

Question 26

T/F: kinesin is a PLUS end-directed microtubular motor based on its movement

Answer 26

true

Question 27

What is the velocity of the movement of kinesin on a single protofilament of a microtubule proportional to?

Answer 27

ATP concentration

Question 28

Explain "processive movement"

Answer 28

movement of KINESIN is PROCESSIVE, meaning it moves along an individual microtubule for a long distance without falling off.

Question 29

KLPs move cargo towards the __________

Answer 29

cell's PLASMA MEMBRANE

Question 30

What movement is dynein responsible for?

Answer 30

the movement of CILIA and FLAGELLA

Question 31

Cytoplasmic dynein is a _____ end directed microtubular motor

Answer 31

minus

Question 32

Name of adaptor required by cytoplasmic dynein to interact with membrane-bounded cargo:

Answer 32

dynactin

Question 33

Kinesins move cargo in one direction, towards the ___ end, and the dyneins move it in the opposite direction, towards the ____ end.

Answer 33

Kinesins move cargo in one direction, towards the PLUS end, and the dyneins move it in the opposite direction, towards the NEGATIVE end.

Question 34

T/F: kinesins and dyneins are ATPases

Answer 34

true

Question 35

What are MTOCs?

Answer 35

"microtubule-organizing centres" Specialized structures for the NUCLEATION of MICROTUBULES. ex. centrosome

Question 36

What is the centrosome responsible for?

Answer 36

-initiation and organization of the microtubular cytoskeleton

Question 37

T/F: centrioles are usually found in groups of 4

Answer 37

false. Centrioles are usually found in pairs

Question 38

Centrosomes contain 2 barrel-shaped _______ surrounded by ________

Answer 38

Centrosomes contain 2barrel-shaped CENTRIOLES surrounded by PERICENTRIOLAR MATERIAL (PCM)

Question 39

Basal Body

Answer 39

- MTOC | - structure where outer microtubules in a cilia and flagella are generated

Question 40

Do plants conatin MTOCs? Where are their microtubules organized?

Answer 40

Plants DO NOT contain MTOCs. THeir microtubules are organized around the surface of the nucleus.

Question 41

What is the name of the protein which is found in MTOCs and is critical for microtubule nucleation?

Answer 41

γ-tubulin

Question 42

What does γ-TURC stand for?

Answer 42

γ-TUbulin Ring Complex

Question 43

γ-TURC complex forms a polypeptide scaffold on which ____γ-tubulin molecules are arranged

Answer 43

13

Question 44

Hydrolysis of what molecule is needed for microtubule assembly?

Answer 44

GTP

Question 45

Proteins called ____ regulate the rate of growth and shrinkage of microtubules

Answer 45

+TIPS

Question 46

Axoneme

Answer 46

- central core of cilia and flagella. | - consists of microtubules in a 9 + 2 arrangement

Question 47

the CENTRAL SHEATH of the axoneme is connected to the a-tubules of peripheral doublets by ____

Answer 47

radial spokes

Question 48

By what are doublets in an axoneme connected to one another?

Answer 48

by an INTERDOUBLET BRIDGE

Question 49

What is IFT?

Answer 49

- "intraflagellar transport" | - process responsible for assembling and maintaining flagella

Question 50

T/F: basal bodies are identical in structure to centrioles

Answer 50

true. basal bodies can turn into centrioles and vise versa