The Cytoskeleton

Question 1

definition of cytoskeleton

Answer 1

three dimensional array of interconnected microfiliments, microtubules, and intermediate filiments

Question 2

what is the cytoskeleton? (on a structural level)

Answer 2

an internal framework that gives a cell its distinctive shape and high level of internal organization

Question 3

what does the cytoskeleton form?

Answer 3

forms a highly structured yet dynamic matrix that helps establish and maintain cell shape

Question 4

what does the cytoskeleton play a role in?

Answer 4

plays a role in cell movement and cell division

Question 5

cytoskeleton serves a framework for positioning and moving what..?

Answer 5

organelles and macromolecules within the cell

Question 6

what are the three structural elements within the cytoskeleton?

Answer 6

microtubules, microfiliments, and intermediate filiments

Question 7

Mictrotubules:

size?

Answer 7

-largest structural element found in cytoskeleton

Question 8

Microtubules:

example of a microtubule?

Answer 8

axoneme of cilia and flagella, the appendages responsible for motility of euk. cells (axoneme of sperm tail)

Question 9

Microtubules:

what else can they form?

Answer 9

also form mitotic spindle fibers that separate chromosomes prior to cell division

Question 10

Microtubules:

what other important role do they have?

Answer 10

also play important role in organization of cytoplasm and the intracellular movement of macromolecules and other materials in the cell

Question 11

Microtubles:

what do they contribute to the cell?

Answer 11

contribute to the overall shape of the cell, spatial disposition of its organelles and the distribution of microfiliments and inermediate filiments

Question 12

Microtubles: Structure? inner and outer diameter?

Answer 12

• Hollow cylinders with outer diameter of about 25nm and inner diameter of about 15nm
• flexible in living cells

Question 13

Microtubules:
wall of microtubules consists of..
each protofiliment is a…

Answer 13

• longitudinal arrays or protofiliments, usually 3 of them arranged side by side around the hollow center, called the lumen
• each protofiliment is a linear polymer of tubulin, a dimeric protein consisting of α-tubulin and β-tubulin

Question 14

Microtubules:
orientation of the tubulin dimers in each of the protofiliments?
what does this orientation do?

Answer 14

oriented in the same direction, such that all subunits face the same end of the microtubule

uniform orientation gives microtubule polarity

Question 15

Microfiliments:

size? diameter?

Answer 15

much thinner than microtubules

diameter of about 7nm = smallest of major cytoskeleton components

Question 16

Microfiliments:

best know for their role in?

Answer 16

in the contractile fibrils of muscle cells

Question 17

Microfiliments:

can form…and therefore influence..?

Answer 17

connections with the plasma membrane and thereby influence locomotion and ameoboid movement, and cytoplasmic streaming

Question 18

microfiliments:

also provide..

Answer 18

the cleavage furrow that divides the cytoplasm of an animal cell after the two sets of chromosomes have been separated by the mitotic spindle fibers

Question 19

Microfiliments:

contribute what to the cell ?

Answer 19

contribute to the development and maintenance of cell shape

Question 20

microfiliments:

polymers of..?

Answer 20

polymers of the protein actin

Question 21

Microfiliment:

each microfiliment consists of

Answer 21

a chain of actin monomers that are assembled into a filament with a helical appearance and diameter of about 7nm

Question 22

Microfiliments:

show polarity?

Answer 22

show polarity; all subunits oriented in same direction

Question 23

Intermediate filiments:

size? diameter?

Answer 23

-in between microtubules and microfiliments, diameter is about 8-12nm

Question 24

Intermediate filiments:

stability?

Answer 24

most stable and the lease soluble constituent of cytoskeleton

Question 25

Intermediate filiments: | what are they regarded as?

Answer 25

regarded as scaffold that supports the entire cytoskeleton framework

Question 26

Intermediate filiments: | also thought to have..

Answer 26

also thought to have tension bearing roles in some cells because they often occur in areas of mechanical stress

Question 27

Intermediate filiments: | from tissue to tissue?

Answer 27

differ in protein composition from tissue to tissue ( in contrast to microtubules and microfiliments)

Question 28

Intermediate filiments: | all intermediate filiments share common structural features..

Answer 28

- all have central rod-like segment - flanking the central region of the protein are N-terminal and C-terminal segments that differ greatly in size and shape

Question 29

Intermediate filiments: basic structural unit? how do they align? what do they form?

Answer 29

- is a dimer of two intertwined intermediate filiment polypeptides - two such dimers align laterally to form a protofilimetn - protofiliments than interact with one another to forom an intermediate filiment that is thought to be 8 protofiliments thick at any point

Question 30

what does recent research show wrt bacteria and archaea

Answer 30

they have polymer systems that function similarly to euk cytoskeleton elements - actin like MreB protein is involved in DNA segregation - tubulin like FTsZ protein is involved in determining where bacterial cells will divide - intermediate filiment like cresctin is a regulator of cell shape

Question 31

Motile Systems: | where does motility occur?

Answer 31

occurs at the tissues, cellular and subcellular levels

Question 32

Motile Systems: | intracellular components move..?

Answer 32

e.g microtubules of the mitotic spindle fibers play a role in the separation of chromosomes during cell division

Question 33

Motile Systems: | how do the microtubules and microfiliments generate movement?

Answer 33

they provide a basic scaffold for specialized motor proteins, or mechanoenzymes, which interact with the cytoskeleton to produce motion at the molecular level

Question 34

in eukaryotes, there are two major motility systems:

Answer 34

1. first involves interactions between specialized motor proteins and microtubules 2. second requires interactions between actin microfiliments and members of the myosin family or motor proteins