The Cytoskeleton Flashcards
definition of cytoskeleton
three dimensional array of interconnected microfiliments, microtubules, and intermediate filiments
what is the cytoskeleton? (on a structural level)
an internal framework that gives a cell its distinctive shape and high level of internal organization
what does the cytoskeleton form?
forms a highly structured yet dynamic matrix that helps establish and maintain cell shape
what does the cytoskeleton play a role in?
plays a role in cell movement and cell division
cytoskeleton serves a framework for positioning and moving what..?
organelles and macromolecules within the cell
what are the three structural elements within the cytoskeleton?
microtubules, microfiliments, and intermediate filiments
Mictrotubules:
size?
-largest structural element found in cytoskeleton
Microtubules:
example of a microtubule?
axoneme of cilia and flagella, the appendages responsible for motility of euk. cells (axoneme of sperm tail)
Microtubules:
what else can they form?
also form mitotic spindle fibers that separate chromosomes prior to cell division
Microtubules:
what other important role do they have?
also play important role in organization of cytoplasm and the intracellular movement of macromolecules and other materials in the cell
Microtubles:
what do they contribute to the cell?
contribute to the overall shape of the cell, spatial disposition of its organelles and the distribution of microfiliments and inermediate filiments
Microtubles: Structure? inner and outer diameter?
- Hollow cylinders with outer diameter of about 25nm and inner diameter of about 15nm
- flexible in living cells
Microtubules:
wall of microtubules consists of..
each protofiliment is a…
- 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
Microtubules:
orientation of the tubulin dimers in each of the protofiliments?
what does this orientation do?
oriented in the same direction, such that all subunits face the same end of the microtubule
uniform orientation gives microtubule polarity
Microfiliments:
size? diameter?
much thinner than microtubules
diameter of about 7nm = smallest of major cytoskeleton components
Microfiliments:
best know for their role in?
in the contractile fibrils of muscle cells
Microfiliments:
can form…and therefore influence..?
connections with the plasma membrane and thereby influence locomotion and ameoboid movement, and cytoplasmic streaming
microfiliments:
also provide..
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
Microfiliments:
contribute what to the cell ?
contribute to the development and maintenance of cell shape
microfiliments:
polymers of..?
polymers of the protein actin
Microfiliment:
each microfiliment consists of
a chain of actin monomers that are assembled into a filament with a helical appearance and diameter of about 7nm
Microfiliments:
show polarity?
show polarity; all subunits oriented in same direction
Intermediate filiments:
size? diameter?
-in between microtubules and microfiliments, diameter is about 8-12nm
Intermediate filiments:
stability?
most stable and the lease soluble constituent of cytoskeleton
Intermediate filiments:
what are they regarded as?
regarded as scaffold that supports the entire cytoskeleton framework
Intermediate filiments:
also thought to have..
also thought to have tension bearing roles in some cells because they often occur in areas of mechanical stress
Intermediate filiments:
from tissue to tissue?
differ in protein composition from tissue to tissue ( in contrast to microtubules and microfiliments)
Intermediate filiments:
all intermediate filiments share common structural features..
- 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
Intermediate filiments:
basic structural unit?
how do they align?
what do they form?
- 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
what does recent research show wrt bacteria and archaea
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
Motile Systems:
where does motility occur?
occurs at the tissues, cellular and subcellular levels
Motile Systems:
intracellular components move..?
e.g microtubules of the mitotic spindle fibers play a role in the separation of chromosomes during cell division
Motile Systems:
how do the microtubules and microfiliments generate movement?
they provide a basic scaffold for specialized motor proteins, or mechanoenzymes, which interact with the cytoskeleton to produce motion at the molecular level
in eukaryotes, there are two major motility systems:
- first involves interactions between specialized motor proteins and microtubules
- second requires interactions between actin microfiliments and members of the myosin family or motor proteins
