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What are the three components of the cytoskeleton?
- name one thing about them
- microtubules: involved in cell division and plant cell wall
- microfilaments: major function is muscle contraction
- intermediate filaments: made of different kinds of proteins
Which two cytoskeletal elements are involved in movement?
It may not be the __. There are various types of movements.
- microtubules and microfilaments
- whole cell movement
All cells have some sort of __; more extensive in __.
History of microtubules
- not much known until the TEM
- -some techniques (osmotetroxide) caused them to not be seen, but with gluteraldehyde, they were more visible
With a light microscope, you aren't really seeing where they are; not specific
Microtubules are components of almost all __ and at least __.
Scientist at Boston College wrote a paper about it= __ (1960s; she pushed __)
--- at first, it was proposed (not by her initially) for chloroplasts and she supported it in the 1960s.
- all euk. cells
- one prokaryote
- Lynn Margulis
The species Margulis saw microtubules in was a __.She said this was the __ in eukaryotes through some sort of __ that occured.
There are actually __ (other than eukaryotes) with microtubules.
- spirochete (a larger bacteria)
- origin of microtubules
- symbiotic relation
What are the associations of microtubules? (fxn)
- 1) motility (principle structure in euk. flagella and cilia)
- 2) cell shape and division
- 3) morphogenesis in plant cells
Structures of microtubues
Length and examples
- straight, longitudinal, not really rigid nor flexible
- depends on function
- ex: axons of nerve cells (10-25 micrometers)
- cilia and flagella (5-200 micrometers)
Another feature (varies) are the __. Not made from the same kind of __ and can differ.
- __ can vary in __ as well.
When acting as cross bridges, what can the side arms be attached to?
- another MT: if connected, less flexibility; more rigid; contributes to the stability of microtubues
- can attack the microtubule to the PM, ER, etc.
- vesicles where they act as a tract and move vesicles along
If the side arm is bound to MT, it __.
Arms contribute to the way that the MT __.
- they may have __.
Why were microtubules first discovered?
- makes up a small percentage of it
- associate with each other
- because they are larger
Function of MT
- cell shape
- motion and movement: cilia and flagella
- role in morphogenesis: affiliated with new cell wall material and orientation
How can you find out if microtubules are involved in movement?
- introduce an environment to depolymerize the MTs and see if it stops; if it does, then the MT are involved
- or look at the cells to see if the MT are present in the area
Cytoskeletal cell shape
example 1: __.
If put in __, what happens?
- parallel to the long axis of the axon, which have alot
- the axons and shape get lost; they retract
Cytoskeletal cell shape
example 2: __.
-Function of the structure mentioned in orientation
- RBC in some fish and amphibians
- MT at the edge of the cell are called marginal bands
- - marginal bands are responsibel for keeping the cells in proper shape; they are very stable and not in mammalian BCs
- four types
- cilia/ flagella
- rapid transport
- animal cells, not in a typical plant cell
- if its in a plant cell, its rare
- pairs (in non-dividing cell, one pair)
- - right angles to each other
- - cylindrical
- ---LENGTH: right at the edge of resolution (2000 Angstrom-4000 Angstroms long)
centrioles never touch each other; between them is a fibrillar protein to hold them togeter
surrounded by PCM
Appearance of centrioles
- major component: __
- occurs in __
- explain A, B, and C
- nine groups, each containing three MTs
- - there are none in the enter= 9+0
- A is complete with all subunits
- B and C are incomplete and share the subunits with A
- no membrane to hold them together; protein holds the triplets together
- arises from?
- what doesn't happen?
- - arises from preexisting centrioles; separate and give rise to a preexisting one
- -do not touch; new one doesn't touch the parent one
- -procentrioles (little buds that come off of it) [parent acts as a MTOC]
What happens in plant cells in terms of MTs?
- what you begin with
- what forms
- what's in the granula looking mass?
- centrioles are needed for flagella
- - what you begin with is a granular, amorphous material (deuterosome)
- - what forms around the endge are centrioles
- - tubulin and dimers; centrioles grow; granular molecule shrinks
Function of centrioles
- basic: help form the spindle
- no connection between centrioles and the mitotic spindle
Suggestions as to why there are centrioles at either pole
- 1) centioles may bot be directly involved, but help recruit material from the PCM
- 2) it guarantees that each daughter gets a pair of centrioles
Centrioles may help __, but also help ensure that __.
- recruit PCM
- each daughter cell has one
Centrioles act as a __ to form flagella; form __.
- Centrioles required to make sure they have an __.
- WIthout a __, you don't have cilia nor flagella.
Centrioles have nothing to do with the microtubules unless what?
- motor flagella
- organized flagellum
- Basal body
- they are making proper material
Cilia and Flagella: structure on bacteria
cylindrical extensions from the surface of the cell; lining it is a bacterial enzyme
What do they differ in? (they= cilia and flagella)
beating pattern; quantity; length
How many of each flagella and clila
Major internal composition of these are __.
- f: a few (1,2 or 4, but the average is two)
- c: a ton
What happens in the axoneme in terms of movement?
- the dynein arms are involved; they move; the doublets are moving relative to one another; A+B do not move as separate things; they move together; relative to the other subunit that's adjacent to it
- dynein walks along the adjacent doublet