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AP BIOLOGY 6.6Dr. Laurie Solis
How do organelles keep their location?
Have you ever wondered how organelles in the cytoplasm keep their place?
Take a look at a cross section of a cell.
Do you think organelles are free flowing?
When better microscopes were invented…
Scientists were able to see that cell’s have a cytoskeleton
Electron and light microscope enabled us to see it!
Cytoskeleton
The cytoskeleton is a network of fibers extending throughout the cytosplasm and keeps the organelles organized!
Cytoskeleton The cytoskeleton
contains microtubules and microfilaments
Microtubules - like the trunk of a tree or a thick branch
Microfilaments are much like smaller finer branches on a tree.
The cytoskeleton is both a:• muscle• and a skeleton,• and is responsible for • cell movement, • cytokinesis, • and the organization of the organelles within the cell.
Cytoskeleton
Cytoskeleton
Maintains the cell’s shape
Gives mechanical support to the cell
Why would this be especially important in animal cells?
Cytoskeleton
Why would this be especially important in animal cells?
Because animal cells lack cell walls to keep its shape!
Cytoskeleton
The cytoskeleton is like a skeleton because
It is strong Keeps the shape of
the cell But also like a muscle
because It can move and bend And change the
shape of the cell
Cytoskeleton
The ability of movement is called
Cell motility
Motor proteins
Motor proteins are the legs that attach to vesicles and walk along the microtubules of the cytoskeleton.
They help move cells to different places
Or, just move parts of cells within the cell structure
http://www.youtube.com/watch?v=qe6ylN906q4
A closer look at microtubules
All eukaryotic cells have microtubules
Hollow rods Constructed from a
protein called tubulin
Can add or reduce particles depending on its activity
Microtubules
Where do the microtubules emerge from?
Centrosome: a region located near the nucleus and considered a microtubule organizing center
Microtubules
Within the centrosome are a pair of centrioles Each are composed of 9 sets of triplet microtubules
arranged in a ring Before an animal ell divides, the centrioles replicate Not all eukaryotes have centrioles: such as yeast and
plant cells
Microtubules
Microtubules have three different functions. They make up the centrioles in a cell, the flagella and cilia of a cell, and they serve as "tracks" for transport vesicles to move along.
Microtubule polymers are extremely sensitive to various environmental effects.
Very low levels of free calcium can destabilize microtubules and this prevented early researchers from studying the polymer in vitro.
Cold temperatures can also cause rapid depolymerization of microtubules.
This fact has a vital inconsistency in cancer treatments as paclitaxel (sold under the trademark taxol, a widely used antineoplastic drug) acts on cytoskeletal microtubules and it is their interaction with elements that regulate the cell cycle that provokes, in the presence of antineoplastic drugs, a series of cellular failures in the cancerous cells that lead to planned cell death or apoptosis.[27]
Homework
How is the cytoskeleton linked to cancer research?
What happens when the cytoskeleton is not working properly?
Why is the cytoskeleton important?
