Dr. 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

 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 q4

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]cancerpaclitaxelantineoplasticcell cycleapoptosis [27]

Homework  How is the cytoskeleton linked to cancer research?  What happens when the cytoskeleton is not working properly?  Why is the cytoskeleton important?