BIO130H1 Chapter Notes -Alpha Helix, Coiled Coil, Nucleoside Triphosphate

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7 Apr 2012
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Pg. 965-988
The Cytoskeleton
Cytoskeleton: Network of filaments
The self-assembly and dynamic structure of cytoskeleton filaments
3 types of cytoskeletal filaments
1. Intermediate filaments: provides mechanical strength
2. Microtubules: positions of membrane enclosed organelles and direct
intracellular transport
3. Actin: determines shape of cell and required for cell locomotion
Need accessory protein to link the filaments to cell components
Accessory proteins are essential to control the assembly of the cytoskeleton
and specific locations; this includes motor proteins convert ATP to ADP and P
to move organelles along a filaments
Cytoskeletal Filaments are Dynamic and Adaptable
Microtubules are found at the center and radiate outwards; so it can form a
mitotic spindle during cell division
Can also form cillia and flagella on the surface of a cell
Tight bundles can transport materials
Plants cells: helps cell wall synthesis
Actin filaments: underlie plasma membrane of animal cells
Provides strength and shape of to its thin lipid bilayer
Form many different cellular projections
Ex. Dynamic structure: lamelipodia and filopodia
Actin based contractile ring: assembles to divide cell into two;
allows for more stability
Microvilli: increases the surface area for absorption
Intermediate filaments: inner face of nuclear envelope
Form protective cage for DNA
In the cytosol they twist together to form long cables that
connect nerve cells to the epithelial cells
Form tough appendages such as hair and fingernails
Example of a dramatic reorganization that occurs in cell division for
fibroblast
Cell Division
Microtubules helps separates into the chromosomes mitotic spindles
Actin helps by forming a contractile ring allowing the cell to separate into
two daughter nuclei
Many cells require rapid cytoskeletal rearrangements
Ex. Neutrophil, white blood cell
The Cytoskeleton can also form Stable Structures
Cytoskeleton is responsible for cell polarity
Ex. Polarized epithelial cells: found in intestines; actin and intermediate
filaments help maintain the difference between the apical surface (absorbs
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