BIOL 212 Lecture Notes - Lecture 27: Situs Inversus, Coiled Coil, Intermediate Filament
18 May 2018
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Lecture 27 Notes
Cytoskeleton
- Cells have filamentous structures inside them that help maintain cell shape and organization
- A protein network of filaments that extends throughout the cytoplasm
- Filaments are built from protein monomers (subunits) that are held together by protein-protein
interactions
- Important for maintaining and changing cell shape, movement, intracellular transport, organelle
positions
- Dynamic, the structure is continuously reorganized
- Cytoskeletal elements can interact with each other and with other proteins in the cells
Major Types of Cytoskeletal Filaments:
- Actin filament
- Microtubules
- Intermediate fibers
Actin Filaments
- Monomer: actin
- Fibers 7 nm thick (thinnest)
- Highly concentrated at cell cortex
- Organized into bundles, networks, gels
- Responsible for cellular shape an contractility
Microtubules
- Monomer: tubulin
- Straight, tubular structures 25 nm thick (thickest filaments)
- One end is attached to MTOC (microtubule-organizing center, centrosome)
- Organize cellular architecture and transport, and also the beating of cilia and flagella
- Hollow cylinders of tubulin
- Have inherent polarity (+ and – end)
- Grow out of organizing structure
- Grow from nucleation sites composed of ϒ-tubulin, grow at their plus ends from ϒ-tubulin ring
complexes of the centrosome
- Establish general coordinate system in cell
Dynamic Instability
- Microtubules show it
- Grow and shrink independently from one another
- Dynamic instability refers to periods of slower growth alternating w/periods of rapid shrinking
- Stems from intrinsic capacity of tubulin molecules to change their affinity to each other based on
binding GTP vs GDP
- Allows for spatial and temporal flexibility of cytoskeletal organization
- GTP hydrolysis changes subunit conformation and weakens bond (less stable with GDP)
growth of microtubules controlled by GTP hydrolysis
Microtubules Can be Stabilized/Destabilized by Drugs
- MAP or drug taxol, longer and less dynamic microtubules
- Catastrophe factor (kinesin 13) or drug colchicine, shorter more dynamic molecules
find more resources at oneclass.com
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Document Summary
Cells have filamentous structures inside them that help maintain cell shape and organization. A protein network of filaments that extends throughout the cytoplasm. Filaments are built from protein monomers (subunits) that are held together by protein-protein interactions. Important for maintaining and changing cell shape, movement, intracellular transport, organelle positions. Cytoskeletal elements can interact with each other and with other proteins in the cells. Straight, tubular structures 25 nm thick (thickest filaments) One end is attached to mtoc (microtubule-organizing center, centrosome) Organize cellular architecture and transport, and also the beating of cilia and flagella. Have inherent polarity (+ and end) Grow from nucleation sites composed of -tubulin, grow at their plus ends from -tubulin ring complexes of the centrosome. Grow and shrink independently from one another. Dynamic instability refers to periods of slower growth alternating w/periods of rapid shrinking. Stems from intrinsic capacity of tubulin molecules to change their affinity to each other based on binding gtp vs gdp.
