Introduction to the Cytoskeleton

Study Notes

The cytoskeleton is a complex and dynamic network of protein fibers that extend throughout the cytoplasm of a cell
It provides structural support, motility, and regulation for the cell, acting as the cell's skeleton and muscle
The cytoskeleton holds organelles in place, moves them, and aids in cell movement.

Provides shape for the cell
Offers protection by resisting deformation
Allows cells to migrate by actively contracting and deforming
Plays a role in many cell signaling pathways
Involved in endocytosis, the uptake of extracellular material
Separates chromosomes during cell division and the cytokinesis stage
Acts as scaffolding to organize cell components and facilitate intracellular transport
Can form a template for cell wall construction
Creates specialized structures such as flagella, cilia, lamellipodia, and protostomes

Actin Filaments (Microfilaments):
- Determine the shape of the cell's surface
- Necessary for whole-cell locomotion
- Drive the pinching of one cell into two during cell division
Microtubules:
- Determine the positions of membrane-enclosed organelles
- Direct intracellular transport (act as tracks for kinesin and dynein)
- Form the mitotic spindle that segregates chromosomes during cell division
- Bind different MAPs (microtubule-associated proteins), microfilaments, and intermediate filaments to maintain cell shape
Intermediate Filaments:
- Provide mechanical strength

All contribute to the cell's strength, shape, and ability to move
All interact with hundreds of accessory proteins that regulate and link filaments to other cell components

Accessory proteins are essential for the controlled assembly of cytoskeletal filaments
They include motor proteins, which convert ATP hydrolysis energy into mechanical force to move organelles along filaments or move the filaments themselves