Overview
This lecture introduces the cytoskeleton in animal cells, describing its functions, structure, and the roles of its three main components: microtubules, intermediate filaments, and microfilaments.
Functions of the Cytoskeleton
- The cytoskeleton provides structural support to the cell.
- It assists in movement both inside and outside the cell.
- It helps transport substances within the cell.
Structure of the Cytoskeleton
- The cytoskeleton consists of three main types of protein filaments: microtubules, intermediate filaments, and microfilaments.
- All three filament types are made of proteins.
Microtubules
- Microtubules are hollow tubes with a diameter of about 25 nanometers.
- They play a role in the mitotic spindle during cell division.
- Microtubules form cilia (hairlike projections for moving substances across the cell surface).
- They also form flagella (tail-like structures for cell movement).
- Microtubules are involved in transporting substances within the cell.
Intermediate Filaments
- Intermediate filaments are about 10 nanometers in diameter.
- They provide structural support to the cell, similar to how springs support a mattress.
- Intermediate filaments help cells resist mechanical stress and maintain their shape.
Microfilaments
- Microfilaments are thin protein filaments about 7 nanometers in diameter.
- They are involved in cell movement from within the cell, unlike cilia and flagella.
- Microfilaments assist in processes like cell division, where the cell pinches to split.
- Pseudopod movement in amoeba and similar cells is powered by microfilaments.
Key Terms & Definitions
- Cytoskeleton — the protein-based internal skeleton of the cell, providing support, movement, and transport.
- Microtubules — thick, hollow protein tubes (25 nm) involved in movement and transport within cells.
- Intermediate Filaments — medium-thickness protein filaments (10 nm) providing structural support and resistance to stress.
- Microfilaments — thin protein filaments (7 nm) involved in cell movement and shape changes.
- Cilia — short, hairlike extensions of a cell made of microtubules, moving substances across the cell surface.
- Flagella — long, tail-like extensions of a cell made of microtubules, moving the entire cell.
- Pseudopods — temporary cell projections for movement and feeding, powered by microfilaments.
Action Items / Next Steps
- Review detailed functions and structures of microtubules, intermediate filaments, and microfilaments in upcoming lessons.