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Cytoskeleton in Animal Cells

Aug 29, 2025

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.