Lecture Notes: Cell Movement

Introduction

• Key Idea: Cells move around to perform their functions.
  • Red Blood Cells: Pumped by the heart, do not swim.
  • Other Cells: Actively move on their own, crucial for development and immune function.

Sperm Cells

• Movement: Essential for fertilization.
  • Flagellum: Tail made of microtubule proteins, propels sperm.
    • In bacteria and archaea, flagella have different structures.
• Importance: Proper movement is crucial for reaching and fertilizing eggs.

White Blood Cells (Neutrophils)

• Function: Part of the immune system, especially against bacterial infections.
  • Movement Process:
    • Travel in bloodstream until signaled (chemotaxis).
    • Stick to blood vessel lining, roll, and then migrate into tissues.
• Mechanism of Movement: Dependent on the cytoskeleton.
  • Cytoskeleton: Provides structure; two theories on movement.

Theories of Cell Movement

Cytoskeletal Model

• Actin Proteins: Polymerize to extend the leading edge of the cell.
  • Microtubules:
    • Act as a rudder to steer direction.
    • Can be fixed or flexible, acting as an anchor to stop movement.

Membrane Flow Model

• Endocytosis and Exocytosis:
  • Plasma membrane internalized as vesicles.
  • Vesicles move to cell front and add membrane.
  • Two types of vesicles:
    • Plasma membrane vesicles: Extend leading edge.
    • Integrin-containing vesicles: Anchor membrane to assist movement.
• Net Effect: Cell crawls forward by continuously adding membrane and anchor points.