Passive Transport Lecture Notes

Overview of Passive Transport

• Definition: Movement of particles through a cell membrane from high to low concentration.
• Energy Usage: Occurs without the use of cellular energy.
• Concentration Gradient: Movement along the concentration gradient.

Types of Passive Transport

1. Diffusion
2. Osmosis
3. Facilitated Diffusion

Diffusion

• Definition: Movement of particles from an area of high concentration to an area of low concentration.
• Process:
  • Does not require energy.
  • Can occur with or without a semi-permeable membrane.
• Example:
  • Solute particles move to achieve equilibrium across the membrane.
  • Air freshener scent spreading in a room illustrates diffusion.

Osmosis

• Definition: Diffusion of water molecules through a permeable membrane.
• Process:
  • Water moves from high water concentration to low water concentration.
  • Achieves equilibrium in concentration of water vs. solute.
• Example:
  • Water passing through a membrane with solute particles too large to pass.

Facilitated Diffusion

• Definition: Diffusion through specialized protein channels in the cell membrane.
• Process:
  • Allows larger particles to move in and out of cells.
  • Occurs without energy, using protein channels like tunnels.
• Characteristics:
  • Moves particles along the concentration gradient naturally.

Summary

• Passive transport is a natural, energy-free process.
• Includes diffusion, osmosis, and facilitated diffusion, each helping maintain equilibrium.
• Essential for maintaining cellular function and balance.