Bulk Transport in Cells

Introduction

• Bulk Transport: Describes the process of how cells take in and export materials.
  • Endocytosis: Process by which cells take in material.
  • Exocytosis: Process by which cells export material.

Endocytosis

• Definition: Endocytosis is the process of taking material into the cell.
  • Endo-: Means internal or within.

Types of Endocytosis

1. Phagocytosis

   • Means "to eat" or "devour."
   • Involves cells taking in solid food particles or even organisms, such as bacteria.
   • Visual Example:
     • Cell engulfs a large food particle.
     • The food particle is surrounded by a membrane of phospholipids within the cell.

2. Pinocytosis

   • Means "to drink."
   • Involves cells taking in fluid that contains solute particles and nutrients.
   • Visual Example:
     • Cell engulfs fluid containing dissolved nutrients and solute particles.
     • Particles are engulfed in a membrane known as a vesicle.

3. Receptor-Mediated Endocytosis

   • Cells have receptors that attach to specific molecules with the right shape.
   • Process:
     • Receptors on the cell attach to solute particles.
     • The cell membrane closes around it, bringing particles into the cell.

Exocytosis

• Definition: The process by which cells export material outside.
  • Exo-: Means outside or external.
• Process:
  • A vesicle inside the cell, containing particles, moves to the cell membrane.
  • The vesicle membrane becomes part of the cellular membrane.
  • The cellular membrane opens to release particles into the extracellular fluid.

Conclusion

• Endocytosis involves taking materials into the cell.
• Exocytosis involves exporting materials out of the cell.