Bulk Transport in Cells

Overview

• Bulk Transport: Describes how cells take in and export material.
• Two main processes: Endocytosis and Exocytosis.

Endocytosis

• Definition: Process by which cells take in material.
• "Endo" means internal or within.

Types of Endocytosis

1. Phagocytosis

• Definition: Cell takes in solid food or organisms (e.g., bacteria).
• "Phago" means to eat or devour.
• Process:
  • Cell bends around and engulfs a large food particle.
  • Food particle is surrounded by a membrane of phospholipids.

2. Pinocytosis

• Definition: Cell takes in fluid containing solute particles and nutrients.
• "Pino" means to drink.
• Process:
  • Cell engulfs fluid with dissolved nutrients and solute particles.
  • Engulfed in a membrane known as a vesicle.

3. Receptor-Mediated Endocytosis

• Definition: Cell uses receptors to attach to specific molecules.
• Process:
  • Receptors on cell surface attach to solute particles.
  • Cell membrane closes around attached molecules, taking them into the cell.

Exocytosis

• Definition: Process by which cells export material.
• "Exo" means outside or external.
• Process:
  • Vesicle inside cell moves to the cell membrane.
  • Vesicle merges with membrane, opening up to release particles outside the cell.

Summary

• Endocytosis: Cells take in material.

  • Includes phagocytosis, pinocytosis, and receptor-mediated endocytosis.

• Exocytosis: Cells expel material.

• Understanding these processes is key in cellular biology for transporting substances in and out of cells.