Biology Lesson 4.5: Exocytosis and Endocytosis

Lesson 4.5: Exocytosis and Endocytosis

• Exocytosis and endocytosis are bulk transport mechanisms for large molecules across the cell membrane.
• Bulk transport involves moving large molecules like proteins, lipids, nucleic acids, carbohydrates, and polysaccharides.
• Humans require transportation for daily living, similar to how cells require bulk transport.
• Cells need to transport large molecules as part of their daily function.

Cellular Architecture and Processes

• Cellular architecture and processes are related, and necessary for cellular function.

Human Needs and Exocytosis/Endocytosis

• Humans need transportation to travel to different destinations.

• This connects to the cell's need for transporting large molecules.

Importance of Transporting Large Molecules

• Transporting large molecules across cell membranes is crucial
• This process is vital for cellular function.

Learning Competency

• The learning objective is to differentiate between exocytosis and endocytosis (STEM_BIO11/12-lg-h-14).

Learning Objectives

• Explain the process of transporting large molecules through exocytosis.
• Describe the mechanism of transporting large molecules through endocytosis.
• Distinguish between phagocytosis, pinocytosis, and receptor-mediated endocytosis.

Bulk Transport

• Bulk transport is used for moving large molecules (like proteins, lipids, nucleic acids etc).

Exocytosis

• Exocytosis is a process where molecules exit the cell using intracellular vesicles.
• these vesicles fuse with the plasma membrane
• Golgi bodies are involved.
• Exocytosis has two types: constitutive and regulated.
• Constitutive exocytosis: Transports proteins (e.g. receptors) that function in the plasma membrane. This is a continuous process.
• Regulated exocytosis: Occurs when a cell receives a signal from outside the cell. Molecules are transported outside the cell in response.

Endocytosis

• Endocytosis is a process where molecules are engulfed by the cell, using vesicles.
• Vesicles bud inward and envelope the substances.
• Vesicles delivers their contents.

Types of Endocytosis

• Phagocytosis: Engulfing and packing solid particles through vacuoles.
• Cells use pseudopodia to engulf particles.
  • Phagocytosis is for defense and repair.
• Pinocytosis: Transports liquids or small particles via vesicles formation.
• Receptor-mediated endocytosis: A specific kind of pinocytosis, using a receptor protein to recognize compatible molecules.

Coated Pits

• Receptor-mediated endocytosis uses coated pits.
  • These pits are coated with a protein and form vesicles.

Summary of Exocytosis vs Endocytosis

• Exocytosis: Molecules exit the cell.
• Endocytosis: Molecules enter the cell.

Case Study

• A case study describes a patient with familial hypercholesterolemia who is experiencing respiratory distress, dizziness, and fatigue.
  • This condition is connected to receptor-mediated endocytosis.