Functions of Proteins in the Plasma Membrane

Introduction

• Focus on functions of proteins within the plasma membrane.
• Discussion covers key functions relevant to Anatomy and Physiology courses (AP1 and AP2).
• Proteins in the plasma membrane are vital for cell communication and operation.

Key Functions of Proteins

1. Receptors

• Function: Facilitate communication by specific chemical attachment.
  • Example: Hormones affecting cellular changes by binding to receptors.
  • Importance: Enables cells to respond to environmental changes.
• Examples of Receptor Malfunction:
  • Diabetes Mellitus: Insulin receptors are unresponsive, impairing glucose utilization.
  • Androgen Insensitivity Syndrome: Defective testosterone receptors preventing hormone effect.

2. Intercellular Junctions

• Function: Form connections between adjacent cells.
  • Proteins in the membranes form junctions for cellular cohesion and communication.
• Types:
  • Junctions preventing disintegration under external forces.
  • Junctions enabling intercellular communication.

3. Channels

• Function: Enable solute movement across the membrane.
  • Proteins can change shape to allow solute entry or exit.
• Types of Channels:
  • Ungated Channels: Constantly open, allowing solute flow (e.g., potassium, sodium).
  • Gated Channels: Open and close, regulating solute movement.
    • Ligand-Gated Channels: Open in response to chemical signals (e.g., sodium channels in muscle contraction).
    • Voltage-Gated Channels: Open with changes in charge (e.g., resting membrane potential changes).

4. Carriers

• Function: Transport solutes across the membrane.
  • Some carriers operate without energy; others require ATP (pumps).
• Pumps:
  • Active transport mechanisms requiring energy, moving solutes against concentration gradients.
  • Example: Sodium-potassium pump, crucial for cell function.

Conclusion

• Overview of four primary functions of proteins in the plasma membrane: receptors, intercellular junctions, channels, and carriers.
• Proteins are essential for cell functionality and communication.
• Note: More protein functions exist beyond the discussed four.