Cell Membrane Structure

Cell Membrane Structure

Fluid Mosaic Model

• The cell membrane is composed of a phospholipid bilayer with embedded proteins
• The phospholipid bilayer is semi-permeable, allowing certain substances to pass through while restricting others
• The fluid mosaic model describes the dynamic and flexible nature of the cell membrane

Phospholipid Bilayer

• Phospholipids are amphipathic molecules with a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail
• The hydrophilic heads face outward, interacting with the aqueous environment
• The hydrophobic tails face inward, away from water
• The phospholipid bilayer is 5-7 nanometers thick

Embedded Proteins

• Integral proteins:
  • Span the entire membrane, interacting with both the lipid bilayer and the external environment
  • Examples: receptors, enzymes, and transport proteins
• Peripheral proteins:
  • Attached to the surface of the membrane, interacting with the lipid bilayer or integral proteins
  • Examples: signaling proteins and adapter proteins

Membrane Fluidity

• The cell membrane is semi-fluid, allowing for lateral movement of lipids and proteins
• Factors affecting membrane fluidity:
  • Temperature: increased temperature increases fluidity
  • Cholesterol content: cholesterol reduces fluidity
  • Saturated vs. unsaturated fatty acids: unsaturated fatty acids increase fluidity