2.6.1 Structure of Cell-Surface Membrane

• Structure of cell surface membrane 

  • Phospholipid bilayer
  • Contain glycoprotein & glycolipid 
  • Channel Protein
  • Carrier protein
  • Cholesterol
• Purpose of Channel/Carrier Proteins:

  • Allows large, water soluble, polar molecules to enter
• Cholesterol = restricts movement to provide stability
• Glycolipids - Carbohydrates bound to lipids; extend from surface of cell; act as cell surface receptors for certain molecules; allow cells to adhere to one another to form tissues.
• Glycoproteins - Carbohydrates attached to external/extrinsic proteins; act as cell surface receptors and neurotransmitters; allow cells to recognise one another & attach to form tissues
• Adaptations of Cell Membranes 

  • Increase in surface area (eg folded membrane)
  • Increase in number of carrier/channel proteins
• Exocytosis and endocytosis transport large particles
• Exocytosis = vesicles containing large particles are fused with the cell surface membrane and released from the cell.
• Endocytosis = particles are enclosed in vesicles made from the cell surface membrane and transported into the cell