Cell membrane

• What does the term "plasma membrane" refer to?

  Cell membranes and organelle membranes
• What model describes the structure of plasma membranes?

  Fluid mosaic model
• What does the "fluid" part of the fluid mosaic model refer to?

  Movement of molecules within the membrane
• What are the main components of the plasma membrane?

  Phospholipids, proteins, glycoproteins, glycolipids, cholesterol
• What does a partially permeable membrane allow?

  Only certain molecules to diffuse through
• What is the arrangement of phospholipids in the bilayer?

  Hydrophilic heads face outside, tails inside
• What charge does the phosphate group in the phospholipid head have?

  Negative charge
• Why are fatty acid tails considered hydrophobic?

  They do not have any charges
• What distinguishes saturated fatty acids from unsaturated fatty acids?

  Saturated has no double bonds; unsaturated does
• What role does cholesterol play in the membrane?

  Restricts lateral movement of molecules
• How does cholesterol affect membrane fluidity at high temperatures?

  Reduces fluidity, making it more rigid
• What are peripheral proteins?

  Proteins that do not span the entire membrane
• What are integral proteins?

  Proteins that span the entire width of the membrane
• What is the function of glycoproteins?

  Act as receptors for cell recognition
• What do channel proteins do?

  Transport water-soluble ions across the membrane
• How do carrier proteins function?

  Change shape to transport larger molecules
• What types of molecules can diffuse through the phospholipid bilayer?

  Lipid-soluble molecules and small gases
• Which substances cannot pass through by simple diffusion?

  Water-soluble substances larger than water
• What are the key features of the fluid mosaic model of the plasma membrane?

  • Phospholipid bilayer with hydrophilic heads and hydrophobic tails
  • Embedded proteins (integral and peripheral)
  • Cholesterol molecules that regulate fluidity
  • Glycoproteins and glycolipids for cell recognition
• What are the functions of the different types of proteins in the plasma membrane?

  • Peripheral proteins: mechanical support, connect to lipids/carbohydrates
  • Integral proteins: transport molecules across the membrane
  • Glycoproteins: act as receptors for recognition
  • Channel proteins: allow water-soluble ions to pass
  • Carrier proteins: transport larger molecules by changing shape