Plasma membrane

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

  It includes 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 orientation do phospholipid heads and tails have in the bilayer?

  Heads face outside, tails face inside
• Why are phospholipid heads hydrophilic?

  They contain a negatively charged phosphate group
• What property makes fatty acid tails hydrophobic?

  They lack any charges
• What distinguishes saturated fatty acids from unsaturated fatty acids?

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

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

  It makes the membrane less fluid
• What are the two types of membrane proteins?

  Peripheral and integral proteins
• What is the function of peripheral proteins?

  Provide mechanical support and connect molecules
• What do integral proteins do?

  Span the entire width of the membrane
• What is the function of glycoproteins and glycolipids?

  Serve as recognition sites and receptors
• How do channel proteins facilitate transport?

  They provide a pore for ions to pass through
• What is the role of carrier proteins?

  Bind larger molecules and change shape to transport
• What does "partially permeable membrane" mean?

  Only certain molecules can diffuse through
• What types of molecules can diffuse through the phospholipid bilayer?

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

  Water-soluble substances larger than water
• What are the key features of the phospholipid bilayer?

  • Composed of two layers of phospholipids
  • Hydrophilic heads face outward
  • Hydrophobic tails face inward
  • Forms a barrier to most water-soluble substances
• What are the functions of different membrane components?

  • Phospholipids: form the bilayer
  • Cholesterol: stabilize membrane fluidity
  • Proteins: transport molecules and provide support
  • Glycoproteins/Glycolipids: act as receptors and recognition sites
• What is the significance of membrane fluidity?

  • Allows movement of proteins and lipids
  • Essential for cell signaling and transport
  • Maintains membrane integrity at varying temperatures