Cell Bio

• Components of cell membrane structure

  • Membrane lipids
  • Membrane proteins
  • Glycocalyx
• Membrane lipids


  • Phosphates + Sphingosines
  • Negatively charged
  • Associated in the inner and outer membrane
  • Hydrophilic
• Fatty acid chains


  • Saturated: All single bonds
  • Unsaturated ("kink"): Contain double bonds
• Cholesterol


  Important for stability
• Integral proteins


  • Strong lipid bond (covalent bond)
  • E.g., Ion channels or carrier proteins
• Peripheral proteins


  • Weak or temporary lipid bonds (hydrogen bond)
  • This allows them to detach and reattach at specific times with specific signals
• Glycocalyx


  Glycoproteins and glycolipids
• Glycocalyx functions


  • Decrease cell dehydration
  • Antigenic function
• MHC I Complex


  A type of identifier that distinguishes between normal human cells and diseased or transplanted cells or foreign organisms
• Blood typing


  Glycocalyx on the RBC surface determines its blood type (Type A, B, or no glycocalyx (type O))
• Temperature and membrane fluidity

  • High temperatures increase fluidity
  • Low temperatures without cholesterol decrease fluidity
• Cholesterol and membrane fluidity

  Little cholesterol increase membrane fluidity, and high cholesterol concentrations decrease it
• Fatty acid types and membrane fluidity

  • Unsaturated: Because of the double bonding, it increases the space between phospholipids ("kink")
  • Saturated: No double bond
• Diffusion across the membrane

  • O2, CO2
  • Small or non-polar structures
  • Lipid soluble (Steroids, hormones)
• Lateral diffusion


  The ability of phospholipids to move side to side within the membrane
• Flippase-floppase


  The ability of phospholipids to move from the inner to the outer membrane (floppase) and vice versa (flippase)
• Membrane protein functions


  • Transport
  • Receptors
  • Cell adhesion
  • Enzymes
  • Cell communication
  • Cell attachment