Membrane Structure

Membrane Structure

1. Phospholipid bilayers

   • form in water due to amphipathic properties of phospholipid molecules
   • hydrophilic - attracted to water
     • phosphate group
   • hydrophobic - repelled by water
     • two hydrocarbon chains
   • amphipathic - substances part philic part phobic
   • phosphate heads
   • hydrocarbon tails
   • stable structures
   • formation
     • add water
       • philics all attracted
       • phobic repelled and attracted to each other
       • forms double layers

2. Membrane proteins

   • structure
     • integral proteins
       • transmembrane
       • mostly hydrophobic
       • embedded into hydrocarbon chains
     • peripheral proteins
       • mostly hydrophilic
       • single hydrocarbon chain anchoring protein to membrane surface
       • attached to integral proteins
   • position
     • proteins oriented to carry out function correctly
     • varying protein content of the membranes
   • function
     • form barrier though which ions and hydrophilic molecules cannot pass
     • hormone binding sites
     • immobilized enzymes
     • cell to cell communication
     • channels for passive transport
     • pumps for active transport

3. Cholesterol in membranes

   • component of animal cell membranes
   • type of lipid; not fat or oil
   • belongs to group steroids
   • mostly hydrohobic
   • one end has a hydroxyl- hydrophilic
   • positioned between phospholipids
   • amount in membrane varies