Ch 11

• Dialysis 

  Occurs at the walls of most animal and plant cells 

  Membranes permit the transfer of:

  Solvent molecules 

  Small solute molecules and ions
• Isotonic solutions: Solutions with identical osmotic pressures

  - Intravenously administered fluids must be isotonic with body fluids 
• Hypertonic solutions -Have osmotic pressure higher than that of the cell fluids
• Hypotonic solutions -Have osmotic pressure lower than that of the cell fluids 
• RBCs in a hypertonic solution undergo crenation 

  - Shrivel up as water moves out of the cells 
• RBCs in a hypotonic solution undergo hemolysis

  • Swell up and rupture as excess water flows into the cells 
• Reverse Osmosis

  • Results when a solution in contact with a pure solvent across a semipermeable membrane is subjected to an external pressure larger than its osmotic pressure
  • Pressure will cause a net flow of solvent from the solution to the solvent 
  • Semipermeable membrane acts as a molecular filter 
  • Removes solute particles
• Reverse osmosis is a water purification process that uses a semi-permeable membrane (synthetic lining) to filter out unwanted molecules and large particles such as contaminants and sediments like chlorine, salt, and dirt from drinking water.
• Desalination 

  • Removal of dissolved salts from a solution 
• Ion Pairing

  • Oppositely charged ions aggregate and behave as a single particle
  • Occurs in solutions
  • Example: NaCl