Osmosis

• it is a special case of diffusion where the solvent (water) passes the membrane down its own concentration gradient

• it is a passive process because water molecules move from high water concentration to low concentration

• can impact the shape and function of the cells

Tonicity

• refers to the capability of a solution to modify the volume of a cell by altering its water content

  • the concentration of solutes within the extracellular fluid can be described as hypertonic, hypotonic, and isotonic

• the movement of water molecules in and out of cells is encouraged by the movement of water across the cell membrane

  • this is why it is important that cells are surround by the extracellular fluid whose solute concentration is equal to the concentration in the intercellular fluid

• osmolarity is the measure of the solute concentration of a solution

1. hypertonic

   • solutions have high osmolarity in comparison to the intercellular fluid

   • solute want to move into the cell down the concentration gradient

2. isotonic

   • solutions have equal osmolarity

   • solutes are already in equilibrium

3. hypotonic

   • solution have a low osmolarity

   • solute wants to move out of the cell down the concentration gradient

• solute can not pass the semi-permeable even if the concentration gradient there is no ability for solute to move along it

• the solvent moves towards the area of high solute concentration

• the driving force of the solvent is the concentration difference of solute between the solution

• the distribution of water to reach equilibrium is a matter of osmosis and not diffusion of solute