Tonicity and Osmolarity PDF

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Summary on tonicity and osmolarity and their differences...

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Tonicity 

Pressure caused by NONPERMEABLE solute particles, like NaCl

Isotonic= Equal number of NONPERMEABLE solute particles, therefore no net movement of water Hypotonic (comparing a cell in a cup of solution) = Solution has less solute particles, therefore net movement of water into cell from solution, causing the cell to expand and eventually lyse. Hypertonic= Solution has more solute particles, therefore net movement of water into solution from cell, causing cell to shrink.

Example: Solution A has 4g/L of protein, Solution B has 4g/L of protein. Therefore they are isotonic. (Protein is a nonpermeable particle)

Osmolarity  

Concentration of solute particles, BOTH PERMEABLE AND NONPERMEABLE Isosmotic= Equal number of particles, Hyposmotic= Solution has less particles, Hyperosmotic= Solution has more particles

Example: Solution A has 4g/L of protein, Solution B has 4g/L of protein and 4g/L of urea (Urea is PERMEABLE particle).    

The solutions are NOT ISOSMOTIC because A has more particles than B. The solutions are ISOTONIC because A has the same number of PERMEABLE particles as B (which is protein). Since Urea is permeable, it will move and eventually be equal on both sides. So Solution A will now have 4g Protein and 2g Urea, same as Solution B As a result, there will be NO NET MOVEMENT OF WATER, supporting the 2 nd statement of being isotonic.

Example: Solution A has 4g/L of protein, Solution B has 4g/L of urea    

Solutions are ISOSMOTIC because A is the same as B Solutions are NOT ISOTONIC as A has more NONPERMEABLE particles than B Urea from B will eventually move and be equal on both sides (as there are more in B than A). Therefore new solutions will be: A has 4g Protein and 2g Urea, B has 2g Urea As a result, there will be a net movement of water from B to A....