osmolarity and tonicity

Concentration

Number of solutes/volume

Always write units

Penetrating solute

Moves across membrane freely

Ex. Urea

Nonpenetrating solute

Water moves for equilibrium to be met

Ex. Ions na+ k+

Osmosis

Water moves to met equilibrium

Water moves from low to high solute concentration

Diffusion

Solute moves from high to low concentration

Partially penetrating

Freely enters membrane but can not leave

Ex. Glucose enters freely but cannot leave because it gets phosphorylated

Solute number

Moles

Osmoles

Concentration

Molarity: Moles/L or molars or M

Osmolarity: osmoles/L or osmoles or OsM

Osmolarity

Compares any 2 solutions

Describes solutions concentrations compared to each other

Diffusion to reach equilibrium

Can be Pen or Nonpen

Units are OsM

Tonicity

Describe solution compared to cell

Describe how solution affects behavior of cell (shrink or swell or nothing)

Osmosis to reach equilibrium

No penetrating matters

No units

Isosmotic

Same Osmolarity

Hypoosmotic

Hyperosmotic

Hypertonic

Water moves out of cell bc more NP outside

Cell shrinks/shrivels

Isotonic

No net movement of water bc equal NP

Normal cell

Hypotonic

Water moves into cell bcless NP outside

Cell swells and eventually bursts

Solute and volume of external solution are infinite to cell

Solute that leaves ECF into cell is replaced in the ECF

TBW

60% of body weight in kg

Intracellular 2/3

Extracellular 1/3

Plasma is 8% of TBW located in ECF and 25% of ECF

Interstitial fluid is 25% of TBW located in ECF

Markers

Indicate volumes of body compartments

Deuterium Oxide D2O Measures TBW

Insulin measures ECF

Evan’s blue measures plasma