- uneven sharing of valence electrons

- enable H2O to interact w/ several ions or molecules

- most important property of H2O

- it keep ionic compound dissolved in H2O

- conduct electricity

- dissociate in H2O to form ions

- inorganic compounds such as acids, bases, and salts

- some proteins are also electrolytes

- contain covalent bonds where atoms share electrons

- don't dissociate in H2O to form ions

- organic compounds eg. urea & glucose

- act as a co-factors needed for optimal enzyme activity

- fluid balance by controlling osmosis of H2O bet. fluid compartments

- acid-base balance

- neuromuscular activity & synaptic transmission

- form essential minerals & nutritional components eg. Na, Ca, Mg, Cl

- fluid balance when amounts of H2O and solutes are present and correctly proportioned

1. plasma membrane - bet. ICF and interstitial fluid

2. blood vessel wall - bet. interstitial fluid and plasma

- 1/3 of body fluids

- 80% interstitial fluid: bet. tissue cells, lymph, CSF, synovial fluid, etc.

- 20% plasma: liquid portion of blood

- include Na+, Cl-, HCO3-

- 2/3 of body fluids

- include K+, Mg+, HPO4 2-

- the chief cation

- 90-95% of all solutes in the ECF

- exerts significant osmotic pressure

- affect plasma vol., blood pressure, ICF, and interstitial vol.

- controlled by Aldosterone by regulating reabsorption & secretion in the kidney

- major anion

- moves easily bet. ECF & ICF thru plasma memb. channel proteins

- absorbed across digestive tract w/ Na+

- reabsorbed w/ Na+ in the kidney

- level in blood controlled by Aldosterone

- by increase/decrease reabsorption of Cl-

- important part of ECF buffer system

- increases in blood when passing thru systemic capillaries picking up CO2

- decreases in pulmonary capillaries when CO2 exhaled

- main regulator is the kidney - form and release when low or excrete excess