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SOLUTIONS/BUFFERS

  The acidity or basicity (alkalinity) of a solution is related to the relative concentrations of H₃O⁺   (Hydronium) and OH^-  (Hydroxide).   If the concentration of H₃O⁺ is more than the concentration of OH^-, the solution is acidic. If the concentration of OH^- is more than the concentration of H₃O⁺, then the solution is basic. If the concentrations of H₃O⁺ and OH^- are equal to one another, the solution is neutral.

There is also an internal relationship between the concentrations of H₃O⁺ and OH^-. They are not independent of one another. As one goes up, the other goes down. They cannot both go up because the higher concentrations of H₃O⁺ and OH^- would react with one another to make water molecules. That is a consequence of the reversibility of the self-ionization reaction of water.  (2H₂O <=> H₃O⁺ + OH^-)

The self-ionization of water is the chemical reaction in which two water molecules react to produce a hydronium (H₃O⁺) and a hydroxide ion (OH^-):

hydronium ion: a water molecule with an added hydrogen ion.

Ex:  H₂O_(l)   +   H₂O_(l)  <==>  H₃O⁺ _(aq)   +  OH^-_(aq)

BUFFERS

Questions: 

Why are buffers so important to living systems?

What are some examples of buffer systems that occur in the human body?

Different pH's will cause molecules to gain and loose electrons (-) and protons (+) (ionize).  If proteins are not kept at the proper pH they will not function properly by assuming nonfunctional shapes because of changing ionic states.  pH is probably the most important single thing the body regulates since it

will affect so many others.  Proteins are a major buffer; sodium bicarbonate and phosphate are others.

BIOLOGICAL BUFFERS

     Many chemical reactions are affected by the acidity of the solution in which they occur. In order for a particular reaction to occur or to occur at an appropriate rate, the pH of the reaction medium must be controlled. Such control is provided by buffer solutions, which are solutions that maintain a particular pH. Biochemical reactions are especially sensitive to pH. Most biological molecules contain groups of atoms that may be charged or neutral depending on pH, and whether these groups are charged or neutral has a significant effect on the biological activity of the molecule. 

     In all multicellular organisms, the fluid within the cell and the fluids surrounding the cells have a characteristic and nearly constant pH. This pH is maintained in a number of ways, and one of the most important is through buffer systems. Two important biological buffer systems are the dihydrogen phosphate system and the carbonic acid system.