 What does it stand for?  Percent Hydrogen ions (H+)

 Measures the amount of H+ in a solution  Goes from 0-14 When H+ (hydrogen ion) and OH- (hydroxide ion) are equal = neutral solution (pH 7) Above pH7 = Basic/Alkaline Below pH 7 = Acidic  pH scale is logarithmic pH 5 is 10 times more acidic than pH 6 pH 4 is 100 times more acidic than pH 6

 Have more H+ than OH-  ( a compound that donates a H+)  pH below 7  As acidity goes up, pH goes down  Sour to the taste  Sharp odor Fruit juice…mmmm HCl  Stomach acid…eewwwww

 Have more OH- than H+  (compound that accepts a proton)  pH above 7  Bitter to the taste  Slippery to the touch  Usually found in household cleaners— bleach, soap, Drano

 Substance that resists pH changes when an acid or base is added  Important for maintaining constant pH levels in organisms

 able to neutralize small amounts of added acid or base, to maintaining the pH of the solution relatively stable.  Buffer solutions have a working pH range/capacity which determine how much acid/base can be neutralized before pH changes, and the amount by which it will change.

 A buffer is able to resist pH change because the two components (conjugate acid and conjugate base) are both present and are able to neutralize small amounts of other acids and bases when the are added to the solution.

 We are made of 70%+ water  Water is a combination of H+ and OH-  In any water sample, some molecules are coming apart into H+ and OH-, called ionization or disassociation Mostly H-O-H Some H+ and some OH- (equal amounts)

 Living cells must maintain a stable level of H+ and OH- within narrow limits in order to survive!  pH influences important reactions in the body

 Every reaction in a living system is dependent (to some extent) on pH  Examples: Marine life cannot live in solutions with a pH less than Some fungi and bacteria only grow in acidic environment Urine has a pH of 6.0 Human blood has a pH of 7.4

 Salivary = amylase  Esophagus  Stomach = pH 1-3 ACID  Hydrochloric Acid, Pepsinogen,  mucus  Small intestine = pH 7-9 BASIC Duodenum Ileum/jejunm  Large Intestine = pH BASIC Ascending, transverse, descending colon