define pH
hydrogen ion concentration
acid
substance that gives up a proton(hydrogen
base
substance that accepts a hydrogen
pH=
-log[H+]=log 1/[H+]
strong acids
completely dissociate in waterEx.sulfuric acid
weak acids
partially dissociate in waterEx. acetoacetic acid
Ka
dissociation constant of weak acids(conjugate base)(H+)/(acid)
pKa=
-logKa
pH range compatible with life
6.8-8
Acidosis
results in depression of CNS (disorientation and comas)
alkalosis
overexcitability of the peripheral and CNS (tingling sensation of nerves, twitching of muscles, spasms)
Consequences of H+ fluctuation
-Changes in excitability of nerve-influences enzyme activity-influences K+ levels-dental implication
K+ levels during acidosis and alkalosis
acidosis: less K+ is secretedalkalosis: more K+ is secreted
buffers
-mixture of undissociated acid and its conjugate base-helps resist changes in pH-works best when pH range is near is pKa
Henderson-Hasselbalch equation
pka=pH-log(A-/HA)
when [HA]=[A-]
pka=pH
ka
0
Buffer systems in human body
-bicarbonate (extracellular fluids)-hemoglobin (red blood cells)- phosphate ( buffers urine)-proteins
Salivary system employs 3 buffer system
-bicarbonate-phosphate-proteins
salvia pH
6-7.5anything below 5.5 results in harm to hard (enamel and dentin) and soft tissues