Acid - Base Balance Flashcards
Regular Body pH
7.4
Acidosis
pH < 7.4
high hydrogen ion concentration
Alkalosis
pH > 7.4
low hydrogen ion concentration
change in pH resulting in death
a change of 0.6 in either direction can result in death
Normal Concentration of Hydrogen Ions
4x10^-8 eq/L or 4x10^5 meq/L
Body Buffers
- Intracellular Fluid
- Blood
- Interstitial Fluid
Intracellular Fluid as a Buffer
- Protein (non-exchangable)
- HPO4^2-
Blood as a Buffer
- Hemoglobin
- Protein (albumin)
- HCO3^-
Interstitial Fluid as a Buffer
- HCO3-
- HPO4^2- (Kidney)
- NH3 (Kidney)
Lines of Defense in an Acid Base Crisis
- Hemoglobin and Proteins
- HCO3^- buffer system (most important)
Protein Anion Buffer System
75% of the body’s buffering power
not physiologically significant
Protein Anion Buffer System Reactions
R-COOH <-> R-COO- + H+
R-NH2 + H+ <-> R-NH3+
Major ECF Buffer Systems
- Bicarbonate
- Phosphate
CO2/HCO3- Bicarbonate Buffer System
Most important ECF buffer
regulation from Lungs, Kidneys, Blood Buffer System
Bicarbonate Buffer System Reaction
CO2 + H2O + Enzyme <-> H2CO3 <-> H+ + HCO3-
Henderson-Hasselbach Equation for Bicarbonate Buffer System
pH= pK + log([HCO3-]/[H2CO3])
or pH = pK +log([HCO3-]/0.3PCO2)
pK = 6.1
Normal Ratio of HCO3 to H2CO3
20:1
Bicarbonate Buffer System
mixture of NaHCO3 and H2CO3
NaHCO3 can react with an acid to make H2CO2, H2CO3 can react with a base to make NaHCO3
Carbonic Anhydrase
enzyme that helps convert CO2 in blood to bicarbonate(HCO3) in the bicarbonate buffer system
When do buffers work best?
When pH is close numerically to pK
Why is the Bicarbonate Buffer system the most important buffer system?
- can be regulated by lungs and kidney (CO2&HCO3-)
- Erythrocytes are capable of “Chloride shift”
- Abundant supplies of Bicarbonate anion are available for buffering (HCO3-:H2CO3, 20:1)