Respiration Lecture 11: Resp. Acid-Base Balance Flashcards
Base
ion or molecule that can accept a H+ atom. A- in HH equation
Acid
molecules containing H+ atoms that can be released into solutions. HA in HH equation.
When is buffer system most resistant to changes in H+?
When pH = pK
Normal extracellular pH range
7.35-7.45
3 main mechanisms to keep pH within normal limits
1) extracellular buffering (don’t actually remove H+ from system)
2) adjustments to blood PCO2 by altering the ventilatory capacity of the lungs (<—THE MAIN METHOD…KNOW!)
3) adjustments to renal acid excretion or base reabsorption
Acidemia
acidic blood (high H+ conc.)
Alkalemia
alkaline blood (low H+ conc.)
where is H ion state measured?
receptors in CSF
weak acid or base
acid or base that incompletely dissociates. (pK is such that it doesn’t completely dissociate)
buffer
reduces changes in pH resulting from the addition of strong acids or bases
What is greatest source of H+?
CO2 (via oxidation of glucose and fatty acids during metabolism)
CO2 is an example of what type of acid?
volatile acid
Non-volatile acids that are sources of H+ in metabolism
sulfuric, phosphoric, hydrochloric, and lactic acids
The #1 blood buffer
Bicarbonate ***** Most important because the buffered H+ ion it can carry can be removed by both the renal and respiratory systems
Other blood buffers besides bicarbonate
phosphate, proteins
Henderson-Hasselbalch Equation
HA H+ + A- and pH = pKa + log [A-]/[HA] DNK
how many pH units around pK can buffer act?
+/- 1 pH unit
Buffer strength is directly proportional to ?
concentration of paired buffer components
Non-bicarbonate buffer systems
Phosphate buffer system
Protein buffer system
Bicarbonate buffer system **
utilizes carbonic anhydrase reaction to maintain blood pH. carbon dioxide (CO2) combines with water to form carbonic acid (H2CO3), which in turn rapidly dissociates to form hydrogen ions and bicarbonate (HCO3- ) as shown in the reactions below. The carbon dioxide - carbonic acid equilibrium is catalyzed by the enzyme carbonic anhydrase; the carbonic acid - bicarbonate equilibrium is simple proton dissociation/association and needs no catalyst. An OPEN SYSTEM via elimination of CO2 and H+ to the environment
Carbonic anhydrase reaction
CO2 + H2O H2CO3 H+ + HCO3-
CO2 = acid (proton donor) HCO3 = base (proton acceptor) H+ = free proton responsible for setting pH
If alveolar pressure decreases due to hypoventilation, what happens to pH?****
increase in PCO2, so pH decreases (increase in H+)
Phosphate buffer system reaction
H2PO4 H+ + HPO4
What happens to acidity of Hb as O2 leaves?
Decreases
