VPY-0048
QUESTION
The plasma pH is best correlated with which of the ratio?
OPTIONS
(A) H2PO4 – : HPO4 –
(B) NH4 + : NH3
(C) HHb : Mb-
(D) H2CO3 : HCO3
ANSWER
(D) H2CO3 : HCO3
EXPLANATION
H2CO3 : HCO3− is the correct option because plasma pH is governed predominantly by the Henderson-Hasselbalch relationship for the bicarbonate buffer system, which relates pH to the ratio of bicarbonate to dissolved carbon dioxide/carbonic acid. The phosphate and hemoglobin systems are important buffers, but their ratios are not the principal determinant of extracellular plasma pH in the question.