What is the primary extracellular chemical buffer system that maintains human arterial blood pH?
Answer and explanation
Correct answer: C. Carbonic acid-bicarbonate buffer system
- Step 1: CO2 produced by cellular respiration hydrates to form weak carbonic acid (H2CO3). Step 2. The equilibrium H2CO3 <=> H+ + HCO3- couples with respiratory exhalation of CO2 and renal excretion of HCO3-, making it the primary extracellular buffer. Answer: Carbonic acid-Bicarbonate buffer system (H2CO3 / HCO3-). Why not the others: Phosphate buffer is primarily intracellular and urinary; Hemoglobin buffers intracellularly within erythrocytes; Ammonium buffer operates primarily in renal tubular lumen.
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