This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
The daily production of hydrogen ion from CO2 primarily buffered by which of the following? 
Select and explain. 
A. Extracellular bicarbonate, B. Red bloed cell bicarbonate, C. Red blood cell hemoglobin, D. Plasma proteins
C: Red blood cell hemoglobin
Answer: C: Red blood cell hemoglobin 
Explanation: Aerobic metabolism produces 13,000 to 24,000 mmol CO2 per day.This yields close to that amount of H+ ions produced per day the reaction CO2 + H20 - 7H2C03 H+ + HCO-3.At the tissues, CO2 diffuses into the red blood cells, where the enzyme carbonic anhydrate accelerates the above reaction. The H+ produced is buffered mainly by the large amount of hemoglobin in the red blood cells. Bicarbonate is not an effective buffer of volatile acid from CO2.