AEMCA Practice Exam

How does extracellular buffering occur?

1. By releasing oxygen into the blood

2. By converting carbon dioxide into carbonic acid

3. By absorbing excess nutrients in the plasma

4. By regulating hormone levels

The correct answer is: By converting carbon dioxide into carbonic acid

Extracellular buffering is a crucial physiological process that helps maintain pH levels in the blood and extracellular fluid. The correct choice involves the conversion of carbon dioxide into carbonic acid, which plays a significant role in the bicarbonate buffering system. When tissues metabolize, they produce carbon dioxide as a byproduct. This carbon dioxide diffuses into the blood, where it can react with water to form carbonic acid (H2CO3). The carbonic acid can then dissociate into bicarbonate (HCO3-) and hydrogen ions (H+). This reaction is reversible and can either contribute to buffering excess acids or manage alkalinity by balancing the pH. Through this mechanism, the buffering system can mitigate pH changes resulting from metabolic processes, providing stability to the biological environment essential for proper cellular function. The bicarbonate can then neutralize excess hydrogen ions, preventing acidosis, while hydrogen ions can help neutralize excess bicarbonate if alkalosis occurs. Other options do not directly relate to the concept of buffering. While oxygen in the blood is essential for cellular respiration, it does not play a role in extracellular pH regulation. Absorbing excess nutrients is related to nutrient management rather than pH balance, and hormone regulation pertains