What are the two main chemicals the body uses to stabilize its pH level?

• A. Sodium and Potassium
• B. Oxygen and Carbon Dioxide
• C. Chloride and Bicarb
• D. Hydrogen Ions and Bicarb

Answer: (D)

Stability of pH hinges on buffering systems that resist changes in hydrogen ion concentration. The most important extracellular buffer is the bicarbonate system, which pairs bicarbonate with carbonic acid formed from CO2 and water. The pH of blood is governed by the ratio of bicarbonate to carbonic acid (and thus CO2), so the body keeps pH steady by adjusting these two players: hydrogen ions and bicarbonate.

When extra acid enters, hydrogen ions combine with bicarbonate to form carbonic acid, which becomes CO2 and water and is expelled by the lungs. When base is added, carbonic acid donates H+ to form bicarbonate, shifting the balance toward HCO3-. The lungs regulate CO2 quickly, while the kidneys adjust bicarbonate more slowly for longer-term stability.

So, the two main chemicals involved in stabilizing pH are hydrogen ions and bicarbonate. The other options are electrolytes or gases that influence pH indirectly but aren’t the primary buffering agents.