Final answer:
Blood acts as a buffer in the body to maintain the pH of the blood. It contains carbonic acid and bicarbonate ions that prevent significant changes in blood pH.
Step-by-step explanation:
Blood acts as a buffer in the body. It contains carbonic acid (H₂CO₃) and bicarbonate ions (HCO₃-) that help maintain the pH of the blood. When there is an excess of hydrogen ions, they react with bicarbonate ions to form carbonic acid, preventing a significant change in blood pH. This buffering system helps keep the body's internal environment stable.