Final answer:
A buffer is a solution that moderates pH changes in biological fluids, critical for homeostasis. It involves a balance of weak acids and bases, such as the carbonic acid-bicarbonate system in human blood, which neutralizes excess H+ and OH- ions.
Step-by-step explanation:
A buffer is a chemical system that helps to maintain a stable pH in biological fluids, which is crucial for homeostasis. The pH of blood and other bodily fluids must be kept within a narrow range, around 7.4, to ensure proper physiological functioning. Buffers work by absorbing excess hydrogen (H+) or hydroxide (OH-) ions that would otherwise cause the pH to fluctuate.
A common buffer system in the human body involves carbonic acid (H2CO3), bicarbonate ion (HCO3-), and carbon dioxide (CO2). This system can convert bicarbonate ions to carbonic acid when there are too many free hydrogen ions, thus lowering the pH, or convert carbonic acid to carbon dioxide and water when there are too many hydroxide ions, thus raising the pH.