The document discusses acid-base balance and buffer systems in the body. It explains that acids are hydrogen ion donors and bases are hydrogen ion acceptors. Buffers stabilize pH by donating or accepting hydrogen ions. The main buffer systems in the body are bicarbonate, proteins, and phosphates. The bicarbonate buffer system uses bicarbonate and carbonic acid to maintain pH. The Henderson-Hasselbalch equation is used to calculate pH based on bicarbonate and carbon dioxide levels. Kidneys help regulate pH by excreting hydrogen ions and reabsorbing bicarbonate. Metabolic acidosis occurs when bicarbonate levels drop, while metabolic alkalosis occurs when b