Final answer:
The stomach has the lowest pH in the body, ranging from 1 to 2, which is vital for digestion and killing bacteria. The human body uses buffering systems, like the bicarbonate system in blood, to maintain the necessary narrow pH range for proper cellular function.
Step-by-step explanation:
The site of the lowest pH in the human body is within the stomach. The stomach has a highly acidic environment with a pH ranging from 1 to 2. This strong acidity is crucial for food digestion and also serves to kill harmful bacteria that might be present in ingested food. The body maintains overall pH balance through several mechanisms, including the use of buffers in body fluids, to ensure cells operate within a narrow pH window necessary for vital functions. The bicarbonate system acts as a buffer in blood, protecting against extreme changes in pH levels that could otherwise lead to significant health issues.