Anatomy and Physiology II Practice Test

How is the pH of blood affected when a fixed acid is buffered?

1. Increases

2. Decreases

3. Remains stable

4. Varies slightly

The correct answer is: Decreases

When a fixed acid is buffered in the blood, the pH is influenced primarily through the buffering system's action to maintain acid-base balance. Buffers work by either absorbing excess hydrogen ions (H+) or releasing them depending on the acidity of the blood. When a fixed acid is introduced into the bloodstream, it contributes additional H+ ions, which can lead to a decrease in pH, indicating increased acidity. However, the buffering agents, such as bicarbonate, proteins, and phosphates, will react with these excess H+ ions to form weaker acids or other compounds, which mitigates the drop in pH. The overall effect of buffering is protective; while there may be an initial decrease in pH when a fixed acid is introduced, the buffering mechanisms help stabilize the pH closer to its normal physiological range. Consequently, while the buffering response dampens significant fluctuations, it ultimately still results in a net decrease in pH due to the introduction of the fixed acid. This illustrates the complexity of the blood's buffering system, as it is designed to ensure that the body's pH remains within a narrow and optimal range for normal cellular function.