Questions: Which buffer system accounts for 75% of all chemical buffering in the body fluids? Multiple Choice The carbonic acid system The phosphate system The bicarbonate system The protein buffer system The ammonium buffer system

The answer is the protein buffer system.

Explanation for each option:

1. The carbonic acid system: This is not the correct answer. The carbonic acid system is part of the bicarbonate buffer system, which is important for maintaining pH balance in the blood but does not account for 75% of all chemical buffering in body fluids.

2. The phosphate system: This is not the correct answer. The phosphate buffer system is more significant in the intracellular fluid and the renal tubular fluid but is not the predominant buffer system in the body.

3. The bicarbonate system: This is not the correct answer. The bicarbonate buffer system is crucial for maintaining blood pH but does not account for the majority of buffering in all body fluids.

4. The protein buffer system: This is the correct answer. Proteins, due to their abundance and the presence of amino acid side chains that can accept or donate protons, account for a significant portion of the body's buffering capacity, particularly in the intracellular fluid.

5. The ammonium buffer system: This is not the correct answer. The ammonium buffer system plays a role in renal physiology but is not the primary buffer system in the body.

In summary, the protein buffer system is the most significant buffer system in the body, accounting for approximately 75% of all chemical buffering in body fluids.