Best buffer of human blood:
**Core Concept**
Human blood contains various buffer systems to maintain its pH homeostasis. The best buffer of human blood is a system that effectively resists changes in pH when acids or bases are added to the blood.
**Why the Correct Answer is Right**
The best buffer of human blood is the bicarbonate buffering system, also known as the bicarbonate buffer system. This system consists of carbonic acid (H2CO3) and bicarbonate ions (HCO3-). The reaction is catalyzed by the enzyme carbonic anhydrase, which facilitates the conversion of carbon dioxide (CO2) to carbonic acid. This system is effective in buffering pH changes because the reaction is reversible, allowing the system to quickly respond to changes in pH.
**Why Each Wrong Option is Incorrect**
**Option A:** While the phosphate buffering system is an important buffer in human blood, it is not the best buffer. The phosphate buffering system is less effective in buffering pH changes compared to the bicarbonate buffering system.
**Option B:** The protein buffering system is also an important buffer in human blood, but it is not the best buffer. The protein buffering system is primarily effective at higher pH values and is less effective in buffering acidic pH changes.
**Option C:** The hemoglobin buffering system is not a significant buffer in human blood. While hemoglobin does have buffering capacity, it is not as effective as the bicarbonate buffering system.
**Clinical Pearl / High-Yield Fact**
The bicarbonate buffering system is the primary mechanism by which the body maintains acid-base homeostasis. This system is critical in preventing severe acidosis or alkalosis.
**Correct Answer: C. The bicarbonate buffering system.**