Bicarbonate moves out of RBC in peripheral tissues in exchange for
**Core Concept**
Bicarbonate transport in red blood cells (RBCs) is crucial for maintaining acid-base balance in the body. The chloride-bicarbonate exchange mechanism is a vital process that occurs in peripheral tissues to regulate the pH of the blood.
**Why the Correct Answer is Right**
In peripheral tissues, the chloride-bicarbonate exchange mechanism is facilitated by the enzyme carbonic anhydrase. This enzyme catalyzes the reversible reaction between carbon dioxide (CO2) and water (H2O) to form carbonic acid (H2CO3), which then dissociates into bicarbonate (HCO3-) and hydrogen ions (H+). To maintain acid-base balance, the bicarbonate ions that move out of RBCs in exchange for chloride ions are transported into the tissue cells, where they can be used to buffer excess hydrogen ions. This process is essential for maintaining the proper pH of the blood.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the movement of bicarbonate out of RBCs is not in exchange for potassium ions. Potassium ions are primarily involved in the sodium-potassium pump, which maintains the resting membrane potential of RBCs.
* **Option B:** This option is incorrect because the movement of bicarbonate out of RBCs is not in exchange for phosphate ions. Phosphate ions are involved in various metabolic processes, including the synthesis of ATP, but they are not directly involved in the chloride-bicarbonate exchange mechanism.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the chloride-bicarbonate exchange mechanism is a critical process for maintaining acid-base balance in the body. This mechanism is often impaired in conditions such as metabolic acidosis, where the ability of RBCs to exchange chloride and bicarbonate ions is disrupted.
**Correct Answer:** C.