What ion is exchanged with bicarbonate at the red blood cell to ensure electroneutrality?

The ion that is exchanged with bicarbonate at the red blood cell to maintain electroneutrality is chloride ions. This process is known as the "chloride shift" or "Hamburger phenomenon."

In red blood cells, carbon dioxide generated from metabolism enters the cells and combines with water to form carbonic acid, which then dissociates into bicarbonate ions and hydrogen ions. To maintain the balance of charge within the cell as bicarbonate ions move out into the plasma, chloride ions move in from the plasma to counteract the positive charge and achieve electroneutrality. This exchange is crucial for proper gas exchange and the overall functionality of red blood cells in transporting carbon dioxide and oxygen throughout the body.

Sodium ions, calcium ions, and potassium ions do not play a direct role in this specific exchange process related to bicarbonate and chloride in the red blood cells.