In addition to oxygen transport, what is another key function of red blood cells?

Red blood cells (RBCs) play a critical role in the transport of carbon dioxide in addition to their primary function of oxygen transport. When tissues produce carbon dioxide as a waste product of metabolism, red blood cells help in transporting it from these tissues back to the lungs for exhalation. This process is vital for maintaining acid-base balance in the body, as CO2 levels can affect blood pH.

Red blood cells achieve this through a combination of processes. They can carry carbon dioxide directly bound to hemoglobin, similar to how they transport oxygen. Additionally, a significant portion of carbon dioxide is converted to bicarbonate ions within red blood cells, which helps to facilitate efficient transport and maintain a stable pH level in the blood.

The other functions listed, such as carrying hormones, regulating blood pressure, and detecting pathogens, are not primary roles of red blood cells. Hormone transport is primarily the function of plasma proteins, blood pressure regulation involves various factors including blood vessel function and heart rate, while detecting pathogens is a role fulfilled by white blood cells.