What is the main function of red blood cells?

The main function of red blood cells is to carry oxygen to body tissues. Red blood cells, or erythrocytes, contain hemoglobin, a protein that binds to oxygen in the lungs and transports it through the bloodstream to various tissues and organs. Once in the tissues, oxygen is delivered to cells where it is needed for metabolic processes, including the production of energy. This process is essential for sustaining life, as oxygen is a critical component of cellular respiration, the process by which cells generate energy.

While red blood cells also play a role in transporting carbon dioxide back to the lungs for exhalation, their primary and most crucial function centers around oxygen delivery. Other options, like fighting infection and regulating body temperature, pertain to different cells and systems in the body rather than the specific role of red blood cells. For instance, white blood cells are responsible for fighting infection, and body temperature regulation is primarily managed by the hypothalamus and various physiological mechanisms throughout the body.