What role do red blood cells play in the body?

Red blood cells (RBCs) play a crucial role in the body primarily by transporting oxygen from the lungs to the tissues and organs, and then returning carbon dioxide from the tissues back to the lungs for exhalation. The presence of hemoglobin, a protein within red blood cells, enables them to bind with oxygen molecules and carry them efficiently through the bloodstream. This function is vital for cellular metabolism, as oxygen is required for the production of energy. Additionally, the reverse process of carbon dioxide removal is equally important for maintaining the body’s acid-base balance. This role is fundamental to respiration and overall physiological function, distinguishing it clearly from the other options presented, which do not accurately describe the primary function of red blood cells.