Red blood cells play a crucial role in the human body by transporting oxygen from the lungs to various tissues and carrying carbon dioxide back to the lungs for exhalation. Their structure, characterized by a biconcave shape, maximizes surface area for gas exchange and improves efficiency. Hemoglobin, a protein within the cells, binds to oxygen, allowing for effective delivery throughout the body. This intricate system is vital for maintaining cellular respiration and overall bodily functions, making red blood cells essential for sustaining life.