Hemoglobin is a vital protein found in red blood cells that is responsible for transporting oxygen from the lungs to the tissues and organs throughout the body. It also helps in carrying carbon dioxide, a waste product, from the tissues back to the lungs for exhalation. Composed of four subunits, each containing a heme group with an iron atom, hemoglobin's structure allows it to efficiently bind and release oxygen molecules. Its proper function is essential for maintaining healthy oxygen levels in the body and supporting overall metabolic processes.