Final answer:
The prosthetic group in each hemoglobin subunit is called heme, which includes an iron atom that binds oxygen, allowing hemoglobin to transport oxygen throughout the body.
Step-by-step explanation:
The prosthetic group in each hemoglobin subunit is called heme. Hemoglobin, a protein found in red blood cells, is crucial for transporting oxygen throughout the body and is comprised of four subunits. Each of these subunits contains a heme group that includes an iron atom at the center. This iron atom is responsible for binding to oxygen, and this interaction enables hemoglobin to carry oxygen from the lungs to other cells in the body. The presence of iron in the heme gives blood its red color, as it changes its oxidation state from +2 to +3 when oxygen is bound and back again when it is released. This reversible binding of oxygen to iron is fundamental to the function of hemoglobin, which is to deliver oxygen and remove some carbon dioxide from the body.