What is hemoglobin classified as?

Hemoglobin is classified as a globular protein and a metalloprotein because it contains iron, which is essential for its function in oxygen transport. It is composed of four polypeptide chains, typically two alpha and two beta chains, each containing a heme group that binds oxygen. Hemoglobin is found in red blood cells and plays a crucial role in transporting oxygen from the lungs to tissues and facilitating the return of carbon dioxide from tissues to the lungs.