Hemoglobin, porphyrin, heme, and ferrihemoglobin are all synonyms for the word "hematin". Hematin is a type of compound found in the blood that is responsible for carrying oxygen throughout the body. This compound is made up of a molecule called heme, which is bound to a protein called globin. When oxygen binds to the heme molecule, it changes shape and allows the blood to carry the oxygen to tissues and organs that need it. The word "hematin" is often used interchangeably with other terms that describe this important compound, which is essential for maintaining the health and vitality of our bodies.