Respiration is a fundamental process of all living things, allowing them to produce energy, stay healthy, and survive. In cells, respiration involves what are known as “respiratory proteins,” e.g. hemoglobin in the blood and myoglobin in muscles.
Respiratory proteins work by binding and releasing small molecules like oxygen, carbon monoxide etc., called ligands. They do this through their “active center,” which in many respiratory proteins is a chemical structure called heme porphyrin.