Respiratory pigment
Respiratory pigment is a substance with a molecule consisting of protein with a pigmented prosthetic group, involved in the physiological transport of oxygen or electrons. A respiratory pigment is a molecule, such as hemoglobin in humans and other vertebrates, that increases the oxygen-carrying capacity of the blood. The four most common invertebrate respiratory pigments are hemoglobin,
hemocyanin, hemerythrin and chlorocruorin. Hemoglobin is bright red when oxygenated, and dark red when deoxygenated, oxygenated hemocyanin is blue in colour, deoxygenated it is almost colourless. Oxygenated chlorocruorin turns from green to red, whereas oxygenated hemerythrin is a violet to pink colour and colourless when deoxygenated.
