Example of Animal Pigments

Animal pigments are those chemical substances present in animal organisms, and that carry a distinctive color. They are characterized by fulfilling very specific functions in certain organs or systems, such as cellular respiration. They differ from Plant Pigments in the type of organism in which they are present. Animals in this case, Vegetables in the other.

The main ones are Hemoglobin and Bilirubin, from which other pigments are derived, whose properties will be defined later.

Hemoglobin 

Hemoglobin, the red blood pigment, is a conjugated protein made up of the pigment itself, Heme, also called Hemochromogen, and Globin, a Protein.

The Heme pigment, similar to the chlorophyll of plants, it is a derivative of porphine, with an iron atom (in the Chlorophyll is Magnesium) bound by covalence to the Nitrogen atoms of the groups Pyrrolic. The Iron removal gives rise to Hematoporphyrin, which has, like Heme, two Carboxyl groups.

The Hemoglobin, purple in color, is oxidized within the body to Oxyhemoglobin, scarlet red

, an unstable compound that gives up oxygen in the tissues, passing back to Hemoglobin.

The Hemoglobin fulfills the biological function of bring to the tissues the oxygen necessary for the respiration of cells. For each Hemoglobin molecule (Iron atom) an oxygen molecule binds, but in an unstable form and without modifying the divalent condition of Iron.

Hemoglobin also binds with Carbon Monoxide gas (CO), forming Carboxyhemoglobin, more stable and not suitable for the breathing process, in which case, death ensues.

Outside the body, a more stable Hemoglobin Oxidation compound is formed: Methemoglobin, brown in color, which by hydrolysis gives, together with Globin, Hematin, which forms salts with the acids known as Hemines.

In many invertebrates (mollusks, crustaceans)Instead of Hemoglobin containing iron, there is another conjugated protein in the blood containing Copper (Cu).

The pigment is blue and is called Hemocyanin. In certain types of tropical mussels, Manganese is the metal in the respiratory pigment, which in its oxidized form is Brown.

By Degradation of Hemoglobin in the Liver, Spleen and other tissues, Bile Pigments are formed, which are Bilirubin, Biliverdin and Bilicianin, which contribute its color to the bile.

Bilirubin

The Bilirubin C₃₂H₃₆OR₆N₄ it's a reddish brown pigment abundant in carnivores that oxidizes to Biliverdin C₃₂H₃₆OR₈N₄, a green pigment, found in large numbers in herbivores. By determined reduction in the intestine by bacteria, Bilirubin is transformed into a brown pigment, Stercobilin, which gives its characteristic color to feces.

Bilirubin is also reduced to Urobilin and Urobilgen, which originate Urochrome, the urine pigment. These pigments are formed from Hematoporphyrin, by breaking a position, resulting in a chain of pyrrolic groups.

Examples of Animal Pigments

Hemoglobin

Oxyhemoglobin

Heme

Carboxyhemoglobin

Methemoglobin

Hematoporphyrin

Hemocyanin

Bilirubin

Biliverdin

Stercobilin

Urobillin

Uroblogen

Urochrome