Biological pigment

In biology, a pigment is any material resulting in color of plant or animal cells, which is the result of selective color absorption. Many biological structures, such as skin, eyes, fur and hair contain pigments (such as melanin) in specialized cells called chromatophores.

Pigment color differs from structural color in that it is the same for all viewing angles, whereas structural color is the result of selective reflection or iridescence, usually because of multilayer structures. For example, butterfly wings typically contain structural color, although many butterflies have cells that contain pigment as well.

Diseases and conditions

A variety of diseases and abnormal conditions that involve pigmentation arise in humans and animals, either from absence of or loss of pigmentation or pigment cells, or from the excess production of pigment.

Albinism is an inherited disorder characterized by total or partial loss of melanin. Humans and animals that suffer from albinism and are called albinos.
Lamellar ichthyosis, also called "fish scale disease", is an inherited condition in which one symptom is excess production of melanin. The skin is darker than normal, and is characterized by darkened, scaly, dry patches.
Melasma is a condition in which dark brown patches of pigment appear on the face, influenced by hormonal changes. When it occurs during a pregnancy, this condition is called the mask of pregnancy.
Vitiligo is a condition in whch there is a loss of pigment-producing cells called melanocytes in patches of skin.

Biological pigments

Heme/porphyrin-based: chlorophyll, bilirubin, hemocyanin, hemoglobin, myoglobin
Light-emitting: luciferin
Lipochromes:
- Carotenoids: alpha and beta carotene, anthocyanin, lycopene, rhodopsin
- Xanthophylls: canthaxanthin, zeaxanthin, lutein
Photosynthetic: chlorophyll, phycobiliproteins
Polyene enolates: a class of red pigments unique to parrots
Other: hematochrome, melanin, urochrome,

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