pigmentkorrels

Pigmentkorrels, or pigment granules, are small particles within cells that contain pigment molecules. In animals the best characterized are melanosomes, specialized organelles inside melanocytes responsible for the synthesis, storage, and transfer of melanin, the pigment that colors skin, hair, and eyes.

Melanin production occurs inside melanosomes through the enzymatic action of tyrosinase, converting tyrosine to melanin. Melanosomes pass through maturation stages and are transported along dendrites to keratinocytes, where they form a protective cap over the nucleus and help determine visible coloration and UV protection. The density and distribution of pigment granules are influenced by genetics, hormones, and exposure to sunlight.

In the eye, pigment granules are present in the retinal pigment epithelium, where melanin helps absorb stray light and reduces glare, contributing to visual acuity and protecting photoreceptors. Lipofuscin is a different aging-related pigment granule that accumulates in lysosomes and increases with age or cellular stress; it is often studied as a biomarker of cellular aging.

In plants and some algae, pigment granules occur in chromoplasts and related plastids, which accumulate carotenoids such as beta-carotene and lycopene, producing orange to red colors in fruits and flowers and aiding light harvesting in photosynthesis. Abnormal pigment granule accumulation can accompany pigmentary disorders, such as albinism, and changes in pigmentation are used in diagnostics and research.