Each rhodopsin molecule consists of an opsin protein covalently linked to a carotenoid chromophore, 11-cis-3-hydroxyretinal. For example, the 11-"cis"-retinal isomer is the chromophore of rhodopsin, the vertebrate photoreceptor molecule. Opsins are responsible for adjusting wavelength dependence of the chromophore light induced isomerization reaction. Phytochromes consist of a protein, covalently linked to a light-sensing bilin chromophore. The proteins use a flavin as a chromophore. Each pigment is constructed from a chromophore and the transmembrane protein, known as opsin. When rhodopsin (Rh) absorbs a photon of light its chromophore, 11-cis-3-hydroxyretinal, is isomerized to all-trans-3-hydroxyretinal. This process occurs via G-protein coupled receptors called opsins which contain the chromophore 11-cis retinal. The chromophore absorbs the photon and undergoes photoisomerization. Phytochromes are proteins with a light absorbing pigment attached called a chromophore. Iodopsin consists of the protein component and a bound chromophore, retinal. In phototransduction, a photon interacts with a chromophore in a light receptor. These conformations both have a complex set of van der Waals interactions with the chromophore. Melanin is considered the primary chromophore for all hair removal lasers currently on the market. Retinal is the chromophore found in rhodopsins.