Opsin

A protein that (along with the Chromophore) makes up a Photoreceptor. The proteins are encoded in the Genome of an individual. They have two functions:

• They change the Peak Sensitivity of the Chromophore. Different peaks are required for Color Vision.
• They act as the first stage of the Visual Transduction Pathway

Humans generally have 5 different Opsins:

• Photopsins (the 3 Cone Opsins)
• Rhodopsin (the Rod Opsin)
• Melanopsin (An Opsin involved with the Circadian Rhythm, but not with vision).