rhodopsin

noun

rho·​dop·​sin rō-ˈdäp-sən 

: a red photosensitive pigment in the retinal rods of the eye of most vertebrates that is important in vision in dim light

called also visual purple

Examples of rhodopsin in a Sentence

Recent Examples on the Web

The 2026 Nobel Prize in Physiology or Medicine is awarded to Karl Deisseroth, Georg Nagel and Peter Hegemann for their discovery of rhodopsin and optogenetics, the ability to control cells using light and genetics. — Jackie Flynn Mogensen, Scientific American, 5 Oct. 2026

It was further determined that microbial rhodopsins could be expressed in other cell types. — Encyclopedia Britannica, 5 Oct. 2026

Even more interesting is the way their visual pigment has shifted; the team found that the shark’s rhodopsin is tuned to shorter, blue wavelengths (which dominate in deep, clear ocean water). — Melissa Cristina Márquez, Forbes.com, 3 Apr. 2026

That's because retinol is essential for producing rhodopsin, the pigment that allows your eyes to adjust to darkness and low-light conditions. — Daryl Austin, USA Today, 7 Dec. 2025

Word History

Etymology

borrowed from German Rhodopsin, from rhod- rhod- + Greek ópsis "appearance, sight, vision" + German -in -in entry 1 — more at optic entry 1

Note: Term introduced by the German physiologist Wilhelm Kühne (1837-1900) and his assistant August Ewald (1849-1924) in "Untersuchungen über den Sehpurpur," Untersuchungen aus dem Physiologischen Institute der Universität Heidelberg, 1. Band (1878), p. 181: "Was den Sehpurpur im Dunkel ändert, pflegt es z. Th. in derselben Weise zu thun, wie das Licht, d.h. erst eine gelbe Materie, dann farblose Substanz hervorzubringen. Der Kürze wegen und um dem Auslande unsere Bezeichnungen zugänglich zu machen, kann man sagen, Rhodopsin werde erst in Xanthopsin, dieses in Leukopsin zersetzt." ("Those things [i.e., reagents] that convert visual purple in darkness in part act in the same manner as light, that is, they first produce a yellow material, then a colorless substance. For the sake of brevity, and in order to make our designations more accessible to foreigners, we can say that rhodopsin is first broken down into xanthopsin ['visual yellow'], and this into leucopsin ['visual white'].") Kühne's selection of the combining element rhod-, usually meaning "red," is somewhat idiosyncratic, given that he is rendering German Sehpurpur ("visual purple") and not Sehrot ("visual red").

First Known Use

1878, in the meaning defined above

Medical Definition

rhodopsin

noun

rho·​dop·​sin rō-ˈdäp-sən 

: a red photosensitive pigment in the retinal rods of marine fishes and most higher vertebrates that is important in vision in dim light, is quickly bleached by light to a mixture of opsin and retinal, and is regenerated in the dark

called also visual purple