Rhodopsin is a protein found in the retina responsible for sensing light. The spelling of this word can be a bit tricky. The initial "r" is pronounced, followed by "h" as in "hot." Then, we have "o" as in "pole," "d" as in "dog," "op" as in "hop," and "sin" as in "thin." When pronounced correctly, it should sound something like "roh-dop-sin." Despite its somewhat challenging spelling, rhodopsin is an essential component of our vision.
Rhodopsin is a light-sensitive pigment found in the rod cells of the retina, which is responsible for enabling vision in low-light conditions. It is composed of a protein called opsin and a derivative of vitamin A called retinal. This pigmented protein plays a vital role in the initial steps of the visual transduction process.
When light enters the eye and reaches the retina, it stimulates the rhodopsin molecules within the rod cells. This absorption of photons causes the retinal component of rhodopsin to undergo a chemical change, resulting in an isomerization of the retinal from a cis to a trans configuration. This process triggers a series of molecular events that ultimately leads to the generation of electrical signals, which are then transmitted to the brain via the optic nerve for visual perception.
Rhodopsin is especially adept at detecting dim light due to its extreme sensitivity to photons. It allows for vision in dark conditions, referred to as scotopic vision. However, rhodopsin is less effective at discriminating colors compared to other types of photoreceptor cells called cone cells, which are responsible for color vision in brightly lit environments. Rhodopsin has a characteristic absorption peak around 498 nm, making it most responsive to blue-green light.
Overall, rhodopsin is a crucial molecule that forms the basis of the initial step in the visual pathway, initiating the process by which light information is converted into electrical signals for visual perception, particularly in low-light settings.
The visual purple, a red pigment found in the external segments of the rods of the retina; it is bleached by the action of light and restored in the dark or by the action of the pigment of the chorioid.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.
The word "rhodopsin" is derived from the Greek words "rhodon" meaning "rose" and "opsis" meaning "sight" or "seeing". Therefore, the term "rhodopsin" can be translated to "rose-colored vision" or "vision related to the rose". This name was given to the visual pigment found in the rod cells of the retina, which is responsible for the initial stages of vision in dim light. The pigment was named so due to its reddish-purple color when exposed to light.