Opsins

Part of speech: noun

Definitions

1. Proteins that play a key role in the detection of light, particularly in the photoreceptor cells of the eyes
2. Molecules essential for vision, responsible for initiating the phototransduction cascade upon absorbing photons
3. Types of light-sensitive proteins found in various organisms, facilitating the conversion of light signals into neural impulses

Etymology: "Opsins" is the plural of "opsin", a term for the light-sensitive proteins found in the eye. It is a plural form, so its story is that of the singular. The word "opsin" is a shortened form of "rhodopsin", the purple pigment in the rods of the retina that enables vision in dim light. The "-in" ending is the standard chemical suffix used for proteins and related compounds, and the first part derives from Ancient Greek "ópsis", meaning "sight". The name therefore combines an old word for seeing with a modern biochemical ending, a coinage that dates from the age of molecular biology rather than from antiquity.