Retinal

Retinal is a vitamin A-derived aldehyde that binds opsin proteins. Light-driven changes in its shape initiate visual signaling in vertebrates.

11-cis-retinal: A bent geometric isomer of retinal that binds opsins in vertebrate photoreceptors before light absorption. This is the light-sensitive form held in visual pigments before a photon arrives.
Vitamin A: A group of fat-soluble compounds needed for vision, development, and epithelial health. Retinal is produced from vitamin A forms obtained from food or recycled in tissues.
Visual cycle: The series of reactions that regenerates 11-cis-retinal for reuse in photoreceptor visual pigments. This cycle restores retinal after light has converted it into the all-trans form.
Retinol: The alcohol form of vitamin A, used in transport and as a precursor to retinal. Retinol is a reducible precursor, whereas retinal is the aldehyde that binds visual opsins.
All-trans-retinal: A straighter geometric isomer of retinal formed when 11-cis-retinal absorbs a photon. Light converts retinal into this shape, changing the attached opsin’s activity.
Retinoid: A class of molecules related structurally or functionally to vitamin A. Retinal belongs to this broader family of vitamin A-related compounds.
Retinitis pigmentosa: A group of inherited retinal disorders that progressively damage photoreceptors and impair vision. Defects in visual-pigment handling or retinoid recycling can contribute to related retinal degeneration.
Retinoic acid: An oxidized vitamin A derivative that regulates gene expression and does not serve as the visual chromophore. Unlike retinal, retinoic acid generally signals through nuclear receptors rather than absorbing light in opsins.
Rhodopsin: A rod-cell visual pigment composed of the protein opsin and the chromophore 11-cis-retinal. Retinal’s best-known vertebrate complex starts the rod response to dim light.
Chromophore: The light-absorbing part of a molecule that gives it the ability to respond to particular wavelengths. Retinal absorbs photons as the chromophore in vertebrate visual pigments.

Linked from 17 pages