Retinaler

Retinaler is not a standard term in English. In most scientific writing, the molecule is referred to as retinal, or as retinals when speaking of multiple retinal molecules in a chemical context. The term may appear in non-English sources or as an informal plural, but retinal and its isomers are the accepted terminology in biology and chemistry.

Retinal is the aldehyde form of vitamin A and serves as a key chromophore in vertebrate vision. It exists mainly as two biologically important isomers: 11-cis-retinal and all-trans-retinal. In rod cells, 11-cis-retinal combines with opsin to form rhodopsin; in cone cells, it combines with cone opsins to form cone pigments. When light is absorbed, 11-cis-retinal is isomerized to all-trans-retinal, triggering a conformational change in the opsin protein and initiating the visual signaling cascade. All-trans-retinal is subsequently reduced to all-trans-retinol and transported to the retinal pigment epithelium, where it is recycled back to 11-cis-retinal through the visual cycle and returned to photoreceptors to reform light-sensitive pigments.

Biological origin and nutrition: retinal is derived from dietary vitamin A, which comes as preformed retinol in animal products and as provitamin A carotenoids (such as beta-carotene) in plants. Deficiency of vitamin A can lead to night blindness and xerophthalmia, while excess retinoids can cause toxicity.

In summary, retinal (not retinaler) is central to the detection of light in the eye, functioning within a cyclical process that regenerates the visual pigments necessary for vision across varying light conditions.