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Vitamin A status involves eye health via two separate functions. Retinal is an essential factor in rod cells and cone cells in the retina responding to light exposure by sending nerve signals to the brain. An early sign of vitamin A deficiency is night blindness. [6]
The pigment, called rhodopsin (conopsin is found in cone cells) comprises a large protein called opsin (situated in the plasma membrane), attached to which is a covalently bound prosthetic group: an organic molecule called retinal (a derivative of vitamin A). The retinal exists in the 11-cis-retinal form when in the dark, and stimulation by ...
Retinal was originally called retinene, [3] and was renamed [4] after it was discovered to be vitamin A aldehyde. [5] [6] Vertebrate animals ingest retinal directly from meat, or they produce retinal from carotenoids – either from α-carotene or β-carotene – both of which are carotenes. They also produce it from β-cryptoxanthin, a type of ...
The retina (from Latin rete 'net'; pl. retinae or retinas) is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs.The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then processes that image within the retina and sends nerve impulses along the optic nerve to the visual cortex to create visual perception.
Retinol, also called vitamin A 1, is a fat-soluble vitamin in the vitamin A family that is found in food and used as a dietary supplement. [3] Retinol or other forms of vitamin A are needed for vision, cellular development, maintenance of skin and mucous membranes , immune function and reproductive development. [ 3 ]
Vitamin A is necessary for proper functioning of the human eye. The photopigment rhodopsin found in human rod cells is composed of retinal, a form of vitamin A, bound to an opsin protein. [35] Upon the absorption of light rhodopsin was decomposed into retinal and opsin through bleaching. [35]
Chemical structure of retinene 1 (retinal). The retinenes (retinene 1 and retinene 2) are chemical derivatives of vitamin A (see retinol) formed through oxidation reactions.. Retinene 1 is better known as retinal and is fundamental in the transduction of light into visual signals in the photoreceptor level of the retina (known as the visual cycle).
Vitamin A in food exists either as preformed retinol – an active form of vitamin A – found in animal liver, dairy and egg products, and some fortified foods, or as provitamin A carotenoids, which are plant pigments digested into vitamin A after consuming carotenoid-rich plant foods, typically in red, orange, or yellow colors. [27]