RHODOPSIN

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THE EYE

PHOTORECEPTORS

RODS

CONES

MECHANISM

VITAMIN A

DEFECTS OF THE EYE

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Rhodopsin is a light absorbing pigment, it efficiently absorbs light in the middle of the visual spectrum with a maximum at 500nm. 

Rhodopsin consists of the protein opsin linked to 11-cis retinal a prosthetic group. Retinal is the light absorbing pigment molecule and is a derivative of vitamin A.  Opsin is a member of the 7TM receptor family.

                                                         11-cis retinal

 

 

 

 

 

 

 

 

Adapted from an adaption of Hargrave 1996. Taken from http://webvision.med.utah.edu/photo1.html  (fig 8) without permission.

Rhodopsin is a protein in the membrane of the rod photoreceptor cell in the retina of the eye. It catalyses the only light sensitive step in vision. The 11-cis-retinal chromophore lies in a pocket of the protein and is isomerised to all-trans retinal when light is absorbed. The isomerisation of retinal leads to a change of the shape of rhodopsin which triggers a sequence of reactions which lead to a nerve impulse. This is transmitted to the brain via the optical nerve.

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11-cis retinal

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11-cis retinal is a powerful absorber of light because it is a polyene; its 6 alternating single and double bonds make up a long unsaturated electron network.