Fig. 3
Schematic illustration showing the location of the visual pigment (opsin plus retinal) at several levels of magnification. A rod photoreceptor is shown on the left. Light enters the rod from below and strikes visual pigment molecules contained in the disc membranes as seen in the top right illustration. The lower right figure shows the opsin protein amino acid structure with the site of retinal attachment within the disc membrane on the 7th transmembrane domain.