The Chemistry of Visual Photoreception

Abstract

One of the most challenging of problems is how the photochemical events triggered when a molecule of visual pigment absorbs a photon are transduced into the electrical events which, passed from neuron to neuron along the visual pathways, result in our sensations. The point of this paper is to describe in some detail the successive stages in the bleaching of two visual pigments—rhodopsin, which is found in rods, and iodopsin, found in cones—in order to end by making some informed guesses as to the most likely phase of bleaching that upon amplification elicits the propagated response. Let us start with rhodopsin.