Fig. 4
From: Opening the “Black Box”: The Genetic and Biochemical Basis of Eye Evolution
Major steps of the phototransduction cascade occurring in an animal photoreceptor. Both ciliary and rhabdomeric pathways begin with light-activated opsin binding a G-protein. Following G-protein activation, phototransduction progresses through a either a PDE pathway culminating in the closure of ion channels or a PLC pathway leading to the opening of ion channels. Vertebrate rod cell reproduced from Cote (2006)