Rhodopsin Amplification Cascade

This simulation models the rod phototransduction cascade that lets a photoreceptor respond to a single photon of light. A photon isomerises rhodopsin into its active state R*, which catalyses activation of many transducin/PDE (phosphodiesterase) complexes; each active PDE molecule then hydrolyses cyclic GMP, and falling cGMP closes cGMP-gated channels in the plasma membrane, cutting off the cell's dark current. The 3D scene renders a rod outer segment as a stack of membrane discs: a flashed or background photon lights up a disc, activated PDE spreads across it as instanced particles driven by a real ODE cascade, and a ring of membrane channels visibly closes as cGMP falls — with live numeric readouts for active rhodopsin, active PDE, cGMP level and photocurrent tracking the same three-stage amplification (rhodopsin → PDE → current) that real electrophysiology experiments measure.