Posted: Oct 09, 2018 7:47 pm
Wortfish wrote:
Well, let's see. What sensory information would nerve cells on the skin have been hitherto receiving?
1. Temperature.
2. Pressure.
3. Taction.
A small cluster of photosensitive cells capable of responding to a few photons would likely not have provided any additional information that wasn't already being received. The signal would not be strong enough without appropriate amplification: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4160332/.
Did you even read your own link?
An integration of biochemical experiments in vitro with electrophysiological recordings from intact rod photoreceptors indicates that the total number of G protein molecules activated in the course of a light response to a single photon is ~16 in the mouse and ~60 in the frog. This further translates into hydrolysis of ~2000 and ~72 000 molecules of cGMP downstream of G protein, respectively, which represents the total degree of biochemical amplification in the phototransduction cascade.
One photon.