The detection of light is a biochemical process involving a signal transduction.
ID: 263987 • Letter: T
Question
The detection of light is a biochemical process involving a signal transduction. The process starts with rod and cone cells, which have GPCRs on their membranes. The rod cells are involved in detection of the intensity of light through their GPCRs, called opsins. There are between 90 to 120 million rod cells in the human retina, which helps handle different shades of light and dark through their GPCR, called opsins, and its ligand, 11-cis-retinal. When 11-cis-retinal binds in to the opsin, it forms a schiff base with a lysine, as shown below: 11-cis Schiff base K296 Counterion (E113) As a photon of light hits the 11-cs-retinal, it isomerizes it to all-trans-retinal. After this event, the G protein is able to bind with the activated GPCR, sending off a signal that results in the cell sending a nerve impulse to the brain. We have frequently talked about ligands binding to GPCRs through intermolecular forces, however in this case, the ligand binds with a covalent interaction. Why is this covalent interaction helpful in activating the G-protein? Why does the conversion of 11 cis-retinal to all-trans-retinal enable the G-protein to be able to bind in? a. b. After the conversion, the newly formed all-trans-retinal breaks its covalent bond and leaves the opsin. Why is this step necessary? If too much light enters the eye, a process called photobleaching occurs, and your eye cannot detect any more light. If you suddenly turn off the lights, then you can't see anything and you have to wait until your eyes adjust. Hypothesize what photobleaching means, and why you cannot detect light right away c.Explanation / Answer
The detection of light is a biochemical process involving a signal transduction.