How are cis and trans isomers used for night vision?
1 Answer
Vision involves the isomerization of 11-cis-retinal to all-trans-retinal.
Explanation:
There are three steps in generating a visual signal.
(a) Isomerization of retinal
When a photon hits a rod or cone cell, a π electron is excited to a higher energy level.
This breaks the
(b) Protein conformational changes
The 11-cis-retinal is bound to a protein.
When the 11-cis- retinal isomerizes to the all-trans form, its new shape no longer fits the protein.
It adopts an energetically unfavourable conformation, and this triggers a series of changes to expel it from the protein.
(c) Generation of nerve impulses
One of the intermediates formed during the expulsion of all-trans-retinal activates an enzyme that triggers a series of biochemical reaction, ultimately producing a nerve impulse to the brain.
