How are cis and trans isomers used for night vision?

Question

Lucy Alessi · Accepted Answer

Vision involves the isomerization of 11-cis-retinal to all-trans-retinal.

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 #"C=C"# double bond between #"C11"# and #"C12"# and allows rotation to form the all-trans isomer.

(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.

Addison Armstrong · Answer

undefined Cis and trans isomers of certain organic compounds, such as retinal, are used in night vision technology. In the human eye, the retinal molecule is part of the rhodopsin pigment found in rod cells. When light enters the eye, it triggers a series of chemical reactions in rhodopsin, ultimately leading to the transmission of nerve signals to the brain, allowing us to perceive light. Cis and trans isomers of retinal have different configurations, with cis-retinal being the inactive form and trans-retinal being the active form. In darkness, rhodopsin contains cis-retinal, which is not responsive to light. When light strikes the retina, it causes cis-retinal to isomerize into trans-retinal, initiating the visual signal cascade. This process allows for the conversion of light energy into nerve impulses, enabling night vision.