[MIA6]

The photochemical event that triggers the sensation of vision in the brain is ____
a. A cis to trans isomerization
b. Ejection of an electron
c. A reversible bond cleavage
d. The emission of a photon
e. Both A and B

I don't know how to analyze those choices. no clue at all. Thanks.

[Grundalizer]

http://www.britannica.com/EBchecked/topic/199272/eye/64941/The-photochemical-process

scroll down to "Transduction process" and read the second paragraph. 

the socalled cis-trans isomerism. In other words, the same group of atoms constituting the retinal molecule can be twisted into a number of different shapes, although the sequence of the atoms is unaltered. While attached to the opsin molecule in the form of rhodopsin, the retinal has a shape called 11-cis, being somewhat folded, while on conversion to prelumirhodopsin the retinal has a straighter shape called all-trans; the process is called one of photoisomerization, the absorption of light energy causing the molecule to twist into a new shape.