| Date | May 2017 | Marks available | 1 | Reference code | 17M.3.hl.TZ2.12 |
| Level | HL | Paper | 3 | Time zone | TZ2 |
| Command term | Identify | Question number | 12 | Adapted from | N/A |
Question
Retinal, one of the many forms of vitamin A, reacts with opsin to produce rhodopsin. Refer to section 35 of the data booklet for one structure of vitamin A.
Identify the structural feature which enables rhodopsin to absorb visible light.
[1]
a.
Outline the change that occurs in the retinal residue during the absorption of visible light.
[1]
b.
Markscheme
«extensive system of» conjugation/alternating single and double «carbon to carbon» bonds
OR
delocalized electrons «over much of the molecule»
Accept “delocalization”.
[1 mark]
a.
cis«-retinal» converts to trans«-retinal»
OR
one of the C=C «fragments in retinal» changes «its configuration» from cis to trans
[1 mark]
b.
Examiners report
[N/A]
a.
[N/A]
b.
