| Date | May 2016 | Marks available | 3 | Reference code | 16M.3.sl.TZ0.9 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Deduce and Predict | Question number | 9 | Adapted from | N/A |
Question
Amino acids, shown in section 33 of the data booklet, can be combined to form polypeptides and proteins.
Deduce the structures of the most abundant form of glycine in three buffer solutions at pH 1.0, 6.0 and 11.0.
A tripeptide, X, containing leucine (Leu), lysine (Lys) and glutamic acid (Glu) is hydrolysed and separated by gel electrophoresis in a buffer solution with a pH of 6.0.
(i) Predict the result of the electrophoresis by labeling the three spots below with the names of the amino acids.
(ii) Deduce the number of tripeptides that could be formed by using the three amino acids of tripeptide X.
Markscheme
Charges must be shown on the correct atoms in each structure for mark. Penalize repeated mistakes once.
Although question asks specifically for structures, accept condensed structural formulas, but charges must be given.
(i)
Award [2] for correct order.
Award [1 max] for Leu in centre if order is incorrect.
(ii)
6
Accept 27.
