The left di-peptide is Val-Lys, and the right one Lys-Val.
These two are, of course, not identical. If a student doesn't understand that trivially that, we have a problem and the only
solution is then to get some physical models for him/her to play with.
The left di-peptide is Val-Lys, and the right one Lys-Val.
Or look at this example (in Dutch).