peptides! :)

[sam0001]

A sample of leucine is added to proline and heated. A series of peptide molecules are formed from
the reaction.
The number of different dipeptide molecules possible in the mixture is:
A. 1
B. 2
C. 4
D. 6

[jasoN-]

Should be 4; L-L, P-P, L-P, P-L.
Note that peptide bonds can be formed on either side of the alpha carbon, i.e. the N-terminus and C-terminus.
L-P and P-L are different in that L-P has formed a peptide bond between the carboxyl group of leucine and the amino group of proline, whereas P-L, the opposite.