Question

Draw the structures of the tripeptides gly-ala-ser and ser-ala-gly. How many other tripeptides are possible using these three amino acids?

Short answer

The three amino acids ala, gly, and ser can form a total of six tripeptides.

Step-by-step solution

To draw structures of the tripeptides

First, we draw the structures of the tripeptides, gly-ala-ser and ser-ala-gly. We must use the individual structures of each peptide and combine.

Hence we get the following structures:

To find the tripeptides

To be able to know how many possible tripeptides are formed using gly, ala and ser, we must combine all the peptides and see how many possible permutations of the three are possible to form without any repetitions, also take into account the order of each peptide.

Thus, aside from (1) gly-ala-ser, and (2) ser-ala-gly, there are four more peptides formed.

There are (3) gly-ser ala, (4) ser-gly-ala. (5) ala-gly, ser, and (6) ala-ser-gly.

Hence, the three amino acids ala, gly, and ser can form a total of six tripeptides.