Question

How many different pentapeptides can be formed using five different amino acids?

Short answer

There are 120 different pentapeptides are possible to form out of five different amino acids.

Step-by-step solution

Basic introduction of pentapeptides

Pentapeptides are peptides composed of five amino acids. Using the example 5′ - AUG UUC CCC AAG GGU UGA - 3′, a peptide containing five amino acids can be formed: met - phe - pro - lys - gly. Specifically, the AUG is a codon for methionine (met).

To find the different pentapeptides

It is possible to form 120different pentapeptides. There are five possibilities for the first place amino acid. The second place has four different possibilities because one amino acid will be already placed in the first place. The third and the fourth place have three or two possibilities following the same logic. The last place will be filled with the remaining amino acid. The last step is to multiply those options$(5·4·3·2·1=120)$

Hence There are 120 different pentapeptides are possible to form out of five different amino acids.