Question

The number of possible tripeptides formed involving alanine (ala), glycine (gly) and valine (val), where no amino acid has been used more than once is

• A. 3
• B. 6
• C. 8
• D. 4

Hint:

When sequence matters and repetition is not allowed, always use permutations.

Answer 1

The Correct Option is B

To determine the number of possible tripeptides that can be formed using the amino acids alanine (Ala), glycine (Gly), and valine (Val) without repeating any amino acid, we need to calculate the permutations of these three distinct amino acids. A tripeptide is a compound made from three amino acids joined by peptide bonds. Since each amino acid must be used exactly once and placed in a unique position, we are looking for the number of permutations of the three amino acids.

The formula for permutations is given by \(n!\), where \(n\) is the number of items to arrange. Here, \(n = 3\) (alanine, glycine, valine).

Thus, the number of permutations is:

\(3! = 3 \times 2 \times 1 = 6\)

This means there are 6 ways to arrange the three different amino acids to form tripeptides. The 6 possible tripeptides are:

1. Ala-Gly-Val
2. Ala-Val-Gly
3. Gly-Ala-Val
4. Gly-Val-Ala
5. Val-Ala-Gly
6. Val-Gly-Ala

Therefore, the number of possible tripeptides is 6.

This explains why the correct answer is 6, as this is the total number of permutations of the three distinct amino acids without repetition.