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Chemistry Question 70 – JEE-MAIN 2025

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A tetrapeptide, "x" on complete hydrolysis produced glycine (Gly), alanine (Ala), valine (Val), leucine (Leu) in equimolar proportion each. The number of tetrapeptides (sequences) possible involving each of these amino acids is :

A tetrapeptide is a chain formed by four amino acid units linked by peptide bonds.

Step 1: Identify the components and their properties✦ Active

The problem describes a tetrapeptide formed from four distinct amino acids: Glycine (Gly), Alanine (Ala), Valine (Val), and Leucine (Leu). The condition "equimolar proportion each" implies that each of these four amino acids must be used exactly once in the tetrapeptide sequence.

💡 Teacher's Secret Hint

Recognize that 'equimolar proportion each' is key to understanding that all four amino acids are distinct and used without repetition.

Step 2: Determine the mathematical approach○ Expand

Since we have 4 distinct amino acids and we are arranging all 4 of them to form a sequence (tetrapeptide), this is a problem of permutations of n distinct items taken n at a time. The number of such permutations is given by n!.

Step 3: Calculate the number of possible sequences○ Expand

Here, the number of distinct amino acids n=4. Therefore, the number of possible tetrapeptide sequences is 4!.

4!=4×3×2×1=24
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