JEE Main 2026 — Jan 28, Shift 1 — Chemistry solution

JEE Main2026Jan 28, Shift 1Chemistry

In the given pentapeptide, find out an essential amino acid (Y) and the sequence present in the pentapeptide:

Choose the correct answer from the options given below:

Solution

Reading from the N-terminus (free $-$ NH $_{2}$ ) to the C-terminus (free $-$ COOH), identify the side chains:

Residue 1: -CH(OH)CH $_{3}$ $\Rightarrow$ Threonine (Thr)

Residue 2: -CH $_{2}$ OH $\Rightarrow$ Serine (Ser)

Residue 3: -CH $_{2}$ COOH $\Rightarrow$ Aspartic acid (Asp)

Residue 4: -H $\Rightarrow$ Glycine (Gly)

Residue 5: -CH $_{3}$ $\Rightarrow$ Alanine (Ala)

Sequence: Thr - Ser - Asp - Gly - Ala. Among these, the essential amino acid is Threonine (humans cannot synthesise it).

$∴$ Option (3).

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