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JEE Main · 2026 · 28 Jan 2026 · Shift 1 · Biomolecules

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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:
  1. (A)(Y): Threonine; (Sequence): Ser - Thr - Asp - Gly - Ala
  2. (B)(Y): Serine; (Sequence): Thr - Ser - Asp - Ala - Gly
  3. (C)(Y): Threonine; (Sequence): Thr - Ser - Asp - Gly - Ala✓ Correct
  4. (D)(Y): Serine; (Sequence): Ser - Asp - Thr - Ala - Gly

Answer: (C)

Solution

Reading the pentapeptide from the free end to the free end, the side chains are (threonine), (serine), (aspartic acid), (glycine) and (alanine), so the chain is Thr\textendash Ser\textendash Asp\textendash Gly\textendash Ala. Of these only threonine cannot be made by the body and must be taken in the diet, while serine is synthesised in the body. The essential amino acid is threonine and the sequence is Thr\textendash Ser\textendash Asp\textendash Gly\textendash Ala.

JEE Main · 2026 · 28 Jan 2026 · Shift 1 · Single correct option

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