Question

Match List-I with List-II

List-I (Molecule) & List-II (Type of peptide)
(A) Aspartame & (I) Tripeptide
(B) Glutathione & (II) Tetrapeptide
(C) Oxytocin & (III) Nonapeptide
(D) Endomorphin & (IV) Dipeptide

• (A) - (I), (B) - (II), (C) - (III), (D) - (IV)
• (A) - (IV), (B) - (I), (C) - (III), (D) - (II)
• (A) - (IV), (B) - (III), (C) - (I), (D) - (II)
• (A) - (IV), (B) - (II), (C) - (I), (D) - (III)

Hint:

Glutathione contains an unusual $\gamma$-peptide linkage rather than the standard $\alpha$-peptide linkage, which protects it from degradation by intracellular aminopeptidases.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Peptides are biological polymers formed by linking amino acids through covalent peptide (amide) bonds.
They are classified as dipeptides, tripeptides, tetrapeptides, or oligopeptides based on the exact number of amino acid residues they contain.

Step 2: Detailed Explanation:
Let us analyze each molecule to determine its peptide classification:
1. Aspartame: This is a widely used artificial sweetener.
Chemically, it is the methyl ester of the dipeptide L-aspartyl-L-phenylalanine, composed of exactly two amino acid residues (aspartate and phenylalanine).
Thus, Aspartame is a dipeptide. (A) matches with (IV).
2. Glutathione: This is an important intracellular antioxidant.
It is a tripeptide with the sequence $\gamma$-glutamyl-cysteinyl-glycine, consisting of three amino acids linked by an atypical peptide bond between the side-chain carboxyl of glutamate and the amine of cysteine.
Thus, Glutathione is a tripeptide. (B) matches with (I).
3. Oxytocin: This is a mammalian hormone synthesized in the hypothalamus.
It consists of nine amino acids structured with a disulfide bridge between two cysteine residues.
Thus, Oxytocin is a nonapeptide. (C) matches with (III).
4. Endomorphin: These are endogenous opioid peptides (Endomorphin-1 and Endomorphin-2) that bind to the $\mu$-opioid receptor.
They are tetrapeptides composed of four amino acid residues (Tyr-Pro-Trp-Phe-NH${}_2$ or Tyr-Pro-Phe-Phe-NH${}_2$).
Thus, Endomorphin is a tetrapeptide. (D) matches with (II).
This gives the match combination: (A) - (IV), (B) - (I), (C) - (III), (D) - (II).

Step 3: Final Answer:
The correct matching sequence is (A) - (IV), (B) - (I), (C) - (III), (D) - (II), which corresponds to option (B).