Dipeptide Gly-Ala Structure Explanation

A dipeptide is formed when two amino acids join via a peptide bond. The notation Gly-Ala (glycyl alanine) indicates that Glycine (Gly) is the first amino acid (N-terminus) and Alanine (Ala) is the second amino acid (C-terminus).

Amino Acid Components

• Glycine (Gly): The simplest amino acid, with the structure $H_2N-CH_2-COOH$.
• Alanine (Ala): An amino acid with a methyl side chain, structure $H_2N-CH(CH_3)-COOH$.

Peptide Bond Formation

The peptide bond forms between the carboxyl group ($-COOH$) of the first amino acid (Glycine) and the amino group ($H_2N-$) of the second amino acid (Alanine), releasing a molecule of water ($H_2O$).

The reaction is:

Structure Analysis of Gly-Ala

The resulting dipeptide, Gly-Ala, has the following structure:

• The free amino group ($H_2N-$) at the beginning belongs to Glycine (N-terminus).
• The peptide bond ($-CO-NH-$) links Glycine's carbonyl carbon to Alanine's amino nitrogen.
• The free carboxyl group ($-COOH$) at the end belongs to Alanine (C-terminus).

This structure matches Option 1.

Correct Option Identification

Comparing the derived structure with the given options:

• Option 1: $H_2N-CH_2– CO – NH – CH(CH_3) – COOH$ - Matches the structure of Gly-Ala.
• Options 2, 3, and 4 represent different arrangements or incorrect peptide bond formations (e.g., Ala-Gly or incorrect termini).

Therefore, the correct structure of Gly-Ala is provided in Option 1.