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:
$ H_2N-CH_2-COOH \quad \text{(Glycine)} \quad + \quad H_2N-CH(CH_3)-COOH \quad \text{(Alanine)} \quad \rightarrow \quad H_2N-CH_2-CO-NH-CH(CH_3)-COOH \quad \text{(Gly-Ala)} \quad + \quad H_2O $Structure Analysis of Gly-Ala
The resulting dipeptide, Gly-Ala, has the following structure:
- The free amino group ($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.
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