Question

What type of peptide is the glycylalanine?

• A. Dipeptide
• B. Tripeptide
• C. Tetrapeptide
• D. Pentapeptide

Hint:

The prefix 'di-' in dipeptide indicates two. Glycylalanine is formed from two amino acids: Glycine + Alanine. Thus, it is a dipeptide.

Answer 1

The Correct Option is D

Step 1: Definition of a peptide A peptide is a chain of amino acids linked by peptide bonds. A peptide bond is an amide linkage formed between the carboxyl group (${-}\mathrm{COOH}$) of one amino acid and the amino group (${-}\mathrm{NH_2}$) of another amino acid with the elimination of a water molecule.
Step 2: Identify the amino acids in glycylalanine Glycylalanine is formed from:

• Glycine (Gly)
• Alanine (Ala)

Step 3: Number of amino acid residues Glycylalanine contains two amino acid residues.
Step 4: Classification of peptides

• Dipeptide $\rightarrow$ 2 amino acids
• Tripeptide $\rightarrow$ 3 amino acids
• Tetrapeptide $\rightarrow$ 4 amino acids
• Pentapeptide $\rightarrow$ 5 amino acids

Step 5: Conclusion Since glycylalanine consists of two amino acids, it is classified as a dipeptide. \[ \boxed{\text{Glycylalanine is a dipeptide \]