Step 1: Understanding the Concept:
Analyze the structural characteristics, classification, and bonding properties (peptide bonds) of standard $\alpha$-amino acids and their polymers.
Step 2: Key Formula or Approach:
Examine the molecular structure for chirality, calculate the peptide bond count using the $(n-1)$ rule, and recall biological classifications (essential vs non-essential) and zwitterionic properties.
Step 3: Detailed Explanation:
(A) Methionine: It is one of the essential amino acids that the human body cannot synthesize and must be obtained through diet. (Correct statement)
(B) Glycine: It is the simplest amino acid. Its $\alpha$-carbon is attached to two identical hydrogen atoms ($H_{2}N-CH_{2}-COOH$). Lacking a chiral center, it is achiral and doesn't show enantiomerism. (Correct statement)
(C) Glycylalanylglutamine: The name indicates it is composed of three amino acid residues: Glycine, Alanine, and Glutamine. It is a tripeptide. A linear polymer of $n$ amino acids contains $(n - 1)$ peptide (amide) bonds. Therefore, a tripeptide contains exactly two peptide linkages, not three. (Incorrect statement)
(D) Zwitterion: In aqueous solution, $\alpha$-amino acids exist as dipolar ions called zwitterions ($H_{3}N^{+}-CHR-COO^{-}$). They can react with both acids (using the $-COO^-$ group) and bases (using the $-NH_3^+$ group), making them amphoteric. (Correct statement)
Step 4: Final Answer:
Statement (C) is the demonstrably incorrect one.