Major Amino Acid in Collagen

An amino acid which forms a major part of collagen is:

Correct Answer: Glycine

Glycine forms the major part of collagen. In fact, every third residue in collagen's triple-helix structure is glycine (Gly-X-Y repeating unit), making it the most abundant amino acid in collagen — approximately 33% of all residues.

Collagen Amino Acid Profile

• Rich in: Glycine (~33%), Proline, Hydroxyproline
• Deficient in: Cysteine and Tryptophan (essential amino acids — hence collagen is a nutritionally poor/incomplete protein)

Why Glycine Is Critical

Glycine's small side chain (just H) is essential — only glycine is small enough to fit inside the tight central helix of the collagen triple helix structure. Substitution of any glycine by a larger amino acid causes diseases like Osteogenesis Imperfecta (brittle bone disease).