Which amino acid is found in all types of collagen?

Glycine is the amino acid that is consistently found in all types of collagen. This prevalence is due to its unique structure, which is small and allows for tight packing of the collagen triple-helix structure. In collagen, the repeating amino acid sequence is typically Gly-X-Y, where "X" and "Y" can be other amino acids, commonly proline and hydroxyproline, but glycine is essential at every third position to maintain the integrity and stability of the collagen molecule. This is crucial for the proper function and structural properties of collagen in the extracellular matrix, contributing to the strength and elasticity of various connective tissues.

The other amino acids listed do not share this universal presence. While proline and symbols like serine may appear frequently in collagen types, they are not present in every collagen type. Alanine, though a common amino acid, is also not universally found in all collagen types. Therefore, glycine’s unique and crucial role in collagen formation underscores its importance in connective tissue biology.