Which of the following options correctly describes a structural feature of collagen that contributes to its high tensile strength?
It is composed of three polypeptide chains wound into a tight triple helix, stabilized by hydrogen bonds, with covalent cross-links connecting adjacent triple helices to form fibrils.
Every third amino acid in its primary sequence is glycine, whose bulky R-group\text{R-group}R-group projects outwards to form ionic bonds that stabilize the quaternary structure.
A high proportion of hydrophilic R-groups\text{R-groups}R-groups on its outer surface makes it highly soluble in tissue fluid, ensuring rapid transport through the circulatory system.
The parallel polypeptide chains are held together in a rigid β\betaβ-pleated sheet conformation primarily by disulfide bridges between adjacent methionine residues.
