FIG. 10.17 Collagen. Type I collagen molecules are organized in a triple helix and grouped into bundles called fibrils, which in turn are grouped into bundles called fibers. This type of arrangement, seen in fibers and steel cables, imparts tremendous strength.
Photo sources: (top to bottom) Tom Grundy/Alamy; Egon Bömsch/imageBROKER/age fotostock; Eye of Science/Science Source.