Cells called fibroblasts form the various fibers in connective tissue in the body.
Collagen consists of groups of white inelastic fibers with great tensile strength.
These fibers include fine fibrils, which are composed of even finer filaments, visible only through the electron microscope. Collagen protein contains an unusually high percentage of the amino acids proline and hydroxyproline. X-ray diffraction studies provide evidence that the protein forms a wavy band, a coiled chain with periodic, i.e., repeating, arrangement of its amino acids. Cartilage is composed of fibrous collagen in an amorphous gel. Collagen dissolved in boiling water becomes denatured to form gelatin .