 Collagen is one of the long, fibrous structural proteins whose functions are quite different from those of globular proteins, such as enzymes.Tough bundles of collagen called "collagen fibers" are a major component of the extracellular matrix that supports most tissues and gives cells structure from the outside, but collagen is also found inside certain cells.Collagen has great tensile strength, and is the main component of fascia, cartilage, ligaments, tendons, bone and skin.