Further amplify the signal. Output molecules - the end of the pathway that facilitates some change in cell behavior. Could be transcription factors, cytoskeleton, etc. Synthesized from alpha-chain genes. Secreted from cell.
Peptidase cleaves the inhibitory ends off, allowing formation of fibrils.
Fibrils assemble laterally to create collagen fibers. Composed of polymers or repeating acid and amino sugars, which attract water. Many of these polymers are attached to core proteins. These may further assemble into very large complexes by association with hyaluronate molecules. Integrins are integral membrane proteins found on the cell surface.