Collagen vs Keratin: what is the difference?

How they differ

These are the two structural proteins most people have heard of, and they build different things by different means. Collagen is a triple helix that gives skin, tendon and bone their tensile strength, and it is rich in glycine and proline. Keratin is a coiled coil packed with cysteine, and the sulfur bridges between those cysteines are what make hair, nail, horn and hoof hard and insoluble. That disulfide bonding is why hair can be permanently waved by breaking and reforming those bridges, and why burning hair smells of sulfur. Collagen dissolves into gelatin when cooked; keratin does not dissolve at all, which is why hair survives in archaeological finds.

Side by side

Common questions

What is the difference between Collagen and Keratin?

These are the two structural proteins most people have heard of, and they build different things by different means. Collagen is a triple helix that gives skin, tendon and bone their tensile strength, and it is rich in glycine and proline. Keratin is a coiled coil packed with cysteine, and the sulfur bridges between those cysteines are what make hair, nail, horn and hoof hard and insoluble.