Collagen as a noun is any of more than 28 types of glycoprotein that forms elongated fibers, usually found in the extracellular matrix of connective tissue. while Keratin as a noun is a protein which hair and nails are comprised of.
Part of speech: noun
Definition: Any of more than 28 types of glycoprotein that forms elongated fibers, usually found in the extracellular matrix of connective tissue.
Part of speech: noun
Definition: A protein which hair and nails are comprised of.
We hope you now know whether to use Collagen or Keratin in your sentence.