Question

•Describe the basic structure of collagen monomers •Explain how amino acid composition of collagen contributes to structure and Explain how collagen fibrils, fibers and sheets are formed and how that relates to their function.

Answer 1

A collagen monomer is a triple helix of three polypeptides. Two polypeptides are similar called alpha 1 and another differs slightly in aminoacid composition called alpha 2 .Each polypeptide is a left handed helix. The three left handed helices are twisted together in to a right handed triple helix (super helix). The super helix is stabilized by number of intrachain H-bonds.

Every third aminoacid in polypeptide is glycine. It also has proline and hydroxyproline contents.High glycine content will stabilize the collagen as it allows very close association of the collagen molecules with one another. Glycine is a very small aminoacid. Close association of collagen fibrils helps in H-bonding and other intermolecular association. In the triple helix, glycine is always placed in the center as it is small ans fits in the small place at the center. The H-bonds between glycine also help in keeping firm and stabilizing the triple helix .

Many collagen monomers bond to form fibrils by covalent cross linkings. Many collagen fibrils form collagen fibers. Number of collagen fibers give rise sheets. Sheets are used to cover different organs such as muscles, collagen fibers are seen in tendons, skin. Tendons are threads joining the muscle to bone which requires strength for attachment. As the collagen fibers are very rigid, they provide proper strength for attachment.