Which statement correctly describes collagen?
- AA collagen molecule consists of three polypeptide chains, each in the shape of a helix. The three chains are wound together into a triple helix called a fibre.
- BA collagen molecule consists of three polypeptide chains, each of which is an $\alpha$-helix. The three chains are wound tightly together into a triple helix. Many of these triple helices bind together as a fibre.
- CA collagen molecule consists of three polypeptide chains wound tightly into a triple helix called a fibre.
- DA collagen molecule consists of three polypeptide chains in which every third amino acid is glycine. The three polypeptides are wound tightly together into a triple helix. Many of these helices form a fibre.