Which of the characteristics of collagen structure listed below contribute to th

Question

Which of the characteristics of collagen structure listed below contribute to the tensile strength of collagen? Collagen is made up of a triplet helix where 3 left-handed helices twist together in a right handed sense. Collagen includes a repeating sequence of amino acids with glycine every 3 amino acids in a helix with about 3 amino acids per turn. The three left-handed helices are staggered to allow close packing between glycine residues and rigidity from the bulky and inflexible proline/hydroxyproline. I I and II I, II, and III Hand III I and III

Explanation / Answer

the correct option is B) l and ll

because

Collagen has great tensile strength because under tension the 3 strands interlock rather than unwind. In real life variable amounts of cross-linking occurs, producing different arrangements for different functions in the body. Its structure of fibres, themselves composed of fibrils made of bundles of these triple helices, lends itself well to fibrous tissues such as tendons and ligaments, and also to skeletal tissues such as cartilage, bone and teeth which are further strengthened by mineral deposition. It is also partly responsible for the structure of skin and blood vessels.

The high glycine content of collagen is important with respect to stabilization of the collagen helix as this allows the very close association of the collagen fibers within the molecule, facilitating hydrogen bonding and the formation of intermolecular cross-links.[13] This kind of regular repetition and high glycine content is found in only a few other fibrous proteins, such as silk fibroin.

Because glycine is the smallest amino acid with no side chain, it plays a unique role in fibrous structural proteins. In collagen, Gly is required at every third position because the assembly of the triple helix puts this residue at the interior (axis) of the helix, where there is no space for a larger side group than glycine’s single hydrogen atom. For the same reason, the rings of the Pro and Hyp must point outward. These two amino acids help stabilize the triple helix

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