Final answer:
The amino acid that is a major component of collagen and small enough to fit in the interior of the triple helix structure is glycine.
Step-by-step explanation:
A major component of collagen is the amino acid glycine, which is the only one small enough to fit in the interior of the collagen triple helix structure. Collagen is composed of three polypeptide chains, and these chains are rich in glycine and proline amino acids. Glycine, being the smallest amino acid, occupies every third position in the collagen chain, which allows the formation of the tightly packed triple helix. The repeating sequence in collagen is Gly-X-Y, where 'X' is often proline, and 'Y' is often hydroxyproline or hydroxylysine, which provide strength to the structure through hydrogen bonding.