Final answer:
Lysine is the amino acid essential for the crosslinking of collagen trimers, crucial for the stability and strength of collagen fibers. The correct option is D.
Step-by-step explanation:
The amino acid critical for crosslinking of collagen trimers is lysine. During the formation and strengthening of collagen fibrils, specific amino acids play crucial roles. Hydroxylysine, derived from lysine by posttranslational modification, can undergo further enzymatic reactions to form crosslinks between collagen molecules, vital for the stability of the collagen fibrils.
While proline and hydroxyproline contribute to the rigidity and triple-helical structure of collagen, the crosslinking that adds to the tensile strength of collagen fibers is facilitated by lysine and its derivative, hydroxylysine. A deficiency in these crosslinks can lead to connective tissue disorders.