( ( ( ( ( Some ( of ( the modifications ) ) ) ( are ( quite extensive ) ) ) -- ) ( ( ( ( ( thyroid hormone ) , ) ( for example ) ) , ) ( is ( ( a modification ) ( of ( ( the ( amino ( acid tyrosine ) ) ) ( with ( ( iodine molecules ) added ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NP (DT Some)) (PP (IN of) (NP (DT the) (NNS modifications)))) (VP (VBP are) (ADJP (RB quite) (JJ extensive)))) (: --) (S (NP (NP (NN thyroid) (NN hormone)) (, ,) (PP (IN for) (NP (NN example))) (, ,)) (VP (VBZ is) (NP (NP (DT a) (NN modification)) (PP (IN of) (NP (NP (DT the) (JJ amino) (JJ acid) (NN tyrosine)) (PP (IN with) (NP (NP (JJ iodine) (NNS molecules)) (VP (VBN added))))))))) (. .)))
Some of the modifications  are quite extensive--thyroid hormone, for example, is a modification of the amino acid tyrosine with iodine molecules added.
(ROOT (S (NP (NNS Catecholamines)) (VP (VBP are) (NP (NP (DT a) (NN class)) (PP (IN of) (NP (JJ amine) (NNS hormones))) (SBAR (WHNP (WHNP (DT that)) (NP (WRB when) (JJ synthesised))) (S (VP (VBP form) (NP (DT the) (JJ amino) (NN acid) (NN tyrosine))))))) (. .)))