( Proteins ( ( are ( composed ( of ( compounds ( called ( ( amino acids ) ( ( linked end ) ( to end ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNPS Proteins)) (VP (VBP are) (VP (VBN composed) (PP (IN of) (NP (NP (NNS compounds)) (VP (VBN called) (NP (NP (JJ amino) (NNS acids)) (VP (VBN linked) (NP (NN end)) (S (VP (TO to) (VP (VB end))))))))))) (. .)))
Proteins are composed of compounds called amino acids linked end to end.
(ROOT (S (NP (DT A) (NN protein)) (VP (VBZ is) (NP (NP (DT an) (JJ organic) (NN compound)) (VP (VBN made) (PRT (RP up)) (PP (IN of) (NP (NP (JJ small) (NNS molecules)) (VP (VBN called) (NP (JJ amino) (NNS acids)))))))) (. .)))