( proteins ( ( are ( ( long chains ) ( of ( amino acids ) ) ) ) . ) )
(ROOT (S (NP (NNS proteins)) (VP (VBP are) (NP (NP (JJ long) (NNS chains)) (PP (IN of) (NP (JJ amino) (NNS acids))))) (. .)))
proteins are long chains of amino acids.
(ROOT (S (NP (DT A) (PRN (-LRB- -LRB-) (NP (NN n)) (-RRB- -RRB-)) (NN protein)) (VP (VBZ is) (VP (VBN formed) (SBAR (WHADVP (WRB when)) (S (NP (JJ amino) (NNS acids)) (VP (VBP are) (VP (VBN linked) (ADVP (RB together)) (PP (IN in) (NP (DT a) (JJ long) (NN chain))))))))) (. .)))