( ( The reader ) ( ( ( must first ) ( know ( that ( enzymes ( are ( proteins ( that ( serve ( as ( ( biological catalyst ) ( in ( chemical reactions ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN reader)) (VP (MD must) (ADVP (RB first)) (VP (VB know) (SBAR (IN that) (S (NP (NNS enzymes)) (VP (VBP are) (NP (NP (NNS proteins)) (SBAR (WHNP (WDT that)) (S (VP (VBP serve) (PP (IN as) (NP (NP (JJ biological) (NN catalyst)) (PP (IN in) (NP (NN chemical) (NNS reactions)))))))))))))) (. .)))
The reader must first know that enzymes are proteins that serve as biological catalyst in chemical reactions.
(ROOT (S (PP (IN In) (NP (DT a) (JJ biological) (NN reaction))) (, ,) (NP (NNS proteins)) (VP (VBP act) (PP (IN as) (NP (NNS catalysts)))) (. .)))