( ( ( ( ( ( Eukaryotic cells ) , ) ( but not ) ) ( prokaryotic cells ) ) , ) ( ( have ( a ( nuclear envelope ) ) ) . ) )
(ROOT (S (NP (NP (JJ Eukaryotic) (NNS cells)) (, ,) (CONJP (CC but) (RB not)) (NP (JJ prokaryotic) (NNS cells)) (, ,)) (VP (VBP have) (NP (DT a) (JJ nuclear) (NN envelope))) (. .)))
Eukaryotic cells, but not prokaryotic cells, have a nuclear envelope.
(ROOT (S (NP (NP (DT The) (JJ main) (NN difference)) (PP (IN between) (NP (ADJP (JJ eukaryotic) (CC and) (JJ prokaryotic)) (NNS cells)))) (VP (VBZ is) (SBAR (IN that) (S (NP (JJ eukaryotic) (NNS cells)) (VP (VBP have) (NP (DT a) (NN nucleus)))))) (. .)))