( ( Animal cells ) ( ( lack ( cell walls ) ) . ) )
(ROOT (S (NP (NNP Animal) (NNS cells)) (VP (VBP lack) (NP (NN cell) (NNS walls))) (. .)))
Animal cells lack cell walls.
(ROOT (S (NP (DT A) (NN cell) (NN wall)) (VP (VBZ is) (RB not) (ADJP (JJ present) (PP (IN in) (NP (NN animal) (NNS cells))))) (. .)))