( ( ( The shape ) ( of ( an ( animal cell ) ) ) ) ( ( ( is not ) ( constrained ( by ( a ( rigid ( cell wall ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN shape)) (PP (IN of) (NP (DT an) (NN animal) (NN cell)))) (VP (VBZ is) (RB not) (VP (VBN constrained) (PP (IN by) (NP (DT a) (JJ rigid) (NN cell) (NN wall))))) (. .)))
The shape of an animal cell is not constrained by a rigid cell wall.
(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))))) (. .)))