( ( ( ( structure ( of ( G ( ( + and ) G ) ) ) ) - ) ( cell walls ) ) . )
(ROOT (NP (NP (NP (NN structure)) (PP (IN of) (NP (NNP G) (NNP +) (CC and) (NNP G)))) (: -) (NP (NN cell) (NNS walls)) (. .)))
structure of G+ and G- 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))))) (. .)))