( Cells ( ( have ( developed ( ( transport mechanisms ) ( able ( to ( ( move ( these substances ) ) ( across membranes ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Cells)) (VP (VBP have) (VP (VBN developed) (S (NP (NN transport) (NNS mechanisms)) (ADJP (JJ able) (S (VP (TO to) (VP (VB move) (NP (DT these) (NNS substances)) (PP (IN across) (NP (NNS membranes)))))))))) (. .)))
Cells have developed transport mechanisms able to move these substances across membranes.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NNS substances)) (VP (VBP pass) (PP (IN through) (NP (DT the) (NN cell) (NN membrane))) (PP (IN without) (S (VP (VBG needing) (NP (DT any) (NN energy)))))))) (, ,) (NP (PRP it)) (VP (VBZ is) (VP (VBN called) (NP (JJ passive) (NN transport)))) (. .)))