( ( Active ( Transport ( Active transport ) ) ) ( ( occurs ( when ( energy ( is ( ( needed ( for ( a substance ) ) ) ( to ( move ( across ( a ( plasma membrane ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Active) (NNP Transport) (NNP Active) (NN transport)) (VP (VBZ occurs) (SBAR (WHADVP (WRB when)) (S (NP (NN energy)) (VP (VBZ is) (VP (VBN needed) (PP (IN for) (NP (DT a) (NN substance))) (S (VP (TO to) (VP (VB move) (PP (IN across) (NP (DT a) (NN plasma) (NN membrane))))))))))) (. .)))
Active Transport   Active transport occurs when energy is needed for a substance to move across a plasma membrane.
(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)))) (. .)))