( ( ( Facilitated diffusion ) ( across ( a ( biological membrane ) ) ) ) ( ( requires ( -LRB- ( ( energy ( , ( or ( transport proteins ) ) ) ) ( -RRB- ( ( ( Facilitated ( ( diffusion moves ) ( ( ( ( a substance ) ( -LRB- ( up ( , ( down -RRB- ) ) ) ) ) ( its ( concentration gradient ) ) ) , ) ) ) and ) ( is ( ( a form ) ( of ( ( -LRB- ( ( active ( , passive ) ) -RRB- ) ) transport ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (JJ Facilitated) (NN diffusion)) (PP (IN across) (NP (DT a) (JJ biological) (NN membrane)))) (VP (VBZ requires) (SBAR (S (-LRB- -LRB-) (NP (NN energy) (, ,) (CC or) (NN transport) (NNS proteins)) (-RRB- -RRB-) (VP (VP (VBD Facilitated) (S (NP (NN diffusion) (NNS moves)) (NP (NP (DT a) (NN substance)) (PRN (-LRB- -LRB-) (ADVP (RB up)) (, ,) (NP (NN down)) (-RRB- -RRB-)) (NP (PRP$ its) (NN concentration) (NN gradient)) (, ,)))) (CC and) (VP (VBZ is) (NP (NP (DT a) (NN form)) (PP (IN of) (NP (PRN (-LRB- -LRB-) (ADJP (JJ active) (, ,) (JJ passive)) (-RRB- -RRB-)) (NN transport))))))))) (. .)))
Facilitated diffusion across a biological membrane requires (energy, or transport proteins) Facilitated diffusion moves a substance (up, down) its concentration gradient, and is a form of (active, passive) transport.
(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)))) (. .)))