( ( When ( ions ( move ( through ( the ( cell membrane ) ) ) ) ) ) ( , ( it ( ( is ( called ( FACILITATED DIFFUSION ) ) ) . ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NNS ions)) (VP (VBP move) (PP (IN through) (NP (DT the) (NN cell) (NN membrane)))))) (, ,) (NP (PRP it)) (VP (VBZ is) (VP (VBN called) (NP (NNP FACILITATED) (NNP DIFFUSION)))) (. .)))
When ions move through the cell membrane, it is called FACILITATED DIFFUSION.
(ROOT (NP (NP (NP (NNP Ion) (NNP channels) (NNP facilitate)) (PRN (-LRB- -LRB-) (PRP s) (-RRB- -RRB-))) (NP (NP (DT the) (NN diffusion)) (PP (IN of) (NP (NP (NNS ions)) (PP (IN across) (NP (DT a) (NN membrane)))))) (. .)))