( Active ( ( transport ( ( An ( energy-expending mechanism ) ) ( ( by which ) ( ( a cell ) ( ( moves ( a chemical ) ) ( across ( ( a cell ) ( ( ( ( membrane ( from ( ( a point ) ( of ( lower concentration ) ) ) ) ) ( to ( ( a point ) ( of ( higher concentration ) ) ) ) ) , ) ( against ( the ( diffusion gradient ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (ADVP (RB Active)) (VP (VB transport) (NP (NP (DT An) (JJ energy-expending) (NN mechanism)) (SBAR (WHPP (IN by) (WHNP (WDT which))) (S (NP (DT a) (NN cell)) (VP (VBZ moves) (NP (DT a) (NN chemical)) (PP (IN across) (NP (NP (DT a) (NN cell)) (VP (VBN membrane) (PP (IN from) (NP (NP (DT a) (NN point)) (PP (IN of) (NP (JJR lower) (NN concentration))))) (PP (TO to) (NP (NP (DT a) (NN point)) (PP (IN of) (NP (JJR higher) (NN concentration))))) (, ,) (PP (IN against) (NP (DT the) (NN diffusion) (NN gradient))))))))))) (. .)))
Active transport An energy-expending mechanism by which a cell moves a chemical across a cell membrane from a point of lower concentration to a point of higher concentration, against the diffusion gradient.
(ROOT (S (NP (JJ Primary) (JJ active) (NN transport)) (VP (VBZ involves) (NP (NP (DT the) (NN forcing)) (PP (IN of) (NP (DT a) (NN substance)))) (PP (IN into) (NP (NP (DT a) (NN cell)) (PP (IN against) (NP (PRP$ its) (NN concentration) (NN gradient)))))) (. .)))