( They ( already ( ( knew ( that ( ( ( ( ( this pump ) , ) ( which ( is ( a ( single ( protein molecule ) ) ) ) ) ) , ) ( ( transports ( three ( sodium ions ) ) ) ( across ( ( the ( cell membrane ) ) ( at once ) ) ) ) ) ) ) . ) ) )
(ROOT (S (NP (PRP They)) (ADVP (RB already)) (VP (VBD knew) (SBAR (IN that) (S (NP (NP (DT this) (NN pump)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (NP (DT a) (JJ single) (NN protein) (NN molecule))))) (, ,)) (VP (VBZ transports) (NP (CD three) (NN sodium) (NNS ions)) (PP (IN across) (NP (NP (DT the) (NN cell) (NN membrane)) (PP (IN at) (NP (RB once))))))))) (. .)))
They already knew that this pump, which is a single protein molecule, transports three sodium ions across the cell membrane at once.
(ROOT (S (NP (DT The) (NN term) (JJ passive) (NN transport)) (VP (VBZ describes) (NP (DT a) (NN way)) (SBAR (IN that) (S (NP (JJ small) (NNS molecules) (CC or) (NNS ions)) (VP (VBP move) (PP (IN across) (NP (NP (DT the) (NN cell)) (VP (VBN membrane) (PP (IN without) (NP (NP (NN input)) (PP (IN of) (NP (NN energy))))) (PP (IN by) (NP (DT the) (NN cell)))))))))) (. .)))