( Helps ( ( ( maintain ( ( a ( constant pH ) ) ( in ( body fluids ) ) ) ) ( by ( ( the ( controlled secretion ) ) ( of ( hydrogen ions ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Helps)) (VP (VBP maintain) (NP (NP (DT a) (JJ constant) (NN pH)) (PP (IN in) (NP (NN body) (NNS fluids)))) (PP (IN by) (NP (NP (DT the) (VBN controlled) (NN secretion)) (PP (IN of) (NP (NN hydrogen) (NNS ions)))))) (. .)))
Helps maintain a constant pH in body fluids by the controlled secretion of hydrogen ions.
(ROOT (S (NP (NP (NNP Processing)) (PP (IN of) (NP (NP (NN filtrate)) (PP (IN in) (NP (DT the) (JJ proximal) (NN tubule)))))) (VP (VBZ helps) (VP (VB maintain) (NP (DT the) (NN ph) (NN level)) (PP (IN in) (NP (NN body) (NN fluid))))) (. .)))