( ( ( The ( basic function ) ) ( of ( the ( cell membrane ) ) ) ) ( ( is ( to ( serve ( as ( ( a ( selective barrier ) ) ( that ( ( regulates ( ( the passage ) ( of ( certain materials ) ) ) ) ( ( ( in and ) out ) ( of ( the cell ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJ basic) (NN function)) (PP (IN of) (NP (DT the) (NN cell) (NN membrane)))) (VP (VBZ is) (S (VP (TO to) (VP (VB serve) (PP (IN as) (NP (NP (DT a) (JJ selective) (NN barrier)) (SBAR (WHNP (WDT that)) (S (VP (VBZ regulates) (NP (NP (DT the) (NN passage)) (PP (IN of) (NP (JJ certain) (NNS materials)))) (PP (IN in) (CC and) (IN out) (PP (IN of) (NP (DT the) (NN cell))))))))))))) (. .)))
The basic function of the cell membrane is to serve as a selective barrier that regulates the passage of certain materials in and out of the cell.
(ROOT (S (NP (NP (DT A) (NN cell) (POS 's)) (NN membrane)) (VP (VBZ provides) (NP (DT a) (NN barrier) (S (VP (TO to) (VP (VB keep) (NP (NN extracellular) (NNS materials)) (PP (IN from) (S (VP (VBG mixing) (PP (IN with) (NP (PRP$ its) (JJ internal) (NNS components))))))))))) (. .)))