( Phospholipids ( ( are ( ( the ( main constituents ) ) ( of ( cell membranes ) ) ) ) . ) )
(ROOT (S (NP (NNS Phospholipids)) (VP (VBP are) (NP (NP (DT the) (JJ main) (NNS constituents)) (PP (IN of) (NP (NN cell) (NNS membranes))))) (. .)))
Phospholipids are the main constituents of cell membranes.
(ROOT (S (NP (NNS Phospholipids)) (VP (VBP are) (NP (NP (DT the) (JJ main) (NN component)) (PP (IN of) (NP (DT the) (NN cell) (NN membrane))))) (. .)))