( ( ( ( ( ( ( ( ( ( Intrinsic factor ) ( -LRB- ( IF -RRB- ) ) ) , ) ( ( a protein ) ( secreted ( by ( gastric ( parietal cells ) ) ) ) ) ) , ) ( ( ( binds ( to ( the ( vitamin ( B 12 ) ) ) ) ) and ) ( ( carries it ) ( to ( ( ( the ( terminal ileum ) ) , ) ( where ( there ( are ( IF receptors ) ) ) ) ) ) ) ) ) , ) and ) ( absorption occurs ) ) . )
(ROOT (S (S (NP (NP (JJ Intrinsic) (NN factor)) (PRN (-LRB- -LRB-) (NP (NNP IF)) (-RRB- -RRB-)) (, ,) (NP (NP (DT a) (NN protein)) (VP (VBN secreted) (PP (IN by) (NP (JJ gastric) (JJ parietal) (NNS cells))))) (, ,)) (VP (VP (VBZ binds) (PP (TO to) (NP (DT the) (NN vitamin) (NNP B) (CD 12)))) (CC and) (VP (VBZ carries) (NP (PRP it)) (PP (TO to) (NP (NP (DT the) (NN terminal) (NN ileum)) (, ,) (SBAR (WHADVP (WRB where)) (S (NP (EX there)) (VP (VBP are) (VP (VBG IF) (NP (NNS receptors))))))))))) (, ,) (CC and) (S (NP (NN absorption)) (VP (VBZ occurs))) (. .)))
Intrinsic factor (IF), a protein secreted by gastric parietal cells, binds to the vitamin B 12 and carries it to the terminal ileum , where there are IF receptors, and absorption occurs.
(ROOT (S (NP (NNS Cells)) (VP (VBP secrete) (VP (VB factor) (NP (DT that) (NN bind)) (PP (TO to) (NP (NNS receptors))))) (. .)))