( It ( ( ( ( ( starts ( in ( the mouth ) ) ) ( where ( ( saliva ( containing ( certain enzymes ) ) ) ( begin ( to ( ( break down ) carbohydrates ) ) ) ) ) ) and ) ( ( continues ( in ( ( ( the stomach ) and ) intestines ) ) ) ( as ( ( ( ( other enzymes ) and ) acid ) ( is ( released ( as ( ( the food ) ( progresses ( through ( the ( digestive tract ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VP (VBZ starts) (PP (IN in) (NP (DT the) (NN mouth))) (SBAR (WHADVP (WRB where)) (S (NP (NP (NN saliva)) (VP (VBG containing) (NP (JJ certain) (NNS enzymes)))) (VP (VBP begin) (S (VP (TO to) (VP (VB break) (PRT (RP down)) (NP (NNS carbohydrates))))))))) (CC and) (VP (VBZ continues) (PP (IN in) (NP (NP (DT the) (NN stomach)) (CC and) (NP (NNS intestines)))) (SBAR (IN as) (S (NP (NP (JJ other) (NNS enzymes)) (CC and) (NP (NN acid))) (VP (VBZ is) (VP (VBN released) (SBAR (IN as) (S (NP (DT the) (NN food)) (VP (VBZ progresses) (PP (IN through) (NP (DT the) (JJ digestive) (NN tract)))))))))))) (. .)))
It starts in the mouth where saliva containing certain enzymes begin to break down carbohydrates and continues in the stomach and intestines as other enzymes and acid is released as the food progresses through the digestive tract.
(ROOT (S (NP (JJ Carbohydrate) (NN digestion)) (VP (VBZ begins) (PP (IN in) (NP (DT the) (NN mouth)))) (. .)))