( Oxygen ( ( is ( consumed ( to ( ( ( ( ( ( provide energy ) ( to cells ) ) , ) ( ( leaving ( carbon dioxide ) ) ( as ( ( ( a ( waste product ) ) , ) ( which ( ( the ( red ( blood cells ) ) ) ( ( carry away ) ( from ( the tissues ) ) ) ) ) ) ) ) ) and ) ( back ( to ( the lungs ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Oxygen)) (VP (VBZ is) (VP (VBN consumed) (S (VP (TO to) (VP (VP (VB provide) (NP (NN energy)) (PP (TO to) (NP (NNS cells))) (, ,) (S (VP (VBG leaving) (NP (NN carbon) (NN dioxide)) (PP (IN as) (NP (NP (DT a) (NN waste) (NN product)) (, ,) (SBAR (WHNP (WDT which)) (S (NP (DT the) (JJ red) (NN blood) (NNS cells)) (VP (VBP carry) (PRT (RP away)) (PP (IN from) (NP (DT the) (NNS tissues))))))))))) (CC and) (VP (VB back) (PP (TO to) (NP (DT the) (NNS lungs))))))))) (. .)))
Oxygen is consumed to provide energy to cells, leaving carbon dioxide as a waste product, which the red blood cells carry away from the tissues and back to the lungs.
(ROOT (S (PP (IN In) (NP (DT the) (NN body))) (, ,) (S (NP (NN oxygen)) (VP (VBZ is) (VP (VBN used) (PP (IN by) (NP (NP (NNS cells)) (PP (IN of) (NP (NP (DT the) (NN body) (POS 's)) (NNS tissues)))))))) (CC and) (S (NP (NN carbon) (NN dioxide)) (VP (VBZ is) (VP (VBN produced) (PP (IN as) (NP (DT a) (NN waste) (NN product)))))) (. .)))