( Metabolism ( ( ( is simply ) ( ( the sum ) ( of ( ( all ( the ( chemical reactions ) ) ) ( taking ( place ( in ( a ( living system ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Metabolism)) (VP (VBZ is) (ADVP (RB simply)) (NP (NP (DT the) (NN sum)) (PP (IN of) (NP (NP (PDT all) (DT the) (NN chemical) (NNS reactions)) (VP (VBG taking) (NP (NP (NN place)) (PP (IN in) (NP (DT a) (VBG living) (NN system))))))))) (. .)))
Metabolism is simply the sum of all the chemical reactions taking place in a living system.
(ROOT (S (NP (NP (DT The) (NN sum)) (PP (IN of) (NP (NP (DT all) (JJ chemical) (NNS reactions)) (SBAR (WHNP (WDT that)) (S (VP (VBP take) (NP (NN place)) (PP (IN within) (NP (DT an) (NN organism))))))))) (VP (VBZ is) (VP (VBN known) (PP (IN as) (NP (NN metabolism))))) (. .)))
The sum of all chemical reactions that take place within an organism is known as metabolism.