( Metabolism ( ( is ( ( the ( sum total ) ) ( of ( ( all ( chemical reactions ) ) ( performed ( by ( an organism ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Metabolism)) (VP (VBZ is) (NP (NP (DT the) (NN sum) (NN total)) (PP (IN of) (NP (NP (DT all) (JJ chemical) (NNS reactions)) (VP (VBN performed) (PP (IN by) (NP (DT an) (NN organism)))))))) (. .)))
Metabolism is the sum total of all chemical reactions performed by an organism.
(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.