( ( ( endergonic ( Chemical reactions ) ) that ) ( ( require ( ( energy input ) ( to begin ) ) ) . ) )
(ROOT (S (NP (NP (JJ endergonic) (NNP Chemical) (NNS reactions)) (NP (DT that))) (VP (VBP require) (S (NP (NN energy) (NN input)) (VP (TO to) (VP (VB begin))))) (. .)))
endergonic Chemical reactions that require energy input to begin.
(ROOT (S (NP (NP (DT The) (NN amount)) (PP (IN of) (NP (NP (NN energy)) (VP (VBN required) (S (VP (TO to) (VP (VB begin) (NP (DT a) (JJ chemical) (NN reaction))))))))) (VP (VBZ is) (VP (VBN known) (PP (IN as) (NP (DT the) (NN activation) (NN energy))))) (. .)))