( ( ( ( ( Cytochrome c ) , ) ( ( a protein ) ( that ( plays ( ( an ( important role ) ) ( in ( aerobic respiration ) ) ) ) ) ) ) , ) ( ( is ( ( an example ) ( of ( ( a protein ) ( commonly ( used ( as ( a ( molecular clock ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (JJ Cytochrome) (NN c)) (, ,) (NP (NP (DT a) (NN protein)) (SBAR (WHNP (WDT that)) (S (VP (VBZ plays) (NP (NP (DT an) (JJ important) (NN role)) (PP (IN in) (NP (JJ aerobic) (NN respiration)))))))) (, ,)) (VP (VBZ is) (NP (NP (DT an) (NN example)) (PP (IN of) (NP (NP (DT a) (NN protein)) (VP (ADVP (RB commonly)) (VBN used) (PP (IN as) (NP (DT a) (JJ molecular) (NN clock)))))))) (. .)))
Cytochrome c, a protein that plays an important role in aerobic respiration, is an example of a protein commonly used as a molecular clock.
(ROOT (S (NP (NP (DT The) (NN structure)) (PP (IN of) (NP (NN mitochondrion)))) (VP (VBZ plays) (NP (NP (DT an) (JJ important) (NN role)) (PP (IN in) (NP (JJ aerobic) (NN respiration))))) (. .)))