( ( ( The ( low concentration ) ) ( of ( calcium ( in ( the cytosol ) ) ) ) ) ( ( allows ( ( calcium ions ) ( to ( function ( as ( ( a ( second messenger ) ) ( in ( calcium signaling ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJ low) (NN concentration)) (PP (IN of) (NP (NP (NN calcium)) (PP (IN in) (NP (DT the) (NN cytosol)))))) (VP (VBZ allows) (S (NP (NN calcium) (NNS ions)) (VP (TO to) (VP (VB function) (PP (IN as) (NP (NP (DT a) (JJ second) (NN messenger)) (PP (IN in) (NP (NN calcium) (NNS signaling))))))))) (. .)))
The low concentration of calcium in the cytosol allows calcium ions to function as a second messenger in calcium signaling.
(ROOT (S (NP (NNP Calcium) (NNP ion)) (VP (VBZ is) (NP (NP (DT an) (NN example)) (PP (IN of) (NP (DT a) (JJ second) (NN messenger))))) (. .)))
Calcium ion is an example of a second messenger.