Sensitivity, response time and imprecision.

<p>(a) Sensitivity, as defined in <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi-1003300-g001" target="_blank">Fig. 1</a>, for the one-component (light blue) and two-component (dark blue) models in response to a step increase of 50% in concentration, with prestimulus values from 0.01 to 100 mM. Bacterial chemotaxis (BC) and photo-transduction (PT) data of, respectively, receptor activity from <i>in vivo</i> FRET and transmembrane current are taken from <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi-1003300-g003" target="_blank">Fig. 3B</a> of <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi.1003300-Sourjik2" target="_blank">[49]</a> (20% step change) and <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi-1003300-g006" target="_blank">Fig. 6B</a> of <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi.1003300-Forti1" target="_blank">[48]</a>. (b) Response time, as defined in <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi-1003300-g001" target="_blank">Fig. 1</a>, and its dependence on the background stimulus. Shown are the one-component model (dashed line), two-component model (dark blue), as well as <i>Dictyostelium</i> data (DC) of ACA calculated from <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi-1003300-g004" target="_blank">Fig. 4C</a> of <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi.1003300-Brzostowski1" target="_blank">[25]</a>, olfactory-transduction transmembrane current data (OT) from <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi-1003300-g001" target="_blank">Fig. 1a</a> of <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi.1003300-Menini1" target="_blank">[27]</a>, and photo-transduction transmembrane current data (PT) from <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi-1003300-g006" target="_blank">Fig. 6B</a> of <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi.1003300-Forti1" target="_blank">[48]</a>. (c) Imprecision, as defined in <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi-1003300-g001" target="_blank">Fig. 1</a>, for the one- and two-component model, BC data in response to MeAsp from <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi-1003300-g002" target="_blank">Fig. 2c</a> of <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi.1003300-Neumann1" target="_blank">[50]</a>, <i>Dictyostelium</i> data (DC) of ACA from <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi-1003300-g004" target="_blank">Fig. 4C</a> of <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi.1003300-Brzostowski1" target="_blank">[25]</a> and transmembrane current PT data from <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi-1003300-g006" target="_blank">Fig. 6B</a> of <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003300#pcbi.1003300-Forti1" target="_blank">[48]</a>.