Fig. 4.

Signal response histograms for the simulated futile cycle (Expressions 7 and 8)(• represents positions of the average, whereas □ represents positions of the stationary states where different). (A) Molecular count histogram of X^* vs. different values of the average enzyme input, 〈E₊(t)〉, generated by the noise driver given in Expression 8. The evolution of the probability distributions of X^* with increase in 〈E₊(t)〉 demonstrates the noise-induced bistability effect. (B) If no external driver is applied, bistable behavior is not observed (uncertainty is due purely to the internal noise).