High Quality Content by WIKIPEDIA articles! The rate-determining step (RDS) is a chemistry term for the slowest step in a chemical reaction. The rate-determining step is often compared to the neck of a funnel; the rate at which water flows through the funnel is determined by the width of the neck, not by the speed at which water is poured in. In similar manner, the rate of reaction depends on the rate of the slowest step. However it is not clear what `slowest step` means. For example does it refer to the step with the smallest rate constant; if the reaction is reversible, does it refer to the ratio of the forward and reverse rate constants or does it simply refer to the step that has the smallest flux? If the latter, then at steady state all steps carry the same flux and therefore there is no slowest step. In metabolic pathways the rate limiting step is better defined and a measure, the flux control coefficient is given to a step to signify how rate-limiting the step is. Theory and experiment also suggests that there is no single rate limiting step but a range of rate limitingness across the entire reaction network.