As long as this subset of reactions dominates, the system can be described by a simpler network based on the subset. However, if the dominance changes, the network structure may shift, with other reactions becoming more prominent and some fading away. This underscores the necessity of using rate constants to identify the dominant reactions within a given environment. Determining these reactions is especially important when considering catalysis. A catalyst is a chemical species that increases the rate of a reaction without being consumed. A catalytic reaction is a reaction in which a catalyst is present at a concentration sufficient to measurably affect the rate. An autocatalytic reaction is a reaction where one of Figure : Different reactions in abstract (A,B) and a concrete example, the formose reaction (C). (A) shows a single reaction with reactants (blue), desired products (green) and undesired products (magenta) . The bottom row of panels provide a key for the font color and size. The first reaction shown in (A) is a reaction with a high yield of a desired product, the second with a high yield of an undesired product, and the third with a low yield of both, due to the low concentration of the limiting reactant. (B) shows a sequence of reactions, where the yield of the intermediate, N, is low due to its short degradation lifetime (resulting in an undesired product) when compared to the timescale for the reaction that forms the desired product. (C) shows the formose reaction, which is autocatalytic in nature, with steps from formaldehyde to both end products and side products, as well as degradation products resulting from the interfering Cannizzaro reaction. In addition we show one further reaction from the cyanosulfidic scenario, converting dihydroxyacetone to acetone and glycerin, a precursor for phospholipid synthesis. 13