If a step is at equilibrium (ΔG is zero), the enzyme catalyzing the reaction will balance the products and reactants and cannot confer directionality to the pathway. These steps (and associated enzymes) are considered unregulated. If a step is not at equilibrium, but spontaneous (ΔG is negative), the enzyme catalyzing the reaction is not balancing the products and reactants and will proceed in the forward direction unless the enzyme function is altered; these steps are considered to be regulated. A common mechanism of regulating enzymes is allosteric control.
Reference 1: Concentration / mM.
Reference 2: Glucose, Glucose-6-phosphate, Fructose-6-phosphate, Fructose-1,6-bisphosphate, Dihydroxyacetone phosphate, Glyceraldehyde-3-phosphate, 1,3-Bisphosphoglycerate, 2,3-Bisphosphoglycerate, 3-Phosphoglycerate, 2-Phosphoglycerate, Phosphoenolpyruvate, Pyruvate, ATP, ADP and Pi.
Source: http://en.wikipedia.org/wiki/Glycolysis
Reference 2: Glucose, Glucose-6-phosphate, Fructose-6-phosphate, Fructose-1,6-bisphosphate, Dihydroxyacetone phosphate, Glyceraldehyde-3-phosphate, 1,3-Bisphosphoglycerate, 2,3-Bisphosphoglycerate, 3-Phosphoglycerate, 2-Phosphoglycerate, Phosphoenolpyruvate, Pyruvate, ATP, ADP and Pi.
Source: http://en.wikipedia.org/wiki/Glycolysis
