Final answer:
In the regulation of glycolysis and gluconeogenesis, phosphofructokinase-2 is the least important molecule among those listed, as it is not directly involved in the regulation of these pathways like the other molecules.
Step-by-step explanation:
The regulation of glycolysis and gluconeogenesis within animal cells is essential to ensure that these two opposing processes do not occur at the same time. Among the listed molecules, phosphofructokinase-2 is least important in the regulation of these pathways. The regulation of glycolysis begins with hexokinase, which phosphorylates glucose to glucose-6-phosphate and is inhibited when phosphofructokinase is inhibited. The primary regulation point of glycolysis is the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate via phosphofructokinase, an enzyme regulated by ATP levels as a negative feedback mechanism.
Fructose-2,6-bisphosphate is an important allosteric regulator for phosphofructokinase, NADH and ATP/ADP are also crucial regulatory molecules reflecting the energy state of the cell, while acetyl CoA connects to glucose catabolism and is also involved in the regulation of pyruvate kinase, the last step in glycolysis.