How many ATP molecules are invested in the initial steps of glycolysis?

In glycolysis, the initial steps require the investment of two ATP molecules. This investment is crucial because it helps to phosphorylate glucose and its derivatives, making them more reactive and priming the pathway for the subsequent breakdown of glucose into pyruvate. Specifically, during the first phase of glycolysis, glucose is phosphorylated to glucose-6-phosphate and subsequently converted to fructose-1,6-bisphosphate, both of which require the addition of phosphate groups supplied by ATP.

The two ATP molecules used during these initial steps are not merely functions of energy expenditure; they represent a critical part of the process of breaking down glucose for energy production, which is later compensated for by the yield of ATP during the later stages of glycolysis. This is why the correct answer indicates that two ATP molecules are invested in the initial steps.