Final answer:
Glycolysis normally results in a net gain of two ATP molecules per glucose molecule. Without the enzyme enolase, glycolysis cannot progress to completion, leading to a net yield of zero ATP.
Step-by-step explanation:
The question asks how many net ATP would be produced by glycolysis per glucose molecule in the absence of enolase. Glycolysis is the metabolic pathway that converts glucose into pyruvate, producing a small amount of energy in the form of ATP and NADH in the process. In glycolysis, a total of four ATP molecules are produced, but two are used in earlier steps resulting in a net gain of two ATP per glucose molecule.
However, in the absence of the enzyme enolase, which catalyzes the formation of phosphoenolpyruvate (a precursor for the final steps that generate ATP), this pathway would not progress past 2-phosphoglycerate, thus no additional ATP would be generated from this point. Consequently, without enolase, the only ATP molecules counted would be the two that were already used up in the process, resulting in a net yield of zero ATP from glycolysis.