Gluconeogenesis shares some, but not all, enzymes with the glycolytic pathway. It would appear to be more efficient if both pathways used all of the same enzymes since the pathways are essentially the reverses of each other. Why don't both pathways use all of the same enzymes?
A) The reactions where enzymes differ occur in different parts of the cell for glycolysis versus gluconeogenesis.
B) Enzymes can catalyze a reaction only in one direction, so naturally the two pathways have some enzymes that differ.
C) In tissues where gluconeogenesis occurs, the glycolytic enzymes are present at extremely low concentrations.
D) Three of the reaction steps in gluconeogenesis would have prohibitively large, positive free energies if they used glycolytic enzymes for their catalysis.