During glycolysis, which molecule is produced that stores energy to be used in later steps?

• A. ATP
• B. NADH
• C. FADH2
• D. CO2

Answer: (A)

In glycolysis the molecule that directly furnishes usable energy for subsequent steps is ATP. During the payoff phase, high-energy phosphate groups are transferred to ADP to form ATP in a process called substrate-level phosphorylation, so the cell ends up with ATP that can power the remaining reactions in glycolysis and other pathways. NADH also carries energy, as high-energy electrons that can be used later to make more ATP in the electron transport chain, but the ATP produced here is the immediate energy currency for continuing glycolysis. CO2 isn’t produced in glycolysis (it’s released later in pyruvate oxidation and the citric acid cycle), and FADH2 is produced in later stages as well.