Here's why:
* Glycolysis: The initial breakdown of glucose to pyruvate in glycolysis produces a net gain of 2 ATP.
* Fermentation: Fermentation regenerates NAD+ from NADH, which is essential for glycolysis to continue. However, fermentation itself doesn't directly produce ATP.
Therefore, the total net gain of ATP from the entire process is the 2 ATP generated during glycolysis.
Important Note: While fermentation is less efficient than aerobic respiration (which yields 36-38 ATP per glucose molecule), it allows the cell to continue generating energy in the absence of oxygen.
