How much ATP is produced from one glucose molecule before oxidative phosphorylation?

The process of cellular respiration involves several stages where glucose is broken down to ultimately produce ATP, the energy currency of the cell. Before the oxidative phosphorylation stage, glucose undergoes glycolysis and the Krebs cycle (also known as the citric acid cycle).

During glycolysis, one molecule of glucose is converted into two molecules of pyruvate. This process generates a net gain of 2 ATP molecules. Additionally, through the Krebs cycle, which processes each pyruvate, the total yield contributes to the production of more ATP, but the question specifically refers to ATP production before oxidative phosphorylation, which occurs later in the mitochondria.

At this stage, the total yield directly from glycolysis is indeed 2 ATP molecules. While further ATP production occurs during oxidative phosphorylation, which would raise the total count, it is important to note that before oxidative phosphorylation and focusing solely on glycolysis, the net ATP production remains at 2.

Thus, the most accurate answer regarding ATP production from one glucose molecule prior to the oxidative phosphorylation phase is 2 ATP.