Final answer:
In anaerobic cellular respiration, only 2 ATP molecules are produced from the glycolysis of one molecule of glucose due to the net gain after accounting for ATPs used and generated in the process.
Step-by-step explanation:
The number of ATP molecules produced during the anaerobic phase of cellular respiration is 2. During anaerobic glycolysis of glucose, ATP is generated in two steps (the 7th and 10th steps) of the glycolysis pathway, resulting in a total of 4 ATPs being produced. However, 2 ATP molecules are also used during earlier steps of glycolysis (the 1st and 3rd steps), which leads to a net gain of only 2 ATPs.
In contrast, aerobic cellular respiration, where oxygen is present, includes glycolysis, the Krebs cycle, and the electron transport chain, allowing for a much higher yield of ATP from a single molecule of glucose. Depending on the efficiency of the electron transport chain and the specific organism, about 36-38 ATP molecules can be generated under these aerobic conditions.