Final answer:
The presence of oxygen is the most critical factor affecting the amount of ATP produced during cellular respiration, as it allows mitochondria to utilize oxidative phosphorylation to generate ATP efficiently.
Step-by-step explanation:
The factor that would most affect the amount of ATP produced during cellular respiration is the amount of oxygen available. Aerobic cellular respiration requires oxygen to produce ATP, and in its presence, the mitochondria can generate large quantities of ATP through the process of oxidative phosphorylation. In contrast, an anaerobic environment, which lacks oxygen, results in the production of far less ATP per glucose molecule because the cell must rely on less efficient processes such as fermentation. Other factors such as the presence of water, the temperature of the fuel, and the pH of the mitochondria also affect the cellular respiration process, but to a lesser degree compared to the availability of oxygen.
When both glucose and oxygen are available to the cell, the mitochondria produce large quantities of ATP. The presence of oxygen allows for the continuation of the electron transport chain, which creates a proton gradient across the mitochondrial membrane. This gradient is harnessed by ATP synthase to produce ATP from ADP and inorganic phosphate.