Final answer:
The phosphorylation potential of ATP in E. coli is higher under aerobic conditions due to the efficiency of oxidative phosphorylation, which is absent in anaerobic respiration, leading to a significantly lower yield of ATP molecules.
Step-by-step explanation:
Researchers have indeed measured the phosphorylation potential of ATP during the growth of E. coli under both anaerobic and aerobic conditions. The phosphorylation potential, which relates to the energy released during the conversion of ATP to ADP, varies significantly between the two states.
Under aerobic conditions, the complete oxidation of glucose via aerobic respiration can yield approximately 30 to 38 molecules of ATP per molecule of glucose, mostly thanks to the process of oxidative phosphorylation. In contrast, under anaerobic conditions, E. coli can only rely on substrate-level phosphorylation through glycolysis for ATP production, which yields a net of two ATP molecules per glucose molecule since oxidative phosphorylation cannot occur without oxygen.
The lowered energy yield of ATP under anaerobic conditions is a consequence of the lack of a terminal electron acceptor, such as oxygen, which is essential for the electron transport chain and the generation of a proton gradient used to synthesize ATP. Therefore, the phosphorylation potential of ATP during anaerobic growth is significantly less than during aerobic growth.
The type of respiration E. coli performs depends on the availability of oxygen. Aerobic respiration is the most efficient method for ATP production and is used when oxygen is present. Under low oxygen conditions, anaerobic respiration or fermentation may occur, resulting in a lower yield of ATP.