Final answer:
Phase III of the ACE IFT model involves oxidative phosphorylation, where ATP is synthesized from ADP and phosphate using energy from the electron transport stage.
Step-by-step explanation:
Phase III of the ACE IFT model is called oxidative phosphorylation, which is an important process in cellular respiration. During this phase, the energy released during the electron transport stage is used to synthesize adenosine triphosphate (ATP) from adenosine diphosphate (ADP) and phosphate (Pi). ATP is a high-energy molecule that serves as the main source of energy for cellular activities.