Final answer:
Multi-cellular organisms primarily obtain energy for ATP synthesis from the catabolism of nutrients through oxidative phosphorylation, a process that involves chemiosmosis within mitochondria or prokaryotic plasma membranes and relies on oxygen as the final electron acceptor.
Step-by-step explanation:
Most multi-cellular organisms obtain energy for the synthesis of ATP during oxidative phosphorylation from nutrients such as sugars, fats, and proteins. This energy is harnessed through a process called chemiosmosis, which takes place within the mitochondria of eukaryotic cells or the plasma membrane of prokaryotic cells.
During glucose catabolism, approximately 90 percent of ATP is produced through oxidative phosphorylation, which is more efficient than substrate-level phosphorylation found in processes like glycolysis or the Krebs cycle.
Oxygen plays a crucial role in oxidative phosphorylation, hence its name, as it is the final electron acceptor in the electron transport chain - a series of chemical reactions where energy from electrons transferred through a series of protein complexes is used to create an electrochemical gradient that ultimately drives the formation of ATP.