Welding 101 Practice Test

Oxygen serves as the final electron acceptor in the mitochondrial electron transport chain, which powers oxidative phosphorylation to produce most of the ATP in aerobic cellular respiration. When oxygen is present, electrons move through the chain, driving proton pumping and allowing ATP synthase to generate large amounts of ATP. Without oxygen, the chain stalls, NADH accumulates, and ATP production drops dramatically, so cells rely on much less efficient pathways. Fermentation and glycolysis can proceed without oxygen, yielding far less ATP, while photosynthesis uses light energy to build sugars and releases oxygen as a byproduct. Therefore, the process that requires oxygen gas is aerobic cellular respiration.