Which process directly produces ATP from ADP during cellular respiration?

The process that directly produces ATP from ADP during cellular respiration involves the electron transport chain. During this stage of cellular respiration, electrons are transferred through a series of protein complexes in the inner mitochondrial membrane. These electrons come from NADH and FADH2, which are generated in earlier stages like glycolysis and the Krebs cycle.

As electrons move through the chain, they release energy, which is utilized to pump protons (H+) across the mitochondrial membrane, creating a gradient. This gradient generates potential energy, which is then used by ATP synthase, an enzyme that produces ATP. When protons flow back into the mitochondrial matrix through ATP synthase, ADP is phosphorylated to become ATP, thus directly linking the electron transport processes to the synthesis of ATP.

While other processes like glycolysis and the Krebs cycle also contribute to ATP production, they do so in slightly different ways. Glycolysis produces ATP through substrate-level phosphorylation, while the Krebs cycle generates electron carriers that feed into the electron transport chain. Fermentation, on the other hand, does not produce ATP via oxidative phosphorylation but instead relies on substrate-level phosphorylation in the absence of oxygen.

Therefore, the electron transport chain is the definitive process in cellular respiration that directly synthesizes ATP through the