Which stage of cellular respiration produces the most ATP?

The Electron Transport Chain is the stage of cellular respiration that produces the most ATP. This process occurs in the inner mitochondrial membrane in eukaryotic cells and involves a series of protein complexes that transfer electrons derived from earlier steps of cellular respiration, such as the Krebs Cycle and glycolysis.

During the Electron Transport Chain, electrons are passed along these complexes and their energy is used to pump protons (H⁺ ions) across the inner mitochondrial membrane, creating a proton gradient. This gradient generates potential energy, which is then used by ATP synthase, an enzyme that synthesizes ATP as protons flow back into the mitochondrial matrix.

Through this process, approximately 28 to 34 ATP molecules can be produced from a single molecule of glucose, making it the most efficient part of cellular respiration in terms of ATP yield. In contrast, the Krebs Cycle and glycolysis produce fewer ATP molecules directly, while fermentation does not efficiently produce ATP and is considered a less effective energy pathway. Therefore, the Electron Transport Chain is vital for maximizing energy production in aerobic conditions.