Here's why:
* Glycolysis: This initial stage of respiration occurs in the cytoplasm and produces a small net gain of 2 ATP molecules.
* Krebs Cycle (Citric Acid Cycle): This cycle takes place in the mitochondrial matrix and generates a few ATP molecules directly, along with electron carriers (NADH and FADH2).
* Electron Transport Chain: This is where the majority of ATP production occurs. The electron carriers (NADH and FADH2) deliver electrons to a series of protein complexes embedded in the inner mitochondrial membrane. As electrons move through these complexes, energy is released, which is used to pump protons across the membrane, creating a proton gradient. This gradient drives ATP synthesis through a process called oxidative phosphorylation, powered by the enzyme ATP synthase.
In summary, while glycolysis and the Krebs cycle contribute a small amount of ATP, the electron transport chain is responsible for the vast majority of ATP produced during aerobic respiration.
