Cellular respiration consists of three main stages: glycolysis, the Krebs cycle (or citric acid cycle), and the electron transport chain. In glycolysis, glucose is broken down in the cytoplasm, producing pyruvate and a small amount of ATP. The Krebs cycle occurs in the mitochondria, where pyruvate is further broken down, releasing electrons and carbon dioxide. The final stage, the electron transport chain, uses the electrons to create a proton gradient that generates a significant amount of ATP. Collectively, these processes convert glucose into usable energy, primarily in the form of ATP, vital for cellular functions.