36 ATPs are made in aerobic respiration. Aerobic respiration includes ALL THREE steps (glycolysis, the Krebs Cycle, and the electron transport system). Since the Krebs Cycle and the electron transport system cannot happen unless glycolysis first happens, aerobic respiration involves all three steps. If oxygen is not present, only step one happens, and that is anaerobic respiration. If oxygen is present, all three steps happen, and that is aerobic respiration.