Final answer:
Carbon dioxide is the primary waste product of aerobic metabolism, released during the transformation of pyruvic acid into acetyl-CoA in the Krebs cycle, whereas lactic acid is a waste product of anaerobic respiration.
Step-by-step explanation:
The primary waste product of aerobic metabolism is carbon dioxide. Aerobic respiration involves the complete oxidation of glucose through the process of glycolysis, followed by the Krebs cycle and the electron transport chain. During aerobic respiration, pyruvic acid derived from glycolysis enters the mitochondria and is transformed into acetyl-CoA, which then goes through the Krebs cycle. In these reactions, carbon atoms are continually stripped from the metabolic intermediates and released as carbon dioxide (CO2).
Furthermore, high-energy electrons are captured in molecules like NADH and FADH2, which subsequently pass these electrons to the electron transport chain to produce ATP. Oxygen plays a crucial role here as the final electron acceptor, combining with protons to form water (H2O) inside the mitochondria. In contrast, if there is a lack of oxygen, anaerobic respiration can occur, in which pyruvic acid is converted into lactic acid, but this is not the main waste product of aerobic metabolism.