Final answer:
Aerobic respiration, including the Krebs cycle and oxidative phosphorylation, occurs in the mitochondria of eukaryotic cells, whereas glycolysis occurs in the cytosol for both aerobic and anaerobic processes. The electron transport chain in aerobic respiration uses oxygen as the final electron acceptor, while anaerobic respiration uses other inorganic molecules. The evolution of metabolic pathways indicates glycolysis as older than the Krebs cycle.
Step-by-step explanation:
The question concerns how aerobic pathways differ from anaerobic pathways in eukaryotic cells. In eukaryotic cells, glycolysis takes place in the cytosol for both aerobic and anaerobic respiration. Aerobic respiration continues in the mitochondria with the Krebs cycle and oxidative phosphorylation. Anaerobic organisms, such as a new species of obligate anaerobe living in hot, acidic conditions, are most likely to rely on glycolysis and may perform fermentation, which does not require oxygen.
The electron transport chain (ETC), part of cellular respiration, occurs on the inner mitochondrial membrane in eukaryotes. Both aerobic and anaerobic respiration involve biochemical cycles where energy is obtained from electrons transferred through the ETC, creating a chemiosmotic gradient for ATP production. However, aerobic respiration uses oxygen as the final electron acceptor, whereas anaerobic respiration uses other inorganic molecules.
The evolution of metabolic pathways suggests that glycolysis is an older and more conserved process than the Krebs cycle, and organisms may have evolved to use oxygen later. The pathways for making ATP in aerobic respiration, including the ETC and ATP synthase, resemble those used in photosynthesis. Both processes use the energy from electron transport to create a chemiosmotic gradient that powers ATP synthase to produce ATP.