Final answer:
In the absence of oxygen, aerobic glycolysis shifts to anaerobic respiration or fermentation, producing lactic acid to regenerate NAD+, allowing continued ATP production despite the lack of oxygen.
Step-by-step explanation:
What Happens When No Oxygen Is Available After Aerobic Glycolysis?
When there is no oxygen available at the end of aerobic glycolysis, cells have to switch from aerobic respiration to an alternative method called anaerobic respiration or fermentation. During this process, pyruvate, which is produced at the end of glycolysis, is not fully oxidized into CO2 and H2O as it would be in the presence of oxygen. Instead, it is converted into lactic acid through the action of lactate dehydrogenase. This conversion is crucial as it regenerates NAD+ from NADH, allowing glycolysis to continue producing a small amount of ATP without oxygen.
Moreover, lactic acid production is particularly important for cells that operate normally in oxygen-poor environments, such as red blood cells (erythrocytes), or during intense exercise when muscles are not receiving enough oxygen to meet their energy demands. However, the lactate buildup can also lead to muscle fatigue and needs to be transported to the liver for conversion back to glucose or pyruvate through the Cori cycle. This anaerobic pathway is efficient for rapid energy generation but only sustainable for short periods.
In summary, the absence of oxygen after glycolysis leads to a shift from oxygen-dependent pathways to anaerobic fermentation, impacting energy production and the biochemical cycling of metabolites within cells.