In the living cells, insufficient oxygen may cause a breakdown of glucose into

In living cells, glucose can be broken down through two processes, aerobic respiration (with oxygen) and anaerobic respiration (without oxygen). If there is insufficient oxygen available for aerobic respiration, the cells will switch to anaerobic respiration. During anaerobic respiration, glucose is broken down into lactic acid. Lactic acid is then transported to the liver, where it can be converted back into glucose when oxygen is available again. This process is commonly known as the "lactic acid fermentation" and occurs in cells like muscle cells during strenuous exercise when there is not enough oxygen available to produce energy through aerobic respiration.