Glycolysis

Glycolysis is the conversion of glucose to lactic acid or carbon dioxide, providing some usable energy, but many times less than oxidation provides 1. This process occurs in the presence or absence of oxygen, with the presence of oxygen normally restraining glycolysis so that glucose is converted to carbon dioxide instead of lactic acid 2. However, in certain conditions such as cancer, extreme trauma, or shock, the presence of oxygen does not prevent the production of lactic acid, a phenomenon known as aerobic glycolysis 4.

Aerobic glycolysis is characterized by the excessive consumption of glucose in the presence of oxygen, resulting in the production of lactic acid and suppression of respiration 6. This process is typical of cancer and is associated with defective respiration, where glucose is consumed too rapidly 6. The products of glycolysis, lactic acid and pyruvic acid, suppress oxidation of glucose, leading to toxic effects and cell death 5.

The relationship between glycolysis and oxygen is complex, with adaptation to hypoxia or increased carbon dioxide limiting the formation of lactic acid and increasing the efficiency of glucose metabolism 5. Carbon dioxide has been shown to have antioxidant properties, inhibiting the generation of active forms of oxygen in human and animal cells 8. Estrogen has also been found to promote anaerobic metabolism, increasing glycolytic metabolism throughout the proliferative phases of the reproductive cycle 7.

The distinction between aerobic and anaerobic glycolysis is not always clear-cut, with both processes occurring in different contexts. However, the consequences of glycolysis, particularly aerobic glycolysis, are significant, contributing to cell death, suppression of respiration, and the development of diseases such as cancer 2.