Glycolysis happens outside the mitochondria in the cytoplasm of the cell. This process is the first step in breaking down glucose to extract energy for cellular activities. During glycolysis, a molecule of glucose is converted into two molecules of pyruvate, generating a small amount of energy in the form of ATP and NADH.
The reason glycolysis takes place in the cytoplasm rather than within the mitochondria is due to its nature as a fundamental and anaerobic process. Since it does not require oxygen and occurs before the aerobic processes of the mitochondria begin, it is essential for cells to be able to perform glycolysis quickly and efficiently, even in low-oxygen conditions. Therefore, the cytoplasm serves as the perfect environment for this crucial metabolic pathway.