Glycolysis is an anaerobic process. This means it does not require oxygen to occur. Glycolysis is the initial stage of cellular respiration and takes place in the cytoplasm of the cell. During this process, one molecule of glucose is broken down into two molecules of pyruvate, generating a net gain of two ATP molecules.
The reason it is classified as anaerobic is that it can occur even in environments devoid of oxygen. Organisms, such as yeast, use glycolysis to produce energy through fermentation when oxygen levels are low, converting pyruvate into ethanol and carbon dioxide.
In summary, while glycolysis can lead to aerobic respiration if oxygen is present (where the pyruvate can enter the mitochondria for further processing), the glycolysis pathway itself operates independently of oxygen, solidifying its classification as an anaerobic process.