Zero oxygen molecules are used during glycolysis.
Glycolysis is a metabolic pathway that breaks down glucose into pyruvate. It's a fundamental process that occurs in the cytoplasm of cells in all living organisms. Importantly, glycolysis does not directly require oxygen. It can proceed under both aerobic (with oxygen) and anaerobic (without oxygen) conditions.
Here's why oxygen isn't involved in the glycolysis pathway itself:
- Glycolysis focuses on substrate-level phosphorylation: The energy to drive ATP production during glycolysis comes directly from the breakdown of glucose and related molecules. This is called substrate-level phosphorylation.
- Oxygen is used later in cellular respiration: While glycolysis doesn't use oxygen, the pyruvate produced can be further processed in the presence of oxygen through the citric acid cycle (Krebs cycle) and oxidative phosphorylation (electron transport chain), which are the processes that do require oxygen.
- Anaerobic fate of pyruvate: If oxygen is not present (anaerobic conditions), pyruvate undergoes fermentation to regenerate NAD+, which is essential for glycolysis to continue.
In summary, glycolysis is an anaerobic process in itself, meaning it doesn't consume oxygen.
