Glycolysis can occur under both aerobic and anaerobic conditions.
Glycolysis is a fundamental metabolic pathway that breaks down glucose into pyruvate. Whether this process continues through aerobic or anaerobic pathways depends on the presence of oxygen.
Glycolysis in Aerobic Conditions
When oxygen is available (aerobic conditions):
- Pyruvate, the end product of glycolysis, enters the mitochondria.
- Inside the mitochondria, pyruvate is converted to acetyl-CoA.
- Acetyl-CoA then enters the citric acid cycle (also known as the Krebs cycle), further oxidizing the molecule and releasing energy.
- The energy released is used in the electron transport chain and oxidative phosphorylation, which generates a significant amount of ATP (approximately 32 ATP molecules per glucose molecule).
Glycolysis in Anaerobic Conditions
When oxygen is limited or absent (anaerobic conditions):
- Pyruvate is converted to lactate (lactic acid) through a process called anaerobic glycolysis or fermentation.
- This conversion regenerates NAD+, which is essential for glycolysis to continue.
- Anaerobic glycolysis produces a much smaller amount of ATP (2 ATP molecules per glucose molecule) compared to aerobic respiration.
Summary
Glycolysis itself doesn't require oxygen, making it possible in both aerobic and anaerobic environments. The fate of pyruvate, the end product of glycolysis, determines whether the overall process is predominantly aerobic or anaerobic.
