The primary fuel for glycolysis is glucose. Glycogen, the stored form of glucose, can also be broken down to glucose and used as fuel for glycolysis.
Glycolysis and its Fuel Source
Glycolysis is a fundamental metabolic pathway that occurs in the cytoplasm of cells. Its primary function is to break down glucose into pyruvate, generating ATP (energy) and NADH (a reducing agent) in the process. Therefore, the main fuel source is glucose itself.
- Glucose: A simple sugar (monosaccharide) that is readily available from the bloodstream or from the breakdown of more complex carbohydrates.
- Glycogen: A polysaccharide stored in the liver and muscles. When energy is needed, glycogen can be broken down into glucose-1-phosphate, which is then converted to glucose-6-phosphate, an intermediate in glycolysis.
Anaerobic Conditions
As the provided reference points out, carbohydrates (glucose/glycogen) are the only macronutrient that can be used for ATP production under anaerobic conditions (without oxygen). While fats and proteins can also be used for energy, they require oxygen for their complete breakdown and energy extraction. Glycolysis, however, can proceed with or without oxygen. In the absence of oxygen, pyruvate is converted to lactate (lactic acid).
Summary
In essence, glycolysis is fueled by glucose obtained directly or derived from glycogen breakdown, allowing cells to generate ATP, even in the absence of oxygen.
