EmbdenMeyerhof

The Embden-Meyerhof pathway, also known as the glycolytic pathway or the anaerobic pathway, is a fundamental metabolic process found in nearly all organisms, from bacteria to humans. It describes the sequence of enzymatic reactions that converts one molecule of glucose into two molecules of pyruvate. This process occurs in the cytoplasm of the cell and does not require oxygen, hence its designation as anaerobic.

The pathway involves ten distinct enzymatic steps, broadly divided into two phases. The first phase, the energy-investment phase, consumes two molecules of ATP to destabilize the glucose molecule and prepare it for cleavage. The second phase, the energy-payoff phase, generates four molecules of ATP and two molecules of NADH. Therefore, the net gain of the Embden-Meyerhof pathway is two molecules of ATP and two molecules of NADH per molecule of glucose.

The pyruvate produced can then enter different metabolic routes depending on the availability of oxygen. Under aerobic conditions, pyruvate is further oxidized in the mitochondria through the citric acid cycle and oxidative phosphorylation, yielding a much larger amount of ATP. In the absence of oxygen, pyruvate is converted into other end products, such as lactate (in animals and some bacteria) or ethanol and carbon dioxide (in yeast and some bacteria), through fermentation. This fermentation process regenerates NAD+ from NADH, which is essential for the continuation of glycolysis. The Embden-Meyerhof pathway is crucial for providing cells with immediate energy and serves as a central hub for carbohydrate metabolism.